Aarhus University Seal / Aarhus Universitets segl

No. 167: Marine areas 2014

Hansen, J.W. (red.) 2015: Marine områder 2014. NOVANA. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 142 s. - Videnskabelig rapport fra DCE - Nationalt Center for Miljø og Energi nr. 167. http://dce2.au.dk/pub/SR167.pdf

Summary

In 2014, the positive development from previous years was maintained in spite of increased run-off and thus increased nutrients from land at the beginning of the year as well as unusually high temperatures and generally light breezes during the summer. These conditions intensified the stratification of the water column and stimulated the development of oxygen depletion in the bottom water. Despite the relatively large run-off at the beginning of the year, the nutrient concentrations were very low, and in some cases the lowest since 1989.

The growth (primary production) and the amount (chlorophyll) of phytoplankton were at a low level, and the water clarity was relatively high – the conditions of the water bodies were, however, slightly worse than in 2013.

The generally positive development of eelgrass in recent years was maintained or improved in most areas in 2014, and in the coastal areas and on the stone reefs the depth distribution of macro algae had increased significantly compared to previous years.

The development of oxygen depletion in the open waters was modest despite the unfavourable weather conditions, but the oxygen depletion in fjords and coastal areas began earlier, ended later and was more intensive than in recent years.

The populations of harbour seal and grey seal were considerably larger than just a few years ago.

In spite of the improved state of the environment, the Danish waters are still very vulnerable to stress and still far away from the objective of good environmental status. In addition to the load of nutrients (eutrophication), the environmental state is also affected by many other conditions such as environmentally hazardous substances, fishery and climate change.

The concentrations of most of the hazardous substances were at the same levels, or lower, as in previous years, but especially the concentrations of mercury, TBT, PCB and one tar compound (PAH) were so high at several locations that adverse biological effects might occur.

In summary, the data from the national monitoring programme show that the effort made to secure an improved marine environment has succeeded, even though the response of the marine environment to reduced stress is very complex and takes a long time.