Limnology Exam 1

Mainly definitions

Lentic

standing waters

Lotic

flowing waters

Francois Forel “father of limnology”

1901 - first text on limnology

Noel Hynes

1970 - first text on lotic ecosystems

Mitsch and Gosseling

1985 - first text on wetlands

G. Evelyn Hutchinson

Treatise on limnology published

Developed lake classification

Molecular structure of water

• Covalent bonds

• Hydrogen bonds (104 degrees apart)

• Tetrahedral arrangement of water molecules

Density-temp relationship

density decreases as temperature increases

Viscosity

A measure of liquids resistance to flow (how difficult it is to move through something)

temp-density-viscosity relations

temp increases as density and viscosity decrease - reason below

temp decreases as density and viscosity increase

why? because as the water temp increases the molecules are more spread apart

Specific heat of water

The amount of heat required to raise or lower the temp of a substance by 1 degree Celsius.

Surface tension

The measure of the strength of the waters surface film.

• reduced strength with increased temps and dissolved organic compounds.

closed basin

endoheic lakes - no outflow, loses water through evaporation

Open basin

exorheic lakes - water flows out of the basin

Glacial

75% of lakes are from glacial origin.

types of glacier lakes -

• kettle lakes

• ice scour lakes

• cirque lakes

• paternoster lakes

Tectonic

formed as a result of the movement/uplift of the earths crust - faulting

old and deep

less productive due to great depths

Volcanic

Ejected volcanic material leaves empty chambers (caldera)

Released lava creates depressions and cavities

relatively unproductive lakes

very little human influence

Coastal

relatively young

formed by water currents depositing large amounts of sediment along a bay

generally blackish water

can be connected right by a ocean

usually higher salt concentration

Riverine (fluvial)

generally small in size and number

contains -

• oxbow lakes-cutoff river bends

• blocked valley lakes-formed when the main river deposits sediment that blocks the tributary

• floodplain or levee lakes-formed when rivers overflow their banks

Landslides

Large movements of earthen material into stream valleys, can dam rivers.

usually from earthquake activity

extremely unstable

can create or make lakes go away

Sinkholes

Solution (karst) lakes- found in basins of highly soluble rock(limestone)

slightly acidic waters

found in limestone regions of the world

man made (reservoirs)

more than 60,000 large reservoirs

hold 14% of global annual runoff

more than a million small reservoirs

*every reservoir has a dam

Littoral zone

near shore region influenced by the wave action and spray

Pelagic/limnetic zone

the open water beyond the littoral zone

Benthic zone

lake bottom

Photic zone (more o2)

upper sunlit waters where photosynthesis occurs

*greater than 1% of light

Aphotic zone (less o2) (profundal zone)

lower layer of water with less than 1% of light

Compensation depth

when photosynthesis meets the rate of respiration

Light meter

Underwater photo cell that measures the vertical extinction of light

Secchi disk

measure of transparency, super important can tell you a lot of information on a lake

*times 2 secchi disk measurement for compensation depth

Epilimnion

Surface, mixed layer

Metalimnion

transition layer, characterized by a rapid decline in temp with depth (thermocline)

Hypolimnion

deep cooler layers of lake below the metalimnion, reduced turbulence and light

Ultraviolet range

100-400nm

visible radiation range

400-700nm

infrared range * long wavelengths

700-3000nm

Solar energy

continuous flow of electromagnetic waves, discrete pulses of energy called quanta or photons

if you have a high reflection on the water surface you have

less light getting in the lake

if you have a low reflection on the water surface you have

more light getting in the lake

Reflection

average loss of reflection is 5-6% on a clear summer day

Scattering

deflection of photons by molecules and particles *shorter wavelengths scatter faster

Transmission

light that passes through the water column

Light irradiance

measure of the number of photons passing through a unit area.

Light attenuation

rapid reduction in light irradiance with depth due to scattering and absorption of solar energy.

Light equation

Iz=Io e^-kz

Iz- irradiance at depth z

Io- irradiance at the surface of the lake

k-vertical extinction coefficient

Equation to solve for kd

kd=(lnIo-lnIz) / z

kd tells you the light structure in a lake, if you have a higher extinction coefficient you have less light getting through the lake.

Eutrophic (lack o2)

nutrient rich (algae)

Oligotrophic (more o2)

Nutrient poor (higher water quality systems)

Watershed

the area of land that drains towards an aquatic ecosystem

unconstrained low gradient

not a lot holding in place

constrained high gradient

keeping it packed in. (ex. elevation changes make this happen)

Stratification

wind induced currents are unable to mix the layers, lake divides into 3 different layers; epilimnion, metalimnion, and hypolimnion

Stability

Likelihood that a stratified lake will stay stratified

Turnover

same density throughout lake, no more zones.

mixing of entire water column

Fetch

length of unobstructed area; lakes that are bigger and have no objects (islands) in the way will have a greater fetch.

