Elsevier

Marine Pollution Bulletin

Volume 56, Issue 9, September 2008, Pages 1609-1617
Marine Pollution Bulletin

Nutrient budgets for European seas: A measure of the effectiveness of nutrient reduction policies

https://doi.org/10.1016/j.marpolbul.2008.05.027Get rights and content

Abstract

Socio-economic development in Europe has exerted increasing pressure on the marine environment. Eutrophication, caused by nutrient enrichment, is evident in regions of all European seas. Its severity varies but has, in places, adversely impacted socio-economic activities. This paper aims to evaluate the effectiveness of recently adopted policies to reduce anthropogenic nutrient inputs to European seas. Nitrogen and phosphorus budgets were constructed for three different periods (prior to severe eutrophication, during severe eutrophication and contemporary) to capture changes in the relative importance of different nutrient sources in four European seas suffering from eutrophication (Baltic Proper, coastal North Sea, Northern Adriatic and North-Western Black Sea Shelf). Policy success is evident for point sources, notably for P in the Baltic and North Seas, but reduction of diffuse sources has been more problematic.

Introduction

European marine ecosystems are being degraded as a consequence of continuously increasing pressure from anthropogenic activities. Several EU reports (EEA, 2001b, EEA, 2003a, EEA, 2003b, EEA, 2006) have highlighted the state of the marine environment, its increasing vulnerability and the need for further and stricter regulation of nutrient release. Eutrophication, a product of anthropogenic nutrient enrichment of water bodies, is an important current state change affecting the integrity of European seas (EEA, 2001a, EEA, 2003a). The EU has already adopted several directives and policies intended, directly or indirectly, to combat eutrophication (e.g. Nitrates Directive, Urban Waste Water Treatment Directive, Water Framework Directive, Common Agricultural Policy). The EU’s Water Framework Directive will coordinate much of this action within national and international catchment-scale (“River Basin District”) boundaries. Special measures and interventions (policy and legal reforms, investments in nutrient reduction technology at source) have been planned and partially implemented through coordinated international and national actions by the regional seas conventions and their secretariats (HELCOM in the Baltic, OSPAR in the North Sea, the Barcelona Convention in the Mediterranean and the Bucharest Convention in the Black Sea), together with associated projects and programmes. A new European Marine Strategy Directive is under review and will provide environmental quality targets (Good Environmental Status) that cannot be achieved without tackling eutrophication.

The intensity and spatial extent of eutrophication in European seas varies widely (Fig. 1), from small hot spots in enclosed bays (e.g. Kastela Bay in the Adriatic Sea, or Izmir Bay in the Aegean Sea), to sub-regional areas (e.g. the Wadden and Adriatic Seas) to almost entire seas (e.g. the Baltic Sea). To compare the effectiveness of nutrient regulation in four European regional seas, one case study of an area affected by eutrophication was selected for each sea, viz.: the Northern Adriatic for the Mediterranean Sea (Justic et al., 1987, Vollenweider et al., 1992), the coastal North Sea for the North-East Atlantic (Brockmann et al., 1988, Pätsch and Radach, 1997), the Baltic Proper (Wulff and Stigebrandt, 1989, Wulff and Stigebrandt, 1990) and the North-Western (NW) Black Sea shelf (Lancelot et al., 2002). The large spatial scale addressed in this study responds directly to the needs of policy-makers to guide the integrated management of Europe’s regional seas.

We applied a comparative aggregated mass balance approach on each sub-regional basin for three time periods. Our aim is to assess and to compare changes over past decades in the nutrient budgets (for nitrogen – N and phosphorus – P) of four sub-regional basins of four European seas. These changes reflect the nutrient loading of coastal waters, and changes in loading due to policy that is largely coordinated at the European scale. Finally we draw implications for the further development of nutrient reduction policy.

Section snippets

Case study areas

The main hydromorphologic characteristics of the four selected areas are summarized in Table 1.

The Northern Adriatic is a shallow enclosed basin (average depth 35 m) located between Italy and the Balkans and delimited by the 100 m isobath. The seabed is gently sloping and mostly sandy or muddy. It receives large fresh water discharges (about 80 km3/yr), particularly from Italian rivers (e.g. Po, Adige, Isonzo, Tagliamento) that drain intensely developed catchments where about 50% of Italy’s

Results

Fig. 2, Fig. 3 present the budgets. The Northern Adriatic appears to have the lowest nutrient fluxes (Fig. 2, Fig. 3a). Anthropogenic input of nitrogen from land-based sources is the major N-source and has been increasing steadily since the 1950s. Despite halving TP loads between the eutrophication and contemporary periods, P fluxes from sediments did not significantly change. This is probably indicative of a legacy of past nutrient enrichment or “memory effect”: historic P inputs accumulate in

Comparison of contemporary regional sea budgets

Comparison of contemporary total fluxes normalized to unit basin volume (Table 3) highlights both the physical characteristics of Europe’s regional seas and the socio-economic characteristics of their catchments.

