polymorpha cultivation MDX-1106 activities (e.g., utilization of the zebra mussel biomass in husbandry). The Curonian Lagoon is a large (1.584 km2), shallow (average depth ∼3.8 m) and mainly freshwater coastal body connected to the south-eastern

Baltic Sea by a narrow (0.4–1.1 km) Klaipeda strait (Fig. 1). The Nemunas River brings 98% of the total freshwater runoff and enters the lagoon in its central area, dividing the water body into two different parts (Gasiūnaitė et al., 2008). The northern part is a transitory riverine-like system transporting fresh water into the sea, where salinity may episodically increase up to 5–6 psu during wind driven short-term inflow events. Seawater inflows of 1–6 days duration are most common and the seawater intrusions are usually restricted to the northern part of the lagoon in rare cases propagating ≥40 km into the lagoon. The lacustrine BIRB 796 southern part is characterized by a relatively closed

water circulation and lower current velocities. Therefore, it serves as a main depositional area of the lagoon (Daunys et al., 2006, Galkus and Jokšas, 1997, Gasiūnaitė, 2000 and Pustelnikov, 1983). Most likely, the zebra mussel D. polymorpha was introduced into the Curonian Lagoon in the early 1800s. The molluscs would have been attached to timber rafts transported via the Central European invasion corridor ( Olenin et al., 1999). However, it may have Ixazomib mouse spread much earlier. According to palaeontological

data, Dreissena could have existed in the Baltic Sea area during the last interglacial, later becoming extinct, before being re-introduced in the early 1800s ( Buynevich et al., 2011 and Starobogatov and Andreyeva, 1994). Zebra mussels are now very abundant in the Curonian Lagoon. They occupy the hard substrates (boulders, embankments, hydrotechnical structures) and soft bottoms (sand, silt or mud) down to 3–4 m depth (Zaiko et al., 2010). The largest area occupied by a zebra mussel community is located in the central part of the lagoon (Gasiūnaitė et al., 2008, Olenina, 1997 and Zaiko et al., 2009). Zebra mussels (D. polymorpha) were collected twice per year, in June and September, in 2006, 2007 and 2008, from two sites within the area of the natural zebra mussel distribution ( Fig. 1). Clumps of mussels were collected manually by wading in the littoral, at 1–1.5 m depth. After collection, mussels were immediately transported to the laboratory, where individual mussels were separated from clumps and frozen at −20 °C until analysis of toxins was performed. Three size classes of the collected mussels were distinguished: <10 mm length, 10–30 mm length and >30 mm length. In total, 108 mussels were collected and analyzed. Sediment core samples were collected from a boat in 2008, July and October.