Original paper

Composition and structure of epilithic diatom assemblages on stones of different size in a small calcareous stream (S Poland)

Wojtal, Agata; Sobczyk, Łukasz

Abstract

In lotic environments the structure and stability of sediments are known to be very important for the development of algal vegetation. Epilithic communities dominate in this kind of water body. Despite numerous ecological and particularly monitoring studies based on epilithic diatoms the more precise data of the structure of diatom associations in discrete habitats are required.This study examines the effects of the size of stones (diameter 32-64 mm, 65-130 mm, 131-260 mm) on the structure of epilithic diatom associations in currents of similar velocity. Qualitative and quantitative analyses have not indicated essential differences in structure of epilithic diatom associations on stones of size studied. The strongest influence on the development of diatom associations was the time and site of sampling, presumably in response to the seasonal occurrence of filamentous algae, submerged vascular plants in adjacent microhabitats, and other environmental factors.A total 149 taxa belonging to 40 genera were recorded. The observed assemblages were largely dominated by stalked (e.g., Achnanthidium minutissimum, A. pyrenaicum, Gomphonema micropus) or adhesive (Amphora spp., Cocconeis spp., Planothidium spp.) diatoms, but motile taxa (e.g., Navicula lanceolata, N. tripunctata) and non-attached Denticula tenuis also occurred frequently. Amongst the widely distributed taxa were a few rarely reported species (e.g., Achnanthidium straubianum, Navicula kuelbsii, Sellaphora nana, Reimeria uniseriata, Stauroneis tackei), and 12 taxa are new to the flora of Poland.

Keywords

bacillariophyceaeepilithoncalcareous streamstone-sizepoland