Relationships between epipelic diatoms, aquatic macrophytes, and water quality in Akarçay Stream, Afyonkarahisar, Turkey

The Akarçay is the most important stream in the Afyonkarahisar region in central Turkey. In this study, the relationships between epipelic diatoms, macrophytes, and the water quality of Akarçay Stream are presented. According to Canonical Correspondence Analysis (CCA), BOD 5 , COD, TDS, NH 4 -N, NO 2 -N, and PO 4 -P had the most significant effects on the diatom and macrophyte community structures of the stream. According to CCA and Correspondence Analysis (CA), dominant diatom species and macrophytes constituted two groups, eutrophic and polluted. While eutraphentic taxa were abundant among upstream diatoms, hypereutraphentic taxa were found downstream in the Akarçay. The diatom assemblages in the sites upstream were generally characterized by an abundance of β-mesosaprobous and α-mesosaprobous species, while the diatom assemblages downstream had a very high abundance of polisaprobous species. Eutrophic and hypertrophic macrophyte taxa (such as Lemna trisulca, Potamogeton nodosus , and Ranunculus sp.) covered a high percentage of the stream bottom. Both diatom indices and macrophyte indices with the exception of the Biological Macrophyte Index of Rivers (IBMR) were correlated with BOD 5 , COD, TDS, NH 4 -N, NO 2 -N, PO 4 -P, and EC. Physicochemical variables, diatom and macrophyte taxa and the results of diatom and macrophyte indices indicated that the Akarçay stream basin is eutrophic and organically polluted.