The structure and diversity of the epipelic diatom community in a heavily polluted stream (the Akarçay, Turkey) and their relationship with environmental variables

Abstract

The structure and diversity of epipelic diatoms and some physico–chemical features of the Akarçay streams were studied in samples collected monthly from four sampling sites between March and December 2008. A total of 107 taxa of epipelic diatoms were identified. While Amphora veneta, A. pediculus, Cocconeis placentula, Cymatopleura solea, Cyclotella meneghiniana, Encyonema minutum, Nitzschia tubicola, Ulnaria ulna, and Sellaphora pupula were dominant upstream, N. palea was dominant with over 65% of total abundance downstream. According to canonical correspondence analysis analysis, BOD5, COD, TDS, pH, nutrients, and conductivity had the most significant effects on diatom community structure. N. palea was strongly and positively correlated with BOD5, COD, TDS, and nutrients. A. pediculus, Navicula cryptocephala, and S. pupula were positively correlated with pH, EC, TDS, and NO3–N. We show that the species diversity values gradually decreased with increasing pollution downstream.