ECOL 417 Module 2

water exists in the hydrosphere in a … meaning the Earth is …

continuous cycle, not going to run out of water

the quality of water …

varies through space and time

human population growth has resulted in …

greater water use and water contamination

water quality has … because …

increased in importance, water quantity cannot be assessed independently of its quality

efficient management of water resources requires …

the application of knowledge about water quality

what are the water quality measures (or variables)? the first indicators to characterize general water quality?

• physical

• chemical

• biological

physical indicators

• total dissolved solids

• total suspended solids

• conductivity

• turbidity

• water colour

chemical indicators

• pH

• biological oxygen demand (BOD)

• dissolved oxygen (DO)

• hardness

• total nitrogen

• total phosphorus

• heavy metals, pesticides, substances that are toxic at low concentrations

biological indicators

• bacteria content: E.coli and coliform bacteria

• ephemeroptera

• plectoptera

• trichoptera

• community composition metrics

• diversity indices

• dominance of pollution tolerant organisms

how is dissolved vs particulate matter defined by

based on their ability to pass through a filter of a specific size

• usually 0.45 microns but not always (when comparing studies we should know if they differentiate)

• distinction is arbitrary - bc particles range in size along a continuum but it is helpful to study water bodies and have a cutoff

(can also be colloidal and gravitoidal)

what is conductivity

the relative amount of electricity that can be conducted by water

what is conductivity typically driven by

Na+, Ca2+, Mg2+, Cl-, SO4 2-

what is specific conductance

the conductivity measure corrected to 25 deg C to allow for comparison between reported measures of conductivty

conductivity

• units are uS/cm

• when measuring, 2 probes are 1cm apart to standardize

• high temp = ions move faster

conductivity table

• distilled water has low conductivity because its low in ions

  • narrow range in this pic, salt in snow increases it

• chloride is a big conductor

what is total dissolved solids (TDS)

the mass of material (inorganic and organic) dissolved in water

• “dissolved” is at the 2 um filter threshold

what is total suspended solids

the dry weight of particles trapped on a filter paper

• this is what doesn’t pass through the filter paper

• reported in mass/volume

what is turbidity

the clarity of a liquid

• measured as the light absorption or light scattering of water

• can be confused with TSS but its really about light scattering or absorbed

example from high arctic lakes (east and west) on melville island, nunavut

COME BACK TO

• both lakes are being impacted by climate change but there has been much more permafrost degradation in the West Lake watershed

what is pH

the concentration of hydrogen ions (acidic vs basic)

pH = -log [H+]

pH cont’d

• central for biological activity (lots of hydrogen ions hitting fish gills will kill fish)

• most aquatic systems are found near neutrality (pH = 7+-1)

how does acid precipitation majorly impact aquatic systems

by lowering the pH several orders of magnitude

• can mobilize metals by increasing solubility at low pH

what is alkalinity

it indicates the capacity to neutralize acids

• NOT how basic it is!

• usually dictated by surrounding material

what is hardness

the sum of magnesium and calcium ions present, an indicator of the ability of water to precipitate soap, important in domestic water supplies

geology controls water hardness

what is the law of conservation of matter

• matter cannot be created or destroyed

• matter can only be transformed from one form to another (rearranged)

• matter can exist in major states

  • solid

  • liquid

  • gas

• dictates why biogeochemical cycles happen

• ex. C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O

what is biogeochemistry

chemistry in an environmental context with an emphasis on the living and non-living (biotic/abiotic) components of an ecosystem

what is biogeochemistry cycle

pathways by which a chemical moves through biotic and abiotic compartments of Earth

• ex. nitrogen in plants, we eat those plants (which is how we get amino acids and etc.)

types of elements that are essential for plant growth

• macronutrients

• micronutrients

macronutrients

• need less of them but still necessary

• C, H, O, N, P, K, S, Mg, Ca, (Si)

  • Si is for certain aquatic plants (diatoms)

limiting macronutrients

N, P, K

• N and P are limiting for aquatic plants

• K is limiting for terrestrial

micronutrients

Fe, Cl, Cu, Mn, Zn, Mo, Bo

what are nutrients

any element required by organisms for growth

C, H, O, N, P, K, S, Mg, Ca, (Si)

nutrients in aquatic ecology

• primarily in reference to elements that are limiting to growth (purs brakes on primary productivity)

