engleski

The effect of drying on colonization of periphyton communities

Surface drying is an important disturbance that shapes biological communities. We tested the effect of drying on the colonization patterns of protozoa and micro-metazoa. A total of 192 glass slides were exposed in replicated 1.5 m experimental flumes that were fed by water from a nearby stream. After an initial colonization period of nine days one third of the slides were air-dried for eight days, rewetted, and the recolonization of periphyton was compared with community on the permanently wet slides. During the initial period (i.e. nine days), we observed distinct colonization pattern starting with single-celled algae, mostly diatoms, followed by flagellates and ciliates. In contrast to the initially slow development of periphyton, recolonization after the dry period was very fast. At the beginning of the re-wetting experiment only desiccated periphyton was detected on glass slides. However, in less than 24 hours flagellates and ciliates appeared in great numbers. Further, drying resulted in a distinctly altered community composition (i.e. first colonizers and dominant species), compared to the composition on the permanently wet slides. The much faster recolonization rate after drying can be explained by the remaining matrix on the glass slides and the encysted forms of microorganisms. In the initial colonization and recolonization experiments species richness increased logarithmically, while ash free dry mass increased exponentially in time. Total biomass and the density of organisms were much higher in the recolonisation experiment.

periphyton; protozoa; drying; rewetting

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