The effects of biomanipulation on the biogeochemistry, carbon isotopic composition and pelagic food web relations of a shallow turf lake

• Published in: Biogeosciences discussions Vol. 2; no. 4; pp. 997 - 1031
• Main Authors: Bontes, B M, Pel, R, Ibelings, B W, Boschker, HTS, Middelburg, J J, Van Donk, Ellen
• Format: Journal Article
• Language: English
• Published: European Geosciences Union 10.08.2005
• Subjects: Asplanchna; Astrophysics; Bacillariophyceae; Chydorus; Continental interfaces, environment; Cosmology and Extra-Galactic Astrophysics; Cyanobacteria; Earth Sciences; Ocean, Atmosphere; Physics; Sciences of the Universe
• ISSN: 1810-6277; 1810-6285

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 O sub(2), low CO sub(2), and more negative delta super(13)C sub(DIC) 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 delta super(13)C signatures and to trace possible shifts in delta super(13)C 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 CO sub(2) availability. super(13)C-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.