Exam 1 Flashcards
Limnology
The study of inland waters
Francois-Alphonse Forel
Widely considered the “Father of Limnology” for pioneering the study of lakes.
Theinemann + Naumann
Dominated Limnology in Europe for a while. First to classify lakes as oligotrophic, eutrophic, and dystrophic.
Edward Birge and Chancey Juday
Joined UW in 1875 and 1905, respectively. Took many measurements across many different lakes, integrating physics, chemistry, and biology.
G.E. Hutchinson and Art Hasler
Modern Limnologist who is a strong advocate for the theoretical basis for the study of lakes. (Yale)
Modern Limnologist who is a strong advocate for the experimental study of lakes. Conducted whole-lake experiments and advocated the conservation of aquatic resources. (UW)
Littoral Zone
The shallows of a body of water. Has lots of plants.
Pelagic Zone
Open water part of a water body. No plants or structures.
Profundal Zone
Deep part of a lake; under the pelagic zone.
Photic Zone
The part of a lake that receives sunlight (at least 1% of incident surface intensity)
Aphotic Zone
Depth at which light does not penetrate with at least 1% of incident surface light intensity.
Epilimnion
The upper temperature zone in a lake
Metalimnion
The middle temperature zone in a lake; temperature profile change is at least 1°C/m
Hypolimnion
Lower temperature zone in a lake, usually the coldest.
Thermocline
Point within the metalimnion where temperature change is greatest.
Significance of lake origin
If there were no other forces acting to maintain them, all lakes would dry up from sedimentation.
Lentic
Lakes/standing water
Lotic
Rivers/flowing water
Graben Lakes
AKA Tectonic Lakes, are the oldest and deepest.
Are formed in a depression in the earth’s crust between two parallel faults.
E.g. Lake Baikal, Tahoe, and Tanganyika
Earthquake Lakes
Landslide from earthquake dams up a river valley, creating a lake.
Glacial Lakes
Most common type of lake, caused by retreat of glacial ice sheet over 10,000+ years
Ice Dam
Ice (usually from a glacier) blocks the drainage of a lake into a river, causing water to build up.
Permafrost Lakes
Lakes created by the melting of permafrost, usually polygonal.
Ice Scour
Created when a glacier scrapes across a landscape. Correspond with boreal forests.
Lakes form in bedrock gouges and occur in areas with little glacial drift (till)
Cirques
Bowl-shaped sloping in valleys that look like an amphitheatre. Lakes occur when the outlet is dammed by glacial drift.
Moraines
Ridges in the landscape formed by glaciers pushing and leaving behind debris after pausing.
Creation of the Great Lakes
Receding and melting glaciers gouge out large basins and fill them in with meltwater.
Kettle Lake Formation
Caused by ice melting in glacial till. Are small with deep, steep sides, in areas with lots of glacial debris (till).
A chunk of the ice sheet gets caught buried in till and leaves water behind when it melts.
Prairie Potholes
Seasonal wetlands caused by uneven deposition of glacial till that fill with rainwater.
Volcanic Lakes
Formed in volcanic craters. Have TINY watershed, usually very clear.
Coastal Lakes
Formed along irregularities in the shore line of the sea or large lakes. Longshore currents deposit sediments in bars or spits that eventually isolate a fresh or brackish-water lake.
Solution Lakes
AKA Karst Lakes.
Rocks dissolved by acidic water -> caves
Usually in limestone
Oxbow Lake
Type of riverine lake formed by the rerouting of a bowed river channel, due to the deposition of sediment onto the inside bank of the turn of river flow and erosion on the outside of the turn.
Floodplain
Type of Riverine Lake consisting of a low-laying area of land adjacent to riverbanks that distributes river overflow over a large area.
Neuston
An organism that lives ON the surface of water, utilizing the surface tension (e.g. water striders)
Which end/color of the light spectrum has the shortest wavelength/highest energy?
Blue. Water is blue because short wavelengths/blue light is scattered the most.
