jesc.ac.cn Journal of Environmental Sciences 2010, 22(8) 1144–1150 Distribution of mercury in different environmental compartments in the aquatic ecosystem of the coastal zone of the Southern Baltic Sea Dominika Saniewska 1 , Magdalena Beldowska 1, * , Jacek Beldowski 2 , Michal Saniewski 3 , Justyna Kwa´ sniak 1 , Lucyna Falkowska 1 1. Institute of Oceanography, University of Gdansk, Al. Pilsudskiego 46, 81-378 Gdynia, Poland. E-mail: d.murawiec@gmail.com 2. Institute of Oceanology, Polish Academy of Sciences, ul. Powstancow Warszawy 55a, 81-712 Sopot, Poland 3. Institute of Meteorology and Water Management, Maritime Branch, ul. Waszyngtona 42, 81-342 Gdynia, Poland Abstract The aim of this study was to characterize mercury (Hg) contamination in the coastal waters of the Southern Baltic Sea, and to investigate transformations of Hg in the initial links of the marine food chain. Concentrations of Hg in water, particulate matter, plankton and macrophytes at various stations in the coastal zone (a bay with restricted water exchange, near an industrial city, river mouths, and the open sea) were measured in 2006–2008. Hg concentrations observed in the Southern Baltic varied greatly, showing the highest average values in all environmental compartments near the river mouths. In shallow, sheltered parts of the gulf, where water exchange is restricted, Hg concentrations in the water and in macrophytes were elevated relative to those in the coastal zone of the deeper part of the bay and in the open Baltic. Distance to the river mouth, terrestrial runoff, and quantity and quality of organic matter were more important than seasonal variations in controlling Hg and Hg SPM concentrations in water samples. Mercury concentrations in the surface microlayer at the air/sea interface were over 10 times higher than those in the bulk surface water. Concentrations of Hg in macrophytes in the winter were significantly higher than those in the warm seasons (spring, summer, autumn). This was probably the combined effect of higher availability of Hg in porewaters and leaf growth inhibition. Key words: mercury; Baltic Sea; coastal zone; water; particulate matter; plankton; macrophytes DOI: 10.1016/S1001-0742(09)60230-8 Introduction The Baltic Sea is an inland sea surrounded by economically-developed and industrialized countries. For this reason, it is particularly vulnerable to anthropogenic pollution originating from urbanized and densely populat- ed Eastern and Central Europe. Pollutants enter the Baltic Sea through terrestrial runoff from the drainage basin and atmospheric deposition; they accumulate and have a toxic impact on the ecosystem of the Baltic Sea. The depth of the Baltic Sea (average 52 m) and low rate of water exchange with the North Sea favor the accumulation of pollutants (HELCOM, 1986). For many years, mercury (Hg) has been recognized as one of the most dangerous anthropogenic pollutants. In offshore marine water, Hg concentrations do not exceed 1 ng/L. A different situation is observed in the coastal zones, where the concentrations can be many times higher than those measured offshore (Mason et al., 1998; Horvat et al., 2003; Laurier et al., 2004). Rivers transport various chemical substances which enter the water with terrestrial runoff from the drainage basin. They are therefore very often considered to be responsible for the pollution of the coastal zones. Hg transported to the sea by rivers is mainly * Corresponding author. E-mail: ryba@ocean.ug.gda.pl accumulated in the coastal areas and estuaries and does not reach the offshore areas (Cossa and Martin, 1991). Investigations of Hg concentration levels in the Baltic Sea have been performed for many years. However, they have been focused mainly on the determination of Hg concentrations in the surface waters and sediments of the offshore areas of the Baltic Sea. Neither seasonal nor diurnal variability of Hg levels in the coastal zone, which is potentially the most polluted area of the Baltic Sea, have been sufficiently characterized (Brzezi´ nska, 1984; Falandysz, 1994; Wrembel, 1997; Pempkowiak et al., 1998; Szefer, 2002; Boszke et al., 2003; Beldowski and Pempkowiak, 2007; Kuss and Schneider, 2007; Bartnicki et al., 2008; Pohl and Hennings, 2008). The goal of this study was to determine Hg concentra- tions in different coastal areas (a bay with restricted water exchange, an industrial city, river mouths and the open sea). To achieve this goal, the concentrations of Hg in several compartments of the marine environment (water, particulate matter, plankton, and macrophytes) at various stations located in the coastal zone of the Southern Baltic Sea were analyzed. These measurements were used to calculate the value of the bioconcentration factor (BCF) for the planktonic organisms and macrophytobenthos. The authors paid particular attention to the river mouths.