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Nitrogen Inputs from Agriculture: Towards Better Assessments of Eutrophication Status in Marine Waters


Nutrient enrichment of coastal marine waters caused by losses of nitrate (NO3 ) from agriculture is an increasing global problem. In the European Union, the Nitrates Directive (ND) of 1991 was meant to be a cornerstone in reducing eutrophication effects in coastal waters downstream from intensively farmed catchments. Although reductions in losses of nitrate have been attained, very few Member States have yet been able to reduce eutrophication effects caused by inputs of NO3 from agriculture. We report trends in concentrations of NO3 and chlorophyll-a (Chl-a) in Danish coastal and open marine waters during the period from 1996 to 2011 together with an assessment of eutrophication status based on multiple indicators (e.g. nutrient concentrations, Chl-a, submerged aquatic vegetation and benthic macroinvertebrates). Despite decreasing concentrations of both NO3 and Chl-a, Danish coastal waters are not yet to be classified as ‘unaffected by eutrophication’. In order to improve future pan-European evaluations of the effectiveness of the ND, we argue for the added value of including indicators and assessment principles from other European Directives, i.e. the Water Framework Directive and the Marine Strategy Framework Directive.

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The work was partially funded via ‘Rammeaftalen 2012-2015’ (i.e. ND reporting) and the Danish MSFD Initial Assessment project (i.e. assessment of eutrophication status). Special thanks to our colleagues Jacob Carstensen, Cordula Göke and Jørgen Windolf for assistance, and to Jens Brøgger Jensen for commenting on an earlier version of the manuscript.

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Correspondence to Jesper H. Andersen.

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The Electronic Supplementary Material to this paper includes two appendices: (S1) An introductory description of the study area and maps of concentrations and trends of nitrogen and chlorophyll-a in Danish marine waters. (PDF 2130 kb)

Appendix S2: HEAT classifications used for Table 2. (PDF 320 kb)

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Andersen, J.H., Fossing, H., Hansen, J.W. et al. Nitrogen Inputs from Agriculture: Towards Better Assessments of Eutrophication Status in Marine Waters. AMBIO 43, 906–913 (2014).

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  • Nitrates Directive
  • Nutrient enrichment
  • Eutrophication
  • Assessment
  • Water Framework Directive
  • Marine Strategy Framework Directive