HELCOM Indicator Fact Sheets for 2006

As the environmental focal point of the Baltic Sea, HELCOM has been assessing the sources and inputs of nutrients and hazardous substances and their effects on ecosystems in the Baltic Sea for almost 30 years. The resulting indicators are based on scientific research carried out around the Baltic Sea under the HELCOM PLC, COMBINE and MORS monitoring programmes. During the past few years, HELCOM Indicator Fact Sheets have been compiled by responsible institutions and approved by the HELCOM Monitoring and Assessment Group. The Indicator Fact Sheets for 2006 are listed in the navigation menu on the left and older ones can be found in the Indicator Fact Sheet archive.

Changing seasons

The water surface temperature during 2005 was characterized by comparatively warm months in January, July as well as October, November and December and was in the annual average the warmest year of the investigation period 1990-2005. The wave climate in the northern Baltic Sea in 2005 was characterised by a stormy January and by a December that was calmer than usually. In spring, summer and autumn the wave climate was typical for each season. 

The 2005/2006 ice season started comparatively late with ice conditions developing during December like in warm winters. Ice conditions gradually became more difficult in the beginning of March with the largest ice cover (210,000 km²) reached on March 16^th.  The ice breaking up was in most waters was about a week later than normal with the Baltic Sea being ice free by the 29^th May 2006.

Life pulsates according to water inflows

The present state of the Baltic Sea is not only the result of anthropogenic pressures but is also influenced by hydrographic forces such as water exchange between the Baltic Sea and the North Sea. After the major Baltic inflow in January 2003, which renewed most of the deep water in the Baltic Sea, a new stagnation period started in 2004 for the deep basins of the Baltic. Hydrogen sulphide levels have steadily increased again in the East Gotland Basin, although the extent of anoxic bottoms is not as great as it was in 2002. 

The Baltic Sea continues to suffer the impacts of human activities

Baltic Sea habitats and species are threathened by eutrophication and elevated amounts of hazardous substances as a result of decades of human activities in the sea and its surrounding catchment area.

The inputs of some hazardous substances to the Baltic Sea have been reduced considerably over the past 20 to 30 years. In particular discharges of heavy metals have decreased. The significant proportion of heavy metals* enter the Baltic Sea via rivers or as direct discharges: 40% for mercury and 50% for cadmium and lead. The remaining share of inputs is mainly from atmospheric deposition of these heavy metals. Dioxin emissions to the air have decreased significantly for some Baltic coastal states (but increased for others), and a 33% reduction in atmospheric depositions of dioxins has been observed from 1990 to 2004. 

A range of anthropogenic activities contirbute to significant nutrient inputs to the sea, which enter the sea either via runoff and riverine input or through direct discharges. Although nutrient inputs from point sources such as industries and municipalities have been cut significantly, the total input of nitrogen to the Baltic Sea is still over 1 million tonnes per year, of which approximately 25 % enters as atmospheric deposition on the Baltic Sea and 75 % as waterborne inputs. The total input of phosphorus to the Baltic Sea is ca. 25 thousand tonnes and enters the Baltic Sea mainly as waterborne input with the contribution of atmospheric deposition being only 1-5 % of the total. The main source of nutrient inputs is agriculture.

The waterborne loads for nitrogen and phosphorus* were significantly higher  in 2004 compared to the previous year, partly due to the natural flutuations in inputs caused by varying hydrographical conditions. Annual emissions of nitrogen from the HELCOM Contracting Parties were lower in 2004 than in 1995. Mainly because of interannual changes in meteorology, no significant temporal pattern in nitrogen depositions to the Baltic Sea and its sub-basins can be detected. The total deposition of nitrogen to the Baltic Sea in 2004 was 214 thousand tonnes with the depositon of oxidized, reduced and total nitrogen 15%, 9% and 13% lower than in 1995. 

Eutrophication intensifies phytoplankton blooms

Eutrophication is the result of excessive nutrient inputs and is an issue of major concern almost everywhere around the Baltic Sea area. The satellite-derived chlorophyll-like pigments in the Baltic Sea are clearly higher than in the Skagerrak and North Sea. The average biomass production has increased by a factor of 2.5 leading to decreased water clarity, exceptionally intense algal blooms, more extensive areas of oxygen-depleted sea beds as well as degraded habitats* and changes in species abundance and distribution.

