Lake Zonation by Biological Production of Organic Matter MP 2.3

Oligotrophic Lakes Low productivity with a small surface area compared to depth Little decomposition because it is so cold so oxygen is plentiful Bottom sediments low in decomposable material (detritus) Shortage of nutrients limits photosynthesis Very clear water

Eutrophic Lakes Nutrient-rich have a small surface area compared to depth Have much detritus on the bottom that supports high rates of photosynthesis. High decomposition rate uses up much of the oxygen in the pond.

Mesotrophic Lakes Have an intermediate level of productivity, less than eutrophic but more than oligotrophic lakes.

Stream Ecology MP 2.4

Streams and Rivers Defined is a body of water that is moving continuously in one direction At the headwaters the water is usually cold and clear (except for glacier streams) with little minerals or nutrients Rivers pick up minerals and nutrients as they head downstream.

Turbidity Becomes more and more turbid (carrying sediment) downstream There is a frequently a visible line where a clear stream enters a turbid one (or vice versa), called the line of turbidity Turbulence stirs up water adding oxygen, slow flowing rivers have less oxygen

Animal Adaptations Animals that live in and around rivers have evolved hydrodynamic body shapes to handle current or live on the downstream side of rocks.

Point Source Pollution Rivers have been a dumping ground for pollutants for centuries because they carry it away from the local area Downstream in a river system pollution accumulates increasing as it moves toward the sea.

Water Quality Ecologists measure water quality by counting the diversity of invertebrates The better the water quality the greater the invertebrate species richness (number of species)