Implementation of European marine policy: New water quality targets for German Baltic waters

Abstract

a b s t r a c tA full re-calculation of Water Framework Directive reference and target concentrations for German coastal waters and the western Baltic Sea is presented, which includes a harmonization with HELCOM Baltic Sea Action Plan (BSAP) targets. Further, maximum allowable nutrient inputs (MAI) and target concentrations in rivers for the German Baltic catchments are suggested. For this purpose a spatially coupled, large scale and integrative modeling approach is used, which links the river basin flux model MONERIS to ERGOM-MOM, a three-dimensional ecosystem model of the Baltic Sea. The years around 1880 are considered as reference conditions reflecting a high ecological status and are reconstructed and simulated with the model system. Alternative approaches are briefly described, as well. For every WFD water body and the open sea, target concentrations for nitrogen and phosphorus compounds as well as chlorophyll a are provided by adding 50% to the reference concentrations. In general, the targets are less strict for coastal waters and slightly stricter for the sea (e.g. 1.2 mg/m³ chl.a summer average for the Bay of Mecklenburg), compared to current values. By taking into account the specifics of every water body, this approach overcomes the inconsistencies of earlier approaches. Our targets are well in agreement with the BSAP targets, but provide spatially refined and extended results. The full data are presented in Appendix A1 and A2.To reach the targets, German nitrogen inputs have to be reduced by 34%. Likely average maximum allowable concentrations in German Baltic rivers are between 2.6 and 3.1 mg N/l. However, the concrete value depends on the scenario and uncertainties with respect to atmospheric deposition. To our results, MAI according to the BSAP may be sufficient for the open sea, but are not sufficient to reach a good WFD status in German coastal waters.

Biotope map of the German Baltic Sea

“…bottom velocity) are modelled over a period from 2003 to 2010 using a regionally adopted version of GETM (Klingbeil et al, 2014). Light penetration depth (LPD, averaged over the vegetation period from March until October), intensity of oxygen depletion (number of days/year < 2 ml/l) and bottom detritus concentration (lmol/l) are modelled over the period from 2000 to 2010 using a regional adaptation of the ERGOM model (Friedland et al, 2012;Schernewski et al, 2015).…”

“…Now, more and more information the abiotic environment is becoming available in full-coverage (Diesing et al, 2014). Fine scale modelling of environmental parameters in the region has been achieved recently (Friedland et al, 2012;Klingbeil et al, 2014;Schernewski et al, 2015). In contrast, point sampling remains the most common method for biological surveys.…”

Looking beyond stratification: a model-based analysis of the biological drivers of oxygen deficiency in the North Sea

“…As the WFD assessment depends strongly on the description of pristine conditions, related to natural nutrient levels ), ecosystem models can provide a consistent picture of the North Sea O 2 dynamics under these pristine conditions and of the effects of WFD reductions (Schernewski et al, 2015). As river load reductions within the WFD regulation affect the entire North Sea ecosystem, also in terms of bottom O 2 conditions, these scenarios can also be interpreted within the frame of the Marine Framework Directive (MSFD), which involves O 2 as one of the main descriptors for the definition of the "Good Environmental Status".…”

Ecosystem services provision today and in the past: a comparative study in two Baltic lagoons

“…Kjerfve (1994) relates this phenomenon with increasing anthropogenic environmental problems. The Szczecin Lagoon has experienced a decrease in water quality, an increase in eutrophication events, a decrease in water transparency and a decrease in the overall ecological status (Humborg et al 2000;Schernewski et al , 2012bSchernewski et al , 2015Schernewski and Wielgat 2001;Wolnomiejski and Witek 2013). The consequence of this decrease is the influence this section exerts in the regulation of other services and sections (Maes et al 2015).…”