HELCOM Baltic Sea Environment Fact Sheets for 2011

As the environmental focal point for 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 fact sheets are based on scientific research carried out around the Baltic Sea under the HELCOM PLC, COMBINE and MORS monitoring programmes. Since 2002, HELCOM Baltic Sea Environment Fact Sheets (previously called HELCOM indicator fact sheets ¹) have been compiled by responsible institutions around the Baltic and approved by the HELCOM Monitoring and Assessment Group for publication. The Baltic Sea Environment Fact Sheets for 2011 and 2010 are listed in the navigation menu on the left and older ones can be found in the Baltic Sea Environment Fact Sheets archive.

Note that HELCOM is developing a "core set" of indicators for assessing the progress towards reaching the goals and objectives of the HELCOM Baltic Sea Action Plan. So far a demonstration set of core eutrophication indicators has been adopted, and work is on-going under the HELCOM CORESET project to develop indicators for hazardous substances and biodiversity.  Some of the Baltic Sea Environment Fact Sheets are being converted into "core indicators".

Changing seasons

The development of the sea surface temperature in the first five month of 2010 was mainly characterized by monthly mean temperatures below the long-term average (2000-2009). March was the coldest month of the year in the Baltic Sea. July was the warmest month of the year with maximum temperatures of 20-23°C. Due to strong atmospheric cooling in the November-December 2010, the sea surface temperature decreased sharply in December. December 2010 was the coldest since 1990, with the exception of 1998 in the western Baltic Sea and 2002 in the central Baltic Sea.

The ice season of 2010-2011 severe and in terms of ice extent the greatest in the Baltic since the record winter of 1986-1987. The largest ice cover (309,000 km²) was reached a few days earlier than average on the 25^th of February. On the 25^th May the Baltic Sea was ice-free. The duration of the ice winter in the northern sea areas of the Baltic Sea was about one month longer than average.

Due to the ice conditions in 2010, wave measurements could be carried out throughout the year only in the open sea area of the Southern Baltic Proper.  In January the wave climate was rougher than usual in the Western Baltic Proper while further north, at stations where measurements could still be carried out, the wave climate was calmer. In the northern parts of the Baltic Sea and in Skagerrak the summer was typical for the season while in the southern parts of the Baltic Sea it was calmer than usual. November was clearly rougher than usual in all the other stations were measurements were made except in Skagerak.

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 meteorological conditions and hydrographic forces such as water exchange between the Baltic Sea and the North Sea. The inflow of waters from the Kattegat into the Baltic Sea during the past decade has followed a quite unusual sequence of events: a warm summer inflow 2002 was followed by a cold gale-forced one in January 2003, and again by a warm summer inflow 2003. All together they terminated the stagnation period in the Baltic deep water started in 1995. The period afterwards was characterized by low inflow activities with only a slight intensification since 2006. Except for the southern Baltic, the stagnation period lasting since 2004/2005 resulted in a continuous increase of hydrogen sulphide concentrations in the central basins. A baroclinic inflow during the summer of 2006, followed by small barotropic inflows in 2007 and 2009 caused again very high temperatures observed in the central Baltic deepwater. As a result of the minor, but frequent, barotropic and baroclinic inflow activity, no hydrogen sulphide was found in the Bornholm Basin in 2008, 2009, 2010 or the first half of 2011.

This stagnation period has resulted in poor oxygen conditions in the deep basins* of the central Baltic. The area of the central Baltic affected by hypoxia (oxygen deficiency) and anoxia (absence of oxygen) remains very high, although a slight improvement (reduction) in the anoxic area has occurred in the last three years. Deep water salinity remains high in the Baltic Proper, which hampers vertical mixing. Hydrogen Sulphide is present in the deep water of the East Gotland Basin, the Northern Baltic Proper and West Gotland Basin.

Meteorological conditions, including wind patterns and precipitation affect the inflow of water from the catchment area and the deposition of pollutants directly onto the sea. Since 2002 the total runoff to the Baltic Sea has been below the mean value except for 2008 and 2010. During 2003 and 2006 the flow rates were extremely low. If 2010 was the first year of many to come with flow rates above mean, or if it was an exception in a longer period of lower flow rates, the future will tell. During the period 1950 – 2010, the total runoff to the Baltic Sea area shows no long-term trend. On the other hand this time period is characterised by dry and wet periods lasting for a couple of years to a decade generally following the NAO index.

