Materials and methods
Lake Īznik, the largest lake in the Marmara region and the fifth largest in Turkey, is located between the districts of Īznik and Orhangazi in the Province of Bursa. A freshwater lake, it located between 40°23׳ and 40°30׳N latitudes and 29°20׳ and 29°42׳E longitudes. The lake, which located 85 m above sea level, has a length of 32 km and a maximum width of 12 km. It is about 15 – 16 km from the Bay of Gemlik. It has a surface are of 310 km2 and a water volume of 12.2 billion cubic meters. Lake Īznik is a tectonic lake extending from the Bay of Gemlik to the Geyve Basin. The maximum depth of the lake (80 m) has been measured near Karacakaya. It is fed by small streams, the most outstanding of which are Karasu, which flows into the lake on its northeastern side, and Sӧlӧz, which flows into the lake on its southwestern side (Saçlıoğlu – Taylor, 1993; Yarar and Magnin, 1997; Ӧztϋrk et al., 2005).