parvum coincided with a mass death of birds and fish [2, 12]. The dinoflagellate Pfiesteria species can harm fish in coastal waters [13, 14] and has caused fish kills under certain circumstances in North http://www.selleckchem.com/products/MLN8237.html Carolina, USA [13]. No Pfiesteria-induced fish kills have ever been reported in Mediterranean coastal waters, while the only, and most unusual, inland ecosystem where Pfiesteria has been reported is Ace Lake, Antarctica [15].While acute fish kills due to toxic algae are well studied, another less obvious impact of toxic/parasitic unicellular eukaryotes is that exposure of aquatic animals to their toxins or parasitism might induce serious sublethal effects, including predisposing these populations to various infectious diseases resulting in, for example, reduction of growth and reproduction [8, 16].

This situation might be even more severe if one considers that we know only a few of the toxic/parasitic eukaryotes that can cause fish kills, while on the other hand our concept on the existing species diversity of the microscopic eukaryotes is still expanding [17]. This led us to investigate the planktonic Cyanobacteria and microeukaryotes of a newly reconstructed lake (Lake Karla, central Greece) during two consecutive fish kill events which occurred in less than six weeks. The aims of this study were to supplement the limited knowledge on the plankton Cyanobacterial and microeukaryotic diversity of newly reconstructed lakes and to identify potentially toxin-producing and parasitic taxa which coincided with the fish kill events and might have deleterious effects on the ecosystem.

2. Materials and Methods2.1. Study AreaLake Karla (Figure 1) is located in central Greece (39��29��02���N, 22��51��41���E). It formerly covered an area of ca. 180km2 but in the beginning of the 1960s it was drained through a tunnel leading the lake’s drainage to the nearby Pagasitikos Gulf. A small permanent marsh remained at the area that once covered the lake. The structure and function of L. Karla was correlated with River Pinios, as the flooding events of the river supplied the lake with water rich in nutrients [18]. Several biological and physical-chemical criteria characterized the lake as a eutrophic but with high stability before its drainage [19]. It was not until the 1990s that the refilling of the lake was decided by inflowing water from the nearby River Pinios.

Its actual filling started in September 2009, after building a peripheral dam which covers 38km2. We sampled in L. Karla in March and April 2010, during two fish kill events. As reported in local newspapers, the dead fish floated in the lake and lined along the shores of a 3.5 to 5km stretch.Figure 1Map of Lake Karla, Greece, and Anacetrapib sampling point (black dot). Black squares show points of inflowing water for reconstruction purposes.