The Determination of Trophic Level of Küçükçekmece Lagoon Lake (İstanbul, Türkiye) by Using Some Environmental Variables with Indicator Benthic Macroinvertebrates Findings

Abstract

In this study, to determine the trophic level of Küçükçekmece Lagoon Lake, water and sediment samplings were performed at five selected stations seasonally during a year between 2014-2015. The water samples were analyzed to determine some environmental variables (water temperature, pH, conductivity, DO (dissolved oxygen), TDS (total dissolved solids), and salinity. NO3-N, NO2-N, SO4-2, PO4-3, SiO2, chlorophyll-a, TP (total phosphorus), and Secchi disc light permeability) and benthic macroinvertebrates were examined to determine indicator organisms in the sampled sediment material. Bray-Curtis Similarity Index was used to the observed environmental results to determine the similarities of the sampling stations. According to this, station 1 (St. 1) located in the center of the lake, and St. 5 located near the sea were found to be different from other sampling stations while the stations located near the creeks were found to have much more similar to each other. In addition, to determine the trophy level of the lake, Carlson Trophic State Index (CTSI) was used to the obtained some physicochemical results (Secchi disc permeability, total phosphorus, chlorophyll-a) and it was found that the lake showed a eutrophic character during all seasons. According to the result of sediment sampling, an average of 350 individuals per m2 (44.3 % belonging Polychaeta group; 29.5 % belonging Chironomidae group; 19.7 % belonging Oligochaeta group; 6.5 % belonging Bivalvia group) in a total of 6 benthic macroinvertebrate taxa (Bivalvia, Polychaeta, Tubificoides benedii (Oligochaeta), Tubificoides sp. (immature Oligochaeta), Limnodrilus hoffmeisteri (Oligochaeta), and Chironomus salinarius (Chironomidae) were determined. Thus, it is observed that the presence of some indicator species supported eutrophic conditions qualitatively. As a result of this study, it was determined that Küçükçekmece Lagoon lake going on to expose the increasing pollution load.