ZOOL318 Freshwater Ecology

Recall the properties of water that make it essential for life as we know it, and think about how these properties influence the form and function of the organisms living in water

Only known medium that can support life
- fluid enough that chemical reactions can occur
- viscous enough that they can be controlled
-really good solvent
- only substance found in all three states of matter
- only common liquid at the earths surface

High specific heat - slow to heat & cool

Highly polar molecule (+ and - poles) ➝ Hydrogen bonding between water molecules,
- many consequences, including stability of liquid water

nearly universal solvent
- bonds other polar molecules (ions, CO2)
- some nonpolar molecules (O2, N2), its not reacting with the water but it forms a physical mixture and can hold a lot of oxygen molecules in addition to h20 which means theres oxygen for aquatic organisms under the water
- solubility is temperature-dependent, the warmer the water the less oxygen, but more dissolved ions, co2, so when its cold its hard to hold on to salts etc in water

Density and Temperature - liquid water heavier than ice
- Lake freezes from the top down
- allows for them to hold fish and other species over winter
- lakes stratify with 4°C water at the bottom, and either warmer or colder water on top (will be going over in more detail later)
- leads to existence of thermoclines etc

Because waters polar and forms strong hydrogen bonds its really sticky (viscosity)
- Small aquatic organisms experience a much more viscous environment than large organisms: Reynolds Number (Re)
- This means organisms can exploit surface tension at the air-water boundary ("neuston")

Understand the major drivers and processes of the hydrological cycle

Hydrology = patterns of water flow through a system (quantity, quality and flux)

Powered by:
- solar energy (evaporation)
- gravity (rain and water flow)

Only around 0.02% of water is in lakes and rivers

Rainfall patterns
- A lot of variability on how much rainfall different regions get
- equatorial evaporation & uplift (most evaporation takes place around equator)
- wind currents moving water
- orographic effects: how landforms shape where precipitation falls
- Check out the infographic in lecture for this (imagine the image is of the southern alps and the difference between west coast and Canterbury in terms of rain)
- Consequences: Variation in water availability

What is a catchment, and how are catchments influenced by their landscape?

Catchment - Land area or basin draining into a common outlet (e.g. river)

Regional council boundaries usually correspond to catchment boundaries

Rivers and their catchments are geologically long-lived, though their exact course varies over time

Lakes within catchments are relatively short-lived

Catchments vary in size, could be due to orographic effects or the topography of the kand

Stream order - can put a number on any given stream like being a 1st order stream, if too come together it becomes a second order stream
1: no tributaries
2: confluence of two first order streams
3: confluence of two second order streams
and so on
- Question for Travis, what happens if a first order and a second order confuent, and is this possible?

River Continuum Concept
- predictable community & ecosystem changes with stream order (stream order is a good predictor of the biology of whats happening within a stream)
- As you move from heavily forested streams 1st order streams and move up to the bigger boys like 5th order where there might be more light hitting the stream, you might get more biofilm and paraphtin production, which means more grazers grazing on biofilm etc, as you get bigger its almost like a moving lake with phytoplankton being produced, less paraphtin because waters not hitting the bottom, this all effects what organisms are living in the different areas of the stream

Catchment discharge = volume moving through a point/time
- Catchment Discharge ≈ rainfall - evaporation
- if rainfall > evaporation → exorheic (open catchment), water will make its way to the ocean
- if rainfall < evaporation → endorheic (closed catchment)

Theoretical Water Residence Time ≈ volume / inflow discharge


Water residence time
- Usually ranges from days to years
- Determines how long processes occurring in a lake can change properties of the water before it exits - -- - Biological processes: - biological uptake, denitrification Chemical processes: - chelation, precipitation
- Physical processes: - photo-oxidation, sedimentation
- Can influence productivity (Increasing residence time by reducing flow can increase algal productivity as theres more time for nutrients to be taken out of water (& blooms), on the other end: lakes with very long residence times tend to be clearer and less productive, less nutrients and material coming into lake)

Residence Time and pollution vulnerability Compartments with short residence time
- constant flux through system
- highly vulnerable to pollution
- but, pollutants flushed out of system rapidly

Compartments with long residence time
- material moves more slowly through system
- more resistant to pollution
- but, slow to eliminate pollutants

Understand how geological features can influence the water chemistry within a catchment

Get quite a bit of

Different rocks have strong influence on the concentrations of major ions in waterbodies as they have different compositions

Ion concentrations tend to increase from headwaters to sea (or large lake), as stream order gets higher you start to accumulate more ions and get higher productivity

Biological consequences of geology
- Can determine the limiting nutrients (more in L5)
- e.g. calcium limits mollusc shell growth →[Ca2+] in UK lakes influences mollusc diversity & abundance

The origin and diversity of lakes on Earth
- Know what types of processes result in lake formation, and some other important ways to characterise lakes

Lake
- standing water body occupying a basin or depression in the landscape
- not part of the ocean (cf. lagoons)
- bigger than a pond


Glacial
e.g. glacial valley lakes (L. Hawea, L. Wakatipu, Tasman Lake)
- Glacier has retreated at some point and left outflow dammed by glacial debris (moraine)

kettle hole lakes
- ice left underground melts

scoured alpine tarns (still glacial)


Geological processes involved in creating lakes
- rift lakes - tectonic subsidence (as the tectonic plates are moving past each other and pulling apart)
- crater lakes - calderas or bolides (Crater Lake, L. Taupo)
- landslide lakes (e.g. when big storms come through it can lead to landslips that block off river flow, green lake example, tend to not last very long)
- lava flows (L. Garibaldi, Canada, function the way a landslide would)


Biological activity of organisms creating lakes
-anthropogenic
- hydroelectricity, drinking water, recreation (L. Dunstan, L. Mahinerangi, L. Benmore)
- Beaver dams


The death of lakes
- Whatever their origin, lakes immediately begin filling with sediment
- Short-lived features of landscapes relative to catchments
- Lake Baikal: oldest (25 my) and deepest lake, more than 2/3 filled already

The structure of lakes and the light environment
- Know how light is transmitted through water, and how this affects biological activity

Increasing DL is just the more messed up lake shape

Why is lake shape/measuring it important
- Might want to know how much shoreline a lake has which might be an indication of whether its phytoplankton (circular) or something else thats the most productive in the lake
- Increasing DL: greater contribution of benthic & riparian productivity
- Increasing DL: More inaccessible littoral habitat for a cool-water predator
- relative depth important, which is the depth of lake relative to surface area (this has an effect on how exposed it is to wind which mixes the water column and can be a determinant of the depth of the thermocline)


The light environment of lakes
- logarithmic extinction of light with depth (light declines logarithmically with depth), at 1% theres not enough light for things to happen atrophic zone
- How fast this decay is depends on characteristics of lake, can compare kd values between lakes, high value means productivity (photic zone) depth is shallow , low means productivity can be happening very deep
- Compensation depth (above compensation depth you can have net productivity of oxygen, but below you get hypertrophic system with more respiration than photosynthesis
- Uneven light absorption across visible/PAR spectrum (effects camouflage strategy depending on light colour, effects colour of organisms because of wanting to stand out in mating shows, can change which colour individuals are favoured)

Water movements in lakes
- Understand different types of water movement and consider how they will affect mixing and stratification of lakes

Water movement Influence distribution of temperature, nutrients, dissolved gases, particulates, organisms etc

Inflows: streams, rivers, groundwater (rivers bring in sediment, nutrients, organism etc, causes mixing etc

Heating: convective mixing of thermocline (more in L4) (can have reasonably well mixed water interacting with atmosphere above a certain depth, but nothing below it)

Wind:
- "normal" waves - horizontal water movement (will contribute to surface mixing, heating)
- Langmuir circulation (- wind produces variable shear, resulting in alternating helical cells, bubbles and buoyant algae accumulate on downwelling lines, can effect mixing to fairly shallow depth, but more than just the waves at the surface)
- seiches (standing waves) (Lake Wakatipu rises and falls by ~20 cm every ~27 minutes, caused by wind or atmospheric pressure, water oscillates around a surface or subsurface node, surface seiches cause 'tides' and can depress the thermocline)

Understand the basics of stratification and mixing, and the role of temperature.

Lotic systems usually in ~thermal equilibrium with the air (lot of turbulence and opportunity for it to be mixed well enough with thermal energy going in and out of water

Lentic systems with higher retention times can show simple or complex temperature variation with depth

Stratification = change in temperature with depth

Densest water at the bottom

sothermal/mixed - temperature and chemistry same at all depths

stratified - warm layer on top, cold water below the thermocline

inverse stratified - water < 4°C on top, usually covered by ice

Thermocline - Zone of rapid temperature change
- Thermocline depth depends mainly on lake size, pushed down by wind or seiches
- For lakes of a similar size, the thermocline gets deeper the more exposed it is as the surface gets more mixed by wind

Lake classification by mixing pattern
- Amictic Lakes - permanently frozen over
- Polymictic Lakes - mix freely throughout the year, at most brief periods of stratification, for example if its shallow so not enough depth to get stratifcation forming, or its really exposed and windy, no real segregation of zones, benthic interacts with water column
- Cold Monomictic Lakes - inverse stratified most of the year, one period of mixing in summer
- Warm Monomictic Lakes - stratified in summer, one period of mixing in winter
- Dimictic Lakes - stratified in summer, inverse stratified and ice-covered in winter, mixing in spring and autumn
- These are all holomictic (mixed at some point)

Meromictic: goes years or longer without fully mixing - e.g. Lakes Malawi and Tanganyika Warm monomictic in surface waters, but a permanently unmixed hypolimnion
- e.g. Lake Vanda Permanent hypersaline hypolimnion, much warmer (20-25°C) than water near ice surface (4-6°C) due to stored solar energy


Mixing pattern is largely determined by a lake's depth and latitude (adjusted for elevation)

Learn how oxygen profiles in lakes are influenced by physical and biological processes

Solubility (max. potential [Dissolved oxygen]) depends on:
- temperature (↓) (as it increases oxygen gets forced out of mixture and ends up in atmosphere)
- salinity (↓)
- atmospheric pressure (↑)

Concentration [DO] determined by:
- solubility
- diffusion from air
- production by photosynthesis
- consumption by respiration (if you have a lot of biological activity from e.g. heterotrophs you can get a lot of depletion)
- loss to chemical oxidation

Oxygen curve types;

Orthograde - low productivity & respiration, colder = high O2 solubility, hypolimnion O2 ≥ surface. combination of there not being much biological activity, (nutrients, nutrient uptake etc) the oxygen will be more determined by physical processes

Clinograde
-Even with same temp you get depletion of oxygen
- high productivity & respiration
- warmer - lower O2 solubility
- hypoxic or anoxic hypolimnion

Can get different patterns in Ologatrophic and eutrophic lakes, lakes with different nutrient levels.

Dissolved Oxygen profiles in Lake Hayes, 1969-1971
- mixing in winter, hypolimnion anoxic by late summer
- Overlayed with thermal stratification, which showed the temperature, thermocline, warmer surface water dropping down and coldere hyperlimbnion and this will overlap with how oxygen levels are changing

Why does it matter if lakes are not mixed and causes;
- persistent anoxia below a certain depth

- Deep hypoxic/anoxic layers:
Favoured by: - warm water → low solubility
- small, deep (high ZR) and sheltered lakes → limited mixing
- turbidity (phytoplankton/solutes) → low light penetration → shallow compensation depth

- Consequences of hypoxic/anoxic layers due to no mixing
- reduced liveable habitat for fish and other organisms
- altered conditions for chemical reactions
- nutrient release from sediment

Know the main forms of inorganic carbon in lakes

Inorganic: three main dissolved forms (DIC)
- dominant form depends on pH
- Have a look at slides for effect of pH, as its higher photosynthesis becomes much harder/impossible to occur

Organic: huge pool of dissolved (DOC) and particulate organic carbon (POC), massive potential resources, can change colour, turbidity etc of lakes.

