Watershed Ecology, Water Chemistry

Front 1

Water Quality and Chemistry

Back 1

• used to understand contaminants (substances that alter water quality) in the water.

Front 2

Examples of watershed contaminants

Back 2

• a lot of sediment
• sewage
• insecticide
• warm water
• falling leaves
• invasive fish species
• diatomaceous earth is harmless in the water
o It is made up of diatom shells tat fall to the ground after diatoms die.

Front 3

Concentration

Back 3

• Parts per billion = ppb = mg/m3
• Parts per million = ppm = mg/L
• Parts per thousand = ppt = 0/00
• Percent % - parts per hundred = 10,000 ppm.

Front 4

• Dissolved solids

Back 4

o Substances dissolved and ionized in water.

Front 5

o TS = total solids
o TDS = total dissolved solids both inorganic and organic

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• Normally 50 ppm – 400 ppm
• Globally 120 ppm
• Increased when something is added to the water
• Always measured in mL
• Can be measured by how well electricity is conducted through water, because they ionize.

Front 6

Specific conductance

Back 6

o Reciprocal of the specific resistance of a solution measured between two electrodes 1 cm2 in area and 1cm apart
o How well electrons flow between probes
• Resistance is measured in ohms
• Conductivity is measured in mhos or Siemens
o Varies with temperature, use m up to 25 degrees C
o Freshwater vs. low, use micros/cm (S x 0.000001)
o Seawater, use mS/cm (S x 0.001).

Front 7

• Conductivity

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o o Usually 2 times TDS
o Relates to nutrient status and runoff events
o Most important: Ca++, Mg++, Na+, K+, HCO3-,SO4--, Cl-
• Good correlation with salinity, especially in seawater.
• Individual ions analyse separately and reported as mg/L (ppm) or mEq/L.

Front 8

Sources of Dissolved solids in water

Back 8

o Rock, Precipaptations, Biotic, point and non point source pollution.

Front 9

Rock (edaphic ions)

Back 9

• dissolve from surrounding rock
o Geology (igneous vs sedimentary)
o Weather, dissolve; re-dox rxns, pH
o Limestone easily erodes by acid rain.

Front 10

• Precipitation

Back 10

o Rain, snow, dust
o Pollution, acid precipitation.

Front 11

• Biotic

Back 11

o Orgs use & cycle ions
• Carbon, nitrogen, etc…

Front 12

• Point and non-point source pollutants

Back 12

o Sewage
o Industrial runoff
o Point source – can identify the pipe
o Non-point source – comes off of fields, cannot be tracked, gas fumes, etc…

Front 13

If waterbody is stratified by temperature (density)

Back 13

then the nutrients can be depleted in some zones, and not mixed with areas where nutrients are still present.
• Name the two

Front 14

Zones according to whether they use or make oxygen

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• Tropholytic zone
o Releases nutrients
o Uses oxygen
o No photosynthesis because it is the bottom layer and can’t absorb the sun’s rays.
o Breaking down food
• Trophogenic zone
o Uses nutrients
o Produces oxygen
o Photosynthesis
o Some phytoplankton can fix nitrogen
o Making food
• Nutrients are at the bottom of the lake
• Stratification is important in the use and availability of ions
• Phosphorus is constantly cycled throughout and never runs out
Oxygen and Other gases.

Front 15

Solubility of gases differs in water and air
• Name three things the oxygen level is affected by

Back 15

o Air pressure (lower at high altitudes)
o Temperature (lower at high temperatures)
• TDS (lower at high solute concentration.

Front 16

How does an increase in temperature affect water temperature and dissolved C02 levels

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• Carbon dioxide prefers dissolving in water
But an Increase temperature, reduce ability for water to absorb gases
Releasing the C02 they had stored in them in to the atmosphere , increasing greenhouse gases and water temperatures.

Front 17

Saturation

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• Ratio of [gas] to potential concentration (at a given temperature, salinity, pressure)
o E.g. [oxygen] si about 15 mg/L at 0 degrees C – [oxygen] of 7 mg/L = 48% saturated
• Supersaturated
o Greater than expected (e.g. from high mixing or photosynthesis).

Front 18

Determining oxygen concentrations in water

Back 18

• Determining and interpretation of oxygen using
o Meter
• Must be calibrated
o Titration
o Iron, nitrates, organics can interfere and cause errors in calculations
• The darker the water, the higher the oxygen
• Oxygen in lakes is also dependent on stratification due to temperature… oxygen is renewed at the surface, but may be cut off from bottom
o Can lead to anoxia in lower regions
• Fish kills, die-offs of other organisms.

Front 19

Sources of Oxygen in rivers/lakes

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• Sources
o Diffusion (atm), slow
• Waves speed up
o Photosynthesis
• Phytoplankton (small and floating
• Macrophytes (big plants)
• Periphyton (attached to rock) (big or small)
• Carbon dioxide and water are mixed to produce a release of a sugar an oxygen.

