Freshwater Ecology Exam #1

isothermal

water temperature is the same from top to bottom

epilimnion

the upper layer of water in a stratified lake

metalimnion

the middle layer of water in a stratified lake

hypolimnion

the lower layer of water in a stratified lake, typically cooler than the water above and relatively stagnant.

thermocline

a steep temperature gradient in a body of water such as a lake, marked by a layer above and below which the water is at different temperatures.

isopleths

lines of equal temperature and concentration

dimictic

stratifies twice per year, summer and winter, located in cooler climates

monomictic

stratifies once per year

cold monomictic

stratifies in winter

warm monomictc

stratifies in summer

amictic

never mixes due to ice cover

polymictic

mixes often, nearly daily

oligomictic

rarely mixes, once per decade or more

meromictic

contains a deep, dense layer that has high salinity and never mixes

orthograde

oxygen is saturated throughout

clinograde

DO is above saturation at the surface and there is little to no DO at the bottom

heterograde

peak DO is at an intermediate depth

photosynthetically active radiation (PAR)

light in wavelengths that plants can use

compensation depth

depth where there is just enough light for photosynthesis and photosynthesis is equal to respiration

euphotic zone

zone where there is enough light for photosynthesis

aphotic zone

zone where there isn't enough light for photosynthesis

electrostriction

density increases when ions are added

scattering

light is deflected by particles (dirt, algae)

light extinction coefficient

measures how strongly a substance absorbs and scatters light

1% level

the depth where 1% of the light reaching the waters surface can reach

trophogenic zone

where photosynthesis is greater than respiration

tropholytic zone

where photosynthesis is less than respiration

turnover

when stratified layers mix and nutrients are released

macrophytes

vascular plants

periphyton

attached algae

eutrophic

bodies of water with high productivity

oligotrophic

bodies of water with low productivity

mesotrophic

bodies of water with moderate productivity

eutrophication

the process of adding nutrients and increasing a water body's productivity

benthic zone

the muddy bottom of a lake, pond, or ocean where lots of bacteria and other decomposers and invertes live

littoral zone

where more than 1% of light reaches the bottom of the water

profundal zone

a region of water where sunlight does not reach

pelagic zone

water column

bathymetric maps

show depth and contour of water bodies

residence time

mean time water spends in a lake

sinuosity (P)

measure of how much curvature a stream has

riffle

shallow, fast water with a rough surface and large rocks

pool

deep, slow moving water with fine, silty sediments

run

deep, relatively fast moving water with smooth surface

index of shoreline development (D sub L)

ratio of shoreline length to the circumference of a circle of the same area

current velocity

speed of water flow

stream gradient

vertical drop of a stream channel per unit of distance

stream discharge (Q)

water volume flowing per unit time

stream order

hierarchy based on tributaries (ie 1st order has no permanent tributaries)

snags

large natural wood lodged in place and stable

lag time

time between peak of rain to peak of water flow

stream channel

section where water typically flows

stream bank

slope to a stream; can be at the edge of the channel or flat then slope up

stream slope (S)

how quickly gradient changes

sediment load (Q sub S)

how much sediment is suspended

median suspended particle size (D sub 50)

average sediment size

alluvium

sediment transported and deposited by streams

aggredation

depostion of alluvium

degradation

erosion of sediments from stream channel

alluvial plain

an area of fertile soil deposited by river floodwaters

bankfull discharge

maximum amount of water before flooding increases to the floodplain