The Northern Adriatic receives the bulk of its nutrients from rivers, although some N derives from atmospheric deposition. This suggests a strong anthropogenic influence on eutrophication. There is net export of nutrients to the Southern Adriatic, but of the four seas, it has the lowest

Final remarks

This study brings together available evidence to compare changes in nutrient budgets in Europe’s regional seas. It highlights the intrinsic differences among the seas in sensitivity to nutrient loading. At one end of the spectrum is the Baltic Proper. With hypoxia and cyanobacteria blooms, it is suffering severely from eutrophication despite receiving the smallest anthropogenic loads. Its sensitivity appears to be caused by limited flushing and climatic events that influence vertical mixing. At

Acknowledgments

The authors want to thank all scientists and institutions that provided data and advice for the implementation of all the budget models. This work has been carried out in the context of the EC-funded FP6 project European Lifestyle and Marine Ecosystems (ELME), contract no. GOCE – CT – 2003 – 505576. A special acknowledgment goes to all colleagues of the ELME project, and in particular to Darius Daunys, Jocelyn de la Cruz, Sven Hille, Olivia Langmead, Christopher Lowe, Sergej Olenin and Rolf

References (72)

  • J. Pätsch et al.

    Long-term simulation of the eutrophication of the North Sea: temporal development of nutrients, chlorophyll and primary production in comparison to observations

    J. Sea Res.

    (1997)
  • G. Radach et al.

    Nutrient dynamics in the North Sea: fluxes and budgets in the water column derived from ERSEM

    Netherlands J. Sea Res.

    (1995)
  • S. Reschke et al.

    The nature of organic matter in the Danube River particles and North-western Black Sea sediments

    Estuarine, Coast. Shelf Sci.

    (2002)
  • O.P. Savchuk

    Resolving the Baltic Sea into seven subbasins: N and P budgets for 1991–1999

    J. Mar. Syst.

    (2005)
  • G. Schernewski et al.

    The trophic state of the Baltic Sea a century ago: a model simulation study

    J. Mar. Syst.

    (2005)
  • B. Schneider et al.

    The surface water CO2 budget for the Baltic proper: a new way to determine nitrogen fixation

    J. Mar. Syst.

    (2003)
  • P. Stalnacke et al.

    Trends in nutrient concentrations in Latvian rivers and the response to the dramatic change in agriculture

    J. Hydrol.

    (2003)
  • F.B. Van Es et al.

    The use of a model to assess factors affecting the oxygen balance in the water of the Dollard

    Netherlands J. Sea Res.

    (1982)
  • R.A. Vollenweider et al.

    Eutrophication, structure and dynamics of a marine coastal system: results of ten-year monitoring along the Emilia-Romagna coast (Northwest Adriatic Sea)

    Sci. Total Environ.

    (1992)
  • Z. Witek et al.

    Nitrogen and phosphorus budgets of the Gulf of Gdansk (Baltic Sea)

    Estuarine, Coast. Shelf Sci.

    (2003)
  • N.M. Almazov

    Stok ratverennykh soleyi biogennykh veschetv kotorye vynoseatsya rekami USSR v Chernoe More

    Naukovi Zapiski Odes. Biol. St. Kiev

    (1961)
  • Behrendt, H., Dannowski, R., Deumlich, D., Dolezal, F., Kajewski, I., Kornmlich, M., Korol, R., Mioduszewski, W.,...
  • Behrendt, H., Huber, P., Kornmilch, M., Opitz, D., Schmoll, O., Scholz, G., Uebe, R., 2000. Nutrient emissions into...
  • W.R. Boynton et al.

    Inputs, transformations, and transport of nitrogen and phosphorus in chesapeake bay and selected tributaries

    Estuaries

    (1995)
  • N. Brion et al.

    The North Sea: source or sink for nitrogen and phosphorus to the Atlantic Ocean?

    Biogeochemistry

    (2004)
  • U. Brockmann et al.

    North Sea nutrients and eutrophication

  • J. Carstensen et al.

    Coastal eutrophication and trend reversal: a Danish case study

    Limnol. Oceanogr.

    (2006)
  • Cociasu, A., 2004. Riverine Inputs. Report No. RER/01/G33/A/1G/31: control on eutrophication, hazardous substances and...
  • D.J. Conley et al.

    Hypoxia in the Baltic Sea and basin-scale changes in phosphorus biogeochemistry

    Environ. Sci. Technol.

    (2002)
  • D.J. Conley et al.

    Coastal eutrophication and the Danish National Aquatic Monitoring and Assessment Program

    Estuaries

    (2002)
  • DaNUbs, 2005. Nutrient management in the Danube Basin and its impact on the Black Sea – final report. Institute for...
  • G.M. Daskalov

    Overfishing drives a trophic cascade in the Black Sea

    Mar. Ecol. Prog. Ser.

    (2002)
  • D. Degobbis et al.

    Long-term changes in the northern Adriatic ecosystem related to anthropogenic eutrophication

    Int. J. Environ. Pollut.

    (2000)
  • J. Druon et al.

    Comparative assessment of large-scale marine eutrophication: North-sea area and Adriatic Sea as case studies

    Mar. Ecol. Prog. Ser.

    (2004)
  • EEA, 2001a. Eutrophication in Europe’s coastal waters. EEA report 7,...
  • EEA, 2001b. Marine and coastal environment – Annual topic update 2000. Topic report 11, EEA, Copenhagen...
  • Cited by (0)

    View full text