The Baltic Sea continues to suffer the impacts of human activities

Baltic Sea habitats and species are threatened 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 reduced considerably over the past 20 to 30 years, in particular discharges of heavy metals. In 2006, the reported waterborne loads of mercury, lead and cadmium* entering the Baltic Sea were 10.8 tonnes, 274 tonnes and 47.5 tonnes, respectively. During the period 1994-2006 riverine annual heavy metal loads (notably cadmium and lead) seem to have decreased for most of Contracting Parties. 

Emissions of heavy metals to the air  from HELCOM countries in 2009 amounted to 105 tonnes of cadmium, 38 tonnes of mercury, and 1,074 tonnes of lead. When compared to emissions in 1990, the emissions decreased by 49% for cadmium, 53% for mercury, and 87% for lead.

During the same period, the amount of cadmium, mercury and lead deposited on the Baltic Sea via the atmosphere has decreased by 48%, 23%, and 72% respectively.

Annual emissions of dioxins and furans from HELCOM countries have decreased by 42% during the period 1990-2009. Since emissions had decreased by 48% in 2000, they have gradually increased from 2001 to 2009.  In the same period, the annual atmospheric deposition fluxes of PCDD/Fs over the Baltic Sea have decreased by 57%. The most significant decrease in PCDD/F atmospheric deposition can be noted for the Belt Sea (67%) and the Kattegat (65%).

A range of anthropogenic activities contribute to the significant inputs of nutrient to the sea, which enter the sea via runoff, riverine input, through direct waterborne discharges or via atmospheric deposition. 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 almost 800,00 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 in 2006 was ca 25,000 tonnes and entered 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 loads to the Baltic Sea is agriculture.

When comparing the 2008 waterborne nutrient loads* to the 10 year average (1999-2008), waterborne nitrogen input load has decreased by about 12%, and phosphorus by almost 20%. The riverine, coastal and point source flow in 2008 was 10% lower than the 10-year flow average suggesting that a large part of the nitrogen and phosphorus reductions are due to hydrological variations. Total waterborne phosphorus inputs have clearly decreased suggesting positive effects of the implementation of load reduction measures in catchment area. It is known that the load reduction measures are particularly efficient for phosphorus in municipal wastewater treatment plants.

For most of the HELCOM countries, there was a decline in the annual emissions of nitrogen to the air during the period 1995 – 2009. The opposite trend can be noticed for ammonia emissions from Finland and Latvia and nitrogen oxides (NOx) emissions from Russia. NOx emissions from Lithuania have remained largely the same . Emissions from outside the Baltic Sea region add to the airborne nitrogen loads entering the Baltic, as do emissions from shipping. Emissions of NO_x, CO and CO₂ from ships as well as fuel and energy consumption have all increased, but SO_x and particulate matter emissions from shipping decreased by 20% and 9.5% respectively from 2009 to 2010. Reductions can be attributed to significant policy changes, which reduce the maximum allowable sulphur content in marine fuels during voyages and harbor stays

Mainly because of interannual changes in meteorological conditions, annual nitrogen depostion to the Baltic Sea and its sub-basins varies significantly from one year to another in the period 1995 - 2008. Annual depositons of oxidised, reduced and total nitrogen in 2009 was respectively 13%, 5% and 10% lower than in 1995. There has, however, been a continous (approximately 10%) increase in oxidised, reduced and total nitrogen deposition on to the Baltic Sea during the period 2002 – 2009.

Eutrophication intensifies phytoplankton blooms

Eutrophication is the result of excessive nutrient inputs to the ecosystem and is an issue of major concern almost everywhere around the Baltic Sea area. The excess nutrients have resulted in an increased average biomass production 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.***

A decrease in summer 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. An increase in water transparency during the last 20 years has been detected in the Bornholm and Arkona Seas and in Kattegat and the Eastern Gotland Basin the decreasing trend has ceased during the past 20 years with the water transparency remaining at about the same level.