Carbon is necessary but rarely limiting for photosynthesis

Lake Nyos in Cameroon: deep, stratified crater lake with underground magma seeps → CO2 and H2CO3 accumulate in the hypolimnion
- Mixing occurred, causing 21 Aug 1986: limnic eruption of >100,000 tonnes of CO2 → 1700 people suffocated within 25km radius
- 2001: To try and prevent this happening in the future, degassing begins → water siphoned from 70m to surface

Nutrients in lakes
- Understand the processes affecting the availability and forms of N and P in lakes

Nutrients - chemical elements required by living organisms, can be grouped into macro (e.g. N, P) and micronutrients (e.g. Mg, Fe)

N cycle dramatically altered by N-fixation for fertilisers and by burning of fossil fuels

Inputs of N
- Atmosphere: - rain (ammonium, nitrate) - particulate fallout (dust, pollen)
- N-fixation by bacteria (heterotrophs, autotrophs)
- Animal excretions - dung, guano, urine Inflows and runoff - organic and inorganic waste
- Anthropogenic - fertilisers, detergents, sewage

Losses of N
- Bacterial denitrification
- Gaseous diffusion to atmosphere
- Sedimentation (may not be permanent)
- Outflows

Actually just look at the lecture slides for inputs and losses of N and P

Input of P is much more dependent on the catchment its in compared with nitrogen, due to coming from phosphorous rocks and being in high or low P level areas where as nitrogen is pretty universal

Forms of Nitrogen in Lakes:

DIN = Dissolved Inorganic N (DIN)
- NH4+ (ammonium - excretion, decay)
- NO3- (nitrate - inflow)
- NO2- (nitrite - minor except in hypoxia)

Dissolved Organic N (DON)

Particulate Organic N (PON)

Analytic forms
- TN = Total Nitrogen (DIN + DON + PON)
- DIN - immediately biologically available

Forms of phosphorous in lakes
- Pi = Dissolved Inorganic P (orthophosphate PO43-)
- Po = Dissolved Organic P
- PP = Particulate P

Analytic forms
- TP = Total Phosphorus (Pi + Po + PP)
- SRP = Soluble Reactive P (Pi + part of Po) SRP = readily available P for organisms to uptake (might need to know the availability of phosphorous over nitrogen to see chances of algal blooms etc)

Nitrogen and Phosphorus concentrations determine the trophic state ("trophic level" in NZ) of a lake:

Phytoplankton requirements and coexistence
- Learn how the mechanisms of species coexistence apply to phytoplankton, and how they can help to resolve the "paradox of the plankton"

Plankton = Aquatic organisms with weak or no locomotory ability
- (vs. nekton = fish & other mobile organisms)
- (vs. seston = all living, dead and inorganic particulate matter)

Can be classified by:
- 1. Size - e.g. microplankton vs. nanoplankton
- 2. Form & Function - e.g. autotrophic (phytoplankton) vs. heterotrophic (zooplankton)

Phytoplankton requirements:
- Light (+ H2O + CO2 → photosynthesis)
- Macronutrients: N, P (H, O, and usually C are readily available) (+ Si for diatoms)
- Micronutrients: Mg, Fe, Co, Mo, Ca, Mn, B, V, Na, K, Cl, Cu, S, Se, Zn
- Vitamins (B12 Thiamine Biotin)

Limiting nutrients: nutrients whose concentration determines the net primary productivity (NPP)
- usually nitrogen (DIN) and/or phosphorus (SRP)
- productivity of species may be limited by other nutrients (e.g. Molluscs need calcium, diatoms need silicon)

Many lakes are Phosphorus Limited
→ adding P increases Net primary productivity (NNP)
→ adding N without P doesn't

NZ lakes often limited by N, or co-limited by N and P
- co-limitation → adding N, P, or N+P increases NPP

Most organisms require elements in a particular ratio due to physiological constraints → Ecological Stoichiometry
- Redfield Ratio: C:N:P = 106:16:1 in bulk marine phytoplankton - N:P usually higher in lakes, possibly due to P limitation
- But, species vary substantially in their uptake rates of N and P

The paradox of the plankton
- The problem: different phytoplankton species have similar requirements (light, CO2, N, P, micronutrients...)
- Essential nutrients are non-substitutable (e.g. nitrogen cant be substituted for something else, it has a specific purpose)
- Because of this you would expect competitive exclusion →the species able to persist on the lowest level of the limiting resource should outcompete all other species

resolving the paradox
Species can be limited by different factors
- some better competitors for different nutrients
- others more resistant to grazing
- others more tolerant (pH, temperature)

Resolving the paradox:
Species can dominate at different times
- seasonal succession
- storage effect - species can 'store' population gains made when conditions favour them

Niche differences permit species to co-exist
- e.g. Anabaena (cyanobacteria) is tolerant of grazing but requires high [P]
- Sphaerocystis (chlorophyte) is tolerant of low [P] but is susceptible to grazing

Seasonal and successional variability
- Know how biotic and abiotic factors influence seasonal dynamics of phytoplankton

Biotic tolerance: zooplankton grazing
- Zooplankton added to & removed from in-lake mesocosms
- Phytoplankton response to grazing depends on size & palatability
- increased or unaffected - cyanobacteria - large chlorophytes
- suppressed - large diatoms - small flagellates

Abiotic tolerance: water temperature & light intensity
- Phytoplankton species often have upper and lower tolerance limits - too much or too little heat or light can limit growth
- Light increases and decreases earlier in the year than temperature → 4 seasonal periods with different phytoplankton assemblages
- slide shows which ones thrive in different light and temp

Storage effect
- Long-term coexistence is more likely if species can store population gains (e.g. extra offspring) for the next time conditions favour its dominance
- Phytoplankton cysts (and zooplankton resting eggs) can lay dormant in the sediment for years to centuries
- This means they can survive through periods of low favourability
- Can wait out periods of drought, hypoxia, darkness etc

Seasonal patterns
- Biologically available nitrogen (DIN) and phosphorus (SRP) show strong seasonal patterns in most lakes:
- This determines biological activity and where nutrients are etc

Seasonal patterns of phytoplankton
- Spring "pulse" Nutrients plentiful, lake has been well mixed Increase in light, Low zooplankton grazing,
- Summer decline when surface nutrients are severely depleted Nutrient depletion, High zooplankton grazing due to clear water
- Autumn secondary pulse, Nutrient renewal, High zooplankton grazing
-Eutrophic or Oligotrophic state can determine peaks, eutrophic

Microbial plankton
- Be aware of the 'microbial loop', and how heterotrophic microbes and viruses contribute to processes in the pelagic food web.

Cyanobacteria (e.g. Anabaena, Aphanizomenon, Microcystis) - dense buoyant aggregations at the surface
- Produce cyanotoxins - neurotoxins (nervous system), hepatotoxins (liver), cytotoxins (cells)
- These are harmful to humans, pets, livestock, zooplankton, fish
- Occurrence linked to nutrient loading and climate warming


Microbial plankton:
- Basically includes everything that not a primary producer or macrozoopankton

The "classic" pelagic food chain
- DIC uptake by phytoplankton
- transfer to grazers & predators

Microbial Loop:
- POC/DOC uptake by bacteria, what you get from vegetation from riparian areas and dead material from algal cells, from zooplankton, from dead fish etc.
- This turns into particulates or dissolved carbon which bacteria can colonise and break down and consume themselves or replenish the supply of dissolved nutrients that get taken up through algal pathway
- integrated back into the food web via grazing from protists & rotifers

Heterotrophic bacteria
- Diverse metabolic functions; diversity often assessed with DNA
- Attach to and break down POM (dead algal cells and fragments)

Lake snow
- Extracellular polysaccharides produced by an introduced diatom Lindavia intermedia (similar to 'didymo' in streams)
- Forms sticky aggregations in the water column →clogs water filtration and fishing equipment
- Globally rare; introduced to Lake Wanaka ~2004, spread to other oligotrophic lakes
- As soon as you have organic material bacteria start to colonise, material will break down and change in its nature, some of this bacteria might get eaten and eventually it leads to this snow like material on the surface

Microbial plankton - Fungi
- Many parasites: - water molds: Oomycetes, chitrids: Chytridiomycetes

Microbial plankton Protozoa
- Add complexity to planktonic food webs:
- feed primarily on bacteria and small phytoplankton
- eaten by zooplankton such as copepods and rotifers

Viruses
- Bacteriophages can control bacteria populations
- Two strategies: lytic - viral DNA proliferates independently using host cell machinery, then lyses the host (highly virulent)
- lysogenic - viral DNA integrated into host DNA, proliferates along with host (less virulent)

Zooplankton diversity, feeding, and antipredator strategies
- Know the major taxonomic and functional groupings of zooplankton, and how they vary in their life history strategy, feeding, and response to predation risk

main groups
- Rotifers
- Cladocerans
- Copepods

Rotifers
"Fast" life history
- small (50-500 µm)
- short generation time (few days)
- some species are facultatively or obligately parthenogenic (no males)
- Use ciliated "wheels" to feed on algae, bacteria, protozoa, or other rotifers

Cladocerans
Relatively fast life history
- large size range (200 µm-6 mm)
- parthenogenic for long periods (in good conditions)
- short generation time (days-weeks), fecund, iteroparous (continously producing offspring)
- Feeding: wide range of particles (algae, bacteria, protozoa) - filter feed continuously and unselectively - mainly herbivorous; a few predators (not in NZ)

Copepods
- Three major groups: Calanoida (planktonic), Cyclopoida (planktonic or benthic), Harpacticoida (primarily benthic)
- Slower life history than cladocerans or rotifers:
- dioecious (males and females)
- many instars to reach maturity (nauplius & copepedite stages), undergo metamorphisis quite a few times
- relatively large (most 1-2 mm as adults) - long-lived (weeks to years)
- Feeding: omnivores and predators, selective
- feed intermittently by filtering and/or seizing particles - low food requirement, resistant to starvation

Zooplankton size has an effect on how smooth or sticky the medium they are living in feels to them (think sticky lecture)
- Reynolds Number: measures whether organisms or objects experience fluid as turbulent & easy to move through (high Re) or viscous (low Re)
- Re = density x velocity x length / viscosity
- smaller ones experience more viscosity
- Makes it harder to approach food particles without pushing it away
- Solution: use appendages (crustaceans) or cilia (rotifers) to channel particles toward mouth rather than reaching out to grab them

Challenge: predation (still about reynolds number)
- Challenge: avoid predators (like damselfly larvae or larval/juvenile fish like galaxias) that can move more quickly and efficiently through the water (and may suction-feed)
- Size-Efficiency Hypothesis:
- Herbivorous zooplankton compete for fine POM
- Large zoop. species more efficient grazers, but more targeted by fish predators
- Low predation → large zoop. dominate
- High predation → small zoop. dominate
- Intermediate predation → all size classes present

How plankton can avoid predation
- Camouflage
-

Temporal dynamics of pelagic communities
- Learn about the drivers of seasonal changes in Zooplankton abundance and composition

How plankton can avoid predation
- Camouflage
- induced morphology

Induced morphology
- happens when predation risk is highewst such as summer
- Most common in summer in organisms that reproduce parthenogenetically for most of the year
- e.g. Daphnia starts to develop longer tail spines and helmets, this often happens when theres inertebrate predators, makes them harder to digest,
- can also become smaller and decrease the amount of pigment
- Chemical cues in the water can induce morphology seasonally


Vertical migration as a way to minimise risk of exposure to predators by not being there:
- Diurnal migrations - crustacean zooplankton, some rotifers, flagellates, insects - varies among species, age classes, sexes & seasons
- 3 basic patterns
- Nocturnal - single maximum at surface at night
- Twilight - two maxima at surface at dawn and dusk
- Reversed - single maximum at surface during the day
- Pattern usually depends on when predators are active

Benthic producers and consumers
- Know the types of benthic primary producers and what factors can control their productivity

Macrophytes (charophytes, flowering plants, ferns)
- submerged
- floating
- emergent (come up out of the water but still part of freshwater to substantial extent, such as roots in water but leaves out)
- freshwater aquatic plants

Periphyton (diatoms + cyanobacteria + chlorophytes...)
- epibenthic
- epiphytic
- epilithic
- epixylic
- Can occur on a variety of substrates

What control primary production
- Nutrients - uptake from both sediment and water (macrophytes rooted in sediment takes nitrogen and phosphorous from sediment, whereas ion get it from the water itself)
- Light: Whereas phytoplankton have some level of buoyancy and can remain in turbulence and photosynthesis, the primary producers are living longer and staying in one place sop there distribution with depth is going to be defined by light controls and things like water clarity. This was seen with Charophytes in NZ.
- Competition: Phytoplankton can shade benthic algae, Periphyton can suppress macrophyte growth (periphyton can grow on macrophytes)
- Grazing: Many invertebrates graze periphyton. Fewer feed directly on macrophytes. Some fish, birds and crustaceans graze macrophytes directly. When there is a loss of macrophytes theres a loss of substrate and sediment integrity, contributing to a flip to phytoplankton dominated states

Learn some of the ecological roles and diversity of benthic invertebrates, and how they respond to environmental variation

Benthic invertebrates:
- Occur on macrophytes, sediment, wood, rocks
- Much more taxonomic diversity than macrozooplankton (due to habitat heterogeneity, more niches available etc)
- Key roles in nutrient transfer and cycling

Predators
- feed on other invertebrates and even small fish (not always gape-limited), e.g. dragonfly larvae

