Results and Confidence

The data underlying the core indicator evaluation are based on regular monitoring data gathered by HELCOM Contracting Parties and reported to the HELCOM COMBINE data base (hosted by ICES). The indicator presents information on the current levels of cadmium, lead and mercury concentrations in selected marine matrices: seawater, fish (muscle and liver tissue) soft body of mussels as well as in the bottom sediment for the assessment period 2011-2016, assessed against regionally agreed threshold values. The values presented in the report refer to the concentrations and mean values calculated from them, while the status assessments are based on the so-called representative concentrations assessed against threshold values, which result from data evaluation (see Assessment protocol), and are considered as values representative of status for the given assessment units.

 

Mercury

Biota

Mercury is analysed in fish muscle as a primary matrix, and the network of sampling station is dense (Results figure 1). The most common species in which Hg is measured are herring and cod in the open sea area and flounder and perch in coastal areas. Concentrations of Hg exceeded the threshold value of 20 µg kg-1 wet weight at the majority of the stations. Concentrations were only lower at a few stations. The mean concentrations on a sub-basin level were above the threshold value in all assessed areas, except the Arkona Basin and some of the Danish and Swedish coastal areas (Key message figure 1). The lowest mean concentration in the Arkona Basin was equal to 17.6 µg kg-1 wet weight and was below the threshold value (20 µg kg-1 wet weight). The Arkona Basin status evaluation, as with all other assessments of each aggregated assessment unit, takes into account data variation within an assessment unit and within the HELCOM region, and this influences the final status assessment (Results figure 1 and Key message figure 1).  In the Gulf of Finland and in the Kattegat Hg concentrations in fish muscle were similar, 34.5 and 36.5 µg kg-1 respectively and the highest value of 58.0 µg kg-1 wet weight was found in the Gdańsk Basin.

 

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Results figure 1. Map presenting station based status of mercury concentrations in biota - fish muscle and mussels (left), and assessment unit based status for mercury in biota. Green colour represents good status and red colour represents not good status. Large filled triangles indicate data series of three or more years for which statistical trends could be assigned (upwards-increasing concentrations or downwards-decreasing concentrations), large filled circles triangles indicate data series of three or more years for which statistical trends could be assigned but where no detectible trend was observed, and full evaluation with MIME Script (see Assessment protocol) was carried out. Small filled circles represent data series of three or more years for which statistical trends could not be assigned due to specific data factors and open circles represent data series of less than three for which statistical trends could not be assigned due to data series length, and these data types are treated with initial status assessment (see Assessment protocol). Click here to access interactive maps at the HELCOM Map and Data Service: Mercury.

 

Taking into account the temporal changes in Hg concentrations in biota, downward trends were recorded for 18 data series, in the case of 43 data series trends were not detectable, and in the 5 data series there were upward trends. Some examples are presented in Results figure 2.

 

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Results figure 2. Long-term trends of mercury concentrations in fish muscle at chosen stations (HQS –threshold value, grey colour- confidence level 95% range (see Assessment protocol).

 

Cadmium

Seawater

The primary matrix for cadmium is water, as the primary threshold value for the core indicator is agreed to be the EQS value for water. This is in conflict with the HELCOM COMBINE monitoring program, where the preferred matrix for monitoring is biota and sediment. As a result, very little data is available for cadmium in water.

Cadmium concentrations in the seawater have been measured by Russia (1995–1998), Germany (1998–2016), Lithuania (2007–2016) and Poland (2011-2016).

The assessment of Cd concentrations in seawater showed that good status was achieved in five open sea basins: Eastern Gotland Basin, Bornholm Basin, Arkona Basin, Bay of Mecklenburg and Kiel Bay (Key message figure 2). Only in a few of the Polish and German coastal areas was good status not achieved, but it should be emphasized that the assessment is widely based on short data series (initial data – see Assessment protocol and Results figures 3-6).

The map shown in Results figure 3 presents monitoring stations and the data series for Cd in seawater (for method description see Assessment protocol). In most cases the representative concentrations of Cd were below the threshold value. Only at some stations in the coastal waters of Gdańsk Basin and the Bornholm Basin the concentrations exceeded 0.2 µg l-1. The representative concentrations aggregated per assessment unit were 0.10 µg l-1 in the Eastern Gotland Basin and in the Bornholm Basin, 0.07 µg l-1 in the Arkona Basin, and 0.02 µg l-1 in the Bay of Mecklenburg and Kiel Bay.

