Eutrophication is a global problem caused by nutrient enrichment, notably phosphorus and nitrogen. The process is enhanced by human activities (anthropogenic eutrophication) and is of increasing concern because of its deteriorating effect on water quality. The most visible effects of eutrophication are excessive algae blooms, which may make water unsuitable for other purposes. In extreme cases of eutrophication algae decomposition may cause oxygen depletion, resulting in the death of most organisms living in the body of water.