Mercury dynamics at the base of the pelagic food web of the Gulf of Gdansk, southern Baltic Sea.

Planktonic organisms, which have direct contact with water, serve as the entry point for mercury (Hg), into the marine food web, impacting its levels in higher organisms, including fish, mammals, and humans who consume seafood. This study provides insights into the distribution and behavior of Hg within the Baltic Sea, specifically the Gulf of Gdansk, focusing on pelagic primary producers and consumers. Phytoplankton Hg levels were primarily influenced by its concentrations in water, while Hg concentrations in zooplankton resulted from dietary exposure through suspended particulate matter and phytoplankton consumption. Hg uptake by planktonic organisms, particularly phytoplankton, was highly efficient, with Hg concentrations four orders of magnitude higher than those in the surrounding water. However, unlike biomagnification of Hg between SPM and zooplankton, biomagnification between zooplankton and phytoplankton was not apparent, likely due to the low trophic position and small size of primary consumers, high Hg elimination rates, and limited absorption.

Mercury concentrations in Antarctic zooplankton with a focus on the krill species, Euphausia superba.

The Antarctic is the most isolated region in the world; nevertheless, it has not avoided the negative impact of human activity, including the inflow of toxic mercury (Hg). Hg deposited in the Antarctic marine environment can be bioavailable and accumulate in the food web, reaching elevated concentrations in high-trophic-level biota, especially if methylated. Zooplankton, together with phytoplankton, are critical for the transport of pollutants, including Hg to higher trophic levels. For the Southern Ocean ecosystem, one of the key zooplankton components is the Antarctic krill Euphausia superba, the smaller euphausiid Thysanoessa macrura, and the amphipod Themisto gaudichaudii - a crucial food source for most predatory fish, birds, and mammals. The main goal of this study was to determine the Hg burden, as well as the distribution of different Hg forms, in these dominant Antarctic planktonic crustaceans. The results showed that the highest concentrations of Hg were found in T. gaudichaudii, a typically predatory taxon. Most of the Hg in the tested crustaceans was labile and potentially bioavailable for planktivorous organisms, with the most dangerous methylmercury (MeHg) accounting for an average of 16 % of the total mercury. Elevated Hg concentrations were observed close to the land, which is influenced by the proximity to penguin and pinniped colonies. In areas near the shore, volcanic activity might be a possible cause of the increase in mercury sulfide (HgS) content. The total Hg concentration increased with the trophic position and ontogenetic stage of predation, specific to adult organisms. In contrast, the proportion of MeHg decreased with age, indicating more efficient demethylation or elimination. The Hg magnification kinetics in the study area were relatively high, which may be related to climate-change induced alterations of the Antarctic ecosystem: additional food sources and reshaped trophic structure.

Mobility and bioavailability of mercury in sediments of the southern Baltic sea in relation to the chemical fractions of iron: Spatial and temporal patterns.

Marine sediments play a significant role as reservoirs for mercury (Hg), a bioaccumulative toxic pollutant that poses risks to human and ecosystem health. Iron (Fe) has been recognized as an influential factor in the complexation and bioavailability of Hg in sediments. However, limited studies have investigated the interactions between the chemical fractions of these elements in natural settings. This study aims to examine the fractions of Hg and Fe in sediments of the Baltic Sea, a region historically impacted by Hg pollution. The Hg fractions were determined using the thermodesorption technique, while sequential extraction was employed to identify the Fe fractions. The findings confirm the crucial role of Fe in the formation, as well as the horizontal and vertical distribution of labile and stable Hg in marine sediments. Factors such as the contribution of organic matter, the presence of reactive Fe, and Fe associated with sheet silicates emerged as significant drivers that positively influenced the content of the most labile Hg fractions, potentially affecting the mobility and bioavailability of Hg in the marine environment.

Mercury in the Polish part of the Baltic Sea: A response to decreased atmospheric deposition and changing environment.

Our review of the literature showed that since the beginning of the socio-economic transformation in Poland in the 1990s, the downward trend in Hg emissions and its deposition in the southern Baltic Sea was followed by a simultaneous decrease in Hg levels in water and marine plants and animals. Hg concentrations in the biota lowered to values that pose no or low risk to wildlife and seafood consumers. However, in the first decade of the current century, a divergence between these two trends became apparent and Hg concentrations in fish, herring and cod, began to rise. Therefore, increasing emission-independent anthropogenic pressures, which affect Hg uptake and trophodynamics, remobilization of land-based and marine legacy Hg deposits, as well as the structure of the food web, can undermine the chances of reducing both the Hg pool in the marine environment and human Hg exposure from fish.

