The lake ecosystem is made up of biotic and abiotic interactions. While the biotic system includes plants, animals and microorganisms the abiotic system includes the non-living factors. Further, the lake ecosystem has three prominent zones- the pelagic or open water zone, the benthic zone made up of bottom and shore regions and the profundal- the deep bottom regions not exposed to light. The community of organisms that live in the benthic zone are referred to as benthos and the invertebrate community includes crustaceans, amphipods, poychaete worms, clams, snail. chironomous midge larvae etc.