The spatial distribution of inorganic (primary bio-available) nutrients (in surface waters, during winter) highlights problem areas, and shows the availability of nutrients for the spring bloom. Changes in the spatial distribution may indicate changes in the hydrography or the effect of remedial works. Dissolved inorganic nitrogen (DIN) levels during December 2010 to February 2011 remained well below the 1993 – 2002 average, except in some nearshore areas. Winter levels of dissolved inorganic phosphorus (DIP) remain above the 1993 - 2002 average in the surface waters from the Western Gotland Basin Baltic Proper to the Bothnian Bay.

In the southern Baltic Sea the phytoplankton biomass  was higher during the spring bloom and high summer. Diatoms dominated the spring bloom species composition and especially the diatom Detonula confervacea showed increase in abundance. During the summer bloom higher amount of blue-green algae was observed. Observed chlorophyll a values were within long term standard deviations except during one week in the southern Baltic Sea. Annual phytoplankton succession followed normal pattern in the Baltic Sea. In the Gulf of Finland the spring bloom was well developed and the peak biomass value was higher than the long term mean.

Cyanobacterial blooms in the Baltic Sea during the summer of 2011 were observed for over a two month period, from 29 June to 5 September. During 30 days from the 7 July, extensive blooms were seen, but the most massive accumulations stayed away this year. The Bothnian Sea which usually blooms in August, also had an unusually prolonged bloom. Even though the bloom was observed for a long time the normalized bloom intensity, extent and duration was low compared to 2010. No comparison should not yet be made with the blooms between 1997 and 2009 since the detection method used during 2010 & 2011 is new.

Due to high variability, no clear trends in the biomass of the bloom forming cyanobacteria genera Aphanizomenon, Nodularia and Anabaena are visible for the period studied (2000-2010).

The satellite-derived chlorophyll-like pigments*** in the Baltic Sea are clearly higher than in the Skagerrak and North Sea. The chlorophyll a concentration*** exceeded 3mg m^-3 for more than 60% of the days during the summer period 2006 (June-September) in the Arkona, Bornholm, Easter Gotland and Northern Gotland Basins and Gulf of Riga and Finland.

Bacterioplankton growth rate  is an indicator of the decomposition of organic matter, and thus indicates the rate of oxygen consumption that may lead to oxygen deficiency in the water column. Bacterioplankton accounts for half of the pelagic oxygen consumption. The bacterioplankton growth rate indicates good trophic status in the off-shore Bothnian Bay and Bothnian Sea. Deep water growth rates were only 50% higher than at corresponding depths in the Atlantic Ocean which lacks excess enrichment. The bacterial growth has declined for at least the past 10 years, suggesting a reduced sedimentation of organic matter in the two basins and thus poorer nutrient status.

Hazardous substances still persistent in the 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. Although there is no consistant trend in mercury concentrations, the concentrations of lead and PCBs have decreased significantly as a result of measures taken to reduce discharges of of these contaminant to the environment. Recent levels of cadmium in herring are not significantly lower compared to the concentrations measured at the beginning of the 1980s, despite measures taken to reduce discharges of cadmium to the environment.

The concentrations of TCDD-equivalents (dioxins) in guillemot eggs show an overall significant decreasing trend, however, not during the recent 20 years. Only one decreasing trend could be observed in herring muscle from the Baltic and the Swedish west coast. The concentrations of TCDD-equivalents are on average higher in the Bothnian Sea compared to the Baltic Proper and the Swedish west coast. TCDD-equivalents show declining trends on most localities due to measures taken to reduce emissions between 1969 and 1985 but after that, this decline has ceased, contrary to e.g. PCBs.

As for the concentrations of flame retardants HBCD in guillemot egg show a significant increase of about 3% per year since 1969, while on the contrary, a decreasing trend is indicated for HBCDD in herring muscle from the same area during the last decade. No trends can be found at the other monitored localities.  

The levels of perfluorooctane sulfonate (PFOS) in Guillemot eggs show a significant increase of 7-10% for the whole time period, which is equal to 25-30 times higher levels in the early 2000s than in the late 1960s. No trend can be observed during the last ten year, but, due to the long environmental half-live of PFOS it cannot be expected that levels will decrease rapidly.

