Dergiler / Turkish Journal of Zoology / 2000 / Cilt: 24 - Sayı: 3
Benthi-planktivorous Fish-Induced Low Water Quality of Lake Eymir Before Biomanipulation
- Sayfa
- 315–326
- DOI
- —
Özet
In this study, Lake Eymir, Eymir inflow 1, Kışlakçı brook and Eymir outflow were sampled monthly betwen March 1997and April 1998 for physico-chemical and biological parameters. Within the catchment of the lake, there are small-scale industries, sewage effluent of TEK residence and recreational activities causing high concentrations of dissolved inorganic nitrogen (DIN) and total phosphorus (TP) in the eymir inflow 1 and in Kışlakçı brook. In Lake Eymir although diversion of sewage effluent of the Mogan municipality to İmrahor valley appeared to have led to a decrease in TP and DIN concentrations compared with those found in 1994, especially the lake TP concentration was still found to be very high (annual mean: 305 µg l -1 ) this may be due to the high inflows concentrations. The lake had a high spring increase in chlorophyll-a concentration which remained relatively low throughout the summer (annual mean: 19 mg -1 ), perhaps due to very low DIN/TP ratios implying possible N-limitation at the very high TP concentration. Moreover, the Secchi depth was also relatively low throughout summer at the low chlorophyll-a concentration possibly due to feeding of the dominant fish tench ( Tinca tinca) and carp ( Cyprinus carpio) of the lake by stirring up the sediment. The densities of large-bodied zooplankters, Daphnia and Arctodiaptomus remained low in summer following the high spring densities probably due to fish prediation exerted on them by tench and carp. In Lake Eymir, top-down or fish-induced control of the water quality appeared to be the predominant factor,following the reduction of 30% of the tench and carp (biomanipulation), has led to very high Secchi depth and densities of the large grazes.
Abstract
In this study, Lake Eymir, Eymir inflow 1, Kışlakçı brook and Eymir outflow were sampled monthly betwen March 1997and April 1998 for physico-chemical and biological parameters. Within the catchment of the lake, there are small-scale industries, sewage effluent of TEK residence and recreational activities causing high concentrations of dissolved inorganic nitrogen (DIN) and total phosphorus (TP) in the eymir inflow 1 and in Kışlakçı brook. In Lake Eymir although diversion of sewage effluent of the Mogan municipality to İmrahor valley appeared to have led to a decrease in TP and DIN concentrations compared with those found in 1994, especially the lake TP concentration was still found to be very high (annual mean: 305 µg l -1 ) this may be due to the high inflows concentrations. The lake had a high spring increase in chlorophyll-a concentration which remained relatively low throughout the summer (annual mean: 19 mg -1 ), perhaps due to very low DIN/TP ratios implying possible N-limitation at the very high TP concentration. Moreover, the Secchi depth was also relatively low throughout summer at the low chlorophyll-a concentration possibly due to feeding of the dominant fish tench ( Tinca tinca) and carp ( Cyprinus carpio) of the lake by stirring up the sediment. The densities of large-bodied zooplankters, Daphnia and Arctodiaptomus remained low in summer following the high spring densities probably due to fish prediation exerted on them by tench and carp. In Lake Eymir, top-down or fish-induced control of the water quality appeared to be the predominant factor,following the reduction of 30% of the tench and carp (biomanipulation), has led to very high Secchi depth and densities of the large grazes.