Kōura (Paranephrops spp.)
- generalist feeders in both lakes and streams
- important mahinga kai species
- Roles in nutrient breakdown

Palaeoindicators - in layers of sediment cores - e.g. head capsules of chironomid larvae
- Species differ in tolerances, so composition can indicate:
- productivity/trophic state
- temperature
- hypolimnetic oxygen

Be aware of several specialist lentic habitats and their distinguishing features

The Profundal Zone (below pelagic habitat where light doesnt reach the lakebed)
Organisms must cope with:
- lack of in situ primary productivity (sinking phytoplankton is major input)
- darkness
- Low oxygen
- hypoxia/anoxia (sometimes)
- Species in the Littoral zone tend to be no real saturation in the uptake of oxygen and so to maximise respiration, metabolism they need high oxygen levels
- As you move towards profundal species, they have changed response curves so they can get to maximum performance on very low levels of oxygen, efficient uptake of DO


Wetlands: Terrestrial habitat permanently or seasonally inundated with standing or flowing water (fresh, saline, or brackish)

Bogs: (wetlands)
- water from precipitation only
- nutrient poor and acidic
- typically dominated by Sphagnum mosses; sometimes carnivorous plants

Fens: (wetlands)
- groundwater input: Leading to more nutrients and less acidic than bogs

Swamps: (wetlands)
- nutrient rich
- inundated (standing or gently flowing water)
on or nutrient rich underneath etc)

Ephemeral wetlands:
- seasonally filled ponds
- major disturbance (eliminates fish, selects for rapid colonisers and drought-tolerant taxa)
- Tend to have lower diversity than permanent ponds

Understand how benthic and pelagic energy channels can be linked in the larger lake food web

Linkages between benthic and pelagic energy channels
- e.g. benthic mussels filterfeeding pelagic phytoplankton
- e.g. Benthic organisms moving into pelagic habitats and bringing nutrients up with them e.g. insect larvae entering the water column to pupate

Common pattern
- benthic and pelagic energy channels are often coupled by generalist top predators
- Mathematical theory: food webs with coupled energy channels should be more stable (resilient to disturbance) when the channels are asymmetric → one channel fast and efficient (e.g. pelagic) → the other slow and inefficient (e.g. benthic)

Fish ecomorphology
- Learn the key ecomorphological traits of freshwater fish and their functional significance

size - bigger you are more types of things you can consume, typically fewer predators to worry about

Gill raker number, spacing and morphology - these form a sieve to help filter food out of the water column, depending on the size spacing can change what food is retained, might be spaced in the right spacing to get zooplankton out of the water

Jaw mechanics - Important aspect of feeding, fish jaws tend to be flexibile and agile and can move, change shape of them.

Body shape - related to diet but also what kind of swimming you need to do such as predator evasion or getting prey fast start fishes like ambush predators tend to have fins positioned towards back which generates thrust but not efficient for swimming long distances at speed. Relative body depth changes when you have species that are more benthic compared with pelagic etc, benthic tends to have bigger, deeper body.

Armour - e.g. threespine stickleback have spines at top, pelvic and along side, this prevents piercing of skin from predators, also helps hold the spine in place so makes them overall more robust

Evolutionary consequences of trophic interactions
- Know several examples where trophic interactions have resulted in ecomorphological trait evolution in fishes

adaptations to availability of different prey types - species adapts to whats available, or because of competition for a food source. A common way to adapt is to modify jaw mechanics.
- Bluegill sunfish can protrude jaw and create suction, this is an adaptation to evasive prey. If you were going after snails you might want different adaptations like grinding teeth
.
As lakes get bigger, get adaptations to consume smaller prey types that are more prevalent in more pelagic environments
- e.g. Threespine stickleback in lakes: gill raker number and length, they are finer in bigger lakes because of above.

Antipredator adaptations
- e.g. mosquito fish. In areas where they have the bigmouth sleeper predator present, they tend to hav e more surface area to get a boost to get away from predator
- You tend to find that with the more predatory fish they are (density/diversity) the more armoured stickleback fish tend to be. You would want less armour when theres less fish predators and you're trying to get away from invertebrates as these make it easier to grab onto you.
-

Ecosystem consequences of rapid evolution
- Understand the concept of an eco-evolutionary feedback, and some possible examples in freshwater fish

- Ecological conditions impose natural selection on populations...
- causing trait evolution...
- which may alter food web interactions and ecosystem processes...
- And thus changes the selective pressures on later generations
- And repeat
- So the environment effects evolution and then this evolution effects the environment

Ecosystem Effects of Adaptation to Prey Availability
- Anadromous alewife eat large zooplankton when in lake
- Large zooplankton recovers when alewifes return to ocean
- Landlocked populations following dams in 1700s - shift to smaller zooplankton community
- Recall: Size-Efficiency Hypothesis Large zooplankton better competitors but more vulnerable to predation (L6)
- Alewife adaptation to feed on the smaller zooplankton: narrower mouth and finer gill raker spacing → weaker control of zooplankton and leading to weaker trophic cascades

Ecosystem Effects of Adaptation to Predators
Guppies from High Predation populations:
- smaller size & lower density
- eat more invertebrates & less algae → trophic cascades by eating more invertebrates → increased productivity → faster decomposition and nutrient cycling
- So one change in food web leads to all this

Lecture 9 Mark Schallenberg Lake management

degradation and restoration trajectory are not the same, might have to pull nutrients back more than thought to gain turbidity and eutrophication

Types of energy sources

• Living biofilms (also called "periphyton")
- benthic algae, fungi, bacteria & protozoa

• Detritus (bodies/fragments of dead organisms & faecal material)
- derived from instream (autochthonous) & terrestrial (allochthonous) production

• CPOM (coarse particulate organic matter; > 1 mm)
- decaying leaves/wood
- derived from terrestrial & aquatic sources

• FPOM (fine particulate organic matter; < 1 mm but > 90 µm)
- particles abraded from CPOM
- invertebrate faeces
- dead microbial organisms & sloughed biofilm

• DOM ('dissolved' organic matter; particles < 90 µm)
- organic carbon leached from detritus or living organisms
- key energy source for heterotrophic microbes



Key energy sources in streams:
autochthonous (in-stream & local) or allochthonous (terrestrial)?

• Many relevant factors, including:
- Channel size/depth (deeper makes it harder for leaf to be retained)
- Substrate size - Water turbidity
- Riparian vegetation & shading (more shading and vegetation means more leaf litter input and shading makes it harder for primary production as less light)
- Local topography (e.g. banks steep or level)
- Rates of terrestrial organic matter input
- Discharge regime
- Retention of organic material (e.g. debris dams?)
- Water temperature

e.g. Lerderderg River, Victoria, Australia
- dense riparian forest
- expect it to be dominated by allocthonous inpuy

e.g. Waiau River
- receives its water from Lake Te Anau (so gets plankton from this lake and since its a few metres deep it gets retained and plankton production happens which is unusual)
- Is quite wide so has less input from terrestrial matter
- doesnt get retained well as it gets washed away by powerful current

e.g. Snout of glacier, Alaska
- extreme environment
- pretty much no organic matter input
- hardly any energy sources and not much going on in the way of primary production

Functional feeding groups

• Lotic macroinvertebrates can be grouped into feeding categories
- shredders (shred / eat CPOM)
- collectors (collect / eat FPOM)
- grazers/scrapers (scrape/graze biofilms)
- predators (eat all of the above)

• Divisions between categories aren't perfect!
- overlap / fuzziness between categories

Factors influencing primary production

primary energy source of shaded forest stream
- dense canopy, not much light so its all about leaf litter
- so mainly allochthonous input
- A little bit of autochthonous input

A desert stream
- Sycamore Creek (Arizona, USA)
- very wide open
- Hardly anything coming from riparian organic matter
- lots of light, warm so good conditions for primary production on surface zones
- 99% autochthonous energy supply
- derived from algal production in the biofilm


Variation of productivity in space and time:
- Taieri river study

• Upper reaches in this grassland river: shallow & clear water - dominated by autotrophic production during both study years (regardless of whether wet or dry summer/autumn)

Lower reaches
- Depended on type of summer you got
- allochthonous-dominated in 1993/94 (wet) - high flows - turbid water - no light saturation - low primary production
- autotrophic in 1994/95 (dry) - clear water - more light - higher primary production

• Seasonal variation in productivity in five Taieri River tributaries
- peak production in spring or summer (4 of 5 streams), more light, warmer temperatures, longer days etc so best period for high primary production



Consequences of variation in autotrophic production:
• Hill et al. (1995) Interplay between periphyton algal biomass and snail grazers
- Experiment in shaded and unshaded sections of a small Tennessee forest stream
- Also low and high snail density
- They found that algal biomass didnt really change between shaded and non-shaded area when snails were normal density
- This is because asnails at high density are really efficient grazer
- When snail density is low, the shaded conditions have almost twice as much biomass, and then in open conditions where theres light its much higher againb
- so snails are making good use and graze it heaps
- In open patches snails grow faster, so are eating more and benefiting from it
-

Sources and processing of detritus in streams & rivers

• Sources
- terrestrial leaves & woody debris (à allochthonous)
- dead algae & macrophytes (à autochthonous)
- terrestrial invertebrates (à allochthonous)

• Detritus colonised by microbial organisms
- increases nutritive value of detritus
- accelerates conversion from CPOM to FPOM
- rate of breakdown influenced by many factors (e.g. water temperature, abrasion, shredder activity, etc.)

Retention of organic material

• Processing takes time
- days to weeks or longer
- pools & debris dams (caused by fallen trees or large tree branches) slow downstream transport
à permits microbial & invertebrate processing

Leaf litter processing and eating
functional feeding groups limitations

check lecture slide

Up to 20% of leaf mass can leach out as dissolved organic matter within a few days, this is taken up by microbes

Shredders
- The shredder Gamarus much prefers conditioned leaves (after microbial colonisation) as fresh leaves & wood have low nutritive value
- So they like both the leaves and the microbes not just the leaves

• Collectors / gatherers
- feed on FPOM
- abundant in biofilms, depositional areas (slow-flowing) & streambed interstices

• Filterers
- passively or actively filter suspended FPOM
- use nets or body parts
- often prefer fairly fast current velocities (e.g. sandfly larvae), as theres a lot of food being carried down with flowing waters

• Shredder-collector facilitation
- feeding activity of shredders produces FPOM (leaf fragments & faeces) this helps collectors!

Scrapers/grazers
- scrape periphyton from hard substrates

• Periphyton / biofilm
- complex of algae (diatoms), fungi, bacteria & FPOM
- relative proportions & hence food value vary depending on environmental conditions:
- light, nutrients, sediment, etc
- low light levels more fungi
- high light higher prop of algae
- fine sediment a lot of inorganic material of no nutritional value


• Remember: considerable simplification of real patterns of feeding behaviours!

Overlap between groups:
• Shredders eat periphyton algae on leaves
• Grazers eat FPOM in periphyton
• Ontogenetic shifts - most shredders & predators are collectors/gatherers as early instars, as they are tiny and cant each much
• Opportunistic feeding - many shredders are opportunistic predators

So not fixed categories but useful in general terms

Stream morphology & energy sources - the River Continuum Concept

• Predicts: Proportions of functional feeding groups in community will reflect local river morphology & upstream conditions
• shredders dominate (forested) headwaters - high CPOM from terrestrial sources & limited light due to shading
• grazers & collectors dominate middle reaches - wider streams, high light in shallow water & FPOM supply from shredders upstream
• collectors dominate lower reaches - low light due to deep, turbid water & abundant and so not much paraphyton growth for grazers, but FPOM supply from upstream so collectors do well
• Highly cited (>12,000 times) but MANY exceptions to this pattern!
- doesnt apply to NZ aswell as headwaters are often tussock streams with a lot of light and not much allochthonous input
- Specialised shredders are rarer in NZ as headwaters are not really forested systems

What is a flow regime?

Spatial and temporal patterns of water flow through a river system

• Flow regime influences multiple variables within river ecosystem

• Examination of flow hydrographs can reveal much about a river system

What are the components of a flow regime?

