Chapter 4.1-4.3

Physcial, Chemcial & Biological Limnology

What percentage of the sun’s light makes it to earth

50%

Autotroph

-Self-producing
-primary producers
-Make inorganic matter organic

Lake

A large body of water in which currents are primarily driven by wind

Limnology

Study of inland waters
lakes (lentic systems) both freshwater and saline
reservoirs, rivers, streams, ponds, springs wetlands etc..

What latitudes are lakes found in

Most abundant in northern latitudes
Most abundant in North America

Lake Formation Mechanisms - Glaciation

Glacier lakes form when a glacier retreats and meltwater fills the whole
kettle hole lakes, great lakes

Lake Formation Mechanisms - Tectonism

Different plate boundaries → distinct lake basins
Deformation of earths crust: faulting, tilting, folding, and warping

Graben Lakes

Oldest, largest, and deepest lakes
Divergent boundaries
An elongated plate that has dropped downward by faults relative to the blocks on either side
Lake Baikal - home of freshwater seal
African rift valley lakes

Lake Formation Mechanisms - Volcanic Activity

Indirectly caused by tectonic activity
Maar Lake: Ejected magma may leave behind fissures that hold water, tend to be shallower (in volcano lake terms)
when roof of crate caves in = larger caldera = crater lake
i.e Crater lake in oregon

Lake Formation Mechanisms - Riverine/Oxbow Lakes

Lakes made when rivers or streams are dammed
‘lakes produced by running water’
When a river erodes the outside banks and deposits sediment on inside banks and pinches away at loop → Oxbow lake

Laurentian Great Lakes were formed by

glaciation (great lakes)

Seasonal Stratification - Winter

Seasonal Stratification - Fall/Spring

Seasonal Stratification - Summer

Epilmnion

top most layer in a thermally stratified lake
warmest and least dense layer

Thermo Stratification

Change in the temperature at different depths in the lake

Seasonal Stratification

In temperate regions where lake water warms up and cools through the seasons, a cyclical pattern of overturn occurs that is repeated from year to year
Storms can cause mixing during stratified periods

Thermocline (metalimnion)

the layer that separates the warm less dense epilimnion and the very dense cold hypolimnion

Hypolimnion

‘under lake’
coldest layer in summer & warmest layer in winter*
*temperate lakes bottom most/hypolimnion layer stays close to 4C throughout the year

Mixing Regimes: Holomictic

Holomictic lakes mix at least occasionally
5 Types of Holomictic Lakes: → if lake is deep enough for hypo
Poly-, Cold Mono-, Warm Mono-, Di-, Oligo-

Mixing Regimes: Meromictic

A lake whose water layers do not intermix
presentation says partial mixing?

Mixing Regimes: Polymictic

Tropical locations where temperatures don’t vary
Mixes throughout the year or continusously
Typically shallow

Mixing RegimesL Cold Monomictic

Mixes once in summer

Mixing Regimes: Warm Monomictic

Mixes once in winter

Mixing Regimes: Dimictic

Mixies twice annually
Great Lakes

Mixing Regimes: Oligomictic

Mixies less than once annually

Mechanisms for Mixing