Title:

Heavy metal pollution in the Baltic Sea, from the North European coast to the Baltic states, Finland and the Swedish coastline to Norway.

Authors:

Sergio Manzetti1,2*

1. Computational Ecotoxicology Group, Computational Biology and Bioinformatics, Department of Cell and Molecular Biology, Uppsala Biomedicinska Centrum BMC, Husarg. 3, Box 596, 751 24 Uppsala, Sweden. 2. Fjordforsk A/S, Bygdavegen 155, 6894 Vangsnes, Norway.

1 Abstract1

Environmental pollution and contamination is a continuous challenge that industrialized and developing countries are facing, affecting entire ecosystems, threatening biodiversity, reducing health and life quality of humans and contributing to the extinction of endangered species. The oceans and seas are the most vulnerable ecosystems to anthropogenic impacts, where heavy metals and other pollutants affect the viability of marine species. In this review, the focus is put on the widespread contamination of heavy metals on the Baltic sea and its marine ecosystems. Three parts are considered: the industrial sources of heavy metals in along the entire Baltic coast and in the Baltic sea, the levels and concentrations of heavy metals found in various phases of the environment (sediments, rivers, lakes and seas) and the accumulation of heavy metals in fish as well as avian species. The results from this review show that the heavy metal-releasing industries impact the marine environment for several decades, and that more efforts are required to restitute the Baltic sea to its original state.

1 Please cite as: Sergio Manzetti. 2020. Heavy metal pollution in the Baltic Sea, from the North European coast to the Baltic states, Finland and the Swedish coastline to Norway. Fjordforsk AS, Technical Reports, 6:8. 1-90.

2 Introduction Heavy metals are a particularly toxic class of inorganic pollutants which have been released to the environment after intense anthropogenic activities on both sides of the Atlantic [1–5], from the early stages of the industrial revolution to the First and Second World Wars and further to the modern industrial age [6–9]. Uncontrolled release of heavy metals is prohibited in most countries [10–13], given their ecotoxicological properties, particularly for aquatic ecosystems, marsh-lands and exposed areas near and at industrial sites [14–19]. The release of heavy metals is therefore subjected to stringent regulations, however many cases of uncontrolled release still occur, making making pollution by heavy metals a priority for environmental legislation and regulations [20]. Recent studies show that a series of revised acts of legislation are at implementation stage for various marine ecosystems, such as for the Baltic sea by the HALCOM Baltic Sea Action plan [20] and the Bremen ministerial Declarations [21], for the coastal waters in Chile (CONAMA plan [22]) and furthermore for other areas [23]. An updated set of acts of legislation [24] have also been published in Norway in 2017 where Hg, Cd, Pb, Cr have been put on the revised list of priority pollutants given considerable contamination in fish and sediments [19,25–28], deriving from outdated and active industrial activity, as well as other major sources of heavy metal contamination such as the sunken German boat “U864” located outside the Norwegian coast north of Bergen containing 65 tons of liquid mercury [29], and contamination from aluminum smelting industries along the Norwegian coastline [19,30–33]. The Baltic sea, which is the focus of this review, has experienced a considerable decline in overall environmental health since the 1950’s, when new industries emerged on its shores after World War II, particularly on the East Baltic coast and further along the south coast-line of the Baltic sea. The Swedish coast line, particularly between the city of Sundsvall and Umeå - on the shores of the Sea of Bothnia, has suffered from a dramatic ecosystem decline by the extensive industrial load on the coastal estuaries, leading to the largest accumulation of pollutants deposited on the shores of any Scandinavian country in history [34]. In this study, we focus therefore on heavy metal pollution in the Baltic Sea and describe the past and present states over several respective sections. The southern parts of the Baltic Sea have been studied more rigorously for heavy metal contamination in recent years [35–37], and studies describe alarming levels of heavy metals in the Polish estuaries, particularly in the seabed of rivers and the coast line where Cs137 isotope has been found in fish along the Southern shoreline of the Baltic (Fig 1) [38]. Concomitantly, the general levels of heavy metals in the Southern Baltic Sea have risen in the last 10 years given the flooding of the river Oder

3 [35], indicating, among other pollution sources from neighboring shores [39–41], that the general state of the estuaries and seas of Baltic marine ecosystem require decade-long efforts to be completely cleared to a sustainable state for the fish species, and to provide a secure marine environment to abolish the dietary risks associated with fish and sea food consumption. The implementation of higher ambitions by the European states is therefore necessary to ensure a complete recovery of the Baltic Sea.

Heavy metal contamination in the Baltic Sea The Baltic Sea is a mediterranean sea belonging to the Atlantic Ocean, which has a limited water influx from its parental ocean, fueled by high-tide currents as well as during the events of low pressures systems arising in the North Atlantic impacting the Danish and South Swedish coast. The Baltic Sea is composed of several shallow bays and estuaries, encompassing the Gulf of Finland, the Gulf of Riga, the Bay of Gdansk, the Sea of Botnhia and the Bay of Bothnia (Fig 2), with an average depth of 50 m with a bottom rich in sand and clay minerals. This sea was formed 130.000 years ago, and has gone through several stages of evolution, encompassing an ice age of lasting approx 100.000 years during the Weichselian glaciation period. The Baltic Sea is composed of scattered Jotnian sediments, aleurolites and conglomerates, with a high percentage of lime stone. The Southern parts of the Baltic sea contain small petroleum reserves, while the eastern parts towards Estonia and the Gulf of Finland are rich in kukersite deposits [42,43]. The geology of the Baltic sea has an important effect on the fate of pollutants, as the clay materials found in the Baltic are very similar to clays that are regularly used for decontamination and remediation purposes of polluted waters and soils, given their highly sorptive properties. Indeed, clay binds organic pollutants reversibly as well as irreversibly and can also catalyze particular chemical reactions [44,45]. The Baltic sea has therefore geophysical properties which increase the absorption of pollutants of both organic and inorganic origin, and can act as an accumulator of water-soluble and insoluble pollutants released from the industrial facilities which are widespread along its shorelines [46].

The Gulf of Gdansk The Gulf of Gdansk (Fig 1, 2) is particularly exposed to heavy metal contamination as well as radioactive nucleides [35,36,47–52] deriving from industrial activity in the Polish region and possibly also from the Russian enclave (Oblast of Kaliningrad), resulting in peak levels registered

4 in the last 30 years: 1.3 mg Mn/gram sediment, 0.1 mg V/g sediment, 0.2 mg Sr/g sediment, 6.7 mg Zn/ g sediment, 4 mg Pb / g sediment and 0.35 mg Ni / g sediment [35]. Similar levels are detected in the Vistula river sediments, at the central part of the Gulf of Gdansk where Zinc levels of 0.25-5.3 mg/g soil, Lead levels up to 0.760 mg/g soil, Cu levels to 0.47 mg/g sediment and Cd levels up to 0.14 mg/g soil were registered [35]. The same study reports that levels of 7mg/g soil of Zinc, 1mg/g soil of Lead and 0.3 mg/ g soil of Cd are measured in the sediments of the tributaries of the Vistula river, further contaminating the shoreline of the Gulf of Gdansk. This contaminated region stretches for more than 200 km from Poland east towards Germany (Fig 1), where an additional source of contamination of the southern Baltic sea joins the spread of pollutants, namely the Oder river and its lagoons located nearby the border of Germany. These regions have been exposed to heavy metal contamination over several decades of industrial activity in Germany and central-eastern Europe, where discharges have gradually deposited in the lagoons of the Oder basin. Particularly Cd, Pb, Zn and Ni contaminate these lagoon sediments, which arrest the dispersion of the pollutants from reaching the Baltic sea, however with a limit [50]. Also, the clay sediments of the lagoon mark a general geological trait of the entire northern part of the European continent, and as in the basins of the Baltic sea, such minerals act as sorbers. When the limits of sorption are surpassed, the unsorbed fraction enters the Baltic sea. After several decades of industrial discharges and more frequent flooding given climate changes, the levels of contamination from the Oder river have thus been a principal source of pollution of the south-western Baltic sea, south of the Dano- Swedish strait [53]. Regular flooding of the Oder river contributes also to increasing this effluence from the Oder lagoons, and particularly Cadmium appears as the most mobile heavy metal to be transported over long during flooding [53]. In particular, 84 to 96% of Cadmium appears in the mobile fractions in the sediment layers, Zn can be present in the mobile sediment layers from 45 to 94%, while lead is associated with the least mobile fractions (30–60%) [53]. One of the sources of these pollutants is from the Mala Panew river, which feeds the Oder river from the lake Jezioro

Turawskie, with very high concentrations of heavy metals, especially Cd (31–960 μg/dm3) and Zn

(300–4,400μg/dm3) in the <20 and <63 μm sediment fractions, which are higher also than exposed regions in Germany, i.e. Mulde River [53]. The contribution of the Ode river and the outlet of the Szczecin Lagoon to the southern Baltic sea have however been reduced since the hyperindustrial period of the 1960-1990, and a decline is observed for certain heavy metals (Table 1). The most recent measurements made in 2004 [35] show a declining trend for Zn, Pb, Cd, Sr and Cu compared to 1996 (Table 1), however no changes are observed for Ni and Co levels, as well as other metals

5 (Vanadium levels have doubled in average concentrations from 1996 to 2004 in the Gulf of Gdansk, Thorium and Iron levels have increased also, while Mo and Al remain unchanged in the same period). Another recent study [37] has reported levels of Zn, Cd, Ni, Cu and Co in Baltic Sea shells, sampled on the coastline of the Gulf of Gdansk and 200 km westward towards the Oder outlet. The study included also samples of the shells taken in the open Baltic sea regions (5 nautical miles from the coast line) and shows alarming development of iron concentrations in the Gulf of Gdansk as well as in waters 20 nautical miles off the coast. Iron appears to be bioaccumulated in sea shells, which display a concentration of iron of 200-300 X the levels of iron registered in the sediments of Gulf of Gdansk 6 years earlier (Table 1). For the other elements, the levels appear rather unchanged for Cd, decreased significantly for Ni, while increased for Cu, Zn and Co (Table 1). The contamination reaches also open sea waters of the Southern Baltic, and in the case of Cu, the contamination appears at highest levels in sea shells taken in a region approximately 10 nautical miles north of Utstka, Poland. Similar patterns occur for Co, which is measured at approx. 6 μg pr. g shell in a region 10 nautical miles north of Władysławowo. Cu is nevertheless measured at alarmingly high 360 μg pr. g shell, also some 1 nautical miles north of Utstka. This trend reveals that this region of the Southern Baltic Sea suffers from decade-long industrial activities conducted along the rivers and estuaries, with particular emphasis on the Oder and Vistula rivers. A more recent and larger study, presented by Zaborska et al [36] describes the state of the Polish coastline, with emphasis on offshore locations some 30-50 nautical miles outside of Władysławowo as well as south-west in an area located some 40 nautical miles south of the Danish island Bornholm, with an extended set of collected samples from the bottom sediments. Here, Zaborska et al measured levels of Pb, radioactive Cs, Cd, Hg, As, Zn and Cu, sampled in surface sediments of 5 cm depth (Cd, Zn, Cu and Pb shown in Table 1). The results show that the levels of Cadmium reached high levels as 1.32 μg/g sediment, and a minimum level of Cd was detected at 0.03 μg/g sediment. Mercury concentrations were lower, with a range between 0.001-0.019 μg/g sediment, a result which was confirmed by a another similar study as well [54]. Arsenic levels were seemingly the highest in the region measured, with peak levels reaching 22.66 μg/g sediment, and a minimum of 0.28 μg/g sediment. Lead levels were also substantially high, ranging from 6.7-86.1 μg/g sediment. The highest level detected by Zarboska et al for any heavy metal was however Zinc, which showed concentrations in the sediment of 7.9-123.1 μg/g. Copper was also highly represented in the sediments, with a range of 1.35-71.32 μg/g sediment. The analysis by Zaborska et al shows also that