Front 20

Sources of loss of Oxygen

Back 20

• Losses
o Respiration (especially at sediment)
o Chemical oxidation
o Temperature effects on solution.

Front 21

• Littoral zone

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o Deep rooted plant area
o Must be rooted in the water
o Based on location.

Front 22

•
• Profundal zone

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o Based on location
o Deep soft sediment.

Front 23

• Sublittoral zone

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o In between the littoral and profundal zone.

Front 24

Hypolimnion Epilimnion

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o Low oxygen
o High oxygen.

Front 25

• Nutrient status
Oligotrophic

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• Low nurients
• high oxygen year round, even if stratified

• Main limiting nutrient in fresh water is phosphorus.

Front 26

• Nutrient status
Eutrophic

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• High nutrients
• High phytoplankton & plant growth
o Produces oxygen
o Oxygen decrease with increase temperature
o high oxygen at surface, low oxygen at bottom when stratified.

Front 27

• Nutrient status
Mesotrophic

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• In between oligotrophic and eutrophic.

Front 28

o Biological oxygen demand (BOD)

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• End of season die-off of plants that sink to bottom and decay and use up the oxygen.
o If a nutrient is missing, the growth stops
o If not enough phosphorus, then other nutrients do nothing.

Front 29

Temperature and oxygen profiles

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• As temperature increases, oxygen decreases
o Oxygen is being used up by organisms
• As temperature decreases, oxygen increases.

Front 30

Seasonal oxygen patterns in lakes
• Relates to temperature patterns
• Temperature stratification patterns

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o Spring: unithermal, mixes with wind (rare anoxia)
o Summer: stratified, epilimnion & hypolimnion especially (anoxia)
o Fall: temperature drops; unithermal, mixes with wind (no anoxia)
o Winter: ice-covered, stratifies, epi & hypo sep. (no anoxia)
• If temperature is the same top to bottom, then oxygen is the same
• Oxygen is high in epilimnion because of photosysthesis
• Lake that goes anoxic at some point is eutrophic.

Front 31

Winter Kill

Back 31

Seasonal die-off of fish due to anoxia
o Shallow lakes, ponds
o Not as common in rivers because fish move towards the light
o Usually winter, but may also be spring or fall
• Fish, if they detect it, can swim to avoid anoxia
1. Oxygen throughout is below fish requirements
2. Low oxygen at bottom, okay at top; mixed during spring overturn, mixed water too low (too fast for fish to adapt)
3. Autumn: rapid decay of plants use oxygen (algal bloom rapidly using up oxygen)
• If very deep pond it takes more to go anoxic.

Front 32

• Factors affecting
Primary Productivity (PP)

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o Physical: sample depth (light), nutrients, temperature
o Season
o Biotic: zooplankton.

Front 33

How do we measure Primary Production in water?

Back 33

Via oxygen concentration in water
• Light and dark bottle method
• Principle
o Light: get photosynthesis (generaties oxygen) plus respiration (uses oxygen)
o Dark: respiration only
• Amount of oxygen produced = LB – DB
o For each mole of oxygen produced, 1 mole carbon dioxide used
• To convert to mg C, multiply by 0.375
o Assumes respiration same in both bottles
• Assumes oxygen can physically increase (not saturated)
• Assumes no animals in sample respiring.

Front 34

Who are Primary producers in lakes/ponds and rivers/streams

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o Lakes/ponds
• Phytoplankton (huge number of photosynthesis) (big producers)
• Littoral macrophytes

o Rivers/streams:
• Epiphytes (attached)
• Macrophytes (big).

Front 35

What does Primary Production represent?

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o Base of food chain (food available to higher trophic levels)
• Primary producers
o Relationship with nutrients entering water body
Relationship with oxygen and BOD (trophic status).

Front 36

What d we measure to get Primary Production ?

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• Gross production : rate of total photosynthesis
• Net production: gross prod. – respiration
• Relates to oxygen through photosysntesis/respiration equation.

Front 37

Carbon in water… more soluable than in air?

Back 37

• More soluble in water than in air.

Front 38

Sources of Carbon to streams

Back 38

o Rainwater – carbon dioxide from atm
o Sub-surface flow – bacterial resp in soil
o Dissolving carbonate rocks (e.g. limestone)
o Respiration of aquatic orgs
o Leaching from detritus.

Front 39

Where to find Carbonate HC03—and insoluable salts?

Back 39

o Hardwater.

Front 40

Carbon as a buffer in the form of C03-- Buffers (resists change) changes in pH

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a. Forms of carbon in water: CO2, HCO3- (bicarbonate ion), CO3-- (carbonate ion), Ca(HCO3)2, CaCO3
b. In pure water may hydrate (add hydrogen ions from water), dissociate (break apart), and complex with cations (e.g. ca++)
Forms different compounds, pH dependent
amt of dissolved CO2 (<1%) is hydrated to form carbonic acid (slow): carbon dioxide plus water releases carbonic acid.