 

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Results figure 3. Map presenting station based status of cadmium concentrations in seawater (left) and assessment unit based status for cadmium in seawater (right). Green colour represents good status and red colour represents not good status. Large filled triangles indicate data series of three or more years for which statistical trends could be assigned (upwards-increasing concentrations or downwards-decreasing concentrations), large filled circles triangles indicate data series of three or more years for which statistical trends could be assigned but where no detectible trend was observed, and full evaluation with MIME Script (see Assessment protocol) was carried out. Small filled circles represent data series of three or more years for which statistical trends could not be assigned due to specific data factors and open circles represent data series of less than three for which statistical trends could not be assigned due to data series length, and these data types are treated with initial status assessment (see Assessment protocol). Click here to access interactive maps at the HELCOM Map and Data Service: Cadmium.

 

Biota - Mussels

The assessment of Cd levels in biota was carried out only on the basis of Cd concentrations in the mussel tissue. Soft body tissue of mussel is a secondary matrix for the Cd status assessment. There is no data available in northern part of the Baltic Sea, while in the western part the coverage of sampling stations is more dense (Results figure 4).

At most sampling stations the representative concentrations of Cd in mussel exceeded the threshold value (960 µg kg-1 dry weight), which was recalculated to wet weight (137.3 µg kg-1 wet weight) as the majority of data is reported as concentration expressed in wet weight.

The mean concentrations calculated for three open sea sub-basins exceeded the threshold level in the Bay of Mecklenburg (351.2 µg kg-1 wet weight), the Arkona Basin (186.4 µg kg-1 wet weight) and in the Eastern Gotland Basin (297.0 µg kg-1 wet weight) (Key message figure 2).

In some areas statistically significant decreasing and increasing trends could be detected, some examples of which are presented in the Results figure 5.

 

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Results figure 4. Map presenting station based status of cadmium concentrations in biota - mussels (left) and assessment unit based status for cadmium in biota (right). Green colour represents good status and red colour represents not good status. Large filled triangles indicate data series of three or more years for which statistical trends could be assigned (upwards-increasing concentrations or downwards-decreasing concentrations), large filled circles triangles indicate data series of three or more years for which statistical trends could be assigned but where no detectible trend was observed, and full evaluation with MIME Script (see Assessment protocol) was carried out. Small filled circles represent data series of three or more years for which statistical trends could not be assigned due to specific data factors and open circles represent data series of less than three for which statistical trends could not be assigned due to data series length, and these data types are treated with initial status assessment (see Assessment protocol). Click here to access interactive maps at the HELCOM Map and Data Service: Cadmium.

 

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Results figure 5. Long-term trends of cadmium concentrations in mussel at chosen stations (HQS – threshold level, grey colour- confidence level 95% range (see Assessment protocol)).

 

Sediment

The assessment based on the Cd concentrations in bottom sediments showed that good status was achieved in the Bothnian Sea and in the Åland Sea in the north, and in the Arkona Basin, Bay of Mecklenburg, Kiel Bay, Great Belt, The Sound and Kattegat in the west (Key message figure 2). Good status was not achieved in five main open sea sub-basins: the Northern Baltic Proper, Western Gotland Basin, Eastern Gotland Basin, Gdańsk Basin and Bornholm Basin, nor in some Polish, German and Danish coastal areas.

Taking into account individual stations (Results figure 6), the lowest mean concentration of Cd in sediments (0.1 mg kg-1 dry weight) was found in at the Great Belt. The concentrations at the levels between 0.2 and 0.4 mg kg-1 dry weight were specific to the Kattegat, The Sound, Kiel Bay, Bothnian Sea and the Åland Sea. The highest mean concentrations, markedly exceeding the threshold value of 2.3 mg kg-1 dry weight, were found in the Eastern Gotland Basin (8.1 mg kg-1 dry weight), Western Gotland basin (7.5 mg kg-1 dry weight) and Northern Baltic Proper (6.1 mg kg-1 dry weight).