6 the most contaminated part in this explored region is a region of approx. 102 nautical miles located 20 nautical miles of Utstka, Poland (see Fig. 1). Zaborska et al, reported also 137Cs levels, which were registered at levels ranging from 0.1 Bq/kg sediment – 256.9 Bq/kg sediment. Among the sites analyzed by Zarboska et al, the areas around Bornholm were however most contaminated by Pb, Cd and Zn in particular, were the pelite sediments which occur at higher depths accumulate more heavy metals than sandy and shallower waters. Supporting studies show this trait in measurements, where the deepest parts of the Southern Baltic in general (Bornholm Basin, Gulf of Gdansk) are the most contaminated by heavy metals [41,48,49,52]. The overall trends (Table 1) show that the levels of Ni, Zn, Cd and Fe in the Gulf of Gdansk have increased in the last years, while Sr, Pb and Cu have decreased, and Co remains stable. Another part of the Gulf of Gdansk of importance is the eastern parts which merge with the coastline waters of Lithuania and Latvia, including the Kaliningrad Oblast. There are few but crucial studies on the state of the Lithuanian waters, where Remeikaitė- Nikienė et al [51] have recently published a status of the distribution of heavy metals in the sediments of the south-eastern Baltic waters, comprising the Lithuanian zone. Here, the levels of Pb, Cu, Cd, Ni, Cr, Zn and Al are generally lower than in the Gulf of Gdansk, with the concentrations of Pb: 1.0-46.3 μg/g sediment; Cu: 0.5-52.3 μg/g sediment; Cd: 0.02-2.2 μg/g sediment; Ni: 1.7-36.9 μg/g sediment; Cr: 2.1-75.4 μg/g sediment; and Zn: 5.1-157.1 μg/g sediment. All values are mainly in the coastline, while 4-5 sampling sites are situated in the outermost part of Lithuanian waters, ~80 nautical miles west of Lithuania, where the waters enter the international zone directly north of the Gulf of Gdansk. In this region, all metals are traced at highest levels, however generally lower than the highest concentrations found in the Gulf of Gdansk (Table 1) [51]. In a recent study by Beldowski et al [55], levels of total mercury, methylmercury, and organic mercury were measured in the sediments off the coast of Gdansk. The concentrations found by Beldowski et al were respectively 0.2 μg/g, 0.005 μg/g and 0.004 μg/g in the Gdansk deep. As expected by previous findings from others (see above) the levels of organic mercury and methylmercury were higher in the Gdansk Bay than in the Gdansk deep, however the levels of total mercury were higher in the Gdansk deep. This shows that the degree of biotic metabolism of Hg is higher in the shallow waters of the Gdansk bay compared to the deep waters of the Gdansk deep. This shows indeed that specialized microbes, such as the iron-reducing bacteria which utilize light in the conversion process, play a part in the transformation of mercury to its organic forms [56,57]. The study by Beldowski suggests also that the levels of total mercury found in the Gdansk Deep exceed the background values by a factor of three, when compared to studies made in the early

7 1990’s [58]. The source of this contamination which exceeds the Gotland deep and the Bonholm deep appears to be the Vistula river, both during floods and during normal influx [55]. The Vistula river is therefore a point of major concern and importance to the HELCOM initiative and Baltic ecosystem protection initiatives. The efforts made over the last decades to reduce contamination in the gulf have however given results, where the levels of several heavy metals have gradually diminished in the waters off the coast of Poland (Fig 3). Mollusks found in the region, particularly Mytilus trossulus, Cardium edule, Myta arcnaria, Theodoxus fluviatilis and Lynnea stagnalis, were analysed in 2003 for levels of mercury and the results showed that concentrations of mercury in the tissue were ranging between 20 – 100 ng/g, where M. trossulus and C. edule had the highest levels of mercury [59]. Crustaceans in the same region display also similar level ranges of mercury, however one species in particular, Perca fluviatilis appears to accumulate more mercury than all other species, with ranges varying between 25-210 ng/g tissue [59]. The results from the study by Barsiene et al indicates also that flounder, herring and eelpout in the Bay of Gdansk, and westward towards the Danish strait have a risk of genotoxic effects of 60-100% [59]. These results are also in good agreement with other studies which show that marine species in this region of the Baltic Sea have alarming expression profiles of biomarkers associated with heavy metals and intoxication [39,60].

The Bay of Riga The bay of Riga (Latvia) is one of the most secluded ecosystems of the Baltic sea. However exposed to limited tidal currents from the Atlantic, it is a brackish water body sheltered by the Kura kurgu hoiuala area and its shallows with the island of Saaremaa forming a barrier to the near the opening of the bay. The bay is up to 60 meters deep over a larger part (20 meters on average) and encompasses a total area of approx. 19.000 km2 (Fig. 4). The bay area forms a sink-like water body which has accumulated pollutants in its deepest parts over decades [61–65]. This region of the Baltic has various species of fish, with Baltic herring, sprat, white bream and bleak as the main species [66,67], as well as turbot and flounder which were nearly extinct in the period between 1970-1990 given anthropological impact [68]. The sediments in this region are similar to the sediments of the Gulf of Gdansk, however, the bedrock is a different type which yields a high degree of coastal erosion [69], leading to sedimentation rates differing from the southwest parts of the Baltic. The source of the contamination of the Bay of Riga is the general pollution in the Baltic sea from the surrounding Baltic countries as well as from the three main rivers from Latvia and

8 from Estonia (Fig 4) [40,70–72]. These rivers are the major source for heavy metal pollution in the Bay of Riga and yearly carry large quantities of heavy metal contaminated waters from several lakes in the eastern parts of Latvia [73]. In these lakes, the concentrations of heavy metals can reach up to 30.4 μg/g sediment for Zn, 3.6 μg/g for Cu, 1.06 μg/g for Cr, 430 μg/g for Fe, 6.4 μg/g for Ba, and 9.3 for Sr [73]. Also, following the same study rather high levels of Mn are also found in the lakes, up to 63 μg/g sediment and in one of the easternmost lakes, As levels peak at 26.1 μg/g sediment, Ni levels reach 27.3 μg/g sediment and Pb levels reach up to 25.2 μg/g sediment, while Cr is found at 24.4 μg/g sediment [73]. Accounting for the multitude of waterways from the Eastern Latvia to the Bay of Riga, the source of contamination in the bay is thus evident, leading to direct deposition of pollutants in the bay as an end-reservoir [71]. Major studies of heavy metal pollution in Bay of Riga have been published by various groups in the last three decades [71,74,75], where the most extensive mapped 138 sediment samples taken in the period 1991-1996 in the Gulf of Riga [71]. Here Leivuori et al [71] traced Cd, Pb, Cu, Zn and Hg in the entire bay with several samples taken in the deepest sites of the bay, where average concentrations were respectively reported to be 3.31 μg/g sediment, 162 μg/g sediment, 103 μg/g sediment, 437 μg/g sediment and 1.5 μg/g sediment. These analyses were made of the uppermost sediments within 5 cm of depth-range and traced back to their source: Zn derived from the three major rivers in the south end of the bay (Fig 4) and the Pärnu river in the North East as well as from the island of Saaremaa (region of Kuressaar), while Cu derived to a larger part from Saremaa and the Pärnu river [71]. Cadmium derived from an industrial-transportation area on the shores of the Ragaciems estuary, in the South East area of the Bay, some 10 km east of the outlet of the three main rivers of Latvia. Lead was instead fed from the 3 southern rivers, the Gauja river, Daugava river and the Lielupe river, while mercury was distributed more generally in the entire southern area originating from the river Gauja [71]. Leivuori et al [71] published also a vertical distribution analysis which showed that the highest levels of Cd and Hg were released from 1950-1980, and accumulated in the top 7 centimeters of the sediments. By this vertical distribution analysis, it was found furthermore that Mercury levels experienced a drop after 1977, while Cd was released at higher loads after 1980 as well. For Zn, Cu and Pb, the release periods appear to have risen steadily from early 1900 with the highest levels registered between 1950 and onward to 1990. The sharpest increase was found for Cu, which was released at twice loads from 1970 to approx. 1985 compared to the 1950’s. Leivuori et al [71] published also data on the levels for other metals, where Ti, V, Ni, Cr, Fe, Mn and Al are of particular interest. These data show that these metals are on average found at higher

9 concentrations in the Bay of Riga compared to the Gulf of Finland. It is however vanadium which was found at very high concentrations, 113 μg/g sediment, as well as chromium (105 μg/g sediment) and nickel (57 μg/g sediment). Yurkovskis [75] published a critical study some four years later, where he updated the levels of heavy metals sediments to quite high magnitudes compared to the study by Leivuori et al [71]. The analysis showed that the content of sedimented heavy metals in suspended matter from water samples taken in the Daugava river and the region of the Gulf around the outlet of Daugava showed excessive levels of Cr: 100-460 μg/g sediment, 60- 250 μg/g for Ni, 30-570 μg/g for Cu, 170-2400 μg/g for Zn, 5-47 μg/g for Cd and 20-270 μg/g for Pb. Yurkovskis [75] correlated also salinity levels to concentrations of two metals, where Mn appears to be the least affected by salinity, displaying stable concentrations in the particulate matter, while Fe was rapidly resuspended at higher salinity levels. Interestingly the process of resuspension for iron followed different speeds of resolvation based on the season of the year. According to Yurkovskis [75], the September and October months appear to give the most rapid resuspension of Fe in the Bay of Riga from the particulate matter [75], which is associated with the seasonal reduction of fresh-water supply to the Bay of Riga from the Eastern parts of the country (and thus an increase in salinity in the bay), while the spring months represent the opposite, with increased melting of snow and a reduction in salinity and therefore higher sedimentation rates of heavy metals. The seasonal changes play also a critical role in the supply of heavy metals to the bay from the rivers and lakes. Poikäne et al [74] studied these patterns and found that spring floods increase transfer of heavy metals from inland water sources, lakes, marsh lands and swamps. Particularly Cr, Al, Fe and Ni were brought to the bay from mainly the river Daugava. The distribution was interestingly different for the heavy metal species: Al and Fe were quickly sedimented in the entire basin of the bay, however Mn, Cd and Zn underwent different sedimentation mechanisms/rates, which affected the oxygen availability in the bottom layers of the Bay of Riga [74]. Mn, which is an active metabolite for many bacteria [76,77], has more detrimental effects for monocellular eukaryotes, diatoms and plankton in the deepest water layers and affects the nutrient levels directly. Additionally, sedimented heavy metals are easily re-suspended and studies show that sedimented heavy metals can quickly be released from the sediment and diffuse 11 m above the sea bed [78], yielding an increase in levels of heavy metals originating from a different period of the industrialization era and affect the present state of an ecosystem. These levels vary based on the sediment chemistry (clay, limestone, etc) and are affected by pH changes and the solubility and redox potential of the ion specie, incurring that particularly deep areas with reduced oxygen supply

10 and lower pH may maintain heavy metals resuspended in the water column for longer times than shallow waters. This implies that the most polluted and deepest parts of the bay (or any affected water body for that matter) may act as reservoirs which resuspend sedimented heavy metals during stages of microbiological activities of the ecosystem. An example of this is during spring and summer season when rising temperatures induce changes in the microbiological profiles of the lower water layers, and salinity, algal blooms and other related events affect the biological profiles and the chemistry/nutrient availability of the respective water layer [30,75,79–82]. Therefore, heavy metals may display, depending on sea bed type, a complex and long-lasting cycle of sedimentation and resuspension. Poikäne et al measured these levels in the Bay of Riga and reported concentrations of 36-690 μg of resuspended Fe pr. liter water, 22-974 μg/l for Al, 590- 4410 ng/ l for Zn, 8-92 μg/l for Mn, 110-1083 ng/l for Cu, 2.7-51.2 ng/l for Cd, 80-990 μg/l for Ni, 80-3130 μg/l for Cr and 90-730 ng/l for Pb [74]. Interestingly, these measured concentrations were statistically correlated to originate from the Daugava river, particularly Fe, Al, Zn, Cu, Cr, Pb and Cd [74]. Conclusively, the prospects for Bay of Riga are critical, as the concentrations measured over the last 20 years have risen for most heavy metals. Figure 5 shows the trends of the concentrations measured in sediment samples taken in the bay since 1996 [71,74,75]

The Gulf of Finland The Gulf of Finland is the easternmost part of the Baltic Sea, with regular freezing conditions throughout cold winters. The sediments of the Gulf of Finland are naturally rich in Mn (MnCO 3), Mb and Fe, which emerge from concretions of the seabed rock [83], however contamination by high levels of heavy metals [84] quickly surpasses these natural background levels. The Gulf of Finland is, similarly to the Bothnia Bay, an estuary which has the tendency to accumulate high levels of contaminants given its reduced water influx from the open Baltic Sea. This part of the Baltic sea has therefore received great attention by environmental chemists in recent years, particularly Russian and Finnish scientists with extended local resources such as ROV, marine ships at disposal from Russian and Finnish authorities, and advanced equipment to sample the shallow sediments of the Gulf of Finland [83–91]. The Eastern parts are particularly polluted [84], given the discharge from industrial plants located on the east/north-east parts of the shores. The majority of these industries, which count over 40 in the Russian part exert activities relying on ferrous and nonferrous metallurgy (production of aluminum alloys), chemicals, pharmaceuticals as well as

