Nitrogen cycling in coastal marine ecosystems

It is generally considered that nitrogen availability is one of the major f actors regulating primary production in temperate coastal marine environmen ts. Coastal regions often receive large anthropogenic inputs of nitrogen th at cause eutrophication. The impact of these nitrogen additions has a profo und effect in estuaries and coastal lagoons where water exchange is limited . Such increased nutrient loading promotes the growth of phytoplankton and fast growing pelagic macroalgae while rooted plants (sea-grasses) and benth ic are suppressed due to reduced light availability. This shift from benthi c to pelagic primary production introduces large diurnal variations in oxyg en concentrations in the water column. In addition oxygen consumption in th e surface sediments increases due to the deposition of readily degradable b iomass. In this review the physico-chemical and biological factors regulati ng nitrogen cycling in coastal marine ecosystems are considered in relation to developing effective management programmes to rehabilitate seagrass com munities in lagoons currently dominated by pelagic macroalgae and/or cyanob acteria. (C) 1999 Federation of European Microbiological Societies. Publish ed by Elsevier Science B.V. All rights reserved.