 

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Results figure 6. Map presenting station based status of cadmium concentrations in sediment (left) and assessment unit based status for cadmium in sediment (right). Large filled triangles indicate data series of three or more years for which statistical trends could be assigned (upwards-increasing concentrations or downwards-decreasing concentrations), large filled circles triangles indicate data series of three or more years for which statistical trends could be assigned but where no detectible trend was observed, and full evaluation with MIME Script (see Assessment protocol) was carried out. Small filled circles represent data series of three or more years for which statistical trends could not be assigned due to specific data factors and open circles represent data series of less than three for which statistical trends could not be assigned due to data series length, and these data types are treated with initial status assessment (see Assessment protocol). Click here to access interactive maps at the HELCOM Map and Data Service: Cadmium.


Lead

Seawater

The primary matrix for lead (Pb) is water, thus an EQS value has only been suggested for water. This is in conflict with the HELCOM Combine monitoring program, where the preferred matrix is biota and sediment (see discussion on Good Environment Status). As a result, very little data is available for lead in water.

Some long-term results for lead concentrations in seawater exist, as measurements by Russia (1995–1998), Germany (1998–2016), Lithuania (2007–2016) and Poland (2011-2016).

The assessment based on Pb concentrations in seawater showed that good status was achieved in three open sea sub-basins: Eastern Gotland Basin, Bornholm Basin and in Bay of Mecklenburg, as opposed to Kiel Bay and Arkona Basin that failed to achieve the threshold (Key message figure 3). Good status was also not achieved in the some Polish coastal areas and in one German coastal area, but it should be pointed out that status assessment is based on relatively short data series, as was the case for Cd.  

In the Lithuanian coastal area the concentrations of Pb in seawater were below the threshold value, while in Polish coastal areas concentrations exceeded the threshold value of 1.3 µg l-1 (Results figure 7).   The average concentrations of Pb in seawater were below the threshold value in the Bornholm Basin – 1.05 µg l-1, the Bay of Mecklenburg - 0.24 µg l-1 and the Eastern Gotland Basin, 1.00 µg l-1. In the Arkona Basin and in the Kiel of Bay the average representative Pb concentrations exceeded slightly the threshold value and were at the level of 1.6 µg l-1 indicating that good status was not achieved (Key message 3).


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Results figure 7. Map presenting station based status of lead concentrations in water (left) and assessment unit based status for lead in water (right). Green colour represents good status and red colour represents not good status. Large filled triangles indicate data series of three or more years for which statistical trends could be assigned (upwards-increasing concentrations or downwards-decreasing concentrations), large filled circles triangles indicate data series of three or more years for which statistical trends could be assigned but where no detectible trend was observed, and full evaluation with MIME Script (see Assessment protocol) was carried out. Small filled circles represent data series of three or more years for which statistical trends could not be assigned due to specific data factors and open circles represent data series of less than three for which statistical trends could not be assigned due to data series length, and these data types are treated with initial status assessment (see Assessment protocol). Click here to access interactive maps at the HELCOM Map and Data Service: Lead.

 

Biota

The assessment of Pb levels in organisms was carried out on the basis of Pb concentrations in fish liver and the mussel tissue (Key message figure 3). Taking into account main open sea sub-basins good status was achieved only in Bothnian Sea and in Kattegat, while in the Bothnian Bay, The Quark, Gulf of Finland, Western Gotland Basin, Eastern Gotland Basin, Gdańsk Basin, Bornholm Basin, Arkona Basin, Bay of Mecklenburg and in the Kiel Bay good status requirements have not been met. 

 

Fish

Fish liver is used as a secondary matrix for Pb assessment. The number of data on Pb in fish liver reported by HELCOM Contracting Parties is quite large and guaranties good coverage of the Baltic Sea (Results figure 10).

The lowest mean concentration of Pb in fish liver was found in the Kattegat (10.4 µg kg-1 wet weight), while the highest value, exceeding the 26 µg kg-1 wet weight several threshold value almost ten-fold, was specific to the Gulf of Finland (203.3 µg kg-1 wet weight). Relatively high concentrations were also found in the Eastern Gotland Basin (70.1 µg kg-1 wet weight) and in the Kiel Bay (49.9 µg kg-1 wet weight).

Considering temporal changes in Pb concentrations in liver of common Baltic fish species – herring and flounder, statistically significant decreasing trends were observed for fish from many of the Baltic Sea assessment areas (Result figure 8). This decrease is most probably the result of the ban on leaded fuels imposed in the 1980s.