11 textile and apparel industries. Many of these sites are also situated along the Neva river, which is a principal carrier of pollutants to the Gulf of Finland. Additionally, the Vyborg Bay, part of the Leningrad Oblast, has been a considerable source of contamination [84], with industrial activity in sawmilling and electrical manufacturing. Alongside these statistics, effluents from Finnish industries are also playing a part in the pollution of the inner parts of the Gulf of Finland, where the paper mill industries on the Kymijoki river have contributed to a decline in ecological health of this marine system over the years. In addition, Finnish industries in the region are quite dominant as well, where eighteen industrial plants of chemical, metallurgic and mining activities border (or have bordered) the shores of the Gulf of Finland until recently [84]. Estonia is a third contributor to the pollution of the Gulf of Finland, with at least three plants, conducting activities in the chemical, the textile and paper mill sectors. The Narva river, running Northwards from the Estonian border with Russia, is also a contributor to the pollution of the Gulf of Finland [92]. According to a recent study on the ecological viability of rivers and estuaries in Estonia [92], the river Muastajogi and Vasalemma are the major contributors of heavy metals to the estuaries, where Cu levels reach 10-12 μg/L, while Zn levels are averagely represented in all Estonian rivers to 2-3 μg/L. Mercury levels are also particularly high in the Kohtla river, with concentrations at 3 μg/L. The majority of these pollutants originate from wastewater treatment plants in the region, which have either old or limited facilities to purify wastewater. Another major source of pollution of the rivers of Estonia, particularly in North-East Estonia, is the mining and processing of oil shale, which is considered to be the major sources of hazardous substance contamination to surface water overall [92]. This surface water eventually runs into the eastern parts of the Gulf, leading to long term accumulation of heavy metals in its sediments. Vallius and Leivuori have published an extended range of studies over the last 20 years on the state of ecological health of the Gulf of Finland [83– 88,93–96], and have conducted several analyses over the years on the contaminated sediments in the entire Gulf of Finland (Eastern and Western parts). In one particular study levels of Cd, Pb, Cu, Zn and Hg were analyzed in sediment sampling sites of the entire Gulf [84]. In this study, which was carried out during the period 1992-1996, sampling was conducted in 1 cm deep sediments and the results were compared to other studies. The results from this study are shown in table 2 and Fig. 6, which show a particular accumulation of mercury in the area of the Nava estuary and the Vyborg Bay [84]. Similar trends are observed for lead, which is mostly localized in the same regions, however with greater emphasis on Vyborg bay and towards the area around the island of Hogland and outside the shoreline of Kotka in Finland. For zinc and cadmium, the contamination is similar,

12 with great emphasis on the Nava estuary and Vyborg bay, however zinc contamination extends beyond the basin of Hogland, and reaches the offshore regions outside Borgå, 40 km east of Helsinki. Copper contamination is more diffused in the northern parts of the Gulf of Finland, with the highest levels found from Vyborg bay throughout the coastline West of Helsinki. In overall, the measurements made by Vallius and Leivouri [84] show that the majority of the contamination areas are localized along the coast of Finland and the Leningrad Oblast, while the shorelines of Estonia appear less contaminated. Indeed, the levels of mercury and cadmium on southern side of the Gulf are up to 4 times lower than on the Northern side, however this is caused by that the rocks and sediment geology contains lower levels of metals, compared to the Northern side [84]. Vallius has furthermore supplied data from 1995 [53] that shows the concentrations of several heavy metals, including Vanadium, Chromium and Mercury (Table 2). The change from 1992 to 1998 years is negligible and concentrations remain rather stable throughout the region of the Eastern Gulf (Table 2). The same areas as described above show also that the pollution of lead, chromium, cobalt and mercury results in the highest levels on the eastern parts of the Gulf, with emphasis on the bay of estuary of the Leningrad Oblast. The same trends are observed in another of the Vallius studies [95], which show an increase in Cr, Co, Ni and Zn in the period from 1995-1998 (Table 2). The Gulf of Finland has since experienced a gradual decline towards 2009, however very moderate for Zn, Cd, Hg and Co. Interestingly however; Cr, V, Ni and Pb levels were registered at higher concentrations in 2009 since 1999 measurements [93,96]. During the 1999 measurements, copper distribution was at its highest levels in the bay of St. Petersburg, as also lead, mercury and chromium. Cadmium levels were however higher in the Finnish waters [96]. The measurements made in 2009 by Vallius [93] showed also that vanadium and zinc levels increased considerably compared to 1999 studies throughout the entire Finnish coastline, while mercury, cadmium and nickel levels remained stable, zinc, chromium and cobalt levels decrease. Cadmium pollution along the Finnish coast line was apparently fed by the polluted Russian waters, as the concentration of the samples increased the more the samples were taken closer to Russian waters. Cobalt, chrome and vanadium however were in overall spread out equally along the Finnish coastline [93]. More recent studies show that the state of the Gulf of Finland is still in an alarming state, where Cd, Hg and especially Zn levels are at higher levels than guidelines impose, where some samples show as high levels of zinc as 639 μg/g sediment, while Hg peaks at 0.70 μg/g, which is the highest registration since 1995 measurements [88]. For the other heavy metals, a gradual decline is reported since the first measurements were made [94]. This more recent report by Vallius shows that the highest levels

13 of heavy metals found in the sediments on the Gulf of Finland are traced to the period between the early 1960’s and the late 1980’s [94]. The concentrations have declined since, however very slowly and appear to remain stable for some metals (see Table 2) which remain trapped in the sediments at various depths [94]. Hg for instance is found at highest levels some 20 cm below the sediment surface (up to 0.4 μg/g) in the Eastern parts of the Gulf of Finland, while Cd accumulates at levels of 2 μg/g from 2 to 15 cm below the sediment surface (in the same part of the Gulf). Similar patterns are observed for Zn, Cu and Pb. In the central part of the Gulf however, Cd concentrations peak to 6 μg/g sediment at 20 cm below the surface of the sediment, which indicates the origin of Cadmium pollution to be most probably from the Finnish industries during the period 1960-1980 [94]. In overall, the studies by Vallius and colleagues [83,84,97,85–88,93–96] show that the contamination in the Finnish and Estonian waters of the Gulf of Finland is still high, and many of the levels of heavy metals in sediments have not decreased over the last 20 years, but rather increased (Table 2). Additionally, in a recent study by Vallius, the Finnish coast was found to have exceeding values of As, Hg, Cd and Zn compared to Canadian sediment quality standards [88]. This study shows that the majority of the heavy metals found, have been deposited at increasing levels with time uo tp the present time, with emphasis on As, Cd, Cr, Pb, Cu and Hg. One question that necessary arises from these data-sets, is, how much does the long-term exposure affect such a vast ecosystem as a whole, and which organisms suffer primarily from these patterns of contamination. All marine organisms suffer from this long term accumulation of heavy metals, however some particular biota are more exposed than others. In a study by Gubelit et al [89] from the Russian Academy of Sciences, a thorough investigation into the distribution of the heavy metals in the coastline was recently published. The study shows that the levels of dissolved heavy metals (ionic species) in surface waters are high, where for instance levels of Ni2+ in water samples were found to be as high as 29 μg/ml, while Zn2+ was registered at 460 μg/ml, and Cu2+ at 104 μg/ml. Barium levels (Ba2+) were also found at alarming levels, 442 μg/ml in surface water. All these measurements were made in the region of Sosnovyj Bor, in the south east end of the Gulf of Finland, in the south part of the Leningrad Oblast. Also, the levels of heavy metals accumulated in algae were registered by Gubelit et al [89], which showed that Zn is found at highest levels in algae compared to other heavy metals, where concentration maxima are 44.80 μg/g and minima are 14.95 μg/g dry weight alga. Chromium levels are also high, with maxima of 18.45 μg/g dry weight, and minima of 3.97 μg/g dry weight alga. Nickel was also found at similar levels in algae, with maxima at 10.4 μg/g and minima of 3.31 μg/g. Gubelit et al [89] made also measurements in the sediments

14 in Russian waters of the Leningrad Oblast, which are reported in Table 2. A study by Berezina et al [91] showed that several critical factors caused by the constant pollution levels are of particular relevance to any ecosystem assessment a) the emergence of opportunistic algae, which deplete the ecosystem for nutrients, b) change in microbiological profile of the sediments, which affect the production of sulfates, nitrates and other vital metabolites for nitrogen and oxygen fixation and transformation, c) alterations of the population of microbenthos, which in turn form the nutrient basis for several species of fish [98–100]. Additionally, heavy metal pollution leads ultimately to hypoxia/anoxia in the bottom layers of the water column and deteriorates the biodiversity of the respective ecosystem and leads to the formation of dead-zones [101]. This was showed in a study were mainly Beggiatoa bacteria were found to thrive in the anoxic environment in the Gulf of Finland, generating low nutrient levels and thus leaving the bottom parts deprived of marine life [102]. The viability of an ecosystem exposed to heavy metals can also be assessed by evaluating the phytoplankton index (saprobity), particularly for short-term threats [91], and give indications on the pelagic productivity in heavy metal polluted waters. Opportunistic algae which deplete the nutrient levels by luxury consumption give furthermore an additional method for forming a diagnosis for heavy metal-contaminated waters, where biodiversity is directly reduced, as also found on land-ecosystems [103]. At last, a biomarker assay for metallothionein activity in the bivalves Mytilus edulis and Macome balthica has been applied in the Gulf of Finland to determine its ecotoxicological condition, by determining the gene-expression response which the named mussels display to heavy metal levels suspended in the water and found in the sediments [104]. The results from the study showed that ecotoxic stress occurs particularly during the April and July months for M. edulis and in June for M. balthica. Similar trends were observed for other enzymes as well, including acetylcholineesterase, catalase and glutathione-S-transferase, which all encompass the category of detoxification enzymes normally used for eco-/toxicity assays [105–107] . Conclusively, the Gulf of Finland has not experienced a sufficiently effective decline in concentrations since the early 1990s, and many heavy metals are still rising in concentration in sediments taken along its shores (Fig 7). Cadmium and mercury are however on the decline, accounting for the measured sediments in the Estonian and Finnish waters (Fig 8).

The Bay of Bothnia and the Bothnian sea (including the Åland Sea)

15 The Bothnian bay is probably one of the most spectacular regions of the Baltic sea, with a wide stretch of coast in contrast with the hilly North-Scandinavian landscape which freezes yearly for several months. The Bothnian bay is rich in bird life including black guillemot, velvet scoter, oystercatcher, lesser black-backed gull, western capercaillie and willow ptarmigan. The Bay of Bothnia has also a thriving seal population, with the ringed and grey seals [108] as the main two species which feed off herring and Baltic sea cod, as well as salmon. The Bothnian bay is the Northern most region of the Baltic sea, and with a vast influx of freshwater from eight major rivers in the region and a limited salt-water supply from the tides of the Atlantic ocean, it is virtually a fresh water body which extends from Kemi in Finland towards the shallow waters between the archipelago of Vasa (coast of Finland) and Umeå in Northern Sweden (Fig 9), a region also known as “The Quark” (Kvarken). From these shallows and Southwards, the Bothnian sea emerges and extends 350 km to the archipelago of Stockholm and the archipelago of Åland (Fig 2, 9). This region has a similar bird life as the Bay of Bothnia, however the sea-life is different, a smaller seal population occurs here - predominantly composed of grey seals [109], and occasionally sightings of both wales (porpoise) [108] and most recently, Atlantic bluefin tuna have been reported, which was extinct in the region until recently [110]. Fish types here include flounder cod, herring, salmon as well as sprat [111]. Interestingly, this region of the Baltic sea has the higher number of protected areas of the entire Baltic: with three protected areas along Finland’s coastline and one along Sweden’s, respectively the Uusikaupunki Archipelago, the Oura Archipelago, the Outer Bothnian Threshold Archipelago (The Quark) and the Trysunda/Ullanger/Ulvoarna/Ulvo [112–115], comprising altogether the Bothnian Sea National Park. This region has been particularly prone to accumulation of environmental pollutants by the reduced influx of oceanic salt water and several natural underwater barriers forming from the archipelago of Åland and Northwards to Kemi. However, the most critical issue with this region of the Baltic has been the release of effluents and pollutants from several industries established on the coastline over the last eight decades. Particular concern has been directed towards the metallurgic, chemical and paper mill industries in the following regions on the Swedish coast line: Obbola-Holmsund with a sulfate-mass industry and a sawmill as well as an industrial harbor; Nordmaling-Rundvik with a board factory and sawmill; Burefjärden with wood carvings, sawmills, and metal smelters; Örviken with pulp mill, sawmill, sulfate factory and metal smelter; Kåge with sawmill; Furuvik in Gävleborg county with wood-impregnation industry, sawmill and papermill; Sundsvall with papermill industries and incineration plants [109,116–126] (Fig. 9). Considering heavy metals only,

16 the majority of heavy metals registered over several decades in sea bed sediments are As, Cu, Zn, Pb, Hg, Cd which have declined steady since their highest levels (registered in 1986) [20,94]. However, given the nature of heavy metal contamination, their ability to re-suspend, bioaccumulate, and magnify in the food chain and their overall slow transformation cycle, a variety works of have been published over the last decades on the state of ecological health of the Sea and the Bay of Bothnia, with both updates on the changes in concentrations over the years and also reporting on trends of heavy metal circulation, sedimentation and re-suspension. Given the extensive size of this section, the various cited studies are subdivided into decennials, in order to have an ordered structure.