(B)lue = (S)hort
BS
Albedo
A measure of how much light is scattered/reflected by the surface of a lake. Higher=more reflective.
Extinction coefficient
Kd, Kd = (ln Io - ln Iz) / z
Io = Surface incident light intensity
Iz = light intensity at depth z
Higher Kd = deeper secchi
Compensation depth
Depth of the bottom of the photic zone.
zeu = (ln 100 - ln 1)/kd
= ln 100/kd
Which is easier to mix and why?
Tropical Lakes
Temperate Lakes
Temperate lakes (cold) are easier to mix because there can be temp differences due to heating of surface waters by the sun.
Relative Thermal Resistance (RTR)
Resistance to mixing. Highest RTR is at thermocline, where the change in T is greatest.
Where on Earth is it difficult to mix lakes?
It requires more energy at LOWER latitudes (closer to equator) because
1) there is a higher difference in max and min temperature/density to bridge
2) warmer overall temperatures are harder to mix
What happens to stratification after a windy spring?
It occurs LATER because the wind keeps the lake mixing/warming from add’l sunlight
Hypolimnion will be WARMER because warmer waters will be pushed down during mixing
Characteristics of Cold Monomictic Lakes
Mix ONCE
Ice-covered for most of the year
Mixing during the summer
No stratification
Characteristics of Dimictic Lakes
Mix TWICE (Spring and Fall)
Ice during winter
Stable summer stratification
Characteristics of Warm Monomictic Lakes
Deep lakes with no winter ice cover
Stable summer stratification
Mixes all winter
Characteristics of Meromictic Lakes
NEVER mixes bc wind energy is never enough to mix
Reasons:
- Salinity - Can be high or low due to road salting or high freshwater inputs
- Depth - Baikal, Malawi, Tahoe
- Small lakes with low fetch/wind energy
- Warm climate
What is the difference between waves and currents?
Waves do not involve the movement of water mass, just a vertical displacement.
Currents do involve the physical movement
What two factors drive mixing?
- Wind
- Cooling and heating at the surface
Surface gravity waves
Are a function of fetch, KE imparted by wind
No directional flow
Wave “breaks”
Surface Seiches
Created when wind pushes the water to raise the level at one end of the lake and lower it at the other.
Can be Uninodal or Binodal
Amplitude: 2-160cm
Period: few mins to 12 hrs
Minor impacts on mixing
Internal Seiches
Form when temperature layers within water get waves (remember video)
Speed - 30 cm/s
Cause movement of water, heat, nutrients between epilimnion and hypolimnion
Can erode the thermocline, resuspend sediments, and generate currents in hypolimnion
Kelvin Waves
The effect of Surface Seiches + Coriolis (spinning) Effect
Looks like a coin at end of a spin
Horizontal currents: wind
Wind literally blows water mass to create a current with 1-4% of wind speed
Coriolis Effect - wind deflected to right of wind direction
Counterclockwise in N Hemisphere
Horizontal Currents: density
Differential cooling and warming in shallow vs deep waters.
Cool water flows down incline to create a current
Langmuir currents
Alternating rotating vortexes of water that lead to white streaks in lakes and oceans. Caused by steady breeze over surface.
Cause rapid mixing of epilimnion and movement of phytoplankton throughout the mixed layer, which rapidly changes the light environment!
Chemical stratification most strongly occurs in which type of -mictic lake?
Meromictic, because less diffusion from mixing.
Mixolimnion
Layer where chemical mixing occurs in meromictic lakes. Can be stratified independent of temperature.
Chemocline
Layer of rapid change in salinity in meromictic lakes.
Monolimnion
Bottom layer of a meromictic lake, which has little to no oxygen.
Halite
Salt AKA NaCl
Major ions of interest to limnologists (Cations and anions)
CATIONS: Ca2+, Mg2+, Na+, K+, and also H+
ANIONS: HCO3- (bicarbonate), CO32- (carbonate), SO42-, Cl-, and also OH-.
