Nutrient cycling and plant dynamics in estuaries: A brief review

Eutrophication of European estuaries due to massive nutrient loading from u rban areas and diffuse runoff from extensively cultivated land areas is ana lysed. Consequences for the ecology of estuaries, namely changes in plant s pecies composition, which also affects heterotrophic organisms, are approac hed based on examples showing that the result is often a fundamental struct ural change of the ecosystem, from a grazing and/or nutrient controlled sta ble systems to unstable detritus/mineralisation systems, where the turnover of oxygen and nutrients is much more dynamic and oscillations between aero bic and anaerobic states frequently occur. Several relevant aspects are exa mined, namely the influence of rooted macrophytes on nutrient dynamics, by comparing bare bottom sediments with eelgrass covered sediments, primary pr oduction and the development of organic detritus, and hydrodynamics and its relations to the spatial distribution of macrophytes in estuarine systems. (C) 1999 Editions scientifiques et medicales Elsevier SAS.