Magnitude (of discharge increase)
- Change in the amount of water moving past fixed location per unit time

• Frequency
- how often flow above a given magnitude recurs over some specified time interval (= return period or recurrence interval)
- e.g. 1 in 100 year flood, 1 in 5 year flood

• Duration
- period of time associated with given flow conditions

• Timing
- predictability of flows of defined magnitude


• Rate of change
- how quickly can flow change? à 'flashy' to stable streams

Interpreting a river hydrograph

Comparing different river systems
• Examination of flow hydrographs can reveal much about a river system
• Great website: http://www.orc.govt.nz/waterinfo/

- Flow patterns depend on:
• large vs small catchments (large have bigger, more sustained floods
• position within catchment (more stable flows higher up in catchment)
• catchment conditions upstream (IF YOU HAVE FORESTED UPSTREAM CATCHMENT IT TENDS TO BE LESS FLASHY THAN GRASS/FARMLAND upstream
• natural vs regulated flows (e.g. flow regime upstream or downstream of a dam)

Ecological responses to flow regimes

Flow regime influences
- Water Quality
- Energy Sources
- Physical Habitat
- Biotic Interactions
- All of this together when measuring stream health influences all of this and ecological integrity


Declining flow & stream conditions :
• Water quantity reduced
- Area of wetted channel reduced
- Connectivity reduced
- Invertebrate & fish densities gets effected
- Food supply for above gets effected

• Water quality
- Evaporation & increasing importance of groundwater for maintenance of flow à Changes to water chemistry, as ground water has different chemistry

• Temperature
- In summer (as flow reduced water temp goes up
- In winter (when flows are low easier for water to freeze)


Impacts of drought
• Short-term
- fish behaviour including activity, movement & dispersal - decreased fish condition due to adverse phys-chem conditions & reduced food supply
- increased fish mortality
- altered invertebrate communities due to altered physchem conditions & fish predation regime, sometimes it can be beneficial if fish die earlier and invertebrates are still there and so predation pressure is reduced

• Long-term
- species composition altered for periods of months to years


Variable Discharge & Invertebrate Communities Clarke et al. (2010)
• Sampled a perennial, intermittent & ephemeral stream in wet & dry periods
- Wallaby Creek water supply catchment, ~50km north of Melbourne
- Mean annual rainfall 1207 mm (1995-2006), altitude 600-800 metres, tall Eucalyptus forest

• Do these different flow regime types have different faunas?
- Streams within 2 km of each other
- measured streams during periods of low and high flow
à Abundance & taxon richness strongly dependent on actual discharge, not long-term flow regime type (in preceding years)
- different from flood disturbance! à Both very similar when all 3 streams are flowing

High Resilience of Stream Communities to Drought Clarke et al. (2010)
• Rapid recolonisation of ephemeral & intermittent streams by perennial stream fauna when flow resumes
- à Stream communities not characterised by longer-term preceding flow patterns
- Recovery of dry streams requires nearby source of perennial stream colonists
- Reduced flow resulted in reduced diversity

Different management regimes have different hydrological outcomes

Types of Flow Regime Alterations:
• Land clearing & urbanisation (e.g. urban streams in NZ & elsewhere)
- Accelerated run-off (and more flashy)
- Reduced average flow

• Hydroelectric (e.g. Clutha River, NZ)
- Rapid falls & rises in discharge year-round

'Run-of-river' water abstraction (e.g. Lindis & Kakanui Rivers, NZ)
- Reduced summer flows (can be quite problematic)

• Irrigation storage dams (e.g. Murray River, Australia)
- Reduced winter discharge (when they get filled up) & increased summer discharge (when water is released for irrigation)
- Reduced small-scale variability
- Altered temperature regime

Impacts of Run-of-River abstraction/diversion

• 'Run of River' (RoR) diversion/abstraction
- Much of NZ's agriculture based on direct abstraction from rivers & streams
- Limited storage of water for irrigation (but now increasing)

Honestly I think just go to the lecture slides for this one

• Short-term RoR diversion (Dewson et al. 2007a)
- Increased densities as water levels dropped
- But limited impact on community composition
- (If rapid declines in water quality result, may produce a different result)

• Long-term RoR diversions (Dewson et al. 2007b)
- Impacts varied in relation to stream condition • Greatest change in pristine stream (reduced density & richness) • Least change in most polluted stream
- Some species highly sensitive to reduced flow

Impacts of Storage based agriculture

Impacts of Water Storage
• Store during wet, release during dry

• Often extended periods of filling & draw down
- Lake Hume (River Murray, Australia) full & empty
- Impacts on aesthetics & erosion

• Reduced flow variability downstream
- Minimum low flow
- Reduced variability due to capture of smaller flood events (they dont make it through to the rive downstream)

• Seasonal reversal of flow due to winter capture & summer supply (release)


Example:


Mitta Mitta River & Murray Cod
• Murray Cod
- Large top predator in Murray River system
- Formerly dominant fish in Mitta Mitta River
- Require sustained period of temperatures > 16 oC for spawning & larval survival

• Lake Dartmouth operation started in 1978
- Trout now dominate Mitta Mitta River
- Temperatures only get >15c for short periods
- Low survival of Murray cod eggs & larvae
- Recruitment failure & declined to extinction over 20 years
- Murray Cod no longer present

Impacts of river regulation &

Altered flow regimes - key points

Impacts of river regulation:
• Complex & pervasive impacts of altered flow regimes
- Changes to flow & temperature affect almost every aspect of stream ecosystem functioning
- Species impacted by reduced flow interact with other species
- Changes in abundance may cascade through food web in expected & unexpected ways
- Cant confidently predict what would happen if flow regime was altered


Altered Flow Regimes - Key Points
• Patterns of flow regime changes differ with type of management
- Hydroelectric generation
- 'Run-of-River' abstraction
- Storage & Supply dams

• Altered flow regimes have pervasive & complex impacts on river systems
- Changes at multiple levels (individual, population, community & ecosystem)
- Context dependency of impacts
- Winners & losers

Invertebrate drift in streams - what is it?

• Aquatic invertebrates drift downstream with the current in running waters (also drifting: algae, bacteria, sometimes fish larvae, dead particulate organic matter, fine inorganic particles, terrestrial invertebrates)

• A feature of all streams and rivers

These animals are bentic stream incvertebrates living on or in the stream bed, so not plankton organisms, but from time to time they go into the drift. This is often an active process (there choice)

• Temporal patterns
- Seasonal ( alot of processes are more active in summer so seasonally drift is generally lower during winter)
- Life stage (often smaller life stages that drift)
- Daily (next slide)

How far do invertebrates drift

Most drift episodes only a few metres (or even centimetres)

one study:
- weak swimmers 10-20m
- better swimmers like sandfly only 3-6m

during floods etc can be several 100m

Why do invertebrates drift (and how)

• During floods: catastrophic drift [passive & active entry into drift], some invertebrates move towards edges to be swept easier

• After floods: dispersal & recolonisation [active & passive], drifts happen at higher frequency after floods, probably more of an active process

• At normal flow: if conditions are unfavourable and undesirable [mainly active, but also passive]
- Abiotic factors inappropriate (e.g. current velocity too slow to get oxygen e.g. mayfly)
- Food availability
- Presence of competitors
- Presence of predators

Food and drift: a net-spinning caddis larva
- Influence of food on probability of drifting
- If they hadnt been fed they were more likely to drift

Competition and drift
- Characteristic 'rearing up' behaviour when larvae encounter each other
- Intruder more likely to drift than resident of the net. But also depends on relative size
- Active as the loser has to drift away

Predation and drift
- The Californian predatory stonefly (Acroneuria) affects the drift rate of its prey (the detrivorous stonefly Taeniopterix)
- Number of prey drifting depends on predator density, the more predators the likelier the encounter and then they will escape through drifting
- Moving from this bad place might put you into the waiting jaws of a fish

The role of fish? Flecker's (1992) study of Venezuelan streams with and without drift-feeding fish
- Not much difference between night and day drifting when there werent drift feeding fish
- The presence of drift-feeding fish may often be the explanation for nocturnal drift
- drift feeding fish need to see prey which is why they drift at night

The continuous redistribution of stream invertebrates

• Patterns in invertebrate drift are remarkably dynamic in space and time
• Drift contributes to a "continuous redistribution" of invertebrates in the stream bed (through animals entering and leaving the drift)
• This redistribution is particularly marked after bed-moving floods that create unpopulated areas of stream bed that can be recolonised by new organisms (Matthaei et al. 1998)
• Drift is only one of the sources of redistribution
• Relative importance of various sources of colonists for recolonisation after disturbance? à two independent experiments in 1976

Williams & Hynes (1976): slow-flowing Canadian stream
- Figuring out percentage of colonists from each sources
- Drift: 41% Aerial: 28% Upstream: 18% Vertical: 19%
- Didnt measure straight after flood

Matthaei et al. (1997)
- Flood-prone gravel-bed river in Switzerland
- Two types of trays, exposed after a fairly large flood
- Drift contributed close to 100% of colonists [Aerial not meas.]



Drift is a key mechanism of how invertebrates distribute themselves in running water

smaller floods cause patchy bed movement, when theres patchy bed movement there arent refuges nearby so vertical and upstream become more important

The hyporheic zone of certain habitats within streams

Where the invertebrates come from that "moved up from within the substrate" in Williams & Hynes's study

Below the flowing water, but above groundwater
- inbetween surface and ground layer

How deep?
- Often 0.5-1m. But up to several m possible (e.g. braided rivers in Canterbury Plains)

How wide?
- Up to 2km! (Flathead River, Montana)


What lives in this zone:
• Permanent fauna
- microcrustaceans, water mites

• Occasional fauna
- e.g. some Chironomidae, mayflies etc. occur at certain times or certain life stages, such as mayfly in earlier stage it is easier to move around when theyre long and thin and small

• Never present
- e.g. some cased caddis flies never occur far below the bed surface (not enough space to move around)

The invertebrates moving up in aforementioned study were the occasional fauna

Microhabitat preferences & mobility of stream invertebrates

Aerial colonists - from how far do they come? (Briers et al. 2004)
• Added a rare stable nitrogen isotope as 15NH4Cl to a stream in Wales, UK
• The 15N passed through the food web and marked >1.5 million stonefly larvae (Leuctra inermis)
• Trapped flying adults in a variety of nearby sites
• Samples screened to determine whether adults contained 15N (each sample was 10 adults)
• Only a small proportion of captured adults were 15N marked
• BUT: Some adults travelled 1 km or more
• Some even moved between catchments

Microhabitat preferences and movements of larval stoneflies
• Pteronarcys - eat algae & have a three - year larval cycle
• Tagged 1000 female larvae (>2.5cm long; 2x3mm tags) • 256 recaptured over 3 months (mean 16 d between recaptures)
• Moved an average of 1.8 m downstream
• Range 40 m upstream; 44 m downstream
• Some moved 6-22 m upstream in a day!
• Bottlenecks: in fast & deep water (runs) with large cobbles and an abundance of periphyton food

Key points

• Invertebrate drift occurs in all streams and rivers
• It sets the scene for understanding much about the dynamics of stream communities
• Drift varies temporally - it is frequently greater at night • Nocturnal drift is often linked to the presence of fish
• Drifting invertebrates often move away from unfavourable locations
• Drift and other mechanisms lead to a continuous redistribution of stream animals
• Within this dynamic system, particular species form aggregations in favourable patches

Effects of competitors on stream communities
- Competition between stream species can reduce growth and survival and cause non-overlapping distributions

Competition between two stream insects (Dudley et al. 1990)
• Larvae of net-winged midges (Blephariceridae) scrape diatoms off rock surfaces in fast-flowing streams
• Larvae of black flies (Simuliidae) filter food particles from the water column (they also like fast flowing as more food particles coming towards them to filter)
• Competition for space not food
• Negative relationship because of Simulium aggression • Remove Simulium, Blepharicera density increased
• Note co-occurrence was common
• When simulium was present
- Blepharicera spent less time grazing
- Simulium caused Blepharicera to spend 5x more time in avoidance
- Diatom ingestion by Blepharicera reduced by 60%
- Growth reduced, mortality increased

Competition between two fish species Brook trout and brown trout in a Michigan stream
- Design: measure daytime positions taken by brook trout (weaker competitor) before & after removal of brown trout
- Without brown trout, brook trout rested in slower-flowing positions with greater shade (better camouflage for bird predators) & fed close to faster flows (! more food!)
- Can only do this when brown trout arent there as they would normally occupy these favourable spots

Effects of competitors?
• May reduce density
• May influence distribution
• May reduce growth and survival

interference compet.: do not use a common resource
exploitative: use the same resource

Effects of grazers
- Invertebrate grazing can change the outcome of competition between algae

Grazing insect mediates algal interactions
- Leucotrichia - a highly sessile caddis larva that lives in a silken retreat, grazing around it
- Filamentous blue-green alga Microcoleus rare inside foraging area (but dominant outside)
- Leucotrichia Can achieve really high densities in stable streams
- Community composition of algae can be quite different in foraging areas vs outside these areas. So grazing influences biodiversity of lower trophic level
- May influence algal species composition
- May influence algal species richness
- May affect course of succession

Effects of predators
- Predation can change prey behaviour and distributions
- Predation by fish can have direct and indirect effects on invertebrate grazers and algae and result in a trophic cascade