Nutrients (Major and Minor) of interest to limnologists
MAJOR: N, P, and Si
MINOR: Lots of them, many metals
Dissolved Gases of interest to limnologists
Mostly O2 and CO2
But also CH4, N2O, and more
CH4 and N2O are more potent greenhouse gases than CO2!
Equivalents
AKA effective charge; charge per weight. Small particle with +2 charge has more equivalents than a large particle with +2 charge
Of which ions is dolomite a major source?
Calcium and Magnesium
Of which ion(s) is Quartzite a major source?
Silicon
What factors affect how much dissolved gas water can hold?
- Temperature
- Altitude (pressure)
- Salinity
Supersaturation (of a gas)
More gas in water than chemical principles predict.
Effect: Gas bubbles into atmosphere (like soda)
Subsaturation (of a gas)
Less gas dissolved than water can hold.
Effect: gas from atmosphere moves in
When is the ATMOSPHERE a SOURCE?
When is it a SINK?
When the lake is SUBsaturated.
When it is SUPERsaturated.
How can ecosystem metabolism affect super/sub-saturation?
How can temperature effect super/sub-saturation?
If P/R adds or removes O2/CO2 faster than they can diffuse in/out of the lake
If temperature changes quickly, it can increase/decrease too quickly for diffusion to maintain 100% saturation.
What is the term to describe the behavior of this DO profile?
Clinograde
What is the term to describe the behavior of this DO profile?
Orthograde
Usually not much biological activity
What is the term to describe the behavior of this DO profile?
Positive Heterograde
What is the term to describe the behavior of this DO profile?
Negative Heterograde
What are the diel/diurnal changes in O2 and CO2 concentrations?
O2 INCREASES during day, DECREASES during night
CO2 DECREASES during day, INCREASES during night
What does color have to do with the trophic state index of a lake?
Brown: Dystrophic, lots of organic and humic substances
Green: Phototrophic, lots of algae and photosynthesizers
Blue: Oligotrophic, low productivity and nutrient content
What happens to O2, Organic Matter, and CO2 when GPP>R?
O2 PRODUCED
Organic matter PRODUCED
CO2 CONSUMED
What happens to O2, Organic Matter, and CO2 when GPP<r>
</r>
O2 CONSUMED
Organic Matter CONSUMED
CO2 PRODUCED
Gross Primary Production (GPP)
Total amount of organic matter produced in an ecosystem.
Ecosystem Respiration (ER)
Breakdown of organic matter in an ecosystem
Net Ecosystem Production (NEP)
NEP = GPP - R
How do levels of the 3 forms of Dissolved Inorganic Carbon (DIC) change with lake pH?
- Lower than ~6.5 - H2CO3 (CO2) dominates
- ~6.5 - 10.5 - HCO3- dominates
- Higher than ~10.5 - CO32- dominates
Remember: this is a self-correcting system!
Acid Neutralizing Capacity (ANC)
Water’s ability to buffer pH change, mostly determined by DIC system.
As acid is added, it combines with the anionic forms of DIC and is neutralized.
As base is added, it combines with H+ and H2CO3 and is neutralized.
Where does DIC come from? How many bicarbs do carbonate and silicate minerals form?
Rock weathering (carbonate minerals form 2 bicarbs, silicates form 1 bicarb)
Is ANC higher in NORTHERN Wisconsin lakes or SOUTHERN Wisconsin lakes?
It is HIGHER in SOUTHERN Wisconsin lakes.
Allochthonous Organic Carbon
Produced OUTSIDE of the ecosystem.
Comes from leaves falling in, and is RECALCITRANT (not easily used by organisms)
AUTOCHTHONOUS Organic Carbon
Produced INSIDE ecosystem
Comes from algae
Is LABILE (easily used by organisms)
What is considered “the great modulator” in aquatic ecosystems and why?
Dissolved Organic Carbon (DOC)
Because: it absorbs light, which affects stratification, photosynthesis, and UV protection
It is food for bacteria
Influences heavy metal availability and pH
