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The effects of biomanipulation on the biogeochemistry, carbon isotopic composition and pelagic food web relations of a shallow turf lake
1Centre for Limnology, Netherlands Institute of Ecology, KNAW, P.O. Box 1299, 3600 BG Maarssen, The Netherlands
2Centre for Estuarine and Marine Ecology, Netherlands Institute of Ecology, KNAW, P.O. Box 140, 4400 AC Yerseke, The Netherlands
Abstract. The effects of fish removal on the biogeochemistry and lower-trophic level food web relations were studied in a shallow eutrophied turf lake. Biomanipulation led to an increase in transparency and macrophyte biomass and decrease in phytoplankton abundance, but zooplankton numbers did not increase. Moreover, fish removal resulted in high pH, high O2, low CO2, and more negative δ13CDIC values than expected, which is proposed to be the likely result of chemical enhanced diffusion with large negative fractionation (-13). By combining fluorescence activated cell sorting and isotope ratio mass spectrometry (IRMS) of fatty acids we were able to obtain group specific δ13C signatures and to trace possible shifts in δ13C resulting from fish removal. Fractionation values of green algae (20) and diatoms (22) were uniform and independent of treatment, while fractionation factors of filamentous cyanobacteria were variable between the treatments that differed in CO2 availability. 13C-labeling of the phytoplankton groups showed that biomanipulation led to increased growth rates of green algae and diatoms at the expense of cyanobacteria. Finally, the primary consumer Chydorus appeared to prefer cyanobacteria, whilst Asplanchna grazed predominantly upon eukaryotes.
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Citation: Bontes, B. M., Pel, R., Ibelings, B. W., Boschker, H. T. S., Middelburg, J. J., and van Donk, E.: The effects of biomanipulation on the biogeochemistry, carbon isotopic composition and pelagic food web relations of a shallow turf lake, Biogeosciences Discuss., 2, 997-1031, 2005. Bibtex EndNote Reference Manager
