These bioclassifications primarily reflect the influence of chemical pollutants. The major physical pollutant, sediment, is poorly assessed by a taxa richness analysis. These criteria apply to flowing water systems only. Through photosynthesis, these tiny plants provide the base for the aquatic food web and, as such, can be a determining factor in overall aquatic production. Phytoplankton populations are dependent upon nutrient availability and other ecological factors such as light, temperature, pH, salinity, organic matter, grazing by higher trophic levels and water velocity.
Phytoplankton are especially useful as indicators of eutrophication.
Surface blooms may be unsightly and deleterious to water quality, causing fish kills, anoxia, or taste and odor problems. The algal bloom program was initiated in 1984 to document suspected algal blooms with actual biovolume and density estimates. Other components of the phytoplankton program include ambient monitoring, lake monitoring, and special studies. To the public, the condition of the fishery is one of the most meaningful indicators of water quality. Fish occupy the upper levels of the aquatic food web and are both directly and indirectly affected by chemical and physical changes in the environment.