The colonization and succession patterns of the periphytic ciliate community in a temperate floodplain lake

An in situ experiment to investigate periphytic community development was conducted on an artificial substrate (glass slides) in a Danube floodplain lake in Croatia. The main aim of the research was to analyze the structure of the ciliate community (Ciliophora, Protozoa) in the periphyton. We wanted to investigate how biotic and abiotic factors change and influence the ciliate community, reflecting not only the temporal community dynamics, but also the complex interactions within the periphyton. The experiment lasted from April to December 2009. To monitor the colonization process, the samples were collected on the 1ˢᵗ, 3ʳᵈ, 5ᵗʰ, 7ᵗʰ and 14ᵗʰ day of exposure. After that, sampling was conducted biweekly, with the aim of studying the successional patterns of the periphytic ciliate community. 116 ciliate taxa were recorded. Non-metric multidimensional scaling indicated that development of the periphytic ciliate community occurred in three phases: initial, intermediate and mature. Water temperature and transparency were the most important parameters influencing the initial and intermediate phases of community development when mainly vagile bacterivorous and algivorous ciliates were present. The mature phase was characterized by higher organic content in the periphyton and an increased concentration of chlorophyll in the water column, indicating the potential food source as the primary factor influencing ciliates. The complex three-dimensional structure of the periphyton also affected the ciliate assemblage throughout the later successional stages. The trophic structure of the ciliates became more diverse during the mature phase, with sessile suspension-feeding and predatory ciliates as dominant groups. The present study shows that the early stages of the periphytic ciliate community are influenced mainly by external abiotic factors, whilst the mature community is characterized by biotic factors.