• need to build biomolecules, proteins, nucleic acis, carbohydrates, lipids, etc

what are primary producers

Algae, aquatic plants, cyanobacteria and many bacteria can use inorganic nutrients like nitrate, ammonium, and phosphate

what are heterotrophs

acquire their nutrients in organic form by consuming other organisms or organic matter

sources of nutrients

• gas exchange in atmosphere (O2 and CO2)

• input from watershed

• weathering of rock (increase phosphorus)

• biological molecules (ex. algael death = source of nutrients for other organisms)

Sockeye salmon

• millions of sockeye salmon return from the ocean to spawn in freshwaters of Bristol Bay watershed

• studies have identified the presence of marine-derived nitrogen (MDN) from salmon in freshwaters and terrestrial environments

nutrient requirements vs. availability

• using the elemental composition of plants and algae and the availability of nutrients in freshwaters, determine which nutrients are in high demand

• in small river N and P had the highest number in average demand/supply (plants and algae / world rivers)

• ex. count # of sockeye every spawning season, would throw dead sockeye to the same spot and in that spot the trees had grown bigger because N if often limiting and trees were getting N from the dead sockeye

what is stoichiometry

how the balance of energy and elements influences living systems

stoichiometry of carbon, nitrogen, and phosphorus at balanced growth

106:16:1 = redfield ratio

if the N:P ratio is well above 16…

more N that algae needs relative to P

• P is limiting element

• C is not limiting so can ignore for a sec

if the N:P ratio is well below 16…

less N that algae needs relative to P

• N is limiting element

• C is not limiting so can ignore for a sec

Leibig’s Law of the Minimum

the element or resource with the least relative amount will limit growth and production

the rate of a process will be limited by…

the rate of its slowest sub-process

• expectation that a single nutrient will limit primary production of a system

how would you experimentally test limiting

dump a bunch of N and P in a lake and see what takes off

• in pic, P is the limiting

what is assimilation

the acquisition (obtaining) of nutrients by organisms

what is remineralization

the breakdown of organic matter into biological forms

process leading to remineralization

1. decomposition

2. leakage (can be a source of organic matter into water)

3. heterotrophic organisms

oxygen

major importance to biological processes in freshwaters

• amount of O2 is expressed as mg/L or mol/L or percentage saturation

what is dissolved oxygen (DO)

the O2 dissolved in oxygen

what is percentage saturation

the concentration of O2 relative to maximum at equilibrium concentration for that solution

• varies with temperature, cold water holds more O2

DO is a function of many factors

• temperature

• pressure (related to altitude)

• salinity

DO temperature changes

solubility decreases as T increases

• in pic, 8 mg/L is about 100% saturates at 25 deg C

DO pressure changes

solubility increases as P increases

DO salinity changes

solubility decreases as S increases

• increase S = more ions = forces O out because gets tighter

• pure water likes to work up = looser

supersaturated

DO concentration is above saturation

• will form O2 bubbles and come out of solution

• happens during certain times of the day (lots of sunlight on vegetation = supersat)

sub-saturation

Do concentrations below saturation

oxic or aerobic conditions

O2 present in the water

anoxic or anaerobic conditions

no O2 present in the water

O2, altitude, and temp

• highest O2 is at low altitude and low temperature

• therefore decreasing altitude and temperature will increase O2

oxygen sources

• atmosphere

  • amount depends on diffusion and turbulence

• photosynthesis

  • 6 CO2 + 6 H2O → 6(CH2O) + 6 O2

oxygen sinks

• diffusion to the atmosphere

• respiration

  • 6(CH2O) + 6 O2 → 6 CO2 + 6 H2O

• chemical oxidation

  • using up O2 in chemical reaction

seasonal patter in DO - oligotrophic

seasonal patter in DO - eutrophic

fish winterkill

• ice sealing off the atmosphere. winter kills dominate in shallow lakes because water doesn’t have a lot of oxygen

• eutrophic lakes also deprive lakes of oxygen

• shallow lakes, eutrophic lakes, heavy snow, sensitive fish species

summer kills

• warming of the epilimnion, less oxygen in the bottom leads to fish getting squeezed in the water column

• shallow lakes, eutrophic lakes, hot spells, little wind

oxygen distribution in streams

• higher swings in eutrophic systems, lower swings in something more oligotrophic

• photosynthesis increases oxygen concentrations in diurnal basis

• in productive rivers, diurnal oscillations in DO concentrations are even more magnified

• respiration at night results in repeated oxic-hypoxic cycles

why is carbon important?

