Signs of recovery in the Baltic Sea
Thirty-five years ago swimming was prohibited in some areas around the Baltic Sea. Today there is an outdoor swimming pool in the harbour of the city of Copenhagen, Denmark because of reductions in pollution loadings. The open waters of the Baltic Sea are also cleaner today as shown in a new unique study by Danish, Swedish and Finnish scientists.
– Our studies have shown improvements in water quality in most parts of the Baltic Sea, says Professor Daniel Conley in the Department of Geology, Lund University.
The article ”Long-term temporal and spatial trends in the eutrophication status of the Baltic Sea”, which has been published recently in the scientific journal Biological Reviews, reveals a unique overview of how the effects of nutrient enrichment has developed in different parts of the Baltic Sea over a 112 year period, from 1901 to 2012.
– Our study documents the very first signs of recovery in the Baltic Sea. Our work clearly demonstrates that long-term efforts to reduce inputs of nutrients – especially nitrogen and phosphorus, now are having large-scale effects.
Significant improvements are seen in the Kattegat. The same positive signals are found on other areas, even in an area like the southern Baltic Proper.
Nutrient enrichment of the Baltic Sea – also known as eutrophication – is often debated in more negative terms, not at least in the media. The coverage of areas depleted of oxygen, so-called dead zones is record high and algal blooms are a significant problem in many areas.
Is it really true that the negative trend of eutrophication in the Baltic Sea has been reversed?
– Yes! The available data show clear improvements, answers Daniel Conley.
– Indicators of environmental conditions show significant improvements in the surface waters, while bottom waters of the sea have worsened. However, overall we see that the improvements outweigh the setbacks.
The study also evaluates monitoring activities and the access to data used for assessing the eutrophication status.
During 1970s and 1980s, all Baltic Sea countries started harmonized and coordinated monitoring activities. But since then, especially during the recent 10 years, data availability has declined.
This decline, especially if it is accelerated, could potentially have profound implications in regard to our capabilities to document temporal trends in the environmental status of the Baltic Sea and to our ability to understand changes in the ecology of the Baltic Sea.
– Billions are being spent on reducing inputs of nutrient to the Baltic Sea in order to reduce the effects of eutrophication. It could seem illogical, that adequate resources are not allocated to document the positive effects of huge investments.
Denmark: Jesper Andersen, NIVA Danmark Water Reasearch + 45 2031 3221
Finland: Alf Norkko, Helsinki University + 338 2941 28104
Sweden: Bo Gustavsson, Stockholm University + 46 8 674 7593
International: Daniel J. Conley, Lund University + 46 7 749 4341