Do trout influence the distribution of populations of native Galaxias
- Only get high density of galaxiids when trout are not there
- Distributions of trout and galaxiids generally do not overlap
- Where trout occur, there are few or no native Galaxias. WHY?:
- Because galxiids tend to be upstream and above waterfalls, trout can not climb this but galaxiids can. But once galaxiids go below this point they get outcompeted and eaten by trout
- Co-existence rare but possible - Disturbance lecture


Do trout influence the behaviour of individual invertebrates? Nesameletus ornatus
• Some streams contain trout, others contain nonmigratory Galaxias fish
• Larvae of the mayfly Nesameletus graze algae in both kinds of streams
• Larvae from trout streams are less active by day (hiding away, not doing what theyre meant to be doing which is grazing)

Consequence of reduced grazing for algal species composition?
• Algal communities studied on surface stones in three streams each with trout or Galaxias
• Trout streams - erect/palatable algal taxa more abundant (These are what the grazers like to eat but they are less active because of the trout)
• Galaxias streams - prostrate/unpalatable taxa more abundant (as the other types were being grazed on intensively)
- So community composition has changed because of fish predation
- Galaxiids have some effect on grazers but not to the extent of trout
- Trout are causing Trophic cascade (higher biomass at lower level)
- Galaxiid are causing trophic trickle

Consequences of the trophic cascade for energy and nutrient flux through the ecosystem?
• Trout stream had much higher algal production (Huryn 1998)
• Nitrate taken up from stream water faster in trout stream (Simon et al. 2004)

summary of effect of predators on next slide

Terrestrial-aquatic linkages
- Terrestrial-aquatic linkages can reduce the strength of trophic cascades in stream communities

Experiment where they reduced terrestrial invertebrate input, and also fish but also the opposite and had all treatments crossed
- Fish, invertebrates and algae sampled

Consequences of this
- Terrestrial invertebrate input: strongly reduced (next up are the effects of this)
- Fish predation pressure: shifted dramatically from terrestrial to aquatic (stream) invertebrates (It used to be around half half but now theyre eating stream invertebrates a lot more)
- Increased fish predation reduced invertebrate biomass in the stream bed
- Fewer stream invertebrates meant reduced grazing pressure which meant higher algal biomass which caused a TROPHIC CASCADE!
- In this small forest stream: Strong terrestrial-aquatic linkages (high input of terrestrial invertebrates) reduce the strength of the trophic cascade in the stream community
- Context dependent, could be quite different in grassland streams as theres less terrestrial invertebrates so the linkage might be weaker

Summary of effect of predators
• May influence behaviour, density and distribution of their prey
• May indirectly affect other species in the food web
• May affect ecosystem processes
• May result in trophic cascades
• Strong terrestrial-aquatic linkages may reduce the strength of predation-induced trophic cascades in streams

Effects of parasites
- Parasitism can also have direct and indirect effects in stream food webs

Influence of a parasite on a stream community (Kohler 1992, 1997)
• Cougourdella is a highly specific microsporidian parasite that attacks the herbivorous caddis Glossosoma nigrior in Michigan streams
• Dramatic reduction in Glossosoma after an outbreak of this parasite

-The parasite-induced decline in Glossosoma leads to increases in densities of....
- food of Glossosoma (algal cells)
- competitors of glossosoma
- and predators of the competitors (as the competitors arent as heavily armoured so plentiful and easier food for the predators)
- a parasite, like a carnivore, can also have far-reaching consequences in the food web
- Glossosoma is good at stopping predators (fat shell thing) but needs stable areas and doesnt cope well with floods

Direct versus indirect effects of fish
- Understanding the impact of fish on stream invertebrate communities depends on a knowledge of invertebrate drift and colonisation

Weak direct versus strong indirect effects of fish on invertebrates (Flecker 1992)
• Fish diversity is high in tropical streams such as those in Venezuela - not just carnivores; also grazers/detritivores
• Enclosure / exclosure experiments (size 115 x 42 x 46 cm); permitted movement of invertebrates but not fish - Effect of predatory fish as opposed to grazing / detritivorous fish?
- Predatory fishes had relatively weak effect on invertebrate abundance
- By contrast: Grazing/detritivorous fish had strong impact on invertebrate abundance!
- Competition more important than predation in this case

Have a look at lecture slide very near end fro immigration/emmigration/drift

Key points

• Competition between stream species can reduce growth and survival and cause non-overlapping distributions
• Invertebrate grazing can change the outcome of competition between algae
• Predation can change prey behaviour and distributions • Predation by fish can have direct and indirect effects on invertebrate grazers and algae and result in a trophic cascade
• Terrestrial-aquatic linkages can reduce the strength of trophic cascades in stream communities
• Parasitism can also have direct and indirect effects in stream food webs
• Understanding the impact of fish on stream invertebrates depends on a knowledge of invertebrate drift

What is disturbance?

A relatively discrete event that tends to remove organisms and opens up space (and typically resources) that can be used by new individuals of the same or other species

Disturbances occur in all ecosystems
• Natural:
- mostly „physical": e.g. wildfire, hurricanes, landslides, floods, waves, volcanic eruptions
- also „biological": e.g. outbreaks of pathogens, herds of elephants, buffalos, pigs
• In addition: disturbances caused by human activities: - (stressors) - e.g. logging, mining, overgrazing

• influence structure, function and diversity of living communities
• are one of the most important causes of spatial and temporal heterogeneity in ecosystems

key feature of important ecological theories:
- Intermediate Disturbance Hypothesis
- Patch Dynamics Concept

disturbance = bed movement for invertebrates
- However for fish it can just be fast flow

In some stream types (or in especially dry years) droughts also important as disturbance events such as black forest stream, however floods are the most common/important around the world and in NZ

In the face of disturbance, individuals or communities may show:
- resilience - the ability to recover rapidly after a disturbance
- resistance - the ability to withstand the disturbance

Direct effects on stream organisms (1 example)

re look at this

Disturbance mediates species interactions (5 examples)

Disturbance and the interactions between two invertebrate grazers
- Some flood disturbance driven by snow melts, but this is buffered by a lake and its a relatively stable area
• The two main actors:
- Leucotrichia, a caddisfly larva, builds a tough retreat that persists from year to year (one generation per year) - Parargyractis, a moth larva, builds a flimsy silken retreat that sloughs off between years (one generation per year)
• The two compete for space within which they graze algae
• Leucotrichia aggressively eliminates other species and monopolises space
• Rolling stones (disturbance) favour the moth
• Physical disturbances disrupt the formation of competitive monopolies by the caddis Leucotrichia
• Experimental overturning of stones reduces the density of Leucotrichia while the moth Parargyractis benefits
- Lorenz equitability was much higher on the smaller stones (the bigger ones Leucotrichia dominated) as these were the ones more likely to be overturned in a flood
- Small stones are disturbed more often = fewer Leucotrichia = more other invertebrate species common = community evenness (= equitability) greater


Disturbance and the impact of exotic mosquito fish on native topminnows
The actors:
- Mosquito fish (Gambusia affinis), a small fish introduced to Arizona in 1926, from lowland streams in the Mexican gulf region
- Gila topminnow (Poeciliopsis occidentalis), an even smaller, native fish
• Topminnows usually become extinct after mosquito fish appear in a stream
- eliminated from most streams in Arizona
• Cases of coexistence occur only in streams that experience severe spates ("flash floods")
- Mosquito fish colonise stream pools in an upstream direction and reduce topminnow densities
- Minor flood: Not much effect on either species
- MAJOR FLOOD: Topminnows -75% Mosquito fish -98%


Trout, native galaxiids & disturbance in NZ
• Floods? Survey in 24 Canterbury streams that differed in their bed stability (McIntosh 2000)
• Galaxiids can cope better with frequent bed disturbances than trout!
• No trout at most unstable sites
• No large trout at unstable sites
• Galaxiids almost across entire stability range
- co-existance at intermediate sites (provided that no large trout there)

• Drought?
- Survey in Manuherikia River catchment, Central Otago (very low rainfall) (Leprieur et al. 2006)
• Galaxiids are better at coping with low flows! (water temperature up to 28ºC, low oxygen concentrations)
= co-existence at sites with fairly high level of water abstraction

• Without disturbance, species interactions would proceed to dominance by the most competitive species - (e.g. Leucotrichia or Hydropsyche in our examples)
• Vulnerable prey also eliminated by the most efficient predators (e.g. mosquito fish or trout)
= Disturbance acts as a "reset mechanism" and enables co-existence, it enable the weaker competitors and more vulnerable prey to survive


Intermediate Disturbance Hypothesis
- Maximum taxonomic richness (not abundance or anything else) should occur in ecosystems that are subject to intermediate levels of disturbance
- Tradeoff between being resilent/resistant to disturbance (highly disturbed environments they thrive) and being the strongest competitors/most efficient predators (stable environments they thrive)

Disturbance and ecological theory
patch dynamics concept

Patch dynamics concept:
• Ecosystems are highly dynamic in four dimensions
• Disturbances play an important role as they create open space for recolonisation and cause changes with time
• Communities are mosaics of patches and organisms can move from one patch to another
• Patches are in different successional stages (open space (recently disturbed) or monoculture of the dominant competitor)

Key points

Disturbance...
• removes organisms and opens up space that can be used by individuals of the same or other species
• can change the outcome of competition between stream invertebrates
• can change the impact of introduced predators on their prey
• is a central feature of important ecological theories

How to quantify physical disturbance in streams?

Need methods
- e.g. An index of disturbance regime
• 54 sites in 27 tributaries of the Taieri
• painted particles - 3 size classes, related to particle sizes at each site, 45 per site
• checked / replaced 5 times 1993-1994
• Disturbance intensity: average % of particles that moved between consecutive sampling dates

Can also use Pfankuch channel stability evaluation
- This gives a "Stream bed" score that is highly correlated (r = 0.78) with movements of painted particles
- faster method

Ecological / evolutionary consequences of disturbance regimes (many years)

• Are particular species traits associated with more physically disturbed streams? (Southwood 1977, 1988; in Townsend et al. 1997)

Species traits of insects in relation to disturbance
-Resilience traits ( recover rapidly after disturbance.)
• small body length (can reproduce faster))
• high adult mobility (good thing for recolonising)
• habitat generalist (good for recolonising as you can go pretty much anywhere)

Resistance traits ( withstand disturbance)
• clinger
• streamlined / flattened (less likely to get washed away)
• 2+ life stages outside stream (period you will be exposed to floods is shorter so reducing risk of getting hit by disturbance)


• Does the Intermediate Disturbance Hypothesis apply in streams?
- Invertebrate taxon richness IS lower in streams with strong or weak disturbance regimes (Townsend et al. 1997b)
- So yes
- Stream (running water) ecosystems tend to be dominated by mobile taxa, the hypothesis was developed for sedentary species
- However the hypothesis still applies


Disturbance regimes can modify terrestrial-aquatic linkages:
- Fishing spider sits on rocks on banks of streams and catches adult insects that have emerged from aquatic invertebrate
1) Site stability (13 sites): ranged from stable (0% moved) to frequently disturbed (60% moved)
2) Biomass of aquatic prey declined with disturbance
3) no such decline for biomass of terrestrial prey
4) Proportion of suitable habitat for spiders (loose rocks) increased with disturbance
5) = Spider abundance (+biomass) peaked at intermediate levels of disturbance
- As prey declines a bit but they also get more suitable habitat with a bit of disturbance
- Ability of a riparian predator to benefit from aquatic prey is greatest at intermediate levels of disturbance,
- however this is not about taxon richness so doesnt confirm hypothesis but its interesting

Conclusions - ecological consequences of disturbance regimes
- Species traits: Resilience and resistance traits more strongly represented in disturbed streams
- Species richness: Taieri River catchment: Support for Intermediate Disturbance Hypothesis
- Terrestrial-aquatic linkages: Can also be strongest at intermediate disturbance levels

Effects of individual disturbance events

How patchy are bed disturbances?
- 2 dimensional pattern of bed movement at Kye Burn (Central Otago, near Dansey's Pass)
• patchy
• variable - different sites and events
• reasonably predictable - size and embeddedness
• Stable surface stones can serve as flood refugia for stream invertebrates

three-dimensional patterns of bed movement (bed movement usually is this)
- used scour chains
- 100 scour chains used at 3 sites
• patchy
• variable - different in neighbouring sites and after different events

"Local disturbance history"
- Most spates and floods cause a small-scale mosaic of scoured, depositional and stable bed patches

ecology in relation to patch history
- 5 random invert. samples collected in scour, fill and stable patches two months after a bed-moving spate
- deleatidium was most dominant species (60%)
- Austrosimulium & Eriopterini: also fill patches
- Isopoda: Scour patches
- Stable: no one taxa

