Benthic macrofauna in Tunca River (Turkey) and their relationships with environmental variables

The numerical and proportional distributions of benthic macroinvertebrates in Tunca (Tundja, Tundzha) River (Edirne/Turkey) were determined from July 2002 to June 2003 at monthly intervals at four different stations. It was found that the benthic macrofauna consisted of 63% Oligochaeta, 24% Chironomidae larvae, and 13% Varia by numbers. According to the Shannon-Wiener index, Tunca River had a diversity of 1.36; station 2 and September were found to have the highest diversity while station 4 and December to have the poorest. According to Bray-Curtis similarity index, stations 2 and 3 and April and May were found to be the most similar to each other while stations 1 and 4 and August and January were found to be the most different from each other for the dynamics of the benthic macrofauna. Also some physicochemical parameters of the water (water temperature, electrical conductivity, pH, dissolved oxygen, chloride, total hardness, NO3--N, NO2--N, sulfate, phosphate, biochemical and chemical oxygen demands) were analyzed. Pearson correlation index supported the relationships between the dynamics of organisms and physicochemical variables. The relation between the number of macroinvertebrates and pH (r = +0.57, P < 0.05) was direct proportional while the relation between the number of macroinvertebrates and NO3--N (r = -0.99, P < 0.05) was inverse proportional. Furthermore, the Chironomidae larvae of Bryophaenocladius muscicola and Mesosmittia flexuella were new records for Turkish Thrace region. High pH and supersaturated oxygen levels, hard water quality, second quality levels of NO3--N, BOD, COD and fourth quality levels of NO2--N as well as the density of 490 individuals m(-2) for 124 taxa and the diversity of 1.36 showed that similar studies should be repeated periodically in Tunca to determine the future of the river.