Benthic diatoms growing on glass slides in the Paranaguá Bay, southern Brazil: taxonomic structure and seasonal variation

Abstract

The taxonomic structure and the seasonal variation (1993/1994) of benthic diatoms and other microalgae growing on glass slides were investigated in the Paranaguá Bay, Southern Brazil. Sixty taxa were identified, mostly benthic, with some tychoplanktonic and planktonic forrns. Some species were observed under the scanning electron microscope as follows: Cyclotella stylorum, Fryxelliella floridana, Gyrosigma cf. balticum, Licmophora sp., Melosira moniliformis, Navicula phyllepta and N. platyventris. Diatoms largely dominated the microphytobenthosand were divided into 8 morphological groups. Solitary motile, colonial plate-like and tube-dwellling species were the most common. Cylindrotheca closterium, Navicula cf. pargemina, N. phyllepta, N. platyventris and Nitzschia spp. were responsible for peaks in ceIl abundance and of chlorophyIl-a observed from December to May and in October. Melosira moniliformis was important in November, March and April. During the study period, the community showed a single-layered structure, numerically dominated by the same species. Taxonomic composition was mixed, with representatives of diverse substrates. Filamentous cyanobacteria and Euglena sp. occurred in some months. The benthic community growing on glass slides is briefly described.