Eutrophication impacts on salt marshes natural metal remediation

Abstract

Salt marshes are a very important part of the estuarine ecosystem, with an important role within the biogeochemical cycles, being areas of high primary production, which also contribute importantly as shoreline stabilizers. Besides, periodical tidal flooding of salt marshes also causes the transport of significant quantities of pollutants, which tend to accumulate in the marsh ecosystem. Therefore, salt marshes are considered to be important sinks namely of heavy metals. Their important role has been recently admitted by the inclusion of these ecosystems in the European Water Framework Directive (WFD). Multiple services of wetlands and its value are already well known, such as excess contaminant and nutrient removal. Nitrogen concentrations in salt marsh sediments have been increasing, mostly owing to the anthropogenic activities increase in the estuarine surrounding areas. This leads to an increase in the halophyte biomass and an apparent reduction in the phytoremediation capacity. Although eutrophication processes apparently reduce the natural remediation capacity of the marsh toward the estuary, it also allows an increase in the potential sink capacity and a reduction of the contaminated detritus export into the estuarine system and into the food web.