Seasonal variations and occurrence of epiphytic diatom assemblages on mats of Cladophora glomerata in Lake Ladik, Samsun, Turkey

Abstract

The composition and seasonal variations of epiphytic diatoms from Lake Ladik were studied using samples collected from one station between June 2000 and May 2001. 50 taxa of diatoms were identified in the epiphyton. Gomphonema olivaceum, Gomphonema minutum and Nitzschia fonticola were particularly important on Cladophora. During the winter several species of Navicula become progressively more important. Gomphonema lateripunctatum was particularly notable. Other diatoms were occasionally abundant, including Cyclotella ocellata, Aulacoseria distans, Cymbella affinis, C ventricosa and Navicula halophila. Fragilaria ulna and Gomphonema ventricosum were conspicuous, owing to their large size, but never numerically abundant. Cluster analysis was applied to the epiphytic algae community. The seasonal variations of the samples were classified according to their similarity levels. Samples were collected, species richness and diversity (Shannon-Wiener, H') were measured monthly. The relationship between the algal composition and physicochemical variables is analyzed by means of Canonical Correspondence Analysis techniques.