TROPHIC STATUS AND THREATS IN ZINAV LAKE (TOKAT/TURKEY)

This study was conducted to determine water quality and trophic state of Zinav Lake, which is located in the Central Black Sea Region of Turkey. Temperature, dissolved oxygen, pH, electrical conductivity, total suspended solids, Secchi disc transparency, ammonia, nitrite, nitrate, total nitrogen, soluble reactive phosphorus, total phosphorus and chlorophyll a were monitored in water column from January 2012 to June 2013. The study showed that Zinav Lake was a dimictic lake, which circulated in spring and fall, and thermally stratified in summer. Hypo-limnetic oxygen deficit and metalimnetic oxygen minima were the cases. Vertical distribution of dissolved oxygen and pH and ammonia accumulation in hypolimnion represented eutrophic/hypereutrophic conditions. The values and ratios of nutrients and chlorophyll a and Secchi disc transparency clearly classified Zinav Lake as eutrophic/hypereutrophic. Allochthonous loadings of organic matter and nutrients from the catchment and the changes in hydrological cycle by a power plant seem to be the most threatening factors controlling the water quality and trophic state in Zinav Lake.