S tudies from the late 1980s and 1990s Söderlund et al [117] studied the accumulation of ten heavy metals in seaweed species, with emphasis on the aquatic moss Fontnalis dalecarlica and Fucus Vesiculosus, which of, the former is widespread in the Bothnian sea and Northern Baltic sea in general. Interestingly, the measured levels of several heavy metals in Fucus Vesiculosus were higher than in the sediments of Bay of Riga, and also accounting the most polluted regions of the Gulf of Finland (i.e. the waters of the Leningrad Oblast at Vyborg bay). Söderlund et al measured alarming levels at 1mg/g of Zn in the sea weed plants, followed by 30-790 μg/g for Fe, 5-590 μg/g for Al, 65-410 μg/g for Mn, 15-67 μg/g for Ni, 31.9 μg/g for Pb and 3.4-24.5 μg/g for Cd (Table 3). The other heavy metals were measured below thresholds. Nevertheless, all heavy metals measured in the study by Söderlund et al [117] were measured at seventeen sites off the Swedish coastline on the Bothnian Sea, and showed a pattern where the acutely polluted sites were respectively in the southern parts of the Bothnian Sea, with Hornsland and Prästgrundet (Region F, figure 9), Grinda (Stockholm archipelago), Örskar (100 km south-east of region G, Fig 9) and Norsten (outer Stockholm archipelago). The source of the pollution in these regions is associated with the release from the major industries of Sundsvall and Gävle which have been active over 6-7 decades (Fig 9). Another particularly polluted region was Nynähamn, which is on the south side of the Stockholm archipelago, and which has been exposed to oil refinery over several years and for the development of chemicals for the military industry [117]. The lake Mäleren in the region of Stockholm and Uppsala has also, according to the study by Söderlung et al, been a source of heavy metal accumulation and contamination of the Stockholm archipelago [117]. Another major source of the heavy metal pollution in the Sea of Bothnia was found to be the Dalälven (the river of Dalarne),

17 which flows out in the Sea of Bothnia in the region of Gävle (Region G, Fig 9) carrying high concentrations of Zn which was found at the highest levels in this part of the Sea of Bothnia [117]. Cadmium however, was found at higher concentrations in the region of Sundsvall (Region F, Fig 9), as also Pb, Co, Cu and Ni. This was associated with both industrial activity in this region, as well as a reduced salinity in the brackish water which lead to higher accumulation of metals in the sea weed [117]. In 1996, Borg and Jonsson [127] published a study on the levels of heavy metals in the Bothnian sea and the northern parts of the Baltic proper. The former region and the archipelago of Stockholm were both found to be contaminated by elevated levels of arsenic and mercury in sediment samples, and distribution patterns showed in agreement with the study by Söderlund et al [117] a dominant prevalence of heavy metal contamination in region F and G (Fig 9), including stable levels of arsenic and mercury in the open Bothnian sea and further east towards the Finnish coast line. The analysis by Borg and Jonsson [127] showed also that the highest levels of mercury were found in the Bay of Bothnia near region C, E and D (Fig 9), as well as North of the Bay, close to the town of Kemi. The concentrations and heavy metal species are reported in Table 3. Enckell et al [128] covered in 1987 the overall state of the Gulf and the sea of Bothnia, where they mapped 47 heavy metal emission sites on the Finnish and Swedish shores, with a majority of the sites being industrial workshops, tanneries and mining areas. Additionally, metal works and chemical plants, including waste incineration sites were mapped, which contributed to the release and deposit of high levels of Fe, Zn, Cu, Pb, Cd, Hg and Cr on the coast line of Kokkola (Finland), and Fe, Zn, Cu near Raahe (Fig 9) [128]. In the sea of Bothnia, the majority of the sites located on the Finnish coastline released a larger number of different heavy metals, with Vanadium and Titanium in addition to the heavy metals mentioned above, particularly in the region of the Kokemänjoki and Eurajoki estuaries and in the Finnish archipelago South- East of Åland (regions L- N and Q, Fig 9). It was found that the pathways of emission of heavy metal particles were by oxygen furnaces for metal works and workshops, and also by the release of water-borne particles and suspensions in volatile droplets [128,129]. Additionally, 4 major heavy metal mines were active along several rivers in the North of Sweden and Finland, releasing heavy metals in the bay via river- ways of Kalixälven (river of Kalix) and Torneälven and utterly 6 mines distributed along the Swedish side, near the major rivers of Luleåälven, Piteälven and Ljusnan and Dalälven south of Sundsvall Enckell et al further found that the sites where titanium and vanadium was released (Fig 9, L-N) showed a dispersion of the heavy metals 20 km off-shore in the deepest sediment layers (30-40 cm) and a total area of 200 km2 where no water organisms were found at all, and the

18 ecosystem was severely disturbed. Fish taken in the region of Kokkola (Fig 9 – region I) such as Cottus Quadricornis (Fourhorn sculpin) were found in several cases with deformed vertebral columns as well as reduced swimming abilities [128]. Outside the region of Pori (Fig 9 - region O) eye defects were registered in Baltic herring, as well as flight of fish from the region. Various species were furthermore found to accumulate different heavy metals, whereas Zn was found particularly at higher concentrations in Mesidotea isopods and Macoma clamps, while Copper was found in both Mesidotea and Baltic sea Herring. Cadmium was equally absorbed in Mesidotea isopods and Macoma clamps, while lead chromium was found mostly in Macoma clamps [128]. Cadmium levels in baltic herring liver were also measured in 2014, and registered to 0.16mg/kg [130]. Mercury however, was found at particularly high concentrations in Baltic herring in the region of Gävle (Sweden) (Fig 9 – region G), which was registered with 0.23 mg Hg pr. kg tissue in 1980 and declined towards 0.025 mg/kg in 1985. Mercury levels have since been registered in baltic herring liver in 2014, where they were traced to 0.020 mg/kg in the coastal waters of Gävle, Umeå, Luleå and Kokkola (Finland) [130]. The original Hg levels in the sediments of the Gävle region were as high as 3mg/kg sediment, and it is estimated that the region outside Gävle contains 6 tons mercury in the sediments [128]. The sediments in the region were found to contain 0.66-0.94 mg/kg Hg in 1980 which has declined stably since. The study by Enckell et al showed interestingly that the wastewater and manufacturing plants around the Bothnian bay discharged yearly up to 129 tons Zn pr. yr, 28.2 ton Cu pr. yr, 14 tons Pb pr. yr, 2.8 tons Cd pr. yr, and 400 kg Hg pr. yr. Furthermore, the amount of Cr released into the bay peaked 7.7 tons pr. yr, 64 tons pr. yr for Ni, and astounding 272 tons pr. yr of arsenic. Cobalt amounts released into the Bay were furthermore 51 tons pr. yr, while iron was released at 1000 tons pr year into the Bay of Bothnia [128]. These figures indicate that the sources of pollution of heavy metals in the bay and Sea of Bothnia were excessive and required rapid regulation and new technologies. In 1995, the relationship between the rapid land-uplifting of the Bothnian Bay (1 cm pr year) and the exposure of sedimented heavy metal pollutants released in the 1940s was published by Leivuori and Niemistö [131], and introduced a new and critical scenario of perpetual re-contamination of a coastal ecosystem. The event of uplifting of the land around the Bothnian sea has endured for 9000 years given the glacial melting of the Fenno-Scandian block [132], and caught the attention of various Scandinavian and European scientists during the 1990s [131,133–135]. The major ecotoxicological implications of this phenomenon have been studied widely since [136–145], however, Leivuori and Niemistö [131,135] were the first to publish quantitative results on this new

19 phenomenon of re-contamination of natural habitats by exposure of “old pollutants” with emerging sediments from the land-uplift process. In their studies, Leivuori and Niemistö measured the levels of heavy metals on the South-Eastern and South-Western coast of the Bothinian sea and the North of the Bothnian Bay. Their study showed that it was the first 5-10 meters of coastline sediments that raised most concern for the coming decades of pollution emergence, as the content of mercury, cadmium, lead and zinc was at it’s highest for both the Bothnian Sea and Bothnian Bay in this depth-range [135]. Arsenic, lead and cadmium were instead found at highest concentrations below 100 meters depth range [131]. The locations of major concern are the region of Rönnskär - Sweden (Fig 9 – region E), with major contamination of the sediments by mercury, the region around Kokkola and Oulu (region H, Fig 9), with the same contamination type, and Rönnskär – Sweden again with alarming levels of lead and cadmium. Other regions such as Kristinakaupunki and Pori in Finland (region L, Fig 9) and Kokkola show also high levels of contamination by lead and cadmium, where both increase by depth [135]. The maximum concentrations of mercury were found at approximately 8 cm beneath the sediment surface, as also for lead. Zinc and cadmium were instead found at the highest concentration between 10 and 16 cm depth and at 2cm and 8-16 cm depth respectively [131]. This pertains that particularly lead and mercury have been released in excessive quantities during a specific period, which was given to be during 1950-1970 [131] while cadmium was released rather stably throughout the period 1920-1990. Zinc was released during a shorter period, from 1930-1950 [131]. Table 3 gives a detailed picture of the levels, locations and periods of the measurements made by Leivuori and Niemistö [131,135]. This rather alarming development of the Bothnian Bay and Sea ecosystem raised the levels of mercury in animal life around the Åland islands, in the Quark shallows, and along the entire west-coast of Finland [146]. Vuorinen et al measured level of Hg and Cd in Baltic herring caught off the coast of Finland, near the Quark, by the town of Pori (region L, Fig 9) and northwards to Kemi, as well as outside Kokkola and about the Åland islands. In their analysis, levels of mercury were 0.0025 mg/kg herring flesh (fished in the Bothnian Bay in 1992), while the highest levels were traced back to 1982, when the concentration was 0.04 mg/kg [146]. For the Bothnian Sea, the levels were similar, ranging from 0.01-0.03 mg mercury pr. kg herring in the period from 1979-1992. The study shows however that the highest levels were found in sea trout around the Åland islands, with 0.16 mg Hg/kg flesh [146]. The variations in the measurements indicated that mercury was and still is a predominant problem of the fish of the Baltic sea.

20 Studies from the 2000s to present. Since the “dark ages” of pollution of the 1970s and 1980s, the 1990s showed the first improvements on reducing pollution to the Bothnian sea, particularly fueled by changes in political relationships between European countries and eastern Baltic states. This gave rise to transnational collaborations among Baltic states, as well as Russia. At the same time, a series of nature protection initiatives were organized, with emphasis on the above-mentioned establishment of National Parks for the Bothnian Sea. However, next to the industrial activities which have experienced a reduction in emissions by more stringent legislation, compared to the period before the 1980s, some improvements were also reported after the region of Stockholm applied tertiary treatment on the sewage released in the Baltic bay, south-west of the Åland sea [147]. In a review by Kautsky and Kautsky [148] the authors argue that the Baltic proper (see next section) is more polluted than the Bothnian marine ecosystem in relation to heavy metal pollution, however the Bothnian system experiences more severe consequences by the reduced circulation compared to the Baltic proper [102]. This attributes the Bothnian ecosystem a particular vulnerability to the persistence of organic contaminants [34,149–152], the resuspension of heavy metals (see above), and the land-uplift of contaminated sediments, which altogether make the Bothnian ecosystem an area of ecotoxicology focus for the new millennium [153]. A particular reason for this is that the source of pollution in the Baltic has recently been debated in a study by Bindler et al [154], where the origin of some heavy metal found in the Bothnian Sea and on the coast line of East Sweden, such as lead and copper, appear to origin from metal ores that have naturally contaminated the environment since the 10th century. These ores are found beneath the surface of the Swedish forests located in the north eastern parts of Stockholm, in an area of 10000 km 2, where the major rivers lead the heavy metals to the largest lake in the Eastern Swedish region, the Mäleren. Mäleren has been a major contributor to the pollution of the Baltic, particularly during the industrial era of 1950- 1970, and since declining in levels of contaminants [154–159]. The levels of lead, which origin from this area were measured by Bindler et al in 2009, who found that particularly lead is found in naturally polluted lakes and rivers at concentrations up to 23.8 μg/g sediment. The lake Mäleren is indeed one of the most polluted of these fresh water estuaries (23.4 μg/g), however Freden - another large lake in the area displays higher levels of Pb (23.8). The concentration of Pb in the Baltic sea at the outlet of this fresh water estuary system, the Stockholm archipelago, is 19.5 μg/g sediment [154]. Lead pollution in this region appears thus to be mainly contributed by natural ores in a large fresh water estuary in the region. This contamination has been enduring for over 4000 years, and the