Effects of beach wrack on the fate of mercury at the land-sea interface - A preliminary study.

Since the 1970s, the amount of aquatic plants and algae debris, called beach wrack (BW), has increased along the shores of industrialised regions. The strong ability of primary producers to accumulate pollutants can potentially result in their deposition on the beach along with the BW. Despite that, the fate and impact of such pollutants on sandy beach ecosystems have not been investigated so far. This study examines the fate of neurotoxic mercury and its labile and stable fractions in BW on sandy beaches of the Puck Bay (Baltic Sea). In addition to BW, beach sediments and wrack-associated macrofauna were also analysed. Rough estimations showed that Puck Bay beaches (58.8 km) may be a temporary storage of 0.2-0.5 kg of mercury, deposited on them along with the BW annually. A large proportion of Hg (89 ± 16%) in a BW was labile and potentially bioavailable. The contribution of Hg fractions in the BW was conditioned by the degree of its decomposition (molar C:N:P ratio). With the progressive degradation of BW, a decrease in the contribution of Hg adsorbed on its surface with a simultaneous increase in the proportion of adsorbed (intracellular), mercury was observed. BW accumulation decreased oxygen content and redox potential and increased methylmercury content in underlying sediments, indicating methylation. Hg concentrations in the studied fauna were up to 4 times higher than in the BW. The highest values occurred in a predatory sand bear spider and the lowest in a herbivorous sand hopper. Regardless of trophic position, most of Hg (92-95%) occurred as an absorbed fraction, which indicates about a 30% increase in relation to its share of BW. These findings suggest the significant role of BW as a mercury carrier in a land-sea interface and increased exposure of beach communities to the adverse effects of mercury in coastal ecosystems.

The impact of sediment, fresh and marine water on the concentration of chemical elements in water of the ice-covered lagoon.

The common use of chemical elements by man has been contributing to their extraction for centuries. As a consequence, they have been directly or indirectly introduced into the biogeochemical cycle. In the framework of many conventions, mining and processing of elements are currently subject to many restrictions. However, their large load that has already been deposited in the soil and bottom sediments can be remobilised and enter the food chain. The identification of factors favouring this process is very important, especially during the period of adopting new legal regulations on limiting the emission of pollutants. It became possible in February 2018 during the persistence of ice cover on the lagoon's surface. This allowed observation of processes, the effect of which in the absence of ice is blurred by wind mixing water. Therefore, an investigation of sources of 25 elements in a lagoon of the southern Baltic has been undertaken, based on the example of the Vistula Lagoon. The results point to the remobilisation of chemical elements (including the toxic ones) from land and bottom sediments, where they have been deposited for decades. These processes led to the accumulation of metals in certain areas of the lagoon. It may result in their uptake and accumulation in the benthic organisms inhabiting the lagoon and further transfer in the food chain. It is of major importance as the lagoons in the southern Baltic fulfil many essential functions in the scope of tourism, economy, and fishery. Thanks to restrictions on the quality of wastewater and the emission of pollutants, it has been noticed a substantial "purifying" effect of rivers, too.

Distribution and bioavailability of mercury in the surface sediments of the Baltic Sea.

The study aimed to determine the level of mercury (Hg) and its labile and stable forms in the surface sediments of the Baltic Sea. The work considers the impact of current and historical sources of Hg on sediment pollution, together with the influence of different environmental parameters, including water inflows from the North Sea. Surface sediments (top 5 cm) were collected in 2016-2017 at 91 stations located in different areas of the Baltic Sea, including Belt Sea, Arkona Basin, Bornholm Basin, Gdansk Basin, West Gotland Basin, East Gotland Basin, and the Bothnian Sea. Besides, the particulate matter suspended in the surface and near-bottom water was also collected. The analysis of total Hg concentration and individual Hg forms in collected samples was carried out using a 5-step thermodesorption method. This method allows for the identification of three labile and thus biologically available, fractions of Hg, which are mercury halides, organic Hg, mercury oxide and sulphate. Two stable fractions, mercury sulphide and residual Hg, were also determined. The highest Hg concentrations, reaching 341 ng g-1, were measured in the highly industrialised Kiel Bay, which was additionally a munition dumping site during and after World War II. High Hg level, ranging from 228 to 255 ng g-1, was also recorded in the surface sediments of the Arkona Basin, which was a result of the cumulative effect of several factors, such as deposition of Hg-rich riverine matter, favourable hydrodynamic conditions and military activities in the past. The relatively elevated Hg concentrations, varying from 60 to 264 ng g-1, were found in the Gdansk Basin, a region under strong anthropopressure and dominated by soft sediments. The sum of labile Hg in sediments was high and averaged 67% (with the domination of organic Hg compounds), which means that a large part of Hg can be released to the water column. It was found that the water inflows from the North Sea intensify the remobilisation of Hg and its transformation into bioavailable labile forms. As a consequence, the load of Hg introduced into the trophic chain can increase. Despite the significant reduction of Hg emission into the Baltic in the last decades, surface sediments can be an important secondary Hg source in the marine ecosystem. This is especially dangerous in the case of the western Baltic Sea.