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. Overall, the Cs-137 activity concentrations in herring and flounder muscle as well as of surface waters in the Baltic Sea basins are approaching pre-Chernobyl levels. In general, the discharges of radionuclides from local nuclear power plants into the Baltic Sea have shown decreasing trends during the last decade and contribute less than 1% of total inputs of radioactivity into the Baltic Sea. 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. Radioactive fallout over the Baltic Sea from the Fukushima accident in Japan in March 2011 is very small and may not be detectable in seawater and fish. The corresponding radiological risks are estimated to be negligible.

Impacts of shipping on the marine environment

A decreasing trend in the number of observed illegal oil discharges, despite rapidly growing density of shipping, increased frequency of the surveillance flights and improved usage of remote sensing equipment, is illustrating the positive results of the complex set of measures known as the Baltic Strategy, implemented by the HELCOM Contracting Parties. Altogether 149 oil spills were observed in 2010, which is 29 less than in 2009 and 61 less than in 2008. 

Furthermore, emissions of nitrogen oxides from shipping contribute to the eutrophication of Baltic Sea.

Ecosystem effects

The biodiversity of the Baltic Sea is affected by a wide range of anthropogenic as well as natural pressures. 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) all have significant impacts on ecosystem structure.***

As phytoplankton is an important component of the ecosystem, changes in phytoplankton events represent changes in the ecosystem. After the atypical range expansion of marine diatoms* to the south-eastern part of the Baltic Sea some of them still occur in phytoplankton, while others disappeared. In 2003-2006 a new marine diatom species appeared in Polish and Lithuanian waters which now often dominate in autumn phytoplankton community. During winter and spring 2007–2008 an unusual increase in a haptophyte** belonging to the genus Chrysochromulina was observed in several parts of the Baltic Sea. Although the reasons for the exceptional and prolonged development of this species are still unknown, monitoring data show that temperature, salinity and PO₄ were higher and DIN lower than average.  If the observed species is C. polylepis, a more regular occurrence of this potentially toxic species might be expected.

Macrobenthic communities*** have also been severely degraded by the increased eutrophication throughout the Baltic Proper and the Gulf of Finland and are below the long-term averages. Populations of the amphipod Monoporeia affinis have crashed in the Gulf of Bothnia and the invasive polychaete Marenzelleria viridis has spread.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, e.g. perch (Perca fluviatilis) and roach (Rutilus rutilus). Furthermore, the effects of changes in fishing pressure were observed in Gulf of Riga and in southern Baltic Proper. In the Gulf of Riga a high exploitation rate of piscivorous fish during mid 1990’s was clearly recognised and in the Baltic Proper, flounder (Platichthys flesus), has increased during the period possibly due to population recovery after a previous high exploitation rate.

The health status and reproductive ability of top predators such as seals and white-tailed sea eagle also reflect the state of the Baltic environment. Although the reproductive health investigated in grey seals has improved since the middle of 1980s and the population has been increasing at about 8% a year since 1990, results after 2005 indicate that the population growth trend is levelling off. The prevalence of intestinal ulcers has increased significantly in investigated juveniles since the mid 1980s and in adults in the 1990s, but these trends are now decreasing. Mean blubber thickness has decreased significantly in investigated 1-4 year old non pregnant grey seals during the last 5-10 years. 

The reproductive health of the Baltic ringed seal* females has improved since the 1970s, especially the prevalence of uterine occlusions has been steadily decreasing from 48% in the late 70’s to 30% in years 1991-2004. A majority of the health problems observed in the Baltic ringed seals have been suggested to be related to the high levels of environmental toxins such as organochlorines. A recent study indicates that PCB and DDE levels have decreased in the Baltic ringed seals and the health status of the seals has subsequently improved during the last decades.

