Human impacts on Nitrogen and Phosphorus concentrations in the North Sea

Abstract

This study evaluates the temporal and spatial variations in nutrient concentrations within the period of 1990-2011, with the aim to assess the effectiveness of legislative implementation and associated control measures within the period. Annual nutrient emission data were been obtained from OSPAR’s Joint Assessment Monitoring Programmes (JAMP’s) to provide values of riverine flow, direct discharge and atmospheric concentration. Temporal assessments of annual nutrient emissions were carried out on a European and national scale, using statistical analysis within periods of legislative change to assess the regional and sub-regional response to legislative implementation. Nutrient data were also obtained from the EEA database “Waterbase” providing winter concentrations from sampling points within the North Sea region. These data were used for spatial analysis of nutrient concentrations within periods of legislative change, which was achieved via the geospatial plotting of values using GIS software. Changes in inputs of nitrate and phosphate have been determined within periods of assessment, indicating positive response to legislative change. However variations in response have been seen on both European and regional scale, indicating varied effectiveness of control measures associated with legislative implementation. Spatial variations within assessment periods have also reflected varied responses of nitrate and orthophosphate concentrations to legislative change on a sub-regional level, indicative of a non-linear relationship between the coastal response to land-based controls of diffuse and point source emissions. Where hydromorphological and physio-chemical factors have been considered, it has also highlighted the need for greater evaluation of the coastal interactions which influence the residence time of nutrients and occurrence of eutrophication. This study concludes that while reductions in emissions have been attributable to legislative change, a combined approach to monitoring and management is required to further understand the behaviour of nutrients within complex aquatic systems and to further the control of emissions and associated impacts of nutrients.