21 most contaminated era can be traced back to 1835 B.C [154]. These data reflect Pb in particular, however also other metals such as Cu, As and Hg have leaked from metal ores into the fresh water estuary over millennia, with As at 12 μg/g 1800 B.C., Cu up to 100 μg/g in 1800 B.C. and Hg at 1 μg/g 1800 B.C [154]. The evident pollution from natural ores in this period may be related to earthquake or other sudden natural events. The results show furthermore that mining activities have had declining influence on pollution since 1900, and were most severe during the 15-18th centuries. A significant contribution to the pollution of the Stockholm archipelago may therefore be attributed to the natural pollution from the metal ores in the local fresh water estuaries, and from 15 th-18th century mining activities. The environmental monitoring of the Bothnian ecosystem has since the early 2000 been greatly represented by research from Swedish authorities, in particular by the Department of Environmental Research and Monitoring of the Swedish Natural History museum on behalf of the Swedish Environmental Protection Agency in the period of 2003-2017 [160]. This extended report mainly focuses on the contamination of pollutants in biota, with emphasis on organic and inorganic pollutants. The report includes the heavy metals Hg, Cd, Ni, Cr, Zn, Cu, Ag, the metalloid As and the chalcogen Se, and reports the accumulation of these elements in Baltic herring, perch and eelpout among other biota. The measurements show that Hg is still a priority pollutant for herring, where levels higher than 40 ng Hg pr. g. herring muscle and found particularly in the region of the southern Bothnian Sea, on the coast of Gävle and south of Stockholm, in the North Baltic proper (Fig 9 - G). Particularly high average levels were found in herring with 40 ng/g w.w. Hg, while the lowest were found in Herring in the Bornholm basin, with 13.1 ng Hg pr g herring. Another recent study shows that Baltic herring in the Bornholm basin displays higher concentrations than 20 ng mercury pr. g muscle [130]. The results show a decline compared to 1980, when the equivalent levels in the region of Gävle were 60-180 ng/g, however the decline is indeed slow and is more rapid in parts exposed to the Atlantic influx [160]. The Northern part of the Bothnian sea were also assessed for levels of Hg in herring, where the levels in the region of Luleå (Fig 9D, Fig 10) are among the highest [130,161]. The region of Kullen and Kinnbäckfjärden (region B and E, Fig 9) and the Stockholm archipelago are also regions where herring is particularly contaminated by mercury (refer to Fig 10). Other parts of the Bothnian sea are near or below the threshold values [160]. Interestingly, the level of Hg in a second fish specie, perch, were found to be as high as 80 ng/g in 2015, in the region of Homöarna, outside Umeå, north of the Quark (Fig. 9 – region A) [160]. The analyses in perch muscle show that the levels of Hg have fluctuated between 40 and 80

22 ng/g over the last 15 years and no significant decrease has been concluded for this specie [160]. High levels of Hg were found also for eelpout, with 50ng/g, however recordings stopped in 2005, and have been measured for only a ten year-period in the same region as for the perch (Fig 9, A). The highest levels for this specie were registered in 2003, when 150 ng Hg pr. g. eelpout muscle were measured by Bignert et al [160]. Measurements of Hg in avian life were also made in this extensive report, and show a gradual decline of mercury in guillemot egg since 1969. The same group reported similar trends for Pb (Fig 10), which has declined in herring liver since the early 1980’s in all regions of the Bothnian sea and Bothnian Bay. The overall trends show however that Pb levels are higher in herring caught off the Southern and Western coast of Sweden, where levels are up to 8 times higher than in the Bothnian marine system. The same accounts for perch, eelpout and mussel, however cod differs from other species in the Bothnian marine system, where it was found with moderately increasing levels of Pb in liver samples from 2005 (0.02 Pb μg/g) to 2015 (0.04 μg/g). The lowest levels of Cd in herring are found in the Bothnian marine system, when compared to the other parts of the Swedish coast, however the concentrations of Cd in herring liver in the marine ecosystem of Bothnia fluctuate significantly during the period 1980-2015, with peak levels found in 2008 at 5.5 μg/g Cd pr d.w. herring liver (off the coast of Gävle Fig 9 – G), and 3.75 μg Cd pr. g d.w. herring liver caught in the same region in 2014 [160]. High Ni levels have been measured outside the region of Gävle (Fig 9 – G), where average concentrations at 2.3 μg/g Ni were found in the period of 2005-2015 in herring. Herring caught in the Bothnian Bay display instead lower levels of accumulation Ni in liver samples in the period 2000-2015, however a sudden increase to 2.8 μg/g was measured in herring caught off the coast of Luleå (Fig 9 – E and Fig 10). Additionally, herring caught recently in off-shore parts of the Bothnian sea has also been found to have high levels of nickel in liver samples, with peaks levels at 2.7 μg/g measured in 2015 [160]. Chromium was also measured by Bignert et al in herring liver (Fig 11), who found that the highest levels are found in herring caught in the Bothnian Bay, which is at the highest concentrations of the whole Swedish coastline including the herring caught in the Dano-Swedish strait and Cattegat. However, on a generally declining trend for entire Swedish coastline, chromium has been found at increasing concentrations outside Luleå (Fig 9 – E) since 2007, while most other locations show declining levels reaching below thresholds. Copper and zinc levels in herring liver are generally high for the entire Baltic sea around the Swedish coastline, ranging from <7 μg Cu pr g in herring liver sampled in open Bothnian sea to >14 μg Cu pr. g in the region of Gävle (Fig 9 – G, Fig 11). Levels of copper in herring liver have been generally stable between 10 -20 μg Cu pr. g during the

23 period of 1980-2016 for the Bothnian marine ecosystem, however a slow decline started after 2005 [160]. The equivalent numbers for perch liver samples show lower levels for perch caught in the Bothian Bay, in the region of the Quark. Zinc levels (Fig 12) are found in herring liver at 80 μg/g and above in the entire Bothnian marine system, with no particular difference between locations. In 2015, herring livers caught off the region of Gävle displayed up to 120 μg Zn pr. g herring liver, and concentrations appear stable. Levels of zinc are also stable for perch caught in the Bothnian marine system. Interestingly, herring caught in the Bothnian marine ecosystem has particular high concentrations of Ag compared to the threshold limits (Fig 12), where levels higher than 0.06 μg/g have been found in herring caught on the coast of the Bothnian sea. Levels in herring of the Bothnian Bay are slightly lower, 0.03-0.06 μg Ag pr g liver. Overall, it appears that a source of silver contamination has affected the ecosystem north of the Quark (Fig 12), where concentrations are considerably higher here than the remainder of the Swedish coastline. Also the region south of Sundsvall and north of Gävle (Fig 9 -F) appears affected by higher Ag levels than otherwise observed, along the Swedish coast. As reported above, the mining activities have led to efflux of heavy metals from the largest rivers entering the Bothnian Sea [160]. Silver pollution is also not associated with natural metal ores [154], as found leaking further south towards the Stockholm archipelago and is thus (as Cd and Hg) associated with industrial and anthropogenic activities over the decades. This region of the Baltic sea has also been studied for levels of heavy metals in the sediment samples [162,163]. The report by Apler and Josefsson (2015) points out several locations along the Swedish coastline, and levels of heavy metals in the sediments [163] and is the currently most updated publication on the theme of heavy metals and the condition of the Swedish waters of the Baltic sea. The parts of the North Bothnian Bay show still high levels of Hg, Cd, Co, Cr, Cu, Zn and Pb compared to national standards. It is particularly Cu, Ni and Pb which have increased in the period from 2003-2014, where respective levels are shown in table 3. Additionally, arsenic poses reason for great concern for the status of the sediments in this region of the Bothnian system, where levels are alarmingly higher than the remainder of the coastline of Sweden. The southern parts of the Bothnian Bay were also measured in the same study and show that critically high levels occur in the sediments particularly for As, Cd, Co, Cu, Hg, Ni, Pb and Zn, summing up to 8 heavy metals found at excess levels compared to the remainder of the coastline [163]. Indeed, this part has been exposed to industrial activities over several decades, including mining and with a very find clay- type found in the sediments, the retention of heavy metals and sorption levels are very high, limiting

24 rates of chemical reactions to take place, in either biotic or inorganic sedimentation reactions. Levels for this region are reported in Table 3. The Bothnian sea was also assessed in the period of 2003-2014 for heavy metal levels at three locations [163], southeast of Sundsvall (Fig 9 – North east of region B), off the coast of Söderhamn (Fig 9 – southeast of region B) and the Åland deep (Fig 9, south east off the coast of region G), which all are areas that have been prone to industrial and mining effluents. The data of these most recent measurements are given in table 3. The Bothnian Sea was also assessed in the period of 2003-2014 for heavy metal levels at three locations [163], southeast of Sundsvall (Fig 9 – North East of Region B), off the coast of Söderhamn (Fig 9 – southeast of region B) and the Åland deep (Fig 9, south east off the coast of region G), which all are areas that have been prone to industrial and mining effluents. The data of these most recent measurements are given in table 3. The overall trends of Table 3 are plotted in Figure 11-18. The plots indicate that the Bay of Bothnia should be a priority area for future plans for reduction of heavy metals in effluents, given the rising concentrations for most heavy metals during the period from 2000 to present (Fig 13, 14). Moving further south beyond the Quark, the Sea of Bothnia results also as a marine ecosystem prone to increased pollution, particularly for arsenic, chromium and cadmium (Fig 15, 16), however a visible decline for other species has resulted over the last decade. The third part of this region of the Baltic sea, the Åland sea, displays rather stable concentrations of heavy metals in the sediments and no marked decrease is observed (Fig 17, 18). Altogether, the Bothnian marine ecosystems including the Åland sea is a region which not only suffers from the pollution from the past 60 years of anthropogenic activity but also experiences increments in heavy metal pollution from more recent events, and with the ongoing land-uplift process, the consequences of sediment pollution increase in gravity, affecting both avian and quadruped species and not only marine species. Remediation of particularly polluted coastlines should be considered, possibly using sand-phytoremediation [164– 168] or similar approaches [169].

The central Baltic sea, the Baltic proper and the West coast of Sweden, including the Dano-Swedish strait, Cattegat and East Skagerrak. The central Baltic sea is a pivotal part of the Baltic marine system as it governs the overall distribution of salt water from the tidal waters of the Atlantic by providing a circulation center about the Gotland island. Additionally, the seasons affect the deep water currents in the Baltic and further

25 contribute to circulate water in the bottom layers of the Baltic sea [170]. This circulation is also a source for spreading nutrients, plankton, snow and ice, however also pollutants, algal colonies and debris from natural and anthropological activities [101,171]. The circulation is very slow and waters in the Baltic have an average residence time of 22 years. This long residence period for the Baltic sea combined with the short half-life (of only a year or less) for heavy metals in their solubilized state [172–174] leads to the enhanced retention and sedimentation of heavy metals, which in modern times originate primarily from the southwestern, southern, south-eastern and eastern shores and rivers. The central Baltic sea pertains also a critical feature which directly affects the fate of environmental pollutants: its deep regions provide a particular environment for the biotic transformation of heavy metals to and from solubilized states [175–178], leading to sedimentation and re-suspension of heavy metals depending on the location in the central Baltic [179]. The levels of heavy metals have increased steadily until the late 1990s [179], and the concentrations have remained rather stable since [163,179]. These stable levels are caused by two major properties of heavy metals in biotic red/ox environments, the first is caused by that heavy metals in these brackish water depths affect one another’s suspension potential leading to variations in the concentration of sedimented and suspended species independently of new pollution [179]. The second feature which yields stable concentrations independently of supply of new pollution lies in the resuspension and sedimentation processes which are determined by the geochemical properties of the bedrock, the availability of light, the carbon sources and underwater currents (Fig 19). The central Baltic Sea is subdivided into three sections which directly impact the residence of heavy metals in suspended and precipitated states, a region with reductive potential, a region with oxidative potential and a region with mixed potential (Fig 20). The largest part around the Gotland basin (including also the southern Baltic proper) pertains oxidative potential, which leads to precipitation reactions for most divalent heavy metals, for instance Fe2+(aq) → FeOOH(s) and Fe2+ (aq) → FeS(s) (Fig 19, 20) [179]. A second part of the central Baltic sea has a reductive potential, where precipitated metals are resuspended and reduced to their divalent state (i.e. Fe3+ → Fe2+) and remain in circulation (Fig 19, 20). A third part of the central Baltic has a mixed red/ox chemistry, leading to longer suspension periods, particularly for some metals such as Pb, Hg and As (Fig 20) [179]. The circulation patterns of the central Baltic transport heavy metals from the more polluted waters from the southern parts of the region (i.e. Gdansk bay and east of the river Oder) and distribute them about the Gotland basin, where the red/ox reactions either precipitate or resuspend them by further currents from the cyclic revolution about Gotland. This mechanism tends to make