• its essential to life

• currency of energy transfer

• carbon is the chemical backbone of organic molecules

  • proteins, nucleic acids, lipids, carbohydrates

• carbon provides a buffering system for lakes to absorb excess acid

• exchanges with the atmosphere and global climate regulation

carbon in lakes

lake carbon cycle - how the C moves between these categories

particulate organic carbon (POC)

living algae, bacteria, zooplankton; detritus, fecal pellets, leaf fragments

particulate inorganic carbon (PIC)

CaCO3, other carbonate minerals

dissolved organic carbon

humic substances (tea coloured water); sugars, amino acids, algal exudates

dissolved inorganic carbon

CO2, H2CO3, HCO3-, CO3 2-, (carbonate system)

typical ranking of carbon in lakes

DIC > DOC > POC

forms of carbon

1. inorganic carbon

2. organic carbon

• inorganic carbon doesn’t provide energy, usually only bonded to oxygen

• organic carbon provides energy, has hydrogen in the bond

inorganic carbon (DIC)

when CO2 is dissolved in water, it exists in a variety of forms:

• carbon dioxide, carbonic acid, bicarbonate, and carbonate

• bicarbonate equilibrium, bicarbonate buffering system

Lake Nyos (Cameroon)

• CO2 released from the magma rises through the rock and enters the lake bottom through springs

• with no mixing, CO2 arriving at the bottom had no route to the surface and the atmosphere, so it kept building up for years

• august 1986 - a massive cloud of CO2 denser than air, poured down the surrounding valleys and suffocated about 1700 ppl and thousands of livestock

organic carbon

particulate organic carbon (POC)

all living and dead organisms, and their parts and feces

dissolved organic carbon (DOC) - humic compounds

• large molecular weight compounds that lend a brownish color to water

• byproduct of the breakdown of other organic compounds

• resistant to microbial use

• humic acids, fulvic acids, humin

• can attach to other organic substances

• can form complexes with metal ions

dissolved organic carbon (DOC) - non-humic compounds

• sugars

• carbohydrates

• amino acids

• urea

• proteins

• pigments

• lipids

carbon origins

• autochthonous

• allochthonous

carbon origin - autochthonous

comes from inside the aquatic system, carbon synthesized through photosynthesis in the lake/stream

carbon origin - allochthonous

comes from outside the aquatic system, carbon synthesized in the drainage and imported in the lake/stream

carbon cycle in lakes

why care about phosphorus in lakes

• essential to all organisms

  • dna, rna, atp, bones, and teeth

• often limiting in lakes

  • high in demand/low in availability

• linked to issues such as:

  • cyanobacteria blooms

  • eutrophication

natural phosphorus sources

• rock weathering (slow)

• mostly apatite Ca5(PO4)+

• no gas phase

• bones

how does phosphorus get into lakes and rivers?

• surface runoff (majority)

  • amplified when it is agricultiral runoff

• precipitation (wet or dry)

• groundwater (very minor)

• streams and rivers (important for lakes)

forms of phosphorus - total phosphorus (TP) ***

• often most important

• measured on unfiltered water

• TP = dissolved P + particulate P

  • dissolved P = passes through the filter

  • particulate P = caught on the filter

  • each part can be organic or inorganic

  • filter is usually 0.45 um

forms of phosphorus - dissolved inorganic phosphate (DIP)

• orthophosphate (PO4 3-)

• the form algae use directly

  • measured in the lab as soluble reactive P (SRP)

• aka as phosphate

forms of phosphorus - particulate inorganic phosphate (PIP)

• P bound to mineral and soil particles

forms of phosphorus - dissolved organic phosphate (DOP)

• dissolved organic compounds released by organisms

forms of phosphorus - particulate organic phosphate (POP)

• P inside living cells and dead organic matter

percent forms of phosphorus

• most P in aquatic ecosystems is in living organisms

• 98.5% is POP

• 1.3% is PIP

• 0.3% SRP (free P)

  • a lake has low SRP, but this doesn’t mean the lake is low in P, P might just be in other forms

phosphorus transformations

• uptake is rapid

• organic P consists of algae + bacteria

external loading

phosphorus in sediments

lake sediments are considered an internal source of phosphorus

internal loading

• quantities of P in the sediments greatly exceed those in the overlying waters

  • decaying organic matter

  • interstitial waters in sediments contain 0.06 to 10 mg/L P soluble

• conditions at the sediment-water interface are key

anoxic sediments release P soluble ____ than oxygenated sediments

1000 times faster