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Results figure 8. Long-term trends of lead concentrations in fish liver at chosen stations (HQS –threshold value, grey colour- confidence level 95% range (see Assessment protocol)).

 

Mussels

Mussel soft body is another secondary matrix for monitoring of Pb levels in the Baltic Sea. Most of the stations, where this monitoring is carried out are located in the western part of the Baltic Sea (Results figure 10). Concentrations of Pb in mussel soft tissues found at that at certain single stations in the Polish coastal areas and in the Danish Straights good status was indicated, as they were below the threshold value (1300 µg kg-1 dry weight and 185.9 µg kg-1 wet weight after recalculation to the wet weight). However, at most locations good status was not achieved. At the same time, in some areas where the long-term measurements are being carried out, a downward trend is observed (Result figure 9).

 

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Results figure 9. Long-term trends of lead concentrations in mussel at chosen stations (HQS –threshold value, grey colour- confidence level 95% range (see Assessment protocol)).

 

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Results figure 10. Map presenting station based status of lead concentrations in biota - fish liver and mussels (left) and assessment unit based status for lead in all biota (right, see also figure 9). Green colour represents good status and red colour represents not good status. Large filled triangles indicate data series of three or more years for which statistical trends could be assigned (upwards-increasing concentrations or downwards-decreasing concentrations), large filled circles triangles indicate data series of three or more years for which statistical trends could be assigned but where no detectible trend was observed, and full evaluation with MIME Script (see Assessment protocol) was carried out. Small filled circles represent data series of three or more years for which statistical trends could not be assigned due to specific data factors and open circles represent data series of less than three for which statistical trends could not be assigned due to data series length, and these data types are treated with initial status assessment (see Assessment protocol). Click here to access interactive maps at the HELCOM Map and Data Service: Lead.

 

Sediment

The assessment based on the Pb concentrations in bottom sediments showed that good status was achieved in the Bothnian Bay, Bothnian Sea, Åland Sea, Northern Baltic Proper, Western Gotland Basin, Kiel bay, Great Belt and in the Kattegat, as well as in some of the German and Danish coastal areas (Key message figure 3 and Results figure 11). Good status was not achieved in five main open sea sub-basins: the Eastern Gotland Basin, Gdańsk Basin, Arkona Basin and Bay of Mecklenburg and in some Polish, German and Danish coastal areas.

The lowest mean concentrations of Pb in sediments, remaining significantly below the threshold value (120 mg kg-1 dry weight) were found in the Great Belt (21.3 mg kg-1 dry weight), Bothnian Sea (23.2 mg kg-1 dry weight) and in Åland Sea (25.8 mg kg-1 dry weight), while the highest value was specific to the Bornholm Basin (125.8 mg kg-1 dry weight).


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Results figure 11. Map presenting station based status of lead concentrations in sediment (left) and assessment unit based status for lead in sediment (right). Map presenting status based on lead concentrations in sediment at each sampling station. Green colour represents good status and red colour represents not good status. Large filled triangles indicate data series of three or more years for which statistical trends could be assigned (upwards-increasing concentrations or downwards-decreasing concentrations), large filled circles triangles indicate data series of three or more years for which statistical trends could be assigned but where no detectible trend was observed, and full evaluation with MIME Script (see Assessment protocol) was carried out. Small filled circles represent data series of three or more years for which statistical trends could not be assigned due to specific data factors and open circles represent data series of less than three for which statistical trends could not be assigned due to data series length, and these data types are treated with initial status assessment (see Assessment protocol). Click here to access interactive maps at the HELCOM Map and Data Service: Lead.

 

Confidence in indicator status evaluation

The overall confidence of the indicator evaluation is high.

The accuracy of the estimation method is considered to be high, and the risk of false status classifications is considered to be very low. The underlying monitoring data is of high quality and regionally comparable.

The data on metal concentrations in seawater is not spatially adequate. Time series are available only for the German area: Bay of Mecklenburg, Bornholm Basin, Great Belt and Kiel Bay. For Eastern Gotland Basin (Lithuanian data) there are available data only for the period 2012-2014. The confidence of the results is low.

The data on metal concentrations in fish and bivalves is spatially adequate and time series are available for several stations, therefore the confidence in the results is high.