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Ecosystems

Author(s): Deanne Erdmann MS

Zonation in Lakes

The photic zone is an area where there is sufficient light for photosynthesis. Within the photic zone, the shallow area found close to shore is designated as the littoral zone, the surface water away from the shore is referred to as the limnetic zone.

The area where very little light penetrates and the primary organisms are heterotrophic is called the profundal (aphotic) zone. The benthic zone (the bottom of lakes) and profundal zone contain organisms that feed off decaying organic matter called detritus. The benthic zone usually has higher biodiversity than the profundal zone.

Lakes are often are categorized as oligotrophic or eutrophic by their production of organic matter. Oligotrophic lakes are generally deeper, have sparse nutrients, and clear blue water. Eutrophic lakes tend to be more shallow and have a rich nutrient supply.