Patch Dynamics Concept
• Ecosystems are highly dynamic in four dimensions (three spatial + time)
• Disturbances create open space for recolonisation and cause changes with time
• Communities are mosaics of patches
• Patches are in different successional stages (open space or monoculture of the dominant competitor)

Patch Dynamics Concept supported for mobile stream invertebrates
• Kye Burn: scour-, fill- and stable patches only a few metres apart
• Deleatidium and Austrosimulium could have dispersed between these patch types within a few days or less (= 75% of the entire community)
- long-term effects of local disturbance history on highly mobile stream organisms (2 months later you still find these patterns)
- Evidence that patch dynamics models can be applied to stream ecosystems

Conclusions - Local Disturbance History
• ...can have long-term effects on the microdistributions of mobile stream invertebrates
• ...can have short- and long-term effects on the microdistributions of river algae

Local Disturbance History Mechanisms?
- Short-term negative effects of local bed disturbance (scour or fill) were often replaced in the longer term by 'indirect' positive effects of this disturbance (via disturbance-induced changes in habitat parameters) so patchy disturbances change microhabitat conditions and then invertebrates go to patch that best suits them

Interplay between disturbance and biotic interactions (predation and competition)
- continued from first Disturbance Lecture

420 US streams: 36-56 years of flow data
- 23% stable or seasonally stable (77% frequently or highly frequently disturbed
- You would imagine it would be similar in NZ and Europe

Biotic interactions may or may not play an important role in frequently disturbed ecosystems - not much research done on this, below is a study on it

Grazing fishes affect algal response to storms in a tropical stream
• The main actors:
- Seven omnivorous tropical fish species
- They dont really like to eat as much Filamentous blue-green algae (here: tightly attached = fairly floodresistant)
- This is there favourite food: Diatoms (here: loosely attached = not floodresistant)
- 3 floods occurred, 2 short ones and one long one
- when grazing fish are working, floods dont have much effect, the biggest flood didnt reduce algal biomass at all
- When fish were excluded, big fluctuations in biomass, floods knock it back quite a lot
- Diatoms are less resistant and tast, but also outcompete the blue green. So when the fish arent grazing the diatoms outcompete the blue greens, then the floods knock them back and then they start to dominate again
- When theres fish they keep the diatoms from being dominant, and so the diatoms never reach high biomass, where as the blue greens gradually increase in biomass
- Essentially the fish grazing results in flood resistant algal communities as without them the diatoms dominate and arent flood resistant
- Not much bed movement in this system

When there is bed movement
- Effects of local disturbance history [BED MOVEMENT] and fish predation on stream invertebrates & algae in the flood-prone Kauru River
- Overall: Disturbance history influenced invertebrate microdistributions more often than fish predation (40% vs 8%)
- In cases where predation had a significant effect (always fewer bugs when fish present): Effect mostly stronger in undisturbed patches
- This supports the hypothesis that suggests that disturbance is more important than interactions
- The other study suggests biotic interactions are just as important

Key points

1) Intermediate Disturbance Hypothesis and Patch Dynamics Concept can be applied to streams
2) Invertebrate resilience and resistance traits are more strongly represented in disturbed streams
3) Disturbance regimes can modify the strength of terrestrialaquatic linkages by influencing aquatic prey supply and suitable habitat for riparian predators
4) Most high-flow events cause a small-scale mosaic of scoured, depositional and stable bed patches
5) This "local disturbance history" can influence the short- and long-term distributions of stream invertebrates and algae
6) Stable bed patches can serve as flood refugia for stream organisms
7) Little is known about the interplay between abiotic disturbance and biotic interactions in frequently disturbed streams
8) One of the first such studies shows that grazing by fish can modify the response of algae to disturbance

Key points

a) Changes to land use generally do matter for stream ecology.
b) Increased nutrient concentrations may lead to increased biodiversity via a subsidy effect at low levels, but at higher concentrations nutrients become a stressor with negative effects.
c) A stressor can be defined as a variable that, as a result of human activity, exceeds its range of normal variation and adversely affects population performance, community composition or ecosystem function.
d) Increased sediment is an important stressor of stream ecosystems.
e) Indices of river 'health' have become increasingly important in the management of streams and rivers, but we need to understand their limitations.
f) A healthy river is, in essence, one that delivers what the community wants: different communities (Maori, anglers, flood engineers) may want different things.
g) Agricultural land use may have direct consequences for human health via the transmission of water-borne pathogens.

Effects of human land use on stream biodiversity

Nice wee infographic at the start of the lecture

What is a stressor?
- A variable that, as a result of human activity (only human activity), exceeds its range of normal variation and often adversely affects population performance, community composition or ecosystem function

fine sediment is higher in agricultural settings, particularly deer and dairy


Invertebrate biodiversity versus development - in theory?
STRESSOR MECHANISMS Increased nutrients (mainly indirect effects)
- food subsidy at lower levels
- affects habitat quality at higher levels due to algal proliferation, smothering and O2 fluctuations.

Increased sediment (mainly direct effects)
- affects habitat quality
- smothering of food
- clogging of gills
- increased drift

Effects of human land use on stream ecosystem health

Ecosystem health measure: Macroinvertebrate Community Index = MC

MCI is lower in agricultural lands than in tussock lands.
- Deer and dairy are the worst with all measurements being mild pollution or below and none being in good health (these were surveys)

Manipulative experiments (next lecture)

Summary - Land use and streams
• Differences in abiotic habitat conditions in streams among land uses
• Subsidy-stress response of biodiversity
• MCI sensitive to development
• MCI affected by nutrients and (not always) sediment (and stream size = discharge)
• Effects of fine sediment on stream organisms mainly negative (correlative & experimental work)

The term healthy is subjective, and doesnt have one definition.
- Some may value streams that can give them the most resources and this is the indicator of health
- Flood engineers might consider a stream that doesnt flood to the surrounding houses as healthy
- Some may only consider a completely pristine stream as healthy
- Some might consider a stream healthy if you can drink/swim in it safely

You could say a healthy river is one that delivers what the community wants

Effects of human land use on cultural values of streams

Most important factors for CSHM (cultural)
Fish safe to eat
Water safe to drink
Would go fishing

- The Cultural Stream Health Measure successfully incorporates aspects of stream health relevant to the Iwi
- It performs as well as the MCI in encapsulating the relationship between land use development and stream health

Effects of human land use on risk of disease transmission

Zoonotic diseases
- Quite a few pathogens found in farmed animals
Transmission via streams possible - need to be considered as well when assessing land use influences on streams

Campylobacteriosis example
- Gastrointestinal illness worldwide caused by Campylobacter jejuni
- Requires mammal or bird host
- Diarrhoea, vomiting, fever, abdominal pain
- Major transmission routes: ◆ contaminated food ◆ inadequately treated drinking water (relevant)◆ swimming , paddling (relevant)◆ person-to-person ◆ farm animal-to-person
- Temporal variation of Campylobacter in the Taieri River (highest during summer)
- Increase in cases when Campylobacter concentrations at Taieri were highest
- Campylobacter per L gets higher as land use increases (particularly dairy and deer)


Gastro example
- Gastrointestinal illness caused by Giardia intestinalis
- Requires mammalian host
- Similar disease symptoms and transmission routes as Campylobacter
- 3x more cases than elsewhere in NZ
- High prevalence in cattle worldwide; 30 - 40% prevalence in NZ
- Identical strains in humans and cattle in NZ
- Potential for transmission = mitigation needed

Do different riparian buffers reduce Giardia in runoff?
- Benefits: reduce water velocity, increase infiltration, habitat for fauna
- Compared 3 native grasses to ungrazed exotic grass: newly planted and after one year
- Most but not all Giardia stopped by grasses
• Newly planted: planting (esp. Carex) causes greater Giardia reduction vs bare soil
• After 1 year: all plants let fewer Giardia through but deep Cortaderia (toe toe) tap-roots reduce Giardia and water
- Plant type matters too: Not all species create the same outcome

Multiple stressors in ecological theory and resource management

General theory of multiple stressors?
- Outcomes - simple or complex (Folt et al. 1999)
- Simple: effect of all stressors combined equal to sum or product of individual effects
- Complex: combined effect larger (= synergistic) or smaller (= antagonistic) than predicted from single effects

- Some stressors provide a subsidy (positive effect) at low levels but have negative effects at higher levels (Odum et al. 1979)

Multiple stressors and management
- Managers need to know causes of harm
- Need to define thresholds of harm
- Almost always multiple stressors at work - managers may get it wrong if stressors interact in unexpected ways
- need to know the way these stressors will interact
- Antagonistic = smaller, synergistic = larger

Approaches to understanding multiple stressors?
- Field survey - realistic but lacks control
- Lab experiment - controlled but realism in question
- Field experiment - reasonably controlled and reasonably realistic
- Ecological modeling - allows "scaling up"

Another stream survey

Conventional farms were the worst at MCI compared to integrated or organic, they also had the highest levels of glyphosate and insecticides so could be a link there

Experiments at three spatial scales

Have a look at lecture slides for details on the studies below

Fine sediment and nutrient addition:
Managers:
- (1) high fine sediment worse than high nutrients
- (2) high nutrients less problematic if sediment low



Sediments, nutrients & reduced stream flow:
Managers:
- Don't abstract water from streams already subjected to elevated fine sediment inputs!


Sediments, nutrients & raised water temperature
Managers:
- Don't reduce riparian shading along streams already subjected to elevated fine sediment inputs


Fine sediment, nutrients & invertebrates (exstream)
Managers:
- High nutrients less problematic than high fine sediment (same conclusion as for larger-scale studies)

Take-home messages for resource managers

- Keep fine sediment out of streams. Bad enough on its own & other stressors make its effects worse
- Don't abstract water or remove riparian vegetation from streams already subjected to elevated fine sediment inputs

Key points

- Land use effects: almost always multiple stressors at work
- Combining surveys and experiments helps us understand multiple stressors
- Nutrients: Often positive effects at low levels but became harmful at high levels in some cases
- Fine sediment: Mainly negative effects, more pervasive than nutrients à important stressor
- Water abstraction: Mainly negative effects on its own; made effects of elevated sediment worse (SYNERGISTIC)
- Raised water temperature: Mixed effects on its own; also made effects of sediment worse (SYNERGISTIC)
- Pesticides used in conventional farming can have negative effects on stream communities too

Estuaries

• 'a semi-enclosed coastal body of water which is connected to the sea either permanently or periodically, has a salinity that is difference from that of the adjacent open ocean due to freshwater inputs, and includes a characteristic biota'. Elliot & Whitfield 2011

• Globally, most large cities built on estuaries
• Important for transport, food harvesting (cockles etc) & production • Waste disposal
• Recreation
• Have received relatively limited study relative to freshwater or marine systems
- < 50 NZ studies on estuarine ecology
- Most focus on large permanently open systems

Types of estuaries

• Permanently open
- High freshwater discharge maintains continuously open mouth
- High gradient coastline with limited sand deposition
• Excessive water abstraction can result in closure of formerly open system (such as what happened to the Murray river in the 1980's and early 2000's, this was also partly due to evaporation)
- Otago estuaries are sometimes closed
Twice daily tidal exchange & freshwater discharge removes pollutants & nutrients (hard to sample as tides shift by an hour every day)
- Tidal variation in water level creates tidal mudflats & wetlands (e.g. Waihola/Waipori wetlands)
- Complex patterns of salt & freshwater mixing, including stratification (salt water pushing in on freshwater)
- Physiologically challenging but highly productive habitats (a lot of dissolved organic matter fluctuates when it hits high salinity environment and gets released as fine organic material meaning bacterial can feed on it and others can feed on this bacteria)

• Local permanently open systems include Taieri, Clutha, Catlins (Catlins has big lake system with big area of mixing, they are different)




• ICOLs (Intermittently Closed and Open Lagoons)
- Common in southern Australia, South Africa, eastern New Zealand
- More prevalent in Southern Hemisphere (partly due to less developed estuaries, more developed could keep them open for transport etc)
- Can comprise majority of estuarine systems along certain coastal regions
- Open or closed periods often highly variable in space & time (In australia theyre seasonally predictable, hot dry summers opposite winters)
- Opening may be seasonally predictable (eastern Australia) or completely unpredictable (Otago, big easterlies can cause rain which flows it open)

Do Communities in Permanently Open & ICOLs Differ?

