Work due 01 Jun 2016

a) Classification The concentrations of nitrogen and phosphorus are reported after classification in three classes (low, medium, high). The classification uses class boundary values for each regional sea; for the NE Atlantic region, separate boundary values were calculated for the Greater North Sea and for the other seas. The classification distinguishes areas with low and high concentrations, but does not take into account that there may be large differences in natural background concentrations within regional seas. These differences are, for example, due to the riverine inputs into coastal waters. What is considered a “low” concentration in coastal waters might be considered “high” in offshore waters. One way of streamlining CSI 021 with nutrient indicators developed under regional seas conventions or European policy objectives, is to apply the same class boundaries, for instance as those used by RSCs or those applied in the WFD for transitional and coastal waters. As the implementation of the MSFD is still in progress, a future option will be to apply the environmental targets that are being developed under the MSFD. The threshold/targets established by the RSCs are already being evaluated and will be taken in consideration in future improvements of the indicator methodology. b) Geographical aggregation In the current methodology, two types of geographical aggregation are performed based on the Country Code and Sea Region. In both cases, differences in physical, chemical and biological characteristics between sampling stations are not taken into account. Measured nutrient concentrations should be related to natural background values that reflect spatial/geographical differences. c) Temporal scale Currently, the winter period is defined as January and February for all stations except for stations east of longitude 15 degrees (Bornholm) in theBaltic Sea. However, this definition may be too broad to reflect the climatic differences across the European sea regions. For example, for the Black Sea, it is suggested to also consider spring concentrations due to the nutrient enrichment of coastal waters as a result of increased riverine inputs (BSC, 2010) whereas annual means are deemed more suitable for the Mediterranean Sea. Adjustments of the definition of seasons per subregion are currently being evaluated and will be taken into consideration in the future revision of the indicator methodology.