Front 41

What is the relationship between carbonic acid

Back 41

bicarbonate and carbonate?. Some of carbonic acid dissociations into bicarbonate and hydrogen ions, and then to carbonate ions, depending on pH:
Carbonic acid plus pH increase, breaks into bicarbonate plus hydrogen ions
Bicarbonate plus pH decrease, breaks into carbonate plus hydrogen ions
pH = 4.5: all carbonic acid, no bicarbonate
pH = 6.4: carbonic acid dissociates to bicarbonate
pH = 8.3: no measurable carbonic acid
pH = 10.4: bicarbonate dissociates to carbonate.

Front 42

How is carbonate related to Ph?

Back 42

• Both CO2 and HCO3- can be used in photosynthesis
o If either is present in water, these complex with free hydrogen ions from acids, to buffer change in pH
• If calcium present, combines readily with CO2 to form calcium carbonate (insoluble) and calcium bicarbonate (soluble)
• If CO2 is removed by photosynthesis or other factor… equation moves right producing more insoluble carbon, which precipitates out (vice versa)
• Number of free hydrogen determines pH
• Photosynthesis is highest between pH from 6 – 10.

Front 43

What happens to carbon dioxide in streams in the daytime?

Back 43

• photosynthesis removes carbon dioxide and pH rises (carbonic acid decreases).

Front 44

What happens to carbon dioxide in streams in the nighttime?

Back 44

• respiration returns carbon dioxide and pH drops (carbonic acid increases).

Front 45

What Ph suggest a high amount of photosynthesis?

Back 45

• Ph 6-10.

Front 46

What is Ph?

Back 46

• Measurement of the acidity of a stream
• Number of free hydrogen determines pH
• Acidity is influenced by plant & algea production
• Both CO2 and HCO3- can be used in photosynthesis
o If either is present in water, these complex with free hydrogen ions from acids, to buffer change in pH
• If calcium present, combines readily with CO2 to form calcium carbonate (insoluble) and calcium bicarbonate (soluble)
• If CO2 is removed by photosynthesis equation moves right producing more insoluble carbon, which precipitates out .

Front 47

Alkalinity

Back 47

o Alkalinity is the ability to buffer pH
o Principle
• When acid is added to solution, hydrogen ions complexed by anions and pH decreases ( C03--)
• Similar pattern for OH-
• pH won’t change until each form complexed main buffers are carbonate and bicarbonate compounds (Ca & Mg)
• expressed as “mg/L CaCO3” though could be other anions.

Front 48

How do you measure alkalinity?

Back 48

• to measure; titrate with acid & pH indicator.

Front 49

Carbonate sources

Back 49

o Canadian shield: v. low alkalinity
• Dominate by granite (igneous rock)
• About 10 for alkalinity
o Sedimentary rocks (prairies, rockies)
• High alkalinity
• Above 100
o Rain and snow water near zero alkalinity must be picked up by dissolving ground materials.

Front 50

What is the equation to determine Ph?

Back 50

pH = -log [H+]
negative log of the concentration of hydrogen.

Front 51

Sources of Hydrogen

Back 51

o Carbonic acid, humic acids (what leaches from the organic layer)
o Rainwater (pH of normal rain is 5.6)
o Acid precipitation
• Sulfuric acid and nitric acid.

Front 52

Effects of altered Ph?

Back 52

o Change form of carbon present (solubility, photosynthesis)
o Changes form of other elements (aluminum becomes toxic to fish)
o Alter internal pH of organisms
• Big fish are less affected because they have low SA:V ratio.

Front 53

Effects of Acidic Ph conditions of biota

Back 53

o Orgs can’t produce calcium carbonate for shells
o Many insects can’t reproduce in low pH
o Many sp. Of phytoplankton die off, are replaced by filamentous algae that isn’t good for food for most
o Shift in microbes from bacteria and fungi to mostly bacteria; affects decomposition of detritus
o Many fish dither stop reproducing or immatures cannot deal with osmotic problems from low pH
o Base of food chain dying off, so even tolerant stage begin to starve to death
o Fungi die at acidic pHs.

Front 54

During Govrn’ments project on low Ph and fish

Back 54

o Small organisms died off first and there was not much to consume for the next trophic levels so the population declined and decreased predatory populations.
• They did not detect acid effects because only measured pH and not alkalinity (buffering ability)
• Did not detect problems with biota since only measured number of adult fish and not their condition or number of young.

Front 55

What is;
Types of wetlands that may be low in pH
Organic acids; good buffering capacity
Contain organisms tolerant to low pH

Back 55

o Bogs, fens, isolated areas w low nutrients.

Front 56

Where can you find PH depressions in lakes/rivers?

Back 56

• littoral zones
o can get acid snow from industrial areas
o rapid snowmelt in sprint causes runoff of v. acid water
o pH can drop rapidly in streams and epilimnion of lakes
cat tails don’t like acid.