• Lill et al. 2010
- Sampled permanently open & ICOLs along Otago coastline
- Late summer, close to estuary mouth
- 26 estuaries, 10 open, 16 ICOLs
- Hyperbenthic communities sampled
- Sampling conducted at night to maximise catch

• 33 hyperbenthic taxa collected in Otago estuaries
- Insect taxa common in closed systems
- Crustacea dominant in open systems
- Mysids dominant in all systems

• Influence of opening / closing greater than salinity
• Mysids have broad salinity tolerances (salinity can be very variable)
• But most species dominate in either open or closed system

Fish in Southern NZ Estuaries
(ties into the card above on how the communities differ)

Fish in Southern NZ Estuaries
• Fasil Taddese 2018
- Littoral communities sampled by seine net
- Communities in open and ICOLS distinct
• Open systems
- Lower abundance but greater diversity
- Marine stragglers and wanderers
• ICOLS
- Higher abundance but lower diversity
- Dominated by common bully (Gobiomorphus cotidianus)
• Importance of maintaining opening status of systems emphasized
- Three estuarine species that are dependent on open state: Estuarine triplefin & Stokel's smelt (Canterbury rivers) in open systems, black flounder in both (borderline freshwater)

Theres a few slides on what type of fish are in each system

Mysids in Estuaries

Mysid distribution and life history

• Dominant Crustacea in many estuaries
- Includes North American & European systems
• Four specis common in Otago estuaries
• Two pelagic open estuary specialists
- Gastrosaccus australis & Tenagomysis macropsis
• Two primarily benthic specialists present in all systems - T. chiltoni & T. novae-zelandiae
• Opportunistic omnivores

Flowing water triggers swimming response, if theres no turbulence they just sink to the bottom

Just have a look at slides

Management of ICOLs

• ICOLs vulnerable to eutrophication & sedimentation, have started to receive a lot more sediments since Europeans arrived

• Often limited & intermittent tidal exchange (Kaikorai can remain closed for months/even a year)
- Evaporation & concentration of solutes

• At downstream end of catchment
- Final catchment sink for nutrients, sediments & pollutants (kaikorai is at the end of an industrial zone so can get quite polluted)

• Minimise inputs of nutrients
• Do this by Maximise flushing of water & pollutants - Maintain inputs of freshwater
• Is artificial berm breeching useful for flushing nutrients?
- 'Berm' refers to sand barrier between estuary & sea
- May be breeched during rain events or artificially
- Regional Councils breech berms to reduce high water levels & flush nutrients
- This worked at lake Elsemere

Effects of ICOL Berm Breech
- It varies
• Schallenberg et al. 2010
- Comparing Lakes Elsemere & Waituna during open & closed phases
- Rush of salinity at Waituna
- Its just all graphs so look at lecture

Trophic status of NZ lakes
- Kind of carried on from management of ICOLs

Most coastal lakes in eutrophic to hypertrophic condition (algal blooms etc occurring)
- Indicative of high inputs of nutrients

Te Waihora / Lake Elsemere & Other Coastal Lakes
- One of the most productive agricultural landscapes in NZ
- Collects all the fine sediments
• Severely degraded large coastal lagoon in Canterbury - NZ's most polluted lake (SoE report 2007)
- High turbidity due to constant wind/wave driven resuspension of nutrient-enriched fine sediments
- Macrophytes limited due to high turbidity
- http://www.mfe.govt.nz/fresh-water/cleanprojects/lake-ellesmerete-waihora

• Locally, Lake Waihola & Hawkesbury Lagoon are eutrophic, & in Southland Waituna Lagoon is deteriorating
- You can see the muddiness from the wind and waves
• Eutrophication due to nutrient enrichment
• https://www.waituna.org.nz

Lecture 19 NZ freshwater fish/migratory species

Barriers to migration, how do they get to where they live - Could estuaries play into this?

examples of migratory fish at very start of lecture

Introduction to NZ freshwater fish

• Dominated by four families of fish
- Galaxiids, Gobiomorphus, Anguilla, Retropinna
• 43 species, 33 endemic species
- ~12 taxonomically indeterminate spp (closely related)
- Largest - longfinned eel
- 1 extinct (Prototroctes oxyrhynchus) (could have been disease)

Biogeography of NZ Fauna
• Migratory & Non-migratory species
- Mostly shared origins with Australian fauna
- Reflects likely past drowning of NZ land mass (much of the rivers would have dissapeared)
- Unstable geological (volcanic eruptions) & climatic (ice age) history (eruptions would have destroyed fish pops and they would have recolonised)
- Recolonisation of land mass through larval dispersal of freshwater species or evolution from marine lineages
- Galaxiids come from Australia as an example

Taxonomic Composition
• Galaxias (whitebait, kokopu, inanga, koaro) 17 species
• Neochanna (mudfish) 5 species
• Prototroctes (grayling) 1 species
• Retropinna (common smelt) 1 species
• Stokellia (Stokell's smelt) 1 species
• Gobiomorphus (Bullies) 7 species
• Anguilla (eels) 3 species
• Cheimarrichthys (torrentfish) 1 species
• Geotria (pouched lamprey) 1 species
• Rhombosolea (black flounder) 1 species
• Aldrichetta (yellow eyed mullet) 1 species
• Mugil (grey mullet) 1 species
- White flounder (endemic)


NZ galaxiids
• Southern Hemisphere distribution
- Also present in South America, South Africa, Australia, New Caledonia & many islands
• Some Migratory species
- Inanga, koaro, banded, shortjaw & giant kokopu
- All amphidromous, although most form land-locked populations (particularly North Island)
• Some Non-migratory species
- All populations in inland lakes are non-migratory
- Complete life-cycles within river/stream habitat without migration
- Pencil galaxiids (mainly alpine but also lowland longjaw)
- Galaxias vulgaris complex (incl Otago galaxiids)
- Evolved from Koaro like ancestors

All about Galaxiids

NZ galaxiids
• Southern Hemisphere distribution
- Also present in South America, South Africa, Australia, New Caledonia & many islands
• Some Migratory species
- Inanga, koaro, banded, shortjaw & giant kokopu
- All amphidromous, although most form land-locked populations (particularly North Island)
• Some Non-migratory species
- All populations in inland lakes are non-migratory
- Complete life-cycles within river/stream habitat without migration
- Pencil galaxiids (mainly alpine but also lowland longjaw)
- Galaxias vulgaris complex (incl Otago galaxiids)
- Evolved from Koaro like ancestors

Southern Hemisphere Galaxiidae Radiation
- All around the southern hemisphere, south america, australia, the islands, south africa, NZ, falkland islands etc
- Had a larval stage in the sea, and so due to larval drift and a little bit of colonisation

NZ Migratory Galaxias
• Inanga (Galaxias maculatus)
- Sth Hemisphere distribution, main whitebait species
• Giant, banded & shortjaw kokopu
- NZ endemics
• Koaro (Galaxias brevipinnis)
- Juveniles have impressive climbing ability (use surface tension on rocks to walk way up)
- Closest to ancestral migratory form
- Given rise to radiations of multiple non-migratory species
• Reduced abundance/distribution due to loss of habitat & predation / competition from introduced species (evidence is anecdotal, like using whitebait to fertilise chickens and vege gardens). And the idea that giant kokopu would have been more abundant because there were more wetlands and now theres less wetlands
- Giant kokopu can be way inland like lake te anau, which suggests when southland was one big swamp they went right across landscape

Gobiomorphus (Bullies)
• Eleotridae have widespread Indo-Pacific distribution
- Many amphidromous & catadromous species
- NZ species closely related to Australian Gobiomorphus
• Four migratory species in NZ (common, bluegill, redfin, giant)
- Bluegil & redfin bully in decline
- Habitat degradation & constraints on downstream larval transport are a concern
- redfin are a riffle species, when you put sediment into water often its the riffles that degrade most severely as they get clogged up with silt
- redfins dont seem to be in same rivers as bluegill and torrentfish, could be something to do with competition but more likely estuaries, blue gills and torrent fish live in areas with fast estuaries that go out quick like Waitaki
- torrentfish and bluegills are very similar
- redfin larvae must have ability to navigate out of estuaries
• Three non-migratory species in NZ (crans, upland & tarndale)
- Tarndale has limited distribution (may not even be a real species)
- Others widespread & common on North or South Island
- Some taxonomic uncertainty
- More abundant further north, particularly up in Northland
- evidence theyre in decline according to fish database but sketchy
- Bullies tend to co-exist with trout quite well
- They are amphidromous I think


Life history tactics effectwhether an organism can live in a certain place
• Life history tactics
- "a set of co-adapted traits designed, by natural selection, to solve particular ecological problems."
- "For example, the life-history tactic of a population of fish living in a lake might consist of its age-specific distribution of growth rates, reproductive efforts, progeny produced and their size, and the genetic system underlying those traits."

Evolution & importance of diadromous migration

Migration
• A seasonal to-and-fro movement of populations between regions where conditions are alternately favorable or unfavorable (including one region in which breeding occurs)
• Spatial scale of migration determines population structuring
• Understanding scale of movement crucial for effective management
- Common bully might only be migrating 2-3 metres but its still migration, such as spawning on benthos spending period of life in the water column as pelagic larvae and then coming back down and living on the benthos

Bullies it tends to be a benthic pelagic migration - could still be several kilometres

Understanding scale of movement is critical for management so you know where the critical habitats are. work has with working out habitat requirements and what they need at adult stages, but very little done at larval stages

When managing fish have to think about the whole life cycle

Life History & Migration
• Central to understanding ecology & evolution of Indo-Pacific freshwater fish spp, including NZ fauna
• Migratory cf. non-migratory has important implications for management
- Life history of migratory spp. spread across broad landscape. Maintenance of migratory pathways crucial
- Restricted distribution for many non-migratory species, often very vulnerable to invasion by non-native species (like trout maybe, but even native species)


Diadromy - Migrating between freshwater and sea

• Diadromous migrations in a diverse range of familes
- Amphidromy > 273 species, Catadromy > 53 species
- Gobiidae, Cottidae, Galaxiidae, Eleotridae, Plecoglossidae etc
- Because its so diverse it must be advantageous
• Widespread geographic distribution
- Dominate Indo-Pacific & Caribbean coastlines & islands,
• Typically (but not exclusively)
- Relatively small species
- Relatively high fecundity (for size), with small eggs (gobiidaes have smallest of any fish)
- So they are going for fecundity by getting small eggs etc so evolving for fecundity
- Often form land-locked populations (puzzling)
• All have pelagic larval stage
- Gives access to small food that lives in lakes like rotifers which you dont get in streams

Have a look at slides for life history of Amphidromy & Catadromy, key difference is catadromy spawn in sea
- Its a continuum though not 2 well defined life histories so not one or the other

Why Amphidromy?
• Bob McDowall (1997)
- Dispersal to isolated new or disturbed habitat, e.g. Hawaiian Islands / east coast New Zealand
- Exploitation of different habitats for adults & larvae
- Maximising fecundity by producing small eggs & pelagic larvae
• McDowall strongly favoured dispersal
- Dispersal widely attributed as primary function of pelagic larvae

Problems with a Dispersive Primary Role for Amphidromy
• Pelagic larvae enable amphidromous fish to disperse & colonise vacant habitat
- How can a 'dispersal & colonisation' trait evolve to exploit unpredictable / catastrophic events? (it cant)
- Successful exploitation of such events a lucky accident
- How could such a trait persist long after disturbance occurred or new habitat created?
• Dispersal away from parental habitat potentially maladaptive (risky) so you wouldnt want all dispersing you wouldnt think
- Energetically expensive & risky
- Predict that larvae should remain close to parental habitat

Amphid vs non Amphid
- non-amphids (stopped migrating) had large eggs like upland bullies. So fecundity has taken a dive but now have robust larvae that can survive in streams
- So its all about fecundity
- The further you seperate the distance of adult habitat from pelagic larval habitat, the Increasing cost of upstream adult migration and Increasing risk of larval starvation
- So you get a competitive balance between the 2 life histories
- Amphidromous has Small egg, High fecundity, Small pelagic larvae, and Recruitment declines with distance from pelagic larval rearing habitat
- Non-migratory Species has Large egg, Low fecundity, Large Benthic larvae, High larval survival in fluvial habitats



Lakes close to coast are still genetically isolated, every lake has its own unique pops so they werent migrating down. This happens in Lake wanaka the fish arent dispersing far
Hypthesis - Most likely in close proximity to natal stream & resist wide dispersal. Degree of exchange likely context dependent

Integrating landscape & life history, how does the landscape work for these fish

Population Connectivity in Galaxias brevipinnis Andy Hicks - PhD thesis 2010
- Isolation of G. brevipinnis Lake Populations
- There was upstream juvenile migration but virtually no downstream migration
- Amphidromy with no adult migration in habitats where passive larval drift to pelagic possible
- Lakes provides pelagic habitat for many species, excluding low fecundity species upstream
- Lakes close to coast are still genetically isolated, every lake has its own unique populations so they werent migrating down. This happens in Lake Wanaka the fish arent dispersing far
Hypothesis - Most likely in close proximity to natal stream & resist wide dispersal. Degree of exchange likely context dependent
- found larvae in river mouths, but not in lake, so living in river mouths and not dispersing far

