Comparison of the biogeochemistry of lakes and estuaries: ecosystem processes, functional groups, hysteresis effects and interactions between macro- and microbiology

This paper reviews the biogeochemistry of carbon, nitrogen, phosphorus and their associated minor elements (iron and sulfur) in rivers, lakes and estuaries. The biogeochemistry of these elements can be explained by the physiology and stoichiometry of the major functional groups of micro- and macrobiota in these ecosystems. Furthermore, the global patterns of nitrogen and phosphorus limitation in freshwater and marine systems are explicable in terms of evolutionary differences between the major functional groups in freshwater and marine ecosystems, and their physiology and stoichiometry, as well as the interactions of carbon, iron, water residence times and ionic strength as the water flows from catchments to the sea. The highly non-linear responses of aquatic ecosystems to changing catchment loads of major and minor elements are explained by the interactions of the major functional groups and by competition between the pelagic and the benthos for nutrients and light.