Stratification Flashcards
Epilimnion
Top layer of water in the summer where sunlight and turbulence due to the wind causes good mixing.
Hypolimnion
In the summer, turbulence does not penetrate lower, hence a poorly mixed stratified layer of cooler water.
Thermocline
The layer separating the epilimnion and the hyplimnion.
Autumn
When the temperature drops, the epilimnion cools and sinks causing overturning and complete mixing.
Winter
Mixing stops at 4 degrees. Further cooling or freezing on the surface results in winter stratification.
Monomictic
One cycle of stratification
Dimictic
Two cycles of stratification
Menomictic
No cycles of stratification
Polymictic
Many cycles of stratification
Euphotic Zone
This is a well lit zone at the upper layer allowing plant growth. Depth depends of turbidity and algae present.
Profundal Zone
Where light cannot penetrate (light intensity is 1% of unattenuated sunlight).
Light compensation level
The transition between the euphotic zone and the profundal zone.
Littoral zone
The shallow water near to the shore in which rooted plants can grow.
Benthic Zone
Bottom settlements. Dead organisms settle to the benthic zone to decompose. Bacteria is always present. The presence of higher life forms depends on oxygen availability.
Oligotrophic
Lakes with low productivity. They tend to be saturated with oxygen and dominated by trout and whitefish.
Lake Productivity
The ability of a lake to support a food web.
Eutrophic
Lakes with high concentrations of nutrients and a resultant high biomass production and poor transparency. The lake can only support warm water fish such as perch and roach because the hypolimnion in the summer become anaerobic.
Mesotrophic
Lakes on the transition between oligotrophic and eutrophic containing whitefish and perch.
Ultra-oligotrophic
Extremely low nutrient lake.
Hyper-eutrophic
Extremely high nutrient lake.
Liebig’s law of the minimum
Liebig’s law of the minimum states growth is controlled by the scarcest resource available - usually phosphorus.
