Marine Research Findings of the VECTORS Project

This website provides access to the research results of the VECTORS project, which can be used to support marine management decisions, policies and governance as well as future research and investment. VECTORS was a large scale project that brought together more than 200 expert researchers from 16 different countries. It examined the significant changes taking place in European seas, their causes, and the impacts they will have on society.

The importance of local nutrient loads for primary production in the Baltic Sea transition zone

Land-based nutrient reductions are necessary to obtain the goal of a good ecological status (GES) according to the Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD). The Danish transition zone is connecting the North Sea and the Baltic Sea. The area is shallow with narrow straits and highly complex hydrodynamics and characterised as eutrophic. It has been under discussion, if local nutrient reductions have a significant impact on GES in the area or if the advections of nutrients from the adjacent seas are of higher importance. This is an important question with regard to national and international management of marine areas. In this study, model scenarios were conducted for i) the planned nutrient reductions by the Danish Water Action Plans (DWAP) and ii) the DWAP combined with the HELCOM Baltic Sea Action Plan 2 (BSAP2) in comparison with year 2009 as a baseline.


Model results show that local nutrient reductions in the Danish transition zone (Baltic Sea) decrease primary production in the coastal areas and mainly in the Western parts and redistribute the production vertically.

Primary production was used as an indicator of eutrophication, because it is directly to nutrient loads across and within marine ecosystems. Annual primary production in the Danish transition zone was on average 150-200 g-C/m2/y from 2001 to 2010. The model results showed that DWAP nutrient reductions will reduce primary production by up to 15% mainly in the coastal areas and in the western part. The BSAP2 reductions strengthen this pattern but further reduce productivity in the open waters. Changes in nutrient loads also redistributed the primary production vertically, where lower nutrients caused a higher primary production below the surface layer. The higher production of oxygen below the pycnocline and the higher amount of organic matter reaching the bottom can potentially have consequences for food webs. In conclusion, National Water Action Plans in the Danish transition zone are important for the future management of local eutrophication problems especially in the coastal areas and in the western part with less water exchange with the Baltic Sea.

Lead Author:

Marie Maar
Aarhus Universitet (NERI)
Date of research:

Related articles:

Modelling future scenarios of biogeochemistry 

Population dynamics of sprat in the Baltic Sea 

Changes on stocks and management in saithe fishery 

The Baltic ATLANTIS model and global change

Variations of mortality of exploited stocks 

Changes in the upper trophic level: impact on fish

|< <  1 2 3 4 5 6 7 8 9 10 ...  > >|

Print this page

The content of this website may be subject to copyright, if you wish to use any of the information or figures please contact the attributed author(s).
This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 266445
© Vectors 2015. Coordinated by Plymouth Marine Laboratory.