Aplicação das concentrações e proporções de nutrientes no diagnóstico da eutrofização

This review adresses the application of concentrations and ratios of nutrients (nitrogen and phosphorus) in the diagnosis of eutrophication in natural waters. We present a brief history of eutrophication and considerations on eutrophicating elements. The use of ratios in the diagnosis of eutrophication has limitations, since there are other parameters that prevent the proliferation of phytoplankton even under optimal nutrient conditions. Assays are used to identify the nutrient limitation to phytoplankton growth, while the trophic state index is used to assess the state of nutritional enrichment of an aquatic ecosystem. This work highlights the importance of the diagnostic study of eutrophication in natural waters subjected to the human impact, and suggests actions to improve their conditions, such as protection of riparian areas, terracing of agricultural areas, use of the required amount of fertilizer, and treatment of effluents from sewage to reduce the loads of N and P for lotic environments.