Investigation of some physical and biological (Benthic macroinvertebrata) features of karasu stream (Kastamonu)

This study was carried out to evaluate and determine the water quality of Karasu stream (Kastamonu) in four seasons (August and October 2019, February and April 2020) using physical and biological parameters. For this aim, sixteen sampling points were chosen, physical parameters were measured in the field, and benthic macroinvertebrate samples were collected in the field, conserved, separated, and identified later at laboratory. Biotic indices (Spanish BMWP, ASPT), and diversity indices (SWDI, SDI, EPT index, EP index, %EPT index) were applied to evaluate and determine water quality. As a result of the study, a total of 41 taxa comprising 14748 individuals were collected and identified in 15 stations along Karasu stream and 1 station in Gökırmak river; 13 of taxa belong to Diptera; 9 taxa belong to Trichoptera; 5 taxa belong to Ephemeroptera; 5 taxa belong to Plecoptera; 4 taxa belong to Coleoptera; 1 taxon belong to each of Odonata, Lepidoptera, Amphipoda, Hirudinea and Oligochaeta. The most individuals were collected at S6 sampling station (1309 individuals), while the fewest individuals were collected at S11 sampling station (185 individuals). As a result of this study, the water quality of Karasu stream was determined as very good/good according to the Surface Water Quality Management Regulation (SWQMR) criteria given by T.C. Ministry of Forestry and Water Affairs. Moreover, the water quality was determined either as unpolluted/slightly polluted (in 13 sampling stations), as slightly polluted/moderately polluted (in S14 and S15 sampling stations) or as polluted/extremely polluted in S16 sampling station, all of which according to ASPT and Spanish BMWP biotic indices. The relatively moderate to high pollution pressure in the lower section of Karasu stream should be monitored and the required precautions should be taken to decrease pollution pressure.