Testing effects of shore height level, sediment characteristics and vegetation cover on the seasonality of zoopsammon communities in the two boreal lakes differing in their trophic state

Abstract

As compared to macroscopic invertebrates zoopsammon communities, i.e. fauna inhabiting interstitial spaces between sand grains are largely understudied and the factors affecting their spatiotemporal variability are not well known. In a field observation, we tested how seasonal variability in the taxonomic composition and density of zoopsammon communities at different shore heights is related to sand temperature, wave activity, sediment characteristics and vegetation cover in the two boreal lakes differing in their trophic state. The mesotrophic Lake Saadjarv had higher number of psammon taxa dominated by protists than the eutrophic Lake Vortsjarv dominated by nematodes. Within each lake, vegetation cover and sediment characteristics explained the largest variability in the spatial and seasonal dynamics of zoopsammon communities. Seasonality differed among taxonomic groups and lakes. The seasonal variability differed slightly among the levels of shore heights with densities being highest at the water line in spring and early summer and upward the water line later on. Due to the presence of strong interaction of temporal and spatial variability in psammon communities, large covariation among environmental variables and a presence of many species-specific interactions with environmental factors, the future studies should test those impact attributes with experimental approaches at the highest taxonomic resolution possible.