26 the central Baltic an accumulator of heavy metals where the bottom sediments display higher heavy metal concentrations than many other sites in the Baltic sea [179]. This region is also prone to efflux from the rivers and lakes east and north of Stockholm, which have been steady sources of heavy metals for millennia from leaked metal ores due to probable seismic events 2-3000 years B.C. [154]. The west and north-by-north west of Gotland have also served as locations for dumping of explosives for decades and displays particularly high concentrations of cadmium, zinc, nickel and copper around the entire Gotland basin [127,163]. The pollution by heavy metals (Zn, Cu, Cd, Co, Fe, As, Mo, Mn, V, Pb, Hg) is therefore steadily high around the entire northern hemicircle of Gotland, while the Southern waters are less affected by such excessive concentrations [127,163,180]. The concentrations of the mentioned metals have been steady in the last 20 years, while nickel concentrations have increased 8-fold during the period from 2003-2008 [163] (Table 4). Mercury levels which originate from the last three decades of industrial contamination [181] have decreased in most parts around the Gotland basin, however recent studies indicate that mercury in these regions is oxidized to the more toxic forms MeHg and MeHg-S by cyanobacteria [182,183], which implies a greater toxic impact for marine species. Additionally, mercury pollution has increased in the eastern and north-eastern Gotland basin and appears to be correlated with a simultaneous release of PCB and lead over the last 80 years and is associated with nuclear weapon tests made by the soviet union during the 1950s (see lead levels in East Central Baltic section in Table 4) [181]. By high levels of heavy metals, the marine life has therefore suffered a great impact in the last decades. According to a recent report [160], Baltic perch from the region north-west of Gotland of Kvadjärden (North Baltic proper) has the highest levels of mercury in liver samples since 1988 (60 ng/g w.w. measured in 2013). On the opposite side of Sweden, on the Western coast, the same dramatic trend results for cod, where the concentrations of Hg have risen steadily since 1980 and peak to 60 ng/g w.w. liver sample (measured in 2015) [160]. The levels in cod have also risen stably since 1980s in the South east region of Gotland, and reached the highest levels since 1980, up to 50 ng/g w.w. liver [160]. The levels of mercury in Stockholm archipelago herring reach also beyond 40 ng/g w.w liver sample (Fig 10) [160]. The same study reports that levels of Cd have also increased in herring (liver samples) on the Western coast of Sweden, around the islands of Väderöarna and Fladen, where averages of Cd concentrations in herring liver surpass 02.4 μg/g d.w. (Fig 21) [160]. Further south and west towards the Danish strait, herring displays also high levels of Ni in liver samples, with averages from 0.26 μg/g and above, while lower levels of nickel

27 are found in herring in the Southern and Northern Baltic proper, up to the Stockholm archipelago [160]. Following the Baltic sea back to the East side of Sweden, towards the Åland sea, nickel levels are slightly lower than the Western, and reach 0.20 μg/g Ni in herring liver samples in the period 2006-2014 (Fig 22) [160]. Levels of Ni in cod and perch liver are generally lower than 0.2 μg/g and have displayed a declining pattern since 1995, when particularly cod caught off the Western coast contained up to 0.5 μg/g Ni in liver samples [160]. Chromium levels are found at quite high concentrations in herring caught in the Dano-Swedish strait, however cod and eelpout caught in the same region, and the Western coastline (Cattegat) and the Northern Baltic proper show levels below thresholds (Fig 11) [34]. Chromium concentrations in other biota are however at concerning levels, as guillemot eggs laid in the region of Southern Gotland have risen in levels of chromium, with up to 1.8 μg/g d.w [160]. The birds hatching in this region are evidently exposed to chromium contamination, which is otherwise not typical for fish caught in the same region. Migratory patterns may however explain these unexpected concentrations, which have risen steadily since 2006 and give reason for concern [160]. Additionally, arsenic levels are found at excessive levels outside the Western coast of Sweden, where herring liver has been sampled recently to 10 μg/g, a pattern which appears recurrent along the entire Western coast [160]. Sediment samples from the central Baltic Sea show that the North, East and West parts of the region are the most affected by heavy metals (Fig 23-28). The summarizing trends for the central Baltic Sea (Fig 23, Table 4) show that the North part of the Central Baltic is stably contaminated by all heavy metals except Zn, Cd and Cu which of the concentrations have declined moderately in the last 10 years [163]. Nickel, chromium and lead have however increased in levels in the sediments, particularly nickel which has nearly doubled in concentration and chromium which has increased considerably over the last 10 years (Fig 23). Cadmium reductions are extremely moderate and appear rather stable since 2003 (Table 4, Fig 23). Cobalt concentrations are also stable in the given period, while mercury has decreased from 0.06 to 0.04 µg/g sediment (Fig 23, Table 4). In the North-West part of the central Baltic, towards the North Baltic proper, concentration of, Zn, Cu, Cd and Ni have risen steadily since 2003 (Fig 24, Table 4). Mercury has also risen from 0.06 to 0.08 µg/g sediment in the same period (Table 4). Cobalt, lead and chromium have been stable since 2003 for this region (Fig 24, Table 4). The North-East part of the central Baltic sea experiences however a moderate decline in Ni and Cd concentrations, however all other heavy metal levels are stable or have increased slightly in the period 2003-2014 (Fig 25, Table 4). Mercury and cadmium levels are also stable for this region, and show only moderate decline for the case of Cd (Fig 25, Table 4). The

28 West part of the central Baltic sea, between Gotland and mainland Sweden, shows a significant decline in the period 1996-2014 for levels of lead, zinc and cadmium compared to other parts of the central Baltic (Fig 26, Table 4), also a moderate reduction in nickel in the sediments. Arsenic, copper and mercury levels appear however still stable for this region, while cadmium has only experienced a minor reduction in levels since 2008, which is virtually unchanged in the entire period 2003-2014 (Fig 26, Table 4). The Eastern parts of the central Baltic sea show a less pronounced decline in levels of most heavy metals, where only lead levels show a marked reduction in concentrations for the period 2003-2014 (Fig 27, Table 4). Most other heavy metals increased in concentrations from 2003 to 2008 and since have slowly declined, with negligible changes for copper, chromium, nickel and arsenic (Fig 27). Mercury levels appear stable for this region, as for all regions of the central Baltic sea, oscillating between 0.05-0.10 µg/g sediment (Table 4). The South region of the Central Baltic (Fig 28) has a similar pollution profile to the Eastern parts of the central Baltic, where only minor reductions are seen in heavy metal concentrations, however these reductions can only be marked as reductions compared to 2008, when measurements showed the highest concentrations over the last 16 years (Fig 28, Table 4). In other words, the period 2003- 2014 shows poor improvements for these regions, particularly for South, East and North region of the central Baltic sea. Additionally, measurements in the South and East parts of the central Baltic region indicate that Cd, Zn, Ni and Pb seem associated to one another (Fig 27, 28), and potentially arise from the same source of pollution, prolonging in the period of 2003-2008. The South Baltic proper (Fig. 29, A), towards the Ode river and Dano-Swedish strait is less polluted than its counterparts in the central Baltic sea. Samples from the Bornholm basin (Table 5) show that this region has little or no deviation from national background given by Swedish authorities. This regards As, Co, Cr, Hg, Ni and Pb. However, for Cd, Cu, and Zn, the deviation from national background is higher, and has increased also in the period from 2008-2014, adding to the list Ni and Pb in the latest measurements made in 2014 (Table 5) [163]. The levels of the two heavy metals have increased quite dramatically, where both have been measured at levels in 2014 five-fold the measurements made in 2008, at slightly different locations (Table 5). The most polluted samples were taken north-east of Bornholm (Fig 29, A), and appear to be part of the cycle of heavy metals from the central Baltic. The southernmost sampling sites of Bornholm (Arkona basin – Swedish- Danish waters) show an increase in the period 2003-2008 for Pb, Zn and Cr, while the other are lower than the North-East parts of Bornholm [163]. An increase in Pb, Zn and Cr in these waters may be related to effluents from the Ode river during several floods since the flood of the century of

29 1997 [184–186], especially accounting for that the exit of the Oder is only 100 nautical miles from the Arkona basin. This increase has also been found to affect the levels of Pb and Zn in liver herring sampled in this very region, which are among the highest in Swedish waters, with Zn levels in herring liver which are stable at 100 µg/g d.w., while Pb levels are at 0.15 µg/g d.w. and Cr levels are stable at 0.05 µg/g d.w. with an exception of 0.15 µg/g registered in 2012 (Fig 10, 11) [160]. The same accounts for Ni levels in herring of this region, which are at the highest levels for the entire Swedish coastline reaching 0.2 µg/g d.w. liver herring measured in 2015 (Fig 22). Moving further up North beyond the Öresund bridge which connects the Scandinavian peninsula with mainland Europe, a second pivotal region was investigated by Swedish authorities. The waters outside Halmstad (Fig 29 B) show an increase in sediment concentrations of Pb, Cr and Ni (Table 5) in a similar fashion as to the Arkona basin measurements [163]. Here, levels of Pb, Cu, Ni and Cd are also among the highest along the Swedish shores for baltic herring (Fig 11, 12, 21, 22), with Cd concentrations in liver samples at 0.6-0.8 µg/g d.w. measured in the period 2010-2014. Cd concentrations were measured at levels below national standards in 2014 however. The equivalent levels accounting for Ni, Cd and Pb are respectively 0.15 µg/g d.w., 0.11 µg/g d.w., 0.04 µg/g d.w. When moving towards the last posts of measurements made by Swedish authorities, the levels outside Göteborg and East Skagerrak (Fig 29 C and D), one can observe general improvements in water quality, and considerable reductions in heavy metal concentrations (Table 5). However, Zn Hg, Cu, Pb and Cr levels are still slightly above national standards. Levels of Cd in eelpoput around the Holmöarna (Fig 29 C), were measured until 2005 and showed a significant increase beyond national standards (2.5 µg/g d.w. liver). Alarming increases in Cu were also registered in eelpout liver in the region of Fjellbacka, close to the East Skagerrak region (Fig 29 D) with levels of 70 µg/ g d.w. liver in 2015 [160]. Mercury levels were particularly high in mussel in the same region in 2005, with 40 ng/g d.w., however these levels have stabilized since and are below national background.

Conclusions In an overall view, the Baltic Sea appears affected by heavy metals contamination in all regions, however the most recent pollution events have occurred in the South-East and Eastern parts, while the major pollution in general which occurred before 1980, where particularly in the Swedish- Finnish waters. The Swedish-Finnish waters, however improved by a series of regulations made in

30 the last 30 years, suffer though from poor circulation from the Atlantic Ocean, and are therefore still affected by old pollution, also including exposed sediments from the uplift of the land in North Sweden. The central Baltic sea is a large reservoir of sediments contaminated from all regions, including the Baltic proper, Estonian waters, Latvian waters as well as Lithuanian/Polish/Russian waters. This is particularly caused by the central Baltic current, which rotates about the Gotland basin and keeps heavy metals in suspension, sedimentation and resuspension by the various microbial communities found in the sediments. The prospects for the Baltic sea in the future are depending on respected legislations made in the regional environmental agreements (i.e. HELCOM) as well as a time-dependent process of mineralization which can require decades, if not centuries for particular parts (i.e. North-East Swedish coastline). Future directions for research include triannal sampling of fish species and sediment-measurements every 5-10 year by nations involved. With further conservation projects and legislation acts on against industrial pollution, the state of the Baltic Sea may be improved considerably within 30-years, possibly making the Baltic Sea a fish- rich sea.

