eutrophic river water flows over large boulders against wooded bank

eutrophication pollution nitrgen rich oxygen poor growth dissolved H2O angling anglers fishing paddling kayaking environment environmental hypoxia conditions hypoxic overfeeding excess nutrients phosphorus farm land stream watershed fluvial geology environmentalism limnology pollutants excess bloom algal event agriculture agricultural ecosystem phytoplankton microalgae epiphytes microphytes damage impact early chemistry biology woodland