e. the Rivers Evros, Nestos and Strymon along the northern coastline, and the Axios, Loudias, Aliakmon and Pinios in Thermaikos Gulf). The most characteristic hydrographic feature of the area is the intrusion of low salinity (29–34), nutrient-rich Black Sea Water (BSW), which occupies the surface layer of the water column (20–40 m) and follows the periphery of the cyclonic gyre (Ovchinnikov 1966), with deflecting branches over the Samothraki

and Thermaikos Plateaus (Ünlüata et al., 1990 and Latif et al., 1991). The North Aegean Sea appears to be mostly influenced by BSW during spring and summer (April to July), when the mean monthly outflow through the Dardanelles Straits reaches 15 000 m3 s−1, corresponding to the increased river runoff and precipitation Selleck Roxadustat over the Black Sea (Oguz and Sur, 1989 and Yüce, 1995). The prevailing wind circulation controls the

flow path of the BSW plume selleck kinase inhibitor in the North Aegean Sea (Vlasenko et al. 1996). In the summer, after passing the Dardanelles, the main branch of the BSW flows south-westwards, under the influence of the annual northerly Etesian winds, with its core water appearing south of Lemnos Island (Poulos et al. 1997). In this region, a well-defined frontal zone is formed as a result of the interaction of the low salinity BSW and the more saline (38.5–39.0) Levantine Intermediate Water (LIW) originating from the Cretan Sea (Ivanov et al., 1989 and Zodiatis et al., 1996). Moreover, a significant oxyclozanide portion flows to the north of Lemnos

Island (Theocharis and Georgopoulos, 1993, Vlasenko et al., 1996 and Zervakis and Georgopoulos, 2002). In the winter, the BSW flows westwards, mostly along the northern coast of Lemnos, where it bifurcates primarily to the north-west and occasionally to the south-west, under the influence of north-easterly (bora-type) gales. This results in the accumulation of cold brackish water over the north-eastern part of the continental shelf, whereas warm and saline LIW appears in the south-eastern part (off Lesvos Island) (Zervakis & Georgopoulos 2002). The vertical structure of the water column in the North Aegean Sea consists mainly of three layers: the low-salinity layer, with increased BSW presence at the surface; the warm and highly saline LIW, at depths from 50 to 400 m; and the very dense North Aegean Deep Water (NADW) at the bottom of each sub-basin (Lykousis et al. 2002). The BSW thickness depends on freshwater discharged through the Dardanelles and on wind shear, inducing vertical mixing with the underlying LIW layer (Zervakis et al. 2000). Through its course in the North Aegean Sea, BSW undergoes modification of its characteristics, gradually reaching a salinity of 38.0 in the region of the Sporades Islands (central and western Aegean Sea). Yuuce (1995) considered the 38.