Relationship of epilithic diatom communities to environmental variables in Homa lagoon (Izmir, Turkey)

Abstract

Spatio-temporal changes in taxonomic composition and structure of a diatom com- munity were assessed between June 2006 and June 2007 at the intertidal zone of Homa lagoon, Izmir, Turkey. The communities were composed of a mixture of epilithic, epiphytic, epipsammic, and occasionally some pelagic diatoms. In total, 87 taxa belonging to 39 genera were identified, of which 39 were used as active taxa in the numerical analysis. The Shannon-Wiener diversity index (H') values were quite variable, varying between 1.00 and 3.39 and correlated with both species richness (r = 0.93) and evenness (J'; r = 0.38). Cylindrotheca closterium, Halamphora veneta, Lic- mophora gracilis, L. lyngbyei, Navicula cryptocephala, N. cincta, and N. ramosissima var. mollis were the overall most abundant taxa throughout the sampling. The relationship between epilithic algal communities and 10 environmental variables was explored using canonical correspondence analysis. According to a Monte Carlo unrestricted permutation test, the silicate and ammonium concentrations were the most important variables in accounting for species distribution.