Marine eutrophication

Abstract

Eutrophication is one of the key local stressors for coastal marine ecosystems, particularly in those locations with many estuaries, intense coastal development or agriculture, and a lack of coastal forests or mangroves. The land-derived import of not only inorganic nutrients, such as nitrate and phosphate, but also particulate and dissolved organic matter (POM and DOM) affects the physiology and growth of marine organisms with ensuing effects on pelagic and benthic community structures, as well as cascading effects on ecosystem functioning. Indicators for marine eutrophication are therefore not only key water quality parameters (inorganic and organic nutrient concentrations, oxygen and chlorophyll availability, and biological oxygen demand), but also benthic status and process parameters, such as relative cover and growth rates of indicator algae, invertebrate recruitment, sedimentary oxygen demand, and interactions between indicator organisms. The primary future challenge lies in understanding the interaction between marine eutrophication and the two main marine consequences of climate change, ocean warming, and acidification. Management action should focus on increasing the efficiency of nutrient usage in industry and agriculture, while at the same time minimizing the input of nutrients into marine ecosystems in order to mitigate the negative effects of eutrophication on the marine realm.