Deterioration of water quality in aquatic system

The need to reduce anthropogenic pollutants inputs to aquatic ecosystems in order to protect drinking-water supplies and to reduce eutrophication, including the proliferation of harmful algal blooms. Nitrogen (N), needed for protein synthesis, and phosphorus (P), needed for DNA, RNA, and energy transfer, are both required to support aquatic plant growth and are the key limiting nutrients in most aquatic and terrestrial ecosystems. Most researchers have concluded that no single factor is responsible, but rather interactions between two or more factors control the rates. River aquatic systems that have been heavily loaded with nutrients can display P limitation, N limitation, and colimitation, and what nutrient is most limiting can change both seasonally and spatial. At the transition between fresh and saline water, P can often be the limiting nutrient. P and dissolved silicate are also often limiting during the spring, with N limitation commonly occurring during summer months. Algal production during summer is supported by rapidly recycled P within the water column or released from sediments.