2002). However, being a powerful filter-feeder, the zebra mussel can greatly reduce algal biomass and negate or mask the ever increasing effects of nutrient pulses (Karatayev et al., 2002 and Dzialowski and Epacadostat Jessie, 2009). Several studies have, therefore, addressed the potential use of zebra mussels in water quality remediation (e.g. Reeders and Bij de Vaate, 1990, Orlova et al., 2004, Elliott et al., 2008, Stybel et al., 2009 and Goedkoop et al., 2011) or sewage sludge treatment (Mackie & Wright 1994). These issues are particularly relevant to large transitional ecosystems, such as the Baltic Seas brackish lagoons, with well-pronounced, anthropogenic eutrophication. When considering the pros and cons of zebra

mussel cultivation for water quality improvement, it is important to identify and assess all possible ecological risks the species may pose. One of the negative

ecological effects of the zebra mussel is associated with its ability to host a diverse range of endosymbionts, including potentially pathogenic parasites of fish and waterfowl (Molloy et al., 1997, Karatayev http://www.selleckchem.com/products/INCB18424.html et al., 2000a, Mastitsky, 2004, Mastitsky, 2005, Mastitsky and Gagarin, 2004, Mastitsky and Samoilenko, 2005 and Mastitsky and Veres, 2010). Increased abundances of such parasites hosted by D. polymorpha in invaded water bodies have repeatedly been documented in Europe ( Molloy et al., 1997, Mastitsky, 2005 and Mastitsky and Veres, 2010). Although D. polymorpha tolerates salinities of up to about 6 PSU and is thus not uncommon in brackish waters ( Karatayev et al. 1998), it is essentially unknown whether the diversity and abundance of D. polymorpha endosymbionts in the invaded brackish waters differ from fresh waters. The only exception we are aware of is the work by Raabe (1956), who observed a considerable negative correlation between salinity and the prevalence of D. polymorpha infection with its commensal ciliate Conchophthirus acuminatus in the Vistula Lagoon, Baltic Sea. Studying the parasites and other endosymbionts of D. polymorpha (e.g. their species composition, Teicoplanin prevalence and

intensity of infection under varying conditions) is deemed an essential part of the integrated assessment of the environmental impact this mollusc can potentially have. Accordingly, we conducted a half-year-long study of the seasonal dynamics of endosymbionts in D. polymorpha from the Lithuanian part of the Curonian Lagoon, SE Baltic Sea. This work adds to a better understanding of the parasitological risks posed by the mollusc in brackish water bodies, and also highlights relevant implications for potential D. polymorpha cultivation (e.g. utilization of zebra mussel biomass in husbandry). The Curonian Lagoon is a large (1.584 km2), shallow (average depth ∼ 3.8 m) coastal water body connected to the south-eastern Baltic Sea by the narrow (0.4–1.1 km) Klaipeda Strait (Figure 1).