Influence of lakes on Galaxias Distribution Mahsa Toorchi - PhD thesis
- Lake 'halo' of fecundity
• G. brevipinnis abundant <20km upstream of lakes (rivers close to lakes, probably because there pelagic life histories are so prolific they just swamp the landscape and low fecundity ones cant survive)
• Non-migratory Galaxias dominant >20km upstream of lakes or streams with no lakes

The significance of pelagic life stages

Because they can dominate idk

Amphidromous fish as metapopulations

• Similar patterns of isolation/exchange in torrentfish & bluegill bully
• Classic metapopulation structure
- Populations separated by space, with somewhat independent population processes, but some level of exchange of individuals
- Metapopulation structure may be by catchment, region or island
- Management needs to reflect spatial scale across which populations are structured

Implications for management

• Management of amphidromous species needs to acknowledge spatial structure
- Can't treat all population as 'same' (problem is we dont what scales the populations are operating on)
• Population processes
- To some degree isolated within each region/catchment
- Need research to delineate / map patterns of connectivity between populations
- Maintain natural patterns of connectivity (where to put dams, where to remove barriers)
- Regional 'reward' for good management (if you look after your own stream it will benefit the region, like whitebait coming back to own stream if you look after it)

Radiations of non-migratory species

Life history and distribution

• Three radiations

• Dwarf inanga (Galaxias gracilis)
- Restricted distribution, evolved from G. maculatus

• Galaxias vulgaris complex
- Evolved from G. brevipinnis-like ancestor
- Widespread all over south island, but severely impacted by trout predation / competition & habitat loss
- Recent taxonomic description of several species
- Greatest diversity in Otago

• Pencil galaxiids
- Older radiation
- Generally alpine distribution
- Impacted by trout & habitat loss with some critically endangered species


Life History & Distribution
• Generally complete life cycle in streams (some in wetlands)
- non-migratory is a blurry term, some drift downstream long distances, just don't have evidence they go back as adults
- Life history traits related to altitude
- Larger eggs/reduced fecundity at higher altitudes
- High altitude species have limited distributions & most threatened by introduced trout (even when theres no barrier they dont tend to go down which is interesting)
- Lower altitude species more widespread and more impacted by landuse change (present with trout but in reduced abundances)

Why are non-migratory fish so threatened?

Threat Status of NZ Freshwater Fishes
• Dunn et al. (2017)
- DoC assessment of conservation status of NZ freshwater fishes
- Expert opinion assessment using defined criteria
- No legal status

• IUCN Red List Assessment
- Completed & released in 2014
- no legal status

• Nationally critical
- Neochanna burrowsius (Canterbury mudfish) (a lot of agriculture has had big effects, last populations are in south canterbury)
- Galaxias aff.cobitus "Waitaki" (Waitaki lowland longjaw) (population swings up and down with droughts so a vulnerable position, they can burrow a metre down into gravel to water though)
- Galaxias "species D" (Clutha flathead) (agriculture, urbanisation and water extraction)
- Galaxias "Teviot" (Teviot flathead galaxias) (agriculture, limited distribution, hydro electric development)

• Nationally endangered
- Galaxias cobitus (lowland longjaw galaxias)
- Galaxias anomalus (Central Otago roundhead galaxias) (agriculture, development)
- Galaxias eldoni (Eldon's galaxias) (limited distribution above falls dam, proposal to raise the dam which would flood habitat and drive it extinct)
- Galaxias pullus (Dusky galaxias) (low fecundity, limited distribution and cant co-exist with trout, luckily in hard to reach areas, this also goes for nevis and aff species)
- Galaxias "Nevis" (Nevis galaxias)
- Galaxias aff paucispondylus "Manuherikea"


Range Restricted Distributions of NonMigratory Galaxias spp.
- What are the processes keeping these fish where they are
- Why havent they changed distributions
- Galaxiid adults look very similar
- What jumps out is egg size varies hugely (different larval ecology)
- Ones with biggest eggs tend to be at highest altitudes (altitude gradients)
- So harder the environment you live and small in, the more resilient and robust larvae you need
- Aldoni and pullis galaxiids are up to 800m in unproductive streams, no small invertebrate prey just insect prey so you need to have a big mouth to even feed, so need big larvae to fit life history through that landscape

- So whats holding these species in place are these changes in life history

- Evolution & Biogeography argue that:
• River capture - Key process isolating various lineages
• Altitude - Headwater and lowland species - Ecological drivers?
- These may play a role as well in holding them back as well

River catchments became swampy allowing gene flow and dispersal Waters et al. 2020
- sea water rise going up and down, landscapes eroding down and getting uplifted
- This doesnt explain how they maintain distribution

Basic ecological research informs management

Evolution & Ecology of galaxis vulgaris
• All vulgaris species Evolved from migratory ancestor
- Originally had small eggs, pelagic larvae
• Adults of migratory & non-migratory species similar
- small, stream-dwelling fish
• Key ecological difference?
- Egg & larval size larger in non-migratory species
- Streams generally turbulent with limited small prey resources (so need to be big to withstand as larvae)
- Egg size increases and fecundity declines with altitude
• Larval ecology important for understanding ecology of galaxiid distributions and interspecific interactions (as adults look similar but larvae have to be adapted to certain areas, theyre the most vulnersble and sensitive part to the environment, if you dont get past larval stage you dont get adults)

The big egg species are poor competitors compared with amphidromous species with tiny eggs coming back in huge numbers
- Across landscape you get saturation of habitats close to coast
- Also saturation of landscape if youve got a lake and those amphidromous species are in the lake
- If landscape is big enough you get non-migratory species evolving, need lots of rivers and streams to get away from non-migratory species?? (why non migratory is that a mistake
- Low fecundity fluvial life histories evolve from migratory species in headwaters. Requires sufficient 'ecological space' Augspurger et al. Reviews in Fish & Fisheries
- on small islands you dont really get non-migratory species

Theres a tradeoff, between lots of offspring but being small and not many offspring but being big, cant have lots and big

Larval size, life history strategy & distribition Galaxias vulgaris species complex
- Small pelagic larvae • High fecundity • High recruitment if many larvae survive • Pelagic larvae in wetlands & slow flowing streams (I think these are migratory??? actually maybe not)
- Large benthic larvae • Low fecundity • Can rear larvae in places where no other larvae can survive • Headwater streams
- This creates distribution across landscape as one cant survive in headwaters and the others can but cant compete with the others, which creates distribution
- Competitive balance between relative rates of recruitment, 2 different strategies
- You see this across the landscape Jones & Closs (2017)

brevipinis rearing in lakes have smaller eggs than ones rearing on the coast, could be a phenotypic maternal control, some evidence that mothers who are food deprived as larvae will produce bigger eggs and vice versa - management implications?

This egg size distribution hasnt been studied in bullies, but suspected to be similar







• 'fast' life history lowland species are metapopulations • 'slow' life history headwater species are isolated, with limited distribution & limited ability to recolonise if population lost Jones & Closs 2016

Fecundity and larval traits influence ability to coexist with introduced trout

Trout and galxiids sometimes co-exist, for example the anomalus
- Complex metapopulation dynamic, larvae drift long distances downstream, you have populations of galaxiids protected from trout above waterfalls up in headwater streams, juveniles are drifting long distances downstream, and we suspect adults to some degree are migrating back upstream., So as long as theres protected areas in the wider catchment they can co-exist together. Would be to our benefit for both galaxiid conservation and trout fisheries managment to put trout barriers in streams and create galaxiid refuges, this would create secure populations of galaxiids and some of the juveniles would flow down stream to lower cathment and feed trout. Win win situation. This could also work is on the shores of wakatipu and wanaka where brevaapinis is in big pops, put trout barriers in, means big whitebate runs into the lake and rainlbow trout can feed. Cant get rid of trout so this would create a sustainable system

low fecundity large species are not dispersing downstream so cant feed trout.

Even when theres no waterfalls at streams sometimes pullus and aldani dont disperse downstream, so distribution is restricted by habitat not just trout
- So dont need to put in expensive mitigation measures in such as barriers to trout migration if galaxiid are restricted anyway, so understanding basic life history is important

relationships between ecological variables
- Galaxiid anomalus lives in big catchments, pullus and aldani only in tiny little streams
- pullus and aldani just dont co-exist with trout, this could be to do with habitat barriers

'fast' life history lowland species are metapopulations and so need to be managed as such. All youre effort should go into protecting protected populations upstream of trout you need to protect them which will susatin pops across landscape

For pullus and aldani just protect headwater populations aslong as there okay not muh else you can do about it

anomalus and the likes are quite heavily effected by land use, where as pullus and aldani are in hard to reach areas so less loss of populations compared with anomalus

Management Implications of Galaxiid Traits
• Impacts of trout on galaxiids have been severe
- but some coexist, whilst others can't
- anomalus and vulgaris seem to be able too (co-existing for 30-40 years), floods and drought knock back trout but galaxiids are more resilient

pullus and aldani cant go downstream as adults Jones & Closs 2015

Galaxiid Traits & Conservation
• Life history gradient from high to low fecundity has conservation implications
- Drives distribution (where they live)
- High altitude species protected by isolation, but small fragmented populations vulnerable to trout invasion and extinction. Unable to coexist with trout.
- Low altitude, high fecundity species persist by dispersal from safe populations, high fecundity and connectedness. Can coexist with trout, albeit at reduced abundance.
- Lowland species vulnerable to land use change (water abstraction etc)
- May be able to expand some species like brookchar, potentially achievable, I think this is about high altitude species)

Lecture 22 Managing NZ Waters - Challenges

have a look at the series of adverse reports could be helpful

LAWA is a good website for water quality

nitrate is hard to monitor/control because its soluble in water we have a high bottom line for nitrate toxicity, at the point its toxic and starts to kill - around 11mlg

most of the land cover in NZ is pasture

Nitrate concentrations might seem algood but thats because theres a high bar for it, should really be dropped

urban isnt too bad for sediment because they tend to be concrete channelised streams

State of the environment 2007

• Good points
- Improving Biological Oxygen Demand

• Bad points - Increasing nutrients in catchments impacted by urban & agricultural land use
- Increasing nitrates & bacteria in many lowland aquifers (groundwater)
- High bacteria in many lowland waterways
- Indicates worsening problem with diffuse discharge
- RMA doesnt say anything about diffuse discharge pollution

• BoD improving (high BOD means high organic inputs and suxcking oxygen out of water, once this gets too high water gets hypoxic, biological oxygen demand, poorly performing swage treatment plants were the issue)
• MCI & Water temperature stable
• Consistent with improvements to point discharge organic pollution
- Fewer point discharges & improved treatment of waste - Fencing out stock from streams

Intensification of NZ Agriculture

This is the main problem
• NZ dairy production
- Risen 77 % in 20 years
- ~2 million dairy cows in 1976, to ~6 million in 2017
- Export value $18.1 billion (2013-14, 37% export earnings
- ~ 40,000 total dairy employment
• Intensive form of agriculture
- ~3 cows per hectare
- Cow produces ~25 litres of urine & ~25 kg faeces per day

Cant really get rid of it as its a massive part of our economy

A big dairy farm produces the same amount of waste as a medium sized town

Resource Management Planning in NZ

• Key elements
- Resource Management Act (most important)
- National Policy Statement on Freshwater (also above regional council power)
- Central government
- Regional Councils
- Stakeholders
- Resource consents

Managing NZ Waters

• Resource Management Act 1991
- Accumulating evidence of freshwater decline drives legislative response
- Note RMA currently under review
- https://www.mfe.govt.nz/publications/rma/new-directionsresource-management-new-zealand
• On-going reform (under RMA)
- National Policy Statement for Freshwater Management 2020 (NPSFM) (important)
- National Objectives Framework (NOF) updated 2020
• https://www.mfe.govt.nz/essential-freshwater-new-rulesand-regulations
• Ongoing updates & consultation
- Regional Water Plans (under development)

Tip for exam

look at how different rules and regulations aim to improve management of nutrients or sediments

Everything we need for this question is on the https://www.mfe.govt.nz/essential-freshwater-new-rulesand-regulations page

Useful Summaries of Legislative Environment

• Essential Freshwater
- https://environment.govt.nz/what-government-isdoing/areas-of-work/freshwater/e/freshwaterreform/

• Science meets politics in developing water management legislation
- https://www.stuff.co.nz/environment/300032530/wate red-down-a-behind-the-scenes-battle-over-politicsscience-and-water-reform