TEMPORAL CHANGES IN WATER QUALITY AND TROPHIC STATUS IN LAKE YENICAGA (BOLU, TURKEY)

Lake Yenicaga is situated on the migration route of birds crossing through the Straits. The area around the lake is an important peat deposit and a wide variety of vegetation types and bird species are found in its basin. Although it is an ecosystem that has the potential to become a candidate site for Ramsar designation, conservation status has not yet been assessed. In recent years, immense pressure due to pollution in Lake Yenicaga has brought eutrophication problem. Within the scope of this study conducted monthly between March 2008 and February 2009 on Lake Yenicaga, the variations in water quality and in trophic status were evaluated by comparing the data obtained during the previous studies. The study included several water quality parameters (K+, Na+, Mg+2, Ca+2, Cl, SO4-2, HCO3-, CO3-2, NO3, NO2, NH4, PO4) and chlorophyll a in three sampling stations. The most notable finding of this study is that the concentration of ammonium in the water column showed a significant increase compared with the past. Beside there was an increase in conductivity in the lake compared to prior periods, it is thought that chlorine may be related to the increase in conductivity. The TSI index values derived from the chlorophyll-a results obtained in Lake Yenicaga during the study period indicate that the lake is on the eutrophic level; however, in some months it is prone to shift from eutrophic to hypereutrophic conditions. An enhancement trend in the eutrophication level was determined. An increase in the amount of ammonia during the study period and the oxygen depletion in the bottom layers in Lake Yenicaga support this view.