Lecture 7b Flashcards
What is the hydrological Cycle:
A biochemical cycle that involves the continuous movement of water on, above and below the surface of the Earth
What contributes to Mass Balance?
Precipitation vs. Evaporation
What Contributes to Lakes? (3)
- Atmosphere
- Lakes
- Groundwater
What does the Atmosphere Contribute to Lakes?
- Gases: N2, CO2, O2
- Nutrients: N, P
- Precipitation
What does the Watershed Contribute to Lakes:
- dissolved minerals from rivers
- changing concentrations of solutes (when water flows over limestone (primarily CaCO3) will contain a high [ ] of Calcium (Ca 2+) and bicarbonate (HCO3 -)
What does the Groundwater Contribute to Lakes:
- Nutrients: N, P
- Toxins
- CO2
Change in Chemistry Caused by Lake Age:
- Certain ions decline with time due to biology and chemistry
- Other chemical factors increase with time due to watershed
- Some nutrients remain constant through time
Salts: Dissolved Solids - Consist of a Few Salts (11)
- Carbonates
- Sulfates
- Calcium
- Magnesium
- Sodium
- Potassium Chlorides
- Silicic acids
- Nitrates
- Phosphate compounds
- Iron
- Manganese compounds
Salts: Dissolved Solids - Consist of a Few Salts (Major) (7)
- Carbonates
- Sulfates
- Calcium
- Magnesium
- Sodium
- Potassium Chlorides
- Silicic Acid
Salts: Dissolved Solids - Consist of a Few Salts (Minor) (4)
- Nitrates
- Phosphate compounds
- Iron
- Manganese compounds
Salts: Total Dissolved Solids (TDS) - how they are done:
- Evaporation (100 - 200 mg/L)
- Endorheic Lakes (10^5 mg/L)
Salts: Inorganic Components:
Via loss on ignition (total = organic + inorganic)
Salts: Specific Conductivity (μS/cm)
- Based on ion strength of the water
- Conductivity = TDS x 0.65 (for normal waters)
Salts: Hardness
Sum of Ca + Mg (+Fe)
Salts: Temporary Hardness
= hardness + HCO3 + CO3
Loss when boiling + scale
Salts: Permanent Hardness
Hardness + SO4 + Cl + PO4
What are Endorheic Basins
- Water drains into a basin without an outlet
- When evaporation > precipitation, dissolved salt accumulate and precipitate
Gasses: Dissolved Gasses
- O2, CO2, and N2
- CO2 and N2 are important for processing through nutrient cycling
Gasses: Dissolved Inorganic Nitrogen (DIN)
- Microbe dependent from N2 found in the atmosphere
- N2 can be fixed by lightning or certain diazotrophs in soil and/or water
- DIN = NO2 + NO3 + NH3 in water
- Certain DIN is used by primary producers as N is needed for building proteins
- Can be limiting under certain conditions, and co-limitation with P
Gasses: Dissolved Inorganic Carbon (DIC)
- Is pH dependent and CaCO3 may be present in bedrock
- CO2 + H2O <-> H2CO3 <-> HCO3 + H+ <-> CO3 + H+ + Ca <-> CaCO3
- Certain DIC is used by primary producers; CO2 is respired by all organisms
- Can be limiting under static and/or high pH conditions
Acidic Lake Water: CO2 between 4 - 6 pH (Componds)
- High in H2CO3 and CO2
- Low HCO3 -
Most Lake Water: CO2 between 6 - 9.5 pH (Componds)
- High HCO3 -
- Low H2CO3 and CO2
- H2CO3 and CO2 become CO3 2-
Alkaline Lake Water: CO2 between 9.5 - 12 pH (Componds)
- Low HCO3 -
and loses HCO3 - - High CO3 2-
Process of Lake Whiting:
- Following intense photosynthesis and
- pH increases and CaCO3 precipitates
Lake Water: Dissolved O2 (DO)
The single most important biologically relevant constituent of water that dictates biological activity and/or potential
O2 Saturation:
The amount of DO that can be held by water in equilibrium with the atmosphere at a particular 1. Temp, 2. Pressure, 3. Salinity
Subsaturated Waters
Are < DO saturation
Supersaturated Waters
Are > DO saturation
How Does O2 Diffuses:
high to low [ ] from the surface to the waters below and the rate is limited by the density and viscosity of water
What does O2 Diffusion Rate depend on (Other than [ ])
The rate is limited by the density and viscosity of water
How Can O2 Mix in Water
By turbulence and currents, and wind-driven spray can lead to supersaturation
What is O2 Introduction a Byproduct of?
Non-cycling photophosphorylation
What is Hypoxia?
deficiency in the amount of oxygen reaching the tissues
What is Anoxia?
An absence of oxygen
Lake Structure: Stratification (Isothermal Conditions)
Well mixed with circulation throughout the water column
Lake Structure: Stratification (Thermal Conditions)
- More buoyancy
- Lack of Mixing (decreased inertia)
- Both lead to density stratification
What is the Epilimnion Layer of Water in the Column?
- Is in contact with atmosphere and well mixed
- Air-water
What is the Metalimnion Layer of Water in the Column?
- Is the Barrier between the epi and hypolimnion layers
- Internal wave movement
- Thermocline (HOD and SOD)
What is the Hypolimnion Layer of Water in the Column?
