Long-term dynamics of microbial biofilm communities of the river rhine

• Main Author: Eßer, Markus
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2006
• Subjects: ddc:570; Antarctic; The Antarctic; Antarc*
• Online Access: https://kups.ub.uni-koeln.de/1799/; https://kups.ub.uni-koeln.de/1799/1/Disskomplett04.07.06.pdf

Composition and succession of all major organism groups in microfilm in a flow channel in the river Rhine were examined in parallel over a period of 14 months. In addition, abiotic parameters were monitored (e.g. temperature, water level, chlorophyll content). Based on these data an additional laboratory experiments involving chromadorid nematodes and bdelloid rotatoria, the first model ever of matter flow in the biofilm of a large river could be developed, possibly representing an important contribution to the identification of relevant interactions in the biofilm system. It could be demonstrated that the matter flow in biofilm of the river Rhine was dominated by protozoans - mostly filtrating species - in the investigated model system; they contributed around 78% to the mean annual metabolism. The most important representatives of heterotrophic flagellates were sessile choanoflagellates with abundances up to 100,000 individuals/cm². Throughout the year, ciliates were mostly dominated by peritrichous ciliates. With respect to individual count, metazoans were dominated by bdelloid rotatoria and chromadorid nematodes, representing together more than 90% of the metazoans during the study period. The densities of chromadorid nematodes were high, even up to 600 ind./cm². Another important result of the current study was the proof of the strong benthic-pelagic coupling in the Rhine. It could be demonstrated that only approximately 2% of the biomass metabolized in biofilm was autochthonously synthesized in the biofilm itself; 98% were imported directly from the pelagial. This high import portion of planctonic organisms controls the benthic microbial metabolic cycling in the investigated system, i.e. biofilm in the Rhine, and therefore also represents an important structuring factor for the planctonic food web. Sampling of ice habitats in the Antarctic demonstrated that also the communities of heterotrophic flagellates in Antarctic were primarily composed of benthic species. Biofilm in slush was dominated by filtrating ...