Strong relationships have been found between white-tailed sea eagle reproductive ability  and concentrations of DDTs and PCBs in their eggs. Reproduction in the Baltic eagle population in the 1970s was reduced to a fifth of the pre-1950 population size. Following bans of DDT and PCB during the 1970s around the Baltic, eagle productivity began to recover in the 1980s and since the mid-1990s is largely back to a pre-1950 level. The population on the Swedish Baltic coast has increased at 7.5% per year between 1990-2010. Nevertheless, on the Swedish coast of the Bothnian Sea, nestling brood size remains below the pre-1950 level and the occurrence of dead eggs is significantly higher than in the Baltic Proper and Bothnian Bay, indicating a possible impact from other contaminants.

The White-tailed Sea Eagle is an example of a bird species which have severely suffered by persecution and later of contamination of the marine environment by hazardous substances. Strict conservation measures and the ban of hazardous substances allowed it to recover, however, until today anthropogenic mortality factors (especially intoxication and collisions) exert a pressure on the population development. It is likely that anthropogenic mortality has an impact on the population development, i.e. it is slowing down the current growth and expansion of the range.

The Great Cormorant was exterminated as a breeding bird in several Baltic countries during the 19^th century. The persecution continued during the 20^th century, and in the early 1960s the European breeding population of the continental subspecies sinensis had declined to 4 000 breeding pairs (bp). As a result of protection measures, breeding pair numbers started to increase during the 1970s and the Cormorant has since expand its range towards the northern and eastern parts of the Baltic. Currently, the species is present in the whole Baltic Sea area, including the northern parts of the Gulf of Bothnia.

The Sandwich Tern started to expand its range to the Baltic Sea area during the first half of the 20^th century, colonising Skåne in 1911, and the Swedish east coast during the 1930s. In the second half of the 20^th century, the range expansion continued to the southern coasts of the western and central Baltic. The Baltic breeding population grew constantly and reached about 2,500 breeding pairs (bp) at the mid-1970s. Since then, despite some fluctuations and frequent shifts of breeding sites, it can be considered as more or less stable.

The southern subspecies of the Dunlin (Calidris alpina schinzii) was once an abundant and widespread breeding bird of the Baltic Sea area. However, during the 20^th century the population declined rapidly and counts currently not more than 500-640 breeding pairs. From many parts of its former Baltic range the Dunlin has disappeared. An extinction of the species in the Baltic region during the next few decades cannot be excluded. The reasons for the rapid decline in both numbers and range in the Baltic Sea area are not well understood, but habitat loss and habitat changes due to changes in land use are likely to play a key role. Increased predation by both mammalian and avian predators represents another significant factor.

Several human activities such as bycatch, noise and chemical pollution, overfishing, and habitat destruction negatively influence the status of the Baltic harbour porpoise**, whose density and distribution has declined considerably during the last several decades, leading to a critically endangered status of the harbour porpoise in the Baltic Proper.

Increasing maritime traffic plays a role in the introduction of alien species into the marine environment. The American comb jelly (Mnemiopsis leidyi)** invaded the southern Baltic Sea in autumn 2006, and was thought to spread to the northern Baltic in August 2007. However, in nucleotide sequence analysis it was shown that all specimens collected from August 2008 to August 2009 were Mertensia ovum, which is an arctic comb jelly species never before reported from the Baltic Sea.

Nine species of phytoplankton have been identified as non-native for the Baltic Sea, of them only one species, the dinoflagellate Prorocentrum minimum (Pavillard) Schiller, can be categorized as an invasive species**, which is spreading and causing significant impacts on plankton community, habitat and ecosystem functioning.

 

* These Baltic Sea Environment Fact Sheets have not been updated since 2010.

**These Baltic Sea Environment Fact Sheets have not been updated since 2009.

***These Baltic Sea Environment Fact Sheets have not been updated since 2008 or earlier. 

 

 

¹ The 17^th meeting of the HELCOM Monitoring and Assessment Group (HELCOM MONAS 17/2012) decided that the "HELCOM indicator fact sheets" should be renamed as “Baltic Sea Environment Fact Sheets” (BSEFSs) to differentiate them from HELCOM Core Indicators, which are used for follow-up of the Baltic Sea Action Plan. Note: On the HELCOM website, only fact sheets published after 2009 have been renamed as Baltic Sea Environment Fact Sheets.

 

Last updated:  21 February 2013