| | | 11.1 Introduction |
Research on coastal eutrophication is lagging at least two decades beyond that in freshwater ecosystems. However, eutrophication problems are widespread in coastal ecosystems throughout Europe (e.g. []), and there is a need to identify research on dose-response relationships for these waters. For an entire range of different coastal ecosystems and mesocosm experiments there seems to exist a universal, robust dose-response relationship between dissolved inorganic nitrogen (DIN) input and primary production ([]; Figure 1). However, frequently increases in autotrophic biomass, not primary production, are used as a measure for eutrophication. Thus the dose-response relationship of nutrient addition and phytoplankton biomass is of primary interest to assess how increases in nutrient supply cause eutrophication effects. Also threshold nutrient levels on a strictly scientific basis and possible `points of no return' have to be defined in order to support legislation and actions to ensure the sustainability of coastal ecosystems. Because of the potentially vast socio-economic consequences of these measures, it is of utmost importance that the scientific advice be based on solid and robust knowledge. Despite of recent and future (e.g. the EU Water Directive) improvements of European water quality, in particular freshwater and the innermost coastal zone, substantial further work has to be carried out to adequately understand the dose-response relationships in the waters of the coastal zone. As we will see, there exists no universal nutrient input -- phytoplankton biomass dose-response relationship for European coastal waters. This induces significant challenges for the abatement of negative impacts of eutrophication and suggests regional differences in nutrient thresholds which remain to be defined in most European coastal seas.
| | | 11.1 Introduction |