Aquatic Ecosystems

What does GPP stand for

gross primary production

What does NPP stand for

Net primary production

What does NEP stand for

Net ecosystem production

What is the difference between NEP and NPP

NPP is the primary production of phytoplankton and the subsequent breakdown which supplies nutrients back to the photic zone.

NEP differs in that after the zooplankton process the phytoplankton, the nutrients sinks out of the photic zone

Describe the process of benthic pelagic coupling

Phytoplankton photosynthesise - organisms decay - organic materials sink to the benthos - resuspension of inorganic matter - resources for pelagic organisms

what is marine snow made of

phytoplankton detritus, poop, pseudofaeces, diatom exoskeletons, diapausing plankton

what is planktonic diapause and what is its advantages

its a period of dormancy in juvenile development

allows adaptation to low food levels, lowers predation rate and increases dispersion

what do bacteria on the sea bed do with marine snow

remineralise it, either aerobically or anaerobically

what is the subtidal pump

-wave action and sand size irregularity creates sand dunes

-pressure differential forces water (and O2) into sediment

-increases aerobic remineralisation

what is bioturbation

-disturbance of sediment caused by animals

-burrowing behaviour brings 02 and organic matter into sediment

-allows for more and deeper aerobic remineralisation

what is biological mixing

-small currents created by suspension feeders

-speeds up rate of aerobic remineralisation

-faster deposition than bacterial activity and doesn't require burial

what are physical upwellings

-wind blowing from land out to sea drags surface waters away from the coast

-nutrient rich water from depths drawn up to surface

what causes zooplankton to emerge from diapause and what does this do to the nutrients in the environment

-physical factors such as photoperiod and temperature cause emergence

-egg cases left behind sink to depth which remixes inorganics

what is the top most layer of the intertidal zone and what is it characterised by

Supralittoral fringe

-lichens, ephemeral algae, periwinkles

what layer is below the supralittoral fringe and what is it characterised by

Midlittoral (or eulittoral)

-barnacles, mussels, limpets, fucoid seaweeds

what layer is below the midlittoral and what is it characterised by

Infralittoral fringe

-red algae turfs or kelps

what characterises the lowest tides

kelp, urchins, small red algae, other sessile animals

what is the main physical stress in each of these zones

Supralittoral fringe - dessication, environmental fluctuation, light exposure

Midlittoral - limpet grazing

Infralittoral fringe - water movement

lowest tides - water movement and light, although not to same degree as other zones

what is the coriolis effect

Air at the equator has to move a larger distance in the same 24hr time period as air further north or south, this causes an apparent force that appears to make winds deflect to the right in the northern hemisphere and to the left in the southern hemisphere.

This creates the seen weather patterns that prevailing winds around the equator blow west, which influences ocean currents

what happens to ocean currents when they meet the western edge of their ocean basin

the warmer equatorial waters travel towards the poles (gulf stream)

what are the main sources of water circulation and where do they affect water the most

-Wind (surface oceanic waters)

-Density differences caused by temperature and salinity (deep oceanic waters)

-Tides (coastal waters)

what direction do hurricanes deflect in the north and south hemispheres

North - deflect right (clockwise)

South - deflect left (counterclockwise)

what are subtropical gyres

rotating systems of currents in ocean basins

what happens to the water elevation in these gyres

water 'piles' up at the surface, raising the water level in the centre of the gyre

what is the definition of eutrophication

increase in nutrents in an aquatic ecosystem that promotes the growth of plants and algae

what are the sources of excess nutrient runoff

-Agriculture & livestock

-Residential runoff (esp septic tanks)

-Urban runoff

what two nutrients are the main causes of eutrophication

Ntrogen and phosphorous

Describe the full process of eutrophication

-Fertilisers provide nitrates, Sewage provides phosphates

-Causes algal bloom (eutrophication)

-Competition for light kills off plants

-Consumers cant consume fast enough, resulting in a build up of dead algae

-Dead plants, dead algae and organic matter from sewage build up as detritus

-BOD (biological oxygen demand) increases as aerobic detritivores break down detritus

-Decomposition uses up O2, killing aerobes (animals, other microrganisms)

-Anaerobic bacteria thrive and release NH4, CH4, H2S

What is the difference between an oligotrophic lake and a eutrophic or hypereutrophic lake, give an example of both

Oligotrophic lakes have low levels of primary production, whereas eutrophic has a higher level of primary production.

