Benthic diatoms in small Estonian lakes — primary niche substratum comparisons

Comparisons of benthic diatom communities were carried out in 12 small Estonian lakes. We compared how substratum type (cobbles versus macrophytes) impact lake ecological status calculations (according to the Water Framework Directive). We hypothesized that in meso- to eutrophic lakes, both communities from macrophytes (epiphyton) and from cobbles (epilithon) would show similar modeling for lake ecological status. In general, epiphyton samples showed a slightly higher ecological status relative to epilithon samples. Comparing studied benthic diatom species assemblages, the number of species was in general higher in the epilithon, but fluctuated more in epiphyton samples. The primary species with abundances ≥ 10% was Achnanthidium minutissimum sensu lato prominently observed in 11 studied lakes. In addition Epithemia sorex dominated in Lake Tamula and Sellaphora atomoides in Lake Uljaste. Our results confirmed our hypothesis that in meso- to eutrophic lakes, the ecological status assessment results were similar using different substrata.