- Is isolated with compounds from isothermal + sediment + biology
- Sediments
Components of Epilimnion:
- Warm
- Low density
- Surface waters
- Well mixed energetic atmospheric contact
Components of Metalimnion:
- Zone of rapid tem change
- Location of internal wave movement
Components of Hypolimnion:
- Cold
- High-density
- Deep waters
- Isolated from atmos
- Contact with sediments
Thermal and Chemical Seasonal Stratification (Winter):
- Surface Ice reduced O2 diffusion into surface waters
- Potential for O2 from ice algae
- Cold water creates increased O2
Thermal and Chemical Seasonal Stratification (Summer):
- O2 content set at the onset of stratification
- Decline in O2 reflects uptake by decomposers inhibiting benthic zone (HOD and SOD)
What is HOD Stand for?
Hypolimnetic Oxygenation Demand
What is SOD Stand for?
Sediment Oxygen Demand
What does Hypolimnetic Oxygen Demand (HOD) do?
- OM from the epilimnion (function (P load))
- Time since onset of stratification
- Volume and hypolimnion
- Temperature
What does Sediment Oxygen Demand (SOD) do?
- Temp
- Nutrient levels
- DO in the overlying water
- Velocity of the water
How Does Hypoxia Occur?
If HOD + SOD approaches DO in the hypolimnion
How does Anoxia Occur?
Occurs if HOD + SOD exceeds DO in the hypolimnion
Different Lake Trophic Statuses?
- Oligotrophic
- Mesotrophic
- Eutrophic
Oligotrophic Lake Status:
- Clear water
- Low nutrient (especially P) input
- Low SA:Vol
- Low algal and macrophyte OM production and accumulation leads to cold hypolimnion with high DO below metalimnion
Mesotrophic Lake Status:
- Moderately clear water
- Medium levels of nutrient input
- Intermediate SA:Vol
- moderate algal and macrophyte OM production and accumulation leads to cool hypolimnion with moderate DO
Eutrophic Lake Status:
- High [algal]
- Receives high nutrients (N and P)
- Low DO
- Highest fish biomass (different species)
- High algal OM production and accumulation leads to warm hypoxia
Dystrophic Lake Status:
- Receives excessive amount of OM
- High algal production and accumulation leads to warm/hot hypolimnion with anoxia
What Happens When Algae Die and Sink to the Bottom:
Microbial action depletes the DO in the benthos (i.e., HOD and SOD) -> hypoxia and/or anoxia conditions that can be lethal to invertebrates and fish
DO Vertical Profiles (Oligotrophic)
- Clear waters
- Often uniformly high DO below metalimnion
DO Vertical Profiles (Eutrophic)
- Turbid waters
- DO decline below metalimnion due to HOD + SOD
DO Vertical Profiles (Mesotrophic)
- Peak DO at DCM (Deep Chlorophyll Maximum) in metalimnion
- DO rich water trap during stratification + heating
DO Vertical Profiles (Mesotrophic)
- DO min due to HOD due to zooplankton + microbe decomp.
What is Silicate Limitation:
Weathering of continental lithosphere (granite) Becomes aluminosilicate clays comprised of Silica (SiO2)
Formula for Silicic Acid
SiO2 + H2O –> H4SiO4
Formula for Silicate:
H4SiO4 –> SO4 ^-4
Orthosilicate:
SO4 -4
Metasilicate:
SO4 -3
Pyrosilicate:
Si2O6 -7
How do Diatoms Use Silicate and Silicic Acid:
To form Biogenic Silica (SiO2) in their cell walls
What happens to Biogenic silica (SiO2) after Death?
Dissolves back to silicate although the process is controlled by:
1. Shrinking rate
2. Temp
3. Bacterial decomp of organism
Otherwise, biogenic silica accumulates in sediments
What Does Anoxia Regenerate?
Phosphorous (P)
What is the Rain pH?
5.6 due to CO2 in air
What is the pH of Acid Rain?
4.2 - 4.4 by NO + SO
How is Acid Rain Neutralized (Buffered):
By ANC (Acid Neutralizing Capacity) in watershed soils
What does acid rain take out of soils?
Toxic metals like Aluminum (Al) from carbonate soils
What Does Acid Rain do to Macroinvertebrates and Vertebrates
Have high mortality and lower reproduction, but certain algae may thrive
What is the DOM and colour changing:
Dissolved Organic Matter can vary widely in color
What is CDOM and Colour changing:
Coloured Dissolved Organic Matter creates brown/yellowish hue to lakes
What Does DOC (Dissolved Organic Carbon) Affect?
- Biological
- Physical
- Chemical Processes
What Does Darker Water Absorbing more Heat Do (4):
- Strengthens stratification
- Lowering mixing depths
- Lowering primary producer productivity due to increased light attenuation
- Increasing energy sources for the microbial loop
What Occurs With Chemical Transformations as Material Sinks:
- Lowers OM
- Lowers Calcium (Ca)
- Increases SiO2
Rate of Sedimentation is Related to What:
- Watershed and lake productivity
- Age of lake
- Size of lake
- Latitude and Climate
- Solids and bedrock
Rate of Sedimentation (Age of lake… what it does)
Sediments accumulate over time
Rate of Sedimentation (Size of lake… What it does)
Larger fetch –> larger waves and shoreline erosion
Rate of Sedimentation (Latitude and Climate… What it does)
Longer growing season –> more organic
Rate of Sedimentation (Soils and Bedrock… What it does)
More erodible bedrock –> more sediments