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42 [153] Linderoth M, Granmo M and Magnusson Å 2015 NATURVÅRDSVERKET: Biologisk effektövervakning av organiska tennföreningar. (SWEDISH NATURE CONSERVATION SOCIETY: Biological power monitoring of organic substances compounds). Report. (Stockholm) [154] Bindler R, Renberg I, Rydberg J and Andren T 2009 Widespread waterborne pollution in central Swedish lakes and the Baltic Sea from pre-industrial mining and metallurgy Environ. Pollut. 157 2132–41 [155] Renberg I, Bindler R, Bradshaw E, Emteryd O and McGowan S 2001 Sediment evidence of early eutrophication and heavy metal pollution of Lake Mälaren, central Sweden AMBIO A J. Hum. Environ. 30 496–502 [156] Willén E 2001 Phytoplankton and water quality characterization: experiences from the Swedish large lakes Mälaren, Hjälmaren, Vättern and Vänern AMBIO A J. Hum. Environ. 30 529–37 [157] Willén E 2001 Four decades of research on the Swedish large lakes Mälaren, Hjälmaren, Vättern and Vänern: the significance of monitoring and remedial measures for a sustainable society AMBIO A J. Hum. Environ. 30 458–66 [158] Willén E 1987 Phytoplankton and reversed eutrophication in Lake Mälaren, central Sweden, 1965–1983 Br. Phycol. J. 22 193–208 [159] Bindler R, Rydberg J and Renberg I 2011 Establishing natural sediment reference conditions for metals and the legacy of long-range and local pollution on lakes in Europe J. Paleolimnol. 45 519–31 [160] Bignert A, Danielsson S, Ek C, Faxneld S and Nyberg E 2017 Comments Concerning the National Swedish Contaminant Monitoring Programme in Marine Biota, 201 7 (2016 years data) (Stockholm) [161] Wiberg A B E G E N K S K 2005 Geografisk variation i koncentrationer av dioxiner och PCB i strömming från Bottniska viken och Norra egentliga Östersjön. (Geographic variation in concentrations of dioxins and PCBs in Herring from the Gulf of Bothnia and the northern Baltic Proper.) - R [162] Severin M, Linderoth M, Apler A and Zillén Snowball L 2015 B eskrivning av delprogrammet Metaller och organiska miljögifter i sediment – kust och hav (Stockholm) [163] Apler A and Josefsson S 2016 Swedish status and trend monitoring programme Chemical contamination in offshore sediments 2003–2014 [164] Chowdhury R, Lyubun Y, Favas P J C and Sarkar S K 2016 Phytoremediation potential of selected mangrove plants for trace metal contamination in Indian Sundarban wetland Phytoremediation (Springer) pp 283–310

43 [165] Pedro C A, Santos M S S, Ferreira S M F and Gonçalves S C HALOPHYTES AS VALUABLE TOOLS IN THE PHYTOREMEDIATION OF COASTAL ENVIRONMENTS CONTAMINATED BY TRACE METALS METHODS, Manag. Assess. 103 [166] Sun W H, Lo J B, Robert F M, Ray C and Tang C-S 2004 Phytoremediation of petroleum hydrocarbons in tropical coastal soils I. Selection of promising woody plants Environ. Sci. Pollut. Res. 11 260–6 [167] Zeeb B A, Amphlett J S, Rutter A and Reimer K J 2006 Potential for phytoremediation of polychlorinated biphenyl-(PCB)-contaminated soil Int. J. Phytoremediation 8 199–221 [168] Smith K E, Schwab A P and Banks M K 2007 Phytoremediation of polychlorinated biphenyl (PCB)-contaminated sediment J. Environ. Qual. 36 239–44 [169] Manzetti S and van der Spoel D 2015 Impact of sludge deposition on biodiversity Ecotoxicology 1–16 [170] Czub M, Kotwicki L, Lang T, Sanderson H, Klusek Z, Grabowski M, Szubska M, Jakacki J, Andrzejewski J and Rak D 2018 Deep sea habitats in the chemical warfare dumping areas of the Baltic Sea Sci. Total Environ. 616 1485–97 [171] Granskog M A and Kaartokallio H 2004 An estimation of the potential fluxes of nitrogen phosphorus, cadmium and lead from sea ice and snow in the northern Baltic Sea Water. Air. Soil Pollut. 154 331–47 [172] Fonselius S H 1969 Hydrography of the Baltic deep basins III [173] Fonselius S and Valderrama J 2003 One hundred years of hydrographic measurements in the Baltic Sea J. Sea Res. 49 229–41 [174] Fonselius S H 1970 On the stagnation and recent turnover of the water in the Baltic Tellus 22 533–44 [175] Thamdrup B, Glud R N and Hansen J W 1994 Manganese oxidation and in situ manganese fluxes from a coastal sediment Geochim. Cosmochim. Acta 58 2563–70 [176] Laanbroek H J 1990 Bacterial cycling of minerals that affect plant growth in waterlogged soils: a review Aquat. Bot. 38 109–25 [177] Yli-Hemminki P, Jørgensen K S and Lehtoranta J 2014 Iron–manganese concretions sustaining microbial life in the Baltic Sea: the structure of the bacterial community and enrichments in metal-oxidizing conditions Geomicrobiol. J. 31 263–75 [178] Nealson K H, Belz A and McKee B 2002 Breathing metals as a way of life: geobiology in action Antonie Van Leeuwenhoek 81 215–22 [179] Hallberg R O 1991 Environmental implications of metal distribution in Baltic Sea sediments Ambio 309–16

44 [180] Kuss J, Krüger S, Ruickoldt J and Wlost K-P 2018 High-resolution measurements of elemental mercury in surface water for an improved quantitative understanding of the Baltic Sea as a source of atmospheric mercury Atmos. Chem. Phys. 18 4361–76 [181] Moros M, Andersen T J, Schulz‐Bull D, Häusler K, Bunke D, Snowball I, Kotilainen A, Zillén L, Jensen J B and Kabel K 2017 Towards an event stratigraphy for Baltic Sea sediments deposited since AD 1900: approaches and challenges Boreas 46 129–42 [182] Kuss J, Cordes F, Mohrholz V, Nausch G, Naumann M, Kruger S and Schulz-Bull D E 2017 The impact of the major baltic inflow of December 2014 on the mercury species distribution in the Baltic Sea Environ. Sci. Technol. 51 11692–700 [183] Kuss J, Wasmund N, Nausch G and Labrenz M 2015 Mercury Emission by the Baltic Sea: A consequence of cyanobacterial activity, photochemistry, and low-light mercury Transformation Environ. Sci. Technol. 49 11449–57 [184] Bischoff A and Wolter C 2001 The flood of the century on the River Oder: effects on the 0+ fish community and implications for floodplain restoration Regul. Rivers Res. Manag. An Int. J. Devoted to River Res. Manag. 17 171–90 [185] Poff N L 2002 Ecological response to and management of increased flooding caused by climate change Philos. Trans. R. Soc. London. Ser. A Math. Phys. Eng. Sci. 360 1497–510 [186] Glenz C, Schlaepfer R, Iorgulescu I and Kienast F 2006 Flooding tolerance of Central European tree and shrub species For. Ecol. Manage. 235 1–13

45 Figures and legends

Figure 1. Locations in the Gulf of Gdansk with sediments and fish contaminated by 137Cesium [28] . The squared regions indicate the most contaminated region in the Gulf of Gdansk [36].

46 Figure 2. Map of the Baltic Sea and locations of the major marine ecosystems and estuaries.

47 Figure 3. Declining concentrations of several heavy metals in sediments of the Gulf of Gdansk. Graph accounts only maximal concentrations measured in the given years of table 1. Measurements for some metals stop midway given in-existing data from the respective studies.

48 Figure 4. Map of the Bay of Riga and its boundaries of Saaremaa and Kura kurgu hoiuala (blue shallows between Saaremaa and mainland to the South-West). Major rivers: A: River Gauja; B: River Daugava; C: River Lielupe; D: River Pärnu.

49 Figure 5. Alarming trends for the levels of several heavy metals in sediments of the Bay of Riga. Graph accounts only maximal concentrations measured in the given period using values published by Leivuori et al, Yurkovskis et al and Poikäne et al [71,74,75].

50 Figure 6. Contamination of heavy metals in the Gulf of Finland. Red-shaded region indicates the region in the Gulf of Finland with the highest levels of Cu, Zn, Hg, Pb and Cd. Data shown in Table 2 and derived from reference [24].

51 Figure 7. Rising concentrations for several heavy metals measured in sediments of the Gulf of Finland. Graph accounts only maximal concentrations measured in the years given in table 2. Measurements for some metals stop midway given in-existing data from the respective studies.

52 Figure 8. Declining concentrations of cadmium and mercury measured in sediments of the Gulf of Finland. Graph accounts only maximal concentrations measured in the years given in table 2. Measurements for some metals stop midway given in-existing data from the respective studies.

53 Figure 9. Map of the Bay and Sea of Bothnia and pollution sources over the last 10 decades. A: Obbola-Holmsund; B: Nordmaling-Rundvik; C: Burefjärden; D: Örviken; E: Kåge; F: Sundsvall;

54 G: Gävle – Furuvik; H: Raahe ; I: Kokkola; J: Kyrönjoki estuary; K: Vaasa; L-N: Kokemäenjoki estuary, mäntyluoto, Eurajoki estuary; O: Rauma; P Naantali; Q: Taalintehdas; R: Koverhar; S: Sköldvik; T: Kymijoki estuary.

55 Figure 10. Levels of mercury and lead contamination in Baltic sea herring, published in 2017 by the Swedish Environmental Authorities [160]. Reprinted with permission from the Swedish Environmental Protection Agency.

Figure 11. Levels of chromium and zinc contamination in Baltic sea herring, published in 2017 by the Swedish Environmental Authorities [160]. Reprinted with permission from the Swedish Environmental Protection Agency.

56 Figure 12. Levels of silver and copper contamination in Baltic sea herring, published in 2017 by the Swedish Environmental Authorities [160]. Reprinted with permission from the Swedish Environmental Protection Agency.

57 Figure 13. Variable trends in the concentrations of heavy metals measured in sediments in the Sea of Bothnia. The plot accounts only maximal concentrations (Table 3). Measurements for some metals start/stop midway given in-existing data from the respective studies.

58 Figure 14. Stable trends in the concentrations of mercury and cadmium measured in sediments in the Sea of Bothnia. The plot accounts only maximal concentrations (Table 3). Measurements for some metals start/stop midway given in-existing data from the respective studies.

59 Figure 15. Increasing concentrations for several heavy metals measured in sediments in the Bay of Bothnia. The plot accounts only maximal concentrations (Table 3). Measurements for some metals start/stop midway given in-existing data from the respective studies.

60 Figure 16. Increasing concentrations for cadmium measured in sediments of the Bay of Bothnia. The plot accounts only maximal concentrations (Table 3).

61 Figure 17. Stable concentrations for several heavy metals measured in sediments of the Åland Sea. The plot accounts only maximal concentrations (Table 3).

62 Figure 18. Stable concentrations of cadmium and mercury measured in sediments of the Åland Sea. The plot accounts only maximal concentrations (Table 3).

63 Figure 19. Sketch of the cycle of transformation of released iron in the environment. Similar states apply for Mn, Cr, Co and V. Ionic Ni, Cu and Zn remain more easily in insoluble suspensions, as their poorly soluble hydroxide forms are more dependent on strongly basic environments to form.

64 Figure 20. The oxidative, reductive and mixed environment in the central Baltic sea. Regions in pink: oxidative environments; regions in purple, reductive environments, regions in grey: mixed chemical potential. 1. Deepest location of the Baltic Sea, the Landsort deep (459 m).

65 Figure 21. Levels of mercury and cadmium in Baltic sea herring, published in 2017. Reprinted with permission from the Swedish Environmental Protection Agency [35].

66 Figure 22. Levels of nickel and cadmium in Baltic sea herring, published in 2017. Reprinted with permission from the Swedish Environmental Protection Agency [160].

67 Figure 23. Stable concentrations for several heavy metals measured in sediments of the North Central Baltic Sea. The plot accounts only maximal concentrations measured during sampling (Table 4).

68 Figure 24. Stable concentrations for several heavy metals measured in sediments of the North- West Central Baltic Sea (North Baltic proper – North West of Gotland). The plot accounts only maximal concentrations measured during sampling (Table 4).

69 Figure 25. Stable concentrations for several heavy metals measured in sediments of the North- East Central Baltic Sea. The plot accounts only maximal concentrations measured during sampling (Table 4).

70 Figure 26. Declining levels for several heavy metals measured in sediments of the West Central Baltic Sea (Baltic Proper). The plot accounts only maximal concentrations measured during sampling (Table 4).

71 Figure 27. Weakly declining levels for several heavy metals measured in sediments of the East Central Baltic Sea. The plot accounts only maximal concentrations measured during sampling (Table 4).

72 Figure 28. Weakly declining levels for several heavy metals measured in sediments of the South Central Baltic Sea. The plot accounts only maximal concentrations measured during sampling (Table 4).

73 Figure 29. The locations of the sampling sites in the South-West Baltic, the Dano-Swedish strait, and the West coast of Sweden. A: Bornholm basin; B: South-Cattegat (Rödebank); C: Cattegat; D: East Skagerrak – North West coast of Sweden.

