Nitrogen cycling: A review of the processes, transformations and fluxes in coastal ecosystems

摘要

The coastal and marine nitrogen cycle occupies a complex, central role within the biogeochemical cycles. Human interventions in the earth system have risen to unprecedented levels, strongly influencing the global nitrogen cycle. The nitrogen cycle in the open ocean compared to coastal ecosystems appears to have remained unharmed, although recent observations have shown increasing anthropogenic influence. Projections suggest that global nitrogen cycle is being altered either directly by the continued addition of anthropogenically created fixed nitrogen to the earth system and its cascading effects, or indirectly through anthropogenically induced climate change. These alterations have the potential to cause positive feedbacks in the climate system, but they are neither well understood nor quantified. In the atmosphere, concentrations of the greenhouse gas, nitrous oxide and of the nitrogen-precursors of smog and acid rain are increasing. This unprecedented nitrogen loading has contributed to long-term decline in coastal fisheries. This article reviews some of the major processes, transformations and fluxes of nitrogen in the coastal ecosystems with reference to mangroves, occurring naturally and also due to human perturbations.