Amictic

never mix because lake is frozen

Holomictic

lake mix completely (top to bottom)

Meromictic

never fully mix

types of holomictic lakes

1. monomictic lakes - 1 period mixing

cold and warm

2. Dimicitic lakes - 2 periods mixing and 2 periods stratification

summer and winter = strat; fall and spring = overturn

3. Polymictic lakes - mix many times a year

Isothermal

Same temperature top to bottom

Cold monomictic lakes

1 period of mixing, frozen all winter, mix briefly at cold temps in summer

overturn during summer

Warm monomictic lakes

1 period of mixing, stratification in summer. does not freeze and mixes all winter

Cold polymictic lakes

mix many times a year, ice covered all winter, may stratify for brief periods during the summer, but it can be interrupted.

Warm polymictic lakes

mix many times a year, never ice over, may stratify for days or weeks at a time.

Meromictic

lakes that never mix and become chemically stratified.

Chemocline

boundary between the mixolimnion and the monimolimnion, below the thermocline *high salinity underneath the boundary

Monimolimnion

does not mix with the upper water, results from accumulation of salts, and high salinity

Biogenic meromixis * have to have a hypolimnion for this to happen

An input of salts due to biological activity (decomposition)

2 main ways this can happen

1. great depth

2. sheltered lakes with relatively small surface area relative to depth

Ectogenic meromixis * have to have a hypolimnion for this to happen

An external events brings salts into a freshwater lake. Saltwater accumulates at the bottom. Can be human influenced

Crenogenic meromixis * have to have a hypolimnion for this to happen

Gases or high salinity groundwater introduced to deep portions of the lake from chemical processes in the earths crust.

*eruptions can happen because of trapped co2

Coriolis force

force that causes moving objects; such as wind, water, or projectiles to curve as a result of the earths rotation.

Wave height

difference between crest and trough

*can be calculated by fetch

Hmax=0.332*F^0.5

Wave length

difference between two crests

Breaker

Occurs because wavelength decreases and height increases near shore. So we have a bigger waves near shore.

Seiches - to dry

refers to periodictic drying exposures of shallow littoral zones.

most often caused by wind induced tilting of the water.

Surface seiche

high level of water goes to one end due to wind. *goes above the still water line. This happens from constant wind blowing from one direction.

Internal seiche

Occurs at the thermocline when a lake is stratified. Detected by the rise and fall of the thermocline. Also tilts the water line. Erodes the thermocline.

Entrainment

mixing of layers for a brief period of time

Currents

no periodicity, forward movement *gradual movement of water

Langmuir circulation

winds can develop a series of vertical helical currents at the surface.

foam streaks form from winds going in one direction. low density in streaks. *lakes have to be big enough for this to happen

Ekman spiral

Deflects surface currents, goes to the right of wind direction. Angle of deflection + water speed declines with depth, the deepest current flows in the opposite direction to wind.

Density induced current

Differential heating throughout the lake creates density currents. Bays and littoral zones heat and cool more rapidly than pelagic areas.

Types -

underflow - colder dense water coming in *flows to the bottom

overflow - warmer water coming in, less dense *stays to the surface

interflow - water is median “middle”

Longshore currents

current flowing parallel to shoreline between the breaker waves and shore. If waves approach at a angle to shoreline from the right, current will be to the left. *this is important in eroding and redepositing sediment

Rip currents

Narrow, fast currents moving offshore. Occur when a longshore current meets a physical barrier and is deflected out.

What I learned from Dr. Bo’s presentation

• The current in rivers and stream will push spilled oil downstream

• Wind has a lot of affect during oil spills causing it to drift into our riparian zones which can cause a lot of issues.

• The sunken oil can smother our benthic bottoms which suffocate macro invertebrates, and destroy spawning grounds.

Research projects happening at CFRE

• Oil particle interactions

• Monitoring and detection of oil

• Biological impacts of oil (MPRI BIO)

VanDorn Sampler

A specialized device used by scientists to collect discrete water samples from a specific depth in lakes, rivers, streams, or the ocean.

Stephen Forbes (1887)

Lakes as super - organisms

Lakes as microcosm

Birge and Juday (1900s)

Wisconsin lakes; UW Madison Comparative limnological surveys