Loch lomond is oligotrophic, dubh lochan is eutrophic

how does sediment level change as a lake goes from oligotrophic to eutrophic

sediment level increases

what is a mesotrophic lake

a state in between oligotrophic and eutrophic in both primary production and sediment buildup

how can eutrophication be controlled top down

bio introductions (e.g. fish like bass), animals that eat the predators of zooplankton, allowing zooplankton to flourish and eat phytoplankton, reducing eutrophication

what is the difference between a pycnocline and thermocline

-Pycnocline is the layer of water in which there is a sharp change in density

-Thermocline is the layer of water in which there is a sharp change in temperature

what causes marine eutrophication

-terrestrial nutrients runoff, combined with wave action oxygenation and sunlight, causes lots of primary production in the surface layers,

-pycnocline (caused by sun heating surface layers and reducing its density) prevents O2 from penetrating deeper (lol)

-dead organic matter decomposes in deeper layers, using up what oxygen there is

what is usually the limiting nutrient in coastal water

nitrogen

what areas of coastline are naturally eutrophic

deltas and salt marshes

what are the first and second largest oceanic dead zones

1st - black sea

2nd - mississippi delta

what are the 10 impacts of coastal eutrophication

-Toxic or non-edible phytoplankton species

-Increase of gelatinous zooplankton

-Decrease in biomass of benthic and epiphytic algae

-Changes in macroalgal composition and biomass

-Reduced water transparency

-Water coloration and odor

-Reduced Dissolved Oxygen (DO) levels

-Fish mass mortality

-Loss of economically important fish stocks

-Reduced aesthetic value of ecosystem

what is included in phytobenthos

microalgae, macroalgae, macrophytes

what groups of macrophytes are found in freshwater

Spermatophyta, Bryophyta, Pteridophyta

what group of macrophytes are the only group found in saltwater

Spermatophytes

What features of seagrass differentiate them from macroalgae

-Complex root structure allows seagrass to anchor into sediment and extract nutrients

-Photosynthesis restricted to leaf cells

-Transports nutrients via circulatory system with veins

-Reproduces via flowers, fruits and seeds

What features of macroalgae differentiate them from seagrasses

-Holdfast secretes polysaccharides to acnhor to hard substrates, doesnt absorb nutrients

-Photosynthesis done by all cells

-Uptakes nutrients from the water via thallus

-Reproduction via spores

what are the two families of seagrass

Hydrocharitaceae and Potamogetonaceae

where are seagrasses found

soft substrates, from the intertidal to max depths of 70m

what are the 8 ecological roles of seagrasses

-Shelter for juvenile animals

-Food for herbivores (e.g. sirenians and turtles)

-Habitat for endangered species

-High primary production

-Interactions with adjacent coral reefs (habitat continuity)

-Filter coastal waters

-Dissipate wave energy

-Stabilise substrate

what are the 8 threats to seagrass

-Terrestrial runoff

-Coastal development and encroachment

-Dredging and Trawling

-Invasive species

-Aquaculture

-Boat damage

-Shipping accidents (spills)

-Climate change

what are the three kinds of macroalgae and what are their dominant pigments

Brown algae: fucoxanthin

Red algae: phycoerythrin

Green algae: Chl a and b

what are the ecological roles of macroalgae

-Habitat

-Food source

-Oxygen producers

-Involved in nitrogen and phosphorous cycles

-Much the same as seagrass

-Indicator species for water quality

why do artificial structures tend to be worse for marine life than natural strucures

-lack complexity and surface area of natural habitats

-only composed of one substrate (usually concrete)

what are some solutions to this issue

eco-engineering: recreating natural complexity by adding stuff to sea walls

what method can be used to mitigate some of the noise produced by infrastructure construction

bubble curtains

how can artificial structures benefit marine life

by providing structure and attachment points where there was none, allows for the creation of new ecosystems

How do electro magnetic fields affect animals

EMFs mesmerise edible crabs and can affect embryo development

how can offshore wind farms act as ecological stepping stones

By providing suitable settlement habitat where it was previously absent, renewable energy structures could improve survival rates of larvae transported offshore, away from adult populations, thereby increasing population genetic diversity and species range expansion

How might ocean sprawl be causing jellyfish blooms

Increasing coastal development creates more attachment points for the polyp stage of jellyfish

how do offshore wind farms affect birds

-displacement of foraging and nesting grounds

-changes to habitats

-collisions with turbines

-attraction

what is the reserve effect

anglers cant fish in windfarms due to risk of entanglement with turbines, and boats wont navigate through them, protecting the marine life in these farms