74 Tables and legends

Table 1. Contamination recordings of selected heavy metals made over the last 20 years in sediments of the Gulf of Gdansk. Concentrations in μg/g sediment. Region Zn Pb Cd Ni Sr Cu Fe Co Ref. and period Gulf of 208- 42-180 1.0-6.9 14-56 148-230 20-133 1.0-4.8 7.2-18 [160] Gdansk 1470 (1996- 2000) Gulf of 61-228 28-90 0.3-1.7 19-49 87-107 15-57 2.8-6.4 5.9-22 [37] Gdansk (2004) Gulf of 400-800 - 0.5-3.5 0.5-2.5 - 30-180 500- 1.5-4.5 [35] Gdansk 3000 (2010) Open 300-700 - 0.5-1.3 1.0-4.0 - 20-380 400- 1.2-5.5 [97] sea (5 2250 n.m. off shorelin e of the Gulf of Gdansk and Oder basin) Gulf of 7.9- 6.7-86.1 0.03- - - 1.35- - - [37] Gdansk 1.32 123.1 71.32 (2017) Gulf of 130.00- 5.00- 1.00- 11.00- - 1.00- - 1.00- [89,94] Gdansk 2.00 33.00 5.61 191.00 56.00 43.00 (2017)

75 Table 2. Contamination recordings of selected heavy metals made over the last 20 years in sediments of the Gulf of Finland. Concentrations in μg/g sediment. Regio Zn Pb Cd Ni V Cu Hg Co Cr Ref. n and period Gulf 199.00 51.00 1.20 - - 43.00. - - - [97] of Finlan d (1992- 1996) Gulf 1.74- 1.79-76 - 1.40- 1.10- 1.50- 0.05- 5.10-.2 1.30- [95] of 223 41.20 63.80 53.30 9.00 3.20 113.00 Finlan d (1993) Gulf 1.61- 1.11-45 0.09- 0.50- 1.10- 1.62- 0.06- 0.87- 1.21- [89] of 190 9.44 38.10 71.40 40.10 7.61 18.00 79.00 Finlan d (1995) Gulf 4.50- 1.10- 0.04- 1.10- 3.20- 1.30- 0.01- 0.50- 2.80- [36] of 223.00 72.30 1.47 44.10 72.30 53.30 0.54 23.20 59.30 Finlan d (1998) Gulf 111- 28.00- 0.80- 25.00- - 25.00- - 12.00- 45.00- [97] of 391.00 61.00 5.20 52.00 377.00 36.00 71.00 Finlan d (1998) Gulf 107- 26-80 0.34- 25-60 57-96 27-57 0.05- - 53-117 [131] of 243 2.19 0.32 Finlan d (1998) Gulf 77.00- 26.00- 0.28- - - 25.00- 0.05- - 57.00- [96] of 2.19 0.39 138.00 513.00 88.00 63.00 Finlan d (1999) Gulf 92.90- 25.70- 0.30- 19.80- 49.40- 27.60- 0.04- 8.32- 45.00- [89,93] of 2.69 54.80 122.00 0.32 25.40 111.00 260.00 65.10 76.30 Finlan

76 d (Coastl ine Finnis h waters only) (2009) Gulf 131.00- 25.30- 0.14- 33.2- - 21.80- - 13.70- 50.20- [84] of 2.04 40.7 95.20 201.00 54.20 48.40 35.80 Finlan d (Outer Finnis h waters only) (2016) Gulf 10.29- 8.40- 0.05- 1.39- - 1.61- 0.01- 1.09- 3.09- [89] of 10.06 0.02 6.28 17.58 83.83 31.60 0.20 67.37 Finlan d (Russi an waters only) (2016)

77 Table 3. Levels of heavy metals measured in sediments from the Sea of Bothnia, Bay of Bothnia and the Åland sea in the period 1990 to present. Concentrations in μg/g sediment. * Measured in dry aquatic moss samples.¤ Measured in Fucus Vesiculosusi.

Regi As Cd Co Cr Cu Fe Hg Mn Ni Pb Al Zn on and peri od Sea - 2.1- 0.27- 0.23- 3.5- 96- - 81-264 3.3-6.6 2.2- 30-2070 94- of 1.5 1.8 16.3 20.3 434 9.5 2830 Both nia (198 8)* [117] Sea - 4.1- 0.22- 0.11- 2.1- 50- - 79-306 4.2-46.4 2.1- 17-382 159- of 3.17 1.44 8.0 11.7 877 17.2 522 Both nia (198 8) ¤ [117] Sea 46-85 0.14- - 48- 19- - 0.01- 2.03- 32-81 17- - 90- of 0.78 97 45 0.15 6.48 60 240 Both nia (199 1- 1993 [131] ) Sea 9-61 0.10- - - - - 0.03- 3.0±1.6 - 24- - 132- of 0.40 0.08 39 216 Both nia (199 5) [135] Sea 35 0.31 22 50 39 64 0.1 2.7 41 40 - 193 of Both nia (199 6)

78 [127] Sea 44.6, 0.28, 16.4, 87.9, 27.4 - 0.07, - 5, 36.5 28, - 159, of 38.7 0.23 16.9 97.2 , 0.06 34.7 145 Both 30.9 nia – Nort h, Sout h (200 3) [163] Sea 160, 0.74, 12.8, 82.8, 23.4 - 0.09, - 34.8, 21.7 - 194, of 57.2 0.2 18.6 98.7 , 0.08 48.2 , 197 Both 42.7 39.5 nia - Nort h, Sout h (200 8) [163] Sea 93, 0.39. 22.1, 80.6, 33.9 - 0.060, - 47, 44.4 23.3 - 162, of 51.6 0.21 21.6 80.8 , 0.08 , 151 Both 37.6 28.1 nia - Nort h, Sout h [163]

Bay 167- 0.23- - 56- 18- - 0.06- 1.87-18 27-58 19- 4.7-6.6 50- of 320 1.98 81 80 0.48 121 320 Both nia (199 1- 1993 ) [131] Bay 7-278 0.40- - - - - 0.02- 8.5±5.3 - 4- - 71- of 0.87 0.34 66 261 Both

79 nia (199 5) [135] Bay 109 0.94 21 37 41 48 0.40 5.5 37 65 - 130 of Both nia (199 6) [127] Bay 135, 1.19, 23.8, 100, 18.8 - 0.163, - 21, 14.6 22.6 - 187, of 140 1.46 27.3 86.6 , 0.31 , 201 Both 49.3 78.3 nia (200 3) (Nort h part, Sout h part) [163] Bay 115, 1.02, 28.3, 94, 42.6 - 0.1, - 46.1, 44.4 - 202, of 169 1.46 40.7 80.4 , 0.27 33.8 , 270 Both 60.2 81.8 nia (200 8) [163] Bay 116, 1.07, 33.3, 85.1, 42, - 0.1, - 51.7, 38.8 - 159, of 189 1.59 40.2 74.6 59.5 0.26 68.8 , 233 Both 68.3 nia (201 4) [163]

Ålan 14 0.63 18 38 39 54 0.18 2.2 38 50 - 226 d sea (199 6) [127] Ålan 19 0.27 15.2 94.9 29.1 - 0.11 - 31.4 35.4 - 165

80 d sea (200 3) [163] Ålan 20 0.37 9.1 96.9 23.9 - 0.09 - 49.8 27.9 - 195 d sea (200 8) [163] Ålan 16 0.34 18.6 81.5 36.5 - 0.08 - 42.6 28.6 - 148 d sea (201 4) [163]

81 Table 4. Contamination recordings of selected heavy metals made over the last 20 years in sediments of the central Baltic sea, around Gotland (North, East, South and West of the island). Concentrations in μg/g sediment. Abbreviations: NE: North-East, SE: South East. For double- sampling in the same region, only the highest concentrations are selected. Regi As Cd Co Cr Cu Hg Ni Pb Zn on and peri od NE 20.4 3.68 7.56 43.8 93.6 0.06 31.9 26.9 253 Cent ral Balti c (200 3) [163 ] NE 16.2 4.03 7.6 39.3 141 0.06 40.1 21.8 318 Cent ral Balti c (200 8) [163 ] NE 17.2 3.23 8.30 65.6 113 0.04 54.4 26.1 220 Cent ral Balti c (201 4) [163 ] N 20.4 3.68 7.56 41.4 93.6 0.06 31.9 26.9 253 Cent ral Balti c. (200 3) [163

82 ] N 16.2 4.03 7.6 39.3 141 0.01 24.9 21.8 318 Cent ral Balti c. (200 8) [163 ] N 17.2 3.23 7.57 48 113 0.04 46.9 17.8 220 Cent ral Balti c. (201 4) [163 ] NW 16.6 3.62 4.70 21.4 104 0.06 24.5 11.7 229 Cent ral Balti c (Lan dsort deep - 2003 ) [163 ] NW 20 5.12 9.51 43.6 179 - 38.6 20.5 423 Cent ral Balti c (Lan dsort deep - 2008 ) [163 ] NW 28.7 6.96 12.6 32.6 229 0.08 82.4 30.7 486

83 Cent ral Balti c (Lan dsort deep - 2014 ) [163 ] W 23 5.4 24 51 91 0.15 65 103 467 Cent ral Balti c (199 6) [127 ] W 20.4 3.07 12.8 51.5 104 0.07 5 25.8 254 Cent ral Balti c (Nor rköpi ng deep – 2003 ) [163 ] W 22 3.92 11.5 61.7 83.8 0.07 39.8 30.8 444 Cent ral Balti c (Nor rköpi ng deep - 2008 )

84 [163 ] W 18.7 3.49 14.8 49.7 86.6 0.07 69.5 28.7 314 Cent ral Balti c (Nor rköpi ng deep – 2014 ) [163 ] E 19 2.92 6.08 32.8 82.1 0.09 5 273 215 Cent ral Balti c (200 3) [163 ] E 32.8 4.63 17.6 63.4 139 0.09 31.9 48.6 447 Cent ral Balti c (200 8) [163 ] E 22.2 3.56 10.4 44.4 104 0.08 53 25.1 246 Cent ral Balti c (201 4) [163 ] S 13.1 1.63 9.07 42.3 59.9 0.10 30.2 25.9 167 Cent ral

85 Balti c (200 3) [163 ] S 19.4 2.54 14.4 65.6 101.8 0.09 24.9 37.3 285 Cent ral Balti c (200 8) [163 ] S 12.8 1.91 10.7 55.6 76.1 0.03 49.4 25.1 164 Cent ral Balti c (201 4) [163 ]

86 Table 5. Contamination recordings of selected heavy metals made over the last 20 years in sediments of the South-West Baltic sea, South Baltic proper, Bornholm basin, the Dano-Swedish Strait and West-coast of Sweden. Concentrations in μg/g sediment. Regi As Cd Co Cr Cu Hg Ni Pb Zn on and peri od Born 14.1 0.87 15.3 85 44.2 0.08 31.6 27.2 62.6 holm - basin , 2003 . (Fig 31, A). [163 ] Born 11.1 0.93 15.9 89.9 57.3 0.07 52 32.5 161 holm - basin , 2010 . (Fig 31, A). [163 ] Born 12.4 0.91 15.1 73.3 44.6 0.07 43.6 53.1 151 holm - basin , 2014 . (Fig 31, A) [163 ] Swe 10.9 0.37 9.25 86 38.6 0.20 27.2 81.3 134

87 dish- Dani sh wate rs, 2003 . (Fig 31, B) [163 ] Swe 17.9 0.27 11.5 89.8 50.4 0.22 9.2 92.4 179 dish- Dani sh wate rs, 2008 . (Fig 31, B) [163 ] Swe 15.8 0.38 9.83 73.8 42.8 0.18 33.6 79.4 127 dish- Dani sh wate rs, 2014 . (Fig 31, B) [163 ] Göte 15.9 0.09 6.75 76.9 10.2 0.12 18.3 27.6 76.8 borg wate rs, 2003 . (Fig 31, B)

88 [163 ] Göte 17.4 0.09 9.3 82.5 15.4 0.09 29.6 30.2 102 borg wate rs, 2008 . (Fig 31, C) [163 ] Göte 16.1 0.10 7.1 69.4 15.1 0.09 20.5 24.6 66.8 borg wate rs, 2014 . (Fig 31, C) [163 ] East 14.8 0.08 7.69 88.4 10.2 0.11 18.1 31.8 80.3 Skag errak , 2003 . (Fig 31, D) [163 ] East 17.5 0.03 11.5 103.4 15.4 0.09 27.7 35.3 118 Skag errak , 2008 . (Fig 31, D) East 15 0.09 9.42 80.4 15.9 0.09 27.0 34.0 79.6 Skag

89 errak , 2014 . (Fig 31, D) [163 ]

90