Status and trends of mercury pollution of the atmosphere and terrestrial ecosystems in Poland.

The goal of this paper is to assess the current status and trends of total mercury (THg) contamination of the atmosphere and terrestrial ecosystems in Poland. The study shows that the reduced domestic and worldwide atmospheric emission of Hg resulted in decreased THg level in the terrestrial biotope and biosphere. Considering that Poland is one of the main Hg emitters in Europe, the THg concentrations in its abiotic environment are still elevated. However, the THg level in terrestrial organisms is relatively low, which is because a large proportion of Hg deposited on land is accumulated in organic-rich soils. Regarding the THg concentration, consumption of wildlife and livestock from Poland is safe for humans. Nevertheless, the authors indicate the need for effective environmental monitoring, based on selected bioindicators, which is crucial considering the slowing reduction of Hg emission combined with the consequences of the changing climate.

Mercury forms in the benthic food web of a temperate coastal lagoon (southern Baltic Sea).

The study was conducted in the coastal zone of the southern Baltic. The research material consisted of macrozoobenthos and elements of its diet. The samples were analysed for Hg and its labile and stable forms, using the thermodesorption method. The results showed that the level of total Hg in zoobenthos was associated with dietary preferences and the share of bioavailable Hg in its food. The Hg fractionation in the macrofauna was conditioned by biological features (morphological structure) and environmental parameters (oxygenation, pH) which shape the mobility and assimilation of Hg. The absorption of the most toxic organic Hg in macrofauna was more effective in aerobic conditions, at low primary production and with the limited inflow of organic matter. The trophic transfer of Hg was favoured by the limited biomass of primary producers, and consequently of zoobenthos. An important factor influencing the biomagnification was also the share of labile Hg in macrozoobenthos.

Forms of mercury in the Baltic mussel (Mytilus trossulus): Human and ecosystem health risk assessment.

Mercury (Hg) is one of the most dangerous environmental pollutants. A significant source of this toxic element to the human body is the consumption of seafood - including the increasingly popular mussels. Mussels also play an important role in the marine ecosystem, providing a food base for fish and birds. The study aimed to determine the level of total Hg and its labile and stable forms in the Baltic mussel (Mytilus trossulus), as well as to indicate the factors that shape them. The research was conducted in the Puck Bay (Polish part of the southern Baltic Sea) in 2012-2013. The study material consisted of M. trossulus mussels, the components of their diet (suspended matter and phytoplankton), and surface sediments. Concentrations of total Hg (HgTOT) and the individual Hg forms were established using the thermodesorption method on a DMA-80 analyser (Milestone). The obtained results showed that the level of Hg concentration in M. trossulus from the Puck Bay was shaped by the individual features of specimens, related to the growth and reproductive cycle of mussels, as well as the quality of food consumed by them. The total share of labile Hg forms in M. trossulus was high, exceeding 90% of HgTOT, and the predominant form was the most dangerous organic Hg. This means that almost all of the Hg accumulated in mussels can be transferred to higher trophic levels. The obtained results showed that Baltic mussels were characterised by levels of HgTOT and organic Hg deemed to be safe for humans. A positive relationship was noted between the HgTOT concentration in a mussel's tissues and the length of its shell. Smaller sized organisms demonstrated not only by lower Hg concentrations, but also by better condition and, consequently, higher nutritional value.

The role of benthic macrofauna in the trophic transfer of mercury in a low-diversity temperate coastal ecosystem (Puck Lagoon, southern Baltic Sea).

