, 2004, Funari and Testai, 2008, Jonasson et al., 2010 and Vasconcelos, 1995). In this study we address the bioaccumulation of microcystins by the invasive zebra mussel Dreissena polymorpha (Pallas 1771), widely distributed and being acknowledged as powerful biofilter ( Karatayev and Burlakova, 1994, Karatayev et al., 2002, Nicholls, 2001, Vanderploeg et al., 2002 and Zaiko and Daunys, 2012). D. polymorpha has an intrinsically high clearance rate that is approximately 10 times that of

other freshwater filter-feeding bivalves ( Vanderploeg et al., 2002). On the other hand, zebra mussel filtration capacity is highly dependent on the environmental conditions and population structure, and may vary in a wide range ( Zaiko and Daunys, 2012). click here These bivalves can efficiently accumulate micropollutants,

are easy to collect in large numbers and are sedentary, reflecting site specific pollution (Bervoets ABT-263 et al., 2005, Hendriks et al., 1998 and Voets et al., 2006). Being themselves resistant to a broad range of environmental conditions (Claudi and Mackie, 1993) and to various types of pollution (Bervoets et al., 2005), they are considered as a proper object for biomonitoring studies (Bervoets et al., 2005 and Smolders et al., 2003). Their bioaccumulation abilities may imply important ecological consequences. Zebra mussels are important food source for some fish and water birds thus might be an agent for toxic substances transfer through the food web (Tucker et al., 1996 and Zimmermann et al., 1997). Another implication

of cyanotoxins bioaccumulation by zebra mussel is related to its potential use for water quality remediation, recently addressed in several studies (Elliott et al., 2008, Goedkoop et al., 2011, Orlova et al., 2004, Reeders and Bij de Vaate, 1990 and Stybel et al., 2009). These issues are particularly relevant for the large transitional ecosystems, such as the Baltic Sea brackish lagoons, with a well pronounced anthropogenically induced eutrophication (Chuseve et al., 2012). Such an option is considered for the Curonian over Lagoon as well, and possible pros and cons being analyzed within the Baltic Sea Region Programme project SUBMARINER (“Sustainable Uses of Baltic Marine Resources”). Since the harvested mussel biomass is not suitable for human consumption, it is often advised for utilization in husbandry as chicken feed, fertilizer or aquafeed for fishfarms ( Lindahl et al., 2005, Schernewski et al., 2012 and Stybel et al., 2009). Therefore it is important to identify and assess the potential risks of transfer of bioaccumulated toxic substances. In this study, we present the potential of zebra mussel to be used as indicator of toxic cyanobacteria occurrence in a eutrophic brakish water coastal lagoon and relation of its bioaccumulative capcity to the age structure and ambient environmental conditions.