Proliferation of endogenous microbial populations caused by eutrophication leads to the establishment of anaerobic environments through increased respiration or biochemical oxygen demand (BOD). One of the causes of excessive eutrophication in water is the release of carbon dioxide, organic carbon compounds and the mineralization of nutrient elements which are the end-products of microbial catabolism. As a consequence of an increased rate of eutrophication, lakes age prematurely, rivers may become choked with algae or aquatic plants and benthic fauna may become smothered.