Annual integrated rates for sedimentation of organic matter* in the Gotland Sea have not show significant trends between 1995 and 2003. The bacterioplankton growth rate in the deep waters of the Gulf of Bothnian suggests at least good conditions in terms of oxygen consumption during the past decade. However, decrease in water clarity has been observed in all Baltic Sea sub-regions over the last one hundred years, with it being most pronounced in the Northern Baltic Proper and the Gulf of Finland.

No rising trend can be detected in spring blooms from 1992 to 2006 in the Gulf of Finland, the northern Baltic Proper or the Arkona Basin. In 2006, the spring bloom in the the Gulf of Finland was less than half the size of last years bloom and negligable in the Arkona Basin.

Due to the poor weather during the summer of 2004, there were no major cyanobacteria blooms that year. As a result, levels of  dissolved inorganic nutrients in the winter nutrient pool remained extremely high throughout the Baltic Proper and led to intense and widespread cyanobacteria bloom in the central Baltic in 2005. In 2005, the abundance of the nitrogen fixing cyanobacteria as well as the ratio between the toxic Nodularia spumigena and the non-toxic Aphanizomenon flos-aquae were almost at the same level as in the previous four years.

Sedimentation of these cyanobacteria, as well as transport by currents, reduced the concentration of dissolved inorganic phosphorus in the central Baltic Proper. Levels remained extremely high in the Arkona Basin and in the Gulfs of Finland and Bothnia, however. This remaining excess phosphorus was the cause of the even-more widespread cyanobacteria blooms of summer 2006. 

Heavy metals and organic pollutant still persistent in marine environment

Despite the considerable reductions in the inputs of some hazardous substances to the Baltic Sea, the concentrations of heavy metals and organic pollutants in sea water are still several times higher in the Baltic Sea compared to waters of the North Atlantic. 

Concentrations of contaminants in fish vary according to substance, species and location, but in general, the concentrations of cadmium, lead and PCBs have decreased. Still the content of dioxins in the fish muscle may exceed the authorized limits set by the European Commission.

Overall the levels of radioactivity in the Baltic Sea water and biota have shown declining trends since the Chernobyl accident in 1986, which caused significant fallout over the area. Radioactivity is now slowly transported from the Baltic Sea to the North Sea via Kattegat. The amount of caesium-137 in Baltic Sea sediments however has remained largely unchanged, with highest concentrations in the Bothnian Sea and the Gulf of Finland.

Ecosystem effects

Variables such as climate-induced changes in temperature and salinity, fishing pressure, as well as variations in bottom water oxygen conditions (climate and eutrophication induced) have significant impacts on ecosystem structure.

In 2005, marine phytoplankton species Cerataulina pelagica, Chaetoceros brevis and Dactyliosolen fragilissimus penetrated far into the Baltic Proper and up to the Lithuanian coast in late autumn. They may indicate warm water inflows that cannot be identified on the basis of salinity measurements.

Despite a lack of consistency, high water temperatures during growth seasons in recent years have possibly affected coastal fish communities in Bothnian Sea. This is reflected as an increased recruitment success and/or increased individual growth rate of dominating, warm water dwelling, species.

The degenerating state of the the Baltic Sea affects marine life in many ways. Macrobenthic communities* have been severely degraded by increased eutrophication throughout the Baltic Proper and the Gulf of Finland and are below the longterm averages. Populations of the amphipod Monoporeia affinis have crashed in the Gulf of Bothnia and the invasive polychaete Marenzelleria viridis has spread.

The lack of salt water inflows has diminished the habitat layer for heterotrophic organisms in general and those of marine origin, such as copepods, in particular. Although the total number of copepods* has not change dramatically, the ratio between different species has been affected which in turn has had consequences in higher trophic levels. Herring, for instance, has suffered from a decline in its favoured diet and now competes with sprat for other species of copepods.

Decrease in observed illegal oil spills

An increase in the number of maritime transportation during the past decade has increased the potential for an increased numbers of illegal oil discharges. Since the late 1990s ships have been required to deliver oil or oily water from the machinery spaces as well as from ballast or cargo tanks to reception facilities in ports. As of 1999, the number of observed illegal oil discharges has gradually been decreasing every year, but in 2004, still almost 300 illegal spills were detected.

*These Indicator Fact Sheets have not been updated since October 2005.

For reference purposes, please cite this indicator fact sheet as follows:
[Author’s name(s)], [Year]. [Indicator Fact Sheet title]. HELCOM Indicator Fact Sheets 2006. Online. [Date Viewed], http://www.helcom.fi/environment2/ifs/en_GB/cover/.

Last updated: 10.10.2006