How can we monitor the effects of artificial structures

-ROVs

-Fishing data

-Box corers (sediment sampling)

-Acoustic monitoring for noise pollution

-eDNA

what is the difference between an ecosystem function and service

function: a process that happens in the ecosystem (e.g. carbon cycle)

service: an ecosystem function that is useful for people

what 7 factors determine the type of habitat

-Substrate composition

-Depth

-Wind strength and direction

-Light level and primary productivity

-Salinity

-Temperature

-Temporal variation in any of these factors

why does the intertidal zone have relatively low biodiversity

Highly temporally and spatially variable in food, oxygen, water presence, light, temperature and salinity

why does the intertidal zone have high primary productivity

-lots of light for photosynthesis

-estuaries are provided nutrients from rivers

why do mussels live higher up the shore when they could grow faster and bigger if they lived deeper down?

Asterias rubens lives deeper down, by living in the intertidal zone they can avoid predation

what is the main species of seagrass in the uk

Zostera marina

what conditions do seagrasses prefer

shallow, calm areas on sand

what is the main uk species of coralline algae

Lithothamnion glaciale (aka maerl)

what conditions do coralline algae prefer

shallow, current swept areas

what conditions do cold water corals prefer

deep (usually >200m), high flow rate with solid substrate to attach to

what is the main uk species of cold water coral

Desmophyllum pertusum

what ecosystem functions do coralline algae provide

-habitat for juvenile animals

-sequesters carbon as CaCO3

-cements together coral reefs

what ecosystem functions do cold water corals provide

-habitat for juvenile animals (esp sharks)

-sequesters carbon in CaCO3 skeleton

-similar to seagrass in their functions

what conditions define the deep sea

-deeper than 200m (edge of the continental shelf)

~4° at depths of 2000m

-low currents

-no light

-physically stable but very variable food supply

How does the deep sea in the mediterranean and red sea differ from oceanic deep sea

Oceanic deep sea currents formed by sea ice formation in the poles creating cold and salty water (dense), this results in the deep sea being around 4°.

The deep sea currents in the med and red in contrast are formed by evaporation at the surface creating salty but warm water, so the deep sea is ~15° in the med and ~20° in the red sea

why are seamounts more biodiverse than the surrounding abyssal plain

sea mounts are volcanic mountains, this produces areas of exposed rock that provides attachment points for animals like corals and sponges.

additionally, seamounts will create upwelling currents, bringing deep, nutrient and oxygen rich waters to its inhabitants

what conditons does a coral reef require

-Temp of 25-31°

-Salinity of 34-37ppt

-High light level (normally in top 30m of water)

-Oligotrophic (so there is little phyoplankton growth to block sunlight)

-Clear water

how biodiverse are coral reefs

-4000 fish species (25% of worlds total)

-800 coral species

-32 out of 34 known phyla (more than rainforests)

what conditions do mangroves require

-shallow water

-waterlogged soil

-sheltered bays, lagoons, leeward side of islands etc

what are features of the arctic ocean (sorry the lecture was disorganised)

-semi enclosed ocean

-coastal and open water connections to atlantic and pacific oceans

-seasonal variation in ice cover

-wide range of terrestrial habitats

-much human use and habitation

what are features of the antarctic ocean

-isolated continent

-no coastal links to other areas

-southern ocean separated from other oceans by steep temperature and salinity gradient

-frozen continent present year round, sea ice is seasonal

-little terrestrial life

-no native humans

what are some factors affecting life in polar waters

-intensely seasonal primary productivity

-high oxygen but low temperatures affect physiological rates

-some animals need antifreeze

-iceberg scouring greatly reduced biomass and diversity of coastal benthic communities

what affects primary productivity in polar waters

-light of course

-in southern ocean iron is major limiting factor away from coasts or icebergs

-in arctic ocean, 25% of primary production occurs on or in sea ice

what are the deepest fish

Snailfish, found at ~8000m

why cant fish live deeper

fish use proteins in their cells to protect them from the effects of depth, but past a certain depth the concentration of these proteins required in their cells would make them hyper-osmotic, and they would take on too much water

what is the chemical reaction that chemosynthetic organisms use to fix CO2

H2S+2O2 → H2SO4

what are cold seeps

areas where methane hydrate or hydrogen sulphide leaks from the seabed