Mercury (Hg) is a global pollutant that affects human and ecosystem health. Hg is a serious threat especially for the marine environment, in which it undergoes bioaccumulation and biomagnification, reaching elevated concentrations in fish and other seafood. The research aimed at investigating the trophodynamics of Hg in the basal links of the marine food chain: benthic macrofauna and its main food sources (i.e. suspended and sediment organic matter, micro- and macrophytobenthos). The results showed that both the amount and the origin of organic matter affected the Hg level in particular trophic groups of macrozoobenthos. The intensive inflow of terrestrial material influenced the enrichment of suspended particles and microphytobenthos in Hg, leading to increased Hg concentrations in filter-feeding macrofauna. The input of Hg-rich marine matter transported from the deeper parts of the Gulf of Gdansk along with the near-bottom currents caused higher Hg levels in deposit feeders. The biomagnification factor (BMF) of Hg through benthic food web was dependent on environmental conditions occurring in the studied areas, in particular, factors favouring the growth and fecundity of macrofauna. Consequently, as a result of biodilution, the trophic transfer of Hg was less effective in a more productive region, despite the elevated Hg concentrations in dietary components of the macrofauna and in the surrounding environment.

Seasonal variation in accumulation of mercury in the benthic macrofauna in a temperate coastal zone (Gulf of Gdansk).

The main source of toxic mercury (Hg) in the human body is the consumption of fish and seafood. Therefore, it is particularly important to indicate the processes that condition Hg accumulation in marine organisms, especially those in the basal links of the food chain, which are rather poorly investigated compared to top predators. The aim of the study was to determine the seasonal variability of Hg concentrations in macrozoobenthic organisms and the factors that condition it. The research was conducted in 2012-2013 in a temperate coastal zone (Gulf of Gdansk). The obtained results showed that both Hg concentrations within one trophic level, and their seasonal variation, may differ significantly if the organisms have different feeding habits. The research also indicated that the seasonal variability of Hg level in macrozoobenthos depended on a number of both biotic factors (primary production volume, biomass and rate of fauna metabolism) and abiotic factors (salinity and ionic composition of water, Eh). The variability of Hg concentrations in macrozoobenthos during the study period was different at the research stations, which were subjected to different land influence (e.g. surface run-off, coastal erosion), and consequently differed in the quantity and quality of organic matter. The increased load of suspended particulate matter (SPM) was also an important factor influencing the increase in Hg concentration in macrozoobenthos, regardless of their trophic status. This indicates that SPM is an important source of food for zoobenthos, even in species that prefer a different feeding strategies. The obtained results also showed the role of climate changes observed in the temperate zone - in particular, the warming of the winter season - in shaping the Hg level in macrozoobenthos. The accumulation of Hg in the bottom fauna occurred most intensively in spring immediately after a long period of icing - Hg concentrations were then much higher than those measured after a mild winter, during which the ice cover persisted for a short time. The warming of the winter season and the extension of the vegetation season contributed to an increase in macrozoobenthic biomass, and consequently to the biodilution of Hg, which could have had a negative effect on the Hg load introduced into the trophic chain.

Mercury fractionation in marine macrofauna using thermodesorption technique: Method and its application.

Mercury (Hg) is one of the most dangerous elements, and its toxicity and ability to accumulate in organisms depend on its chemical form. There are numerous methods of Hg speciation analysis, out of which the least expensive and the least time-consuming one is thermodesorption. The method has been successfully used for the analysis of abiotic samples - soils and sediments. The aim of this study was to verify whether the simplified thermodesorption method can be used in the analysis of the tissues of animal organisms from different trophic levels. Hg fractionation analyses were performed on a DMA-80 analyser (Milestone, Italy). The results presented in this paper are the first published data on Hg fractionation by thermodesorption method in animal tissues. The study showed that the 5-step thermodesorption method can be applied to various types of environmental matrices, which makes it universal. This method is of great importance in terms of estimating the Hg uptake and transfer in the trophic chain, and also enables the assessment of global Hg circulation in the environment. The presented method does not require previous digestion of samples or the use of expensive reagents. It can also be used for the preliminary selection of samples for MeHg analysis. The results obtained by this 5-step fractionation could be comparable with different research, conducted using other Hg analysers.

Coastal erosion-a "new" land-based source of labile mercury to the marine environment.

Mercury (Hg) can be introduced into the marine environment in many different ways. In the case of the Baltic Sea, rivers and atmospheric deposition are the predominant ones. However, in the face of ongoing climate change, a new potential source, coastal erosion, is starting to become more important and is currently considered to be the third largest source of Hg in the Gdansk Basin region. It is especially significant along sections of coastline where, due to the higher frequency of extreme natural phenomena such as storms, heavy rains, and floods, increased erosion processes have already been noted. Cliffs, which account for about 20% of the Polish coastline, are particularly vulnerable. The aim of the study was to estimate the annual load of labile Hg entering the Gdansk Basin as a result of coastal erosion. Samples of down-core sediments (0-65 cm) were collected in the years 2016-2017 from selected cliffs situated in the Gulf of Gdansk area. The thermodesorption method was used to distinguish between labile and stable fractions of Hg. Considering the mean total Hg concentrations in the collected sediments (9.7 ng g-1) and the mean share of labile (64%), bioavailable mercury, it was estimated that the load of labile Hg originating from coastal erosion entering the Gdansk Basin is 10.0 kg per year. The load can increase by up to 50% in the case of episodic abrasion events during heavy storms and rains.

