Lakes consist of layers that differ in chemical composition, illumination and temperature.
As a result, microorganisms are not evenly distributed throughout lakes. Instead, each organism finds the layer that best fits its requirements and calls that region home. Oxygenic photoautotrophs - primary producers that fix carbon and produce oxygen. Anoxygenic photoautotrophs - obtain energy to fix carbon from photosynthesis using hydrogen sulfide, e. These organisms are being actively studied as potential tools in bioremediation.