Ciliates versus other components of the microbial loop in the psammolittoral zone: horizontal distribution

The objective of this study was to determine the abundance and biomass of microbial loop components in 2 lakes of different trophic status. The lakes (mesotrophic and eutrophic ones) were located in the Łęczna-Włodawa Lakeland. The effect of selected physical and chemical water parameters on this group of organisms was also analyzed. Psammon samples were collected during 3 seasons: spring, summer, and autumn 2011. In each of the lakes, samples were collected in the euarenal, higroarenal, and hydroarenal zones. The highest abundance and biomass of the microbial loop components were recorded in spring in the eutrophic lake. The mesotrophic lake showed an increase in flagellates in autumn with a decline in the abundance of ciliates. In the mesotrophic lake, the density of individual elements of the microbial loop was correlated with temperature and total organic carbon, and in the eutrophic lake with pH, chlorophyll a, and ammonium nitrogen. In both lakes, a significant correlation occurred between bacteria and ciliate abundances. In both trophic types of lakes, the highest correlations between bacteria and heterotrophic protists were noted in hydroarenal zone. In the euarenal and higroarenal zones, the correlations were weaker.