Mercury in suspended matter of the Gulf of Gdansk: Origin, distribution and transport at the land-sea interface.

The coastal regions of inland seas are particularly vulnerable to Hg pollution. An important carrier of toxic Hg in the marine environment is suspended matter originating from multiple sources. The present study was conducted in the Gulf of Gdansk and its adjoining land in the years 2011-2013. The results indicated that the HgSPM (Hg bound with suspended particulate matter) concentrations varied horizontally and vertically and were dependent on the water dynamics and the composition of organic matter. Conditions favourable for the accumulation of matter and adsorption of reactive gaseous mercury led to increasing HgSPM levels, which are especially hazardous in the case of semi-enclosed areas such as estuaries. These conditions also increase the Hg loads into the trophic chain through suspension feeders. Moreover, the HgSPM concentration was significantly affected by seasonal phenomena (mainly coastal erosion) and the quantity and quality of primary production (phytoplankton blooms, mainly Mesodinium rubrum).

Coastal erosion as a source of mercury into the marine environment along the Polish Baltic shore.

The climate changes in recent years in the southern Baltic have been resulting in an increased frequency of natural extreme phenomena (i.e. storms, floods) and intensification of abrasion processes, which leads to introduction of large amounts of sedimentary deposits into the marine environment. The aim of this study was to determine the mercury load introduced to the Baltic Sea with deposits crumbling off the cliffs-parts of the coast that are the most exposed to abrasion. The studies were carried out close to five cliffs located on the Polish coast in the years 2011-2014. The results show that coastal erosion could be an important Hg source into the marine environment. This process is the third most important route, after riverine and precipitation input, by which Hg may enter the Gulf of Gdansk. In the Hg budget in the gulf, the load caused by erosion (14.3 kg a(-1)) accounted for 80 % of the wet deposition and was 50 % higher than the amount of mercury introduced with dry deposition. Although the Hg concentration in the cliff deposits was similar to the natural background, due to their large mass, this problem could be significant. In addition, the preliminary studies on the impact of coastal erosion on the Hg level in the marine ecosystem have shown that this process may be one of the Hg sources into the trophic chain.

Macrophyta as a vector of contemporary and historical mercury from the marine environment to the trophic web.

Macrophyta are the initial link introducing toxic mercury to the trophic chain. Research was carried out at 24 stations located within the Polish coastal zone of the Southern Baltic, in the years 2006-2012. Fifteen taxa were collected, belonging to four phyla: green algae (Chlorophyta), brown algae (Phaeophyta), red algae (Rhodophyta) and flowering vascular plants (Angiospermophyta), and total mercury concentrations were ascertained. The urbanisation of the coastal zone has influenced the rise in Hg concentrations in macroalgae, and the inflow of contaminants from the river drainage area has contributed to an increase in metal concentration in vascular plants. At the outlets of rivers possessing the largest drainage areas in the Baltic (the Vistula and the Oder), no increases in mercury concentration were observed in macrophyta. Increase in environmental quality and a prolonged vegetative season results in the growing coverage of algae on the seabed and in consequence leads to rapid introduction of contemporary mercury and Hg deposited to sediments over the past decades into the trophic chain. Thriving phytobenthos was found to affect faster integration of Hg into the trophic web.

Mercury loads into the sea associated with extreme flood.

Floods are an important factor determining riverine pollution loads, including toxic mercury (Hg). The impact of the Vistula River flood in 2010, which was the biggest one recorded in 160 years and its influence on marine environment was studied. Mercury concentration was analyzed in river and sea water, suspended matter, phytoplankton and sea surface sediment. Flood and gulf water contained several times higher concentration of Hg (exceeded reference values safe for aquatic organisms) than before or after the flood. In 2010 the Vistula introduced into the Baltic ca. 1576 kg of Hg, of which 75% can be attributed to the flood water. Increase of water temperature, decrease of oxygen content contended increasing of dissolved mercury concentration, which was transported far into the Baltic. This phenomenon led to an increase of Hg concentration in phytoplankton and during many months in surface sediments. It is a potential threat to marine organisms.