Projects
Role of a mixotrophic chrysophyte in a food web with the toxic cyanobacterium Microcystis aeruginosa
The toxic cyanobacterium Microcystis aeruginosa is a nuisance in many freshwater systems, forming dense surface blooms. The mixotrophic chrysophyte Ochromonas is able to graze efficiently on M. aeruginosa and has been suggested as a possible biological control agent against Microcystis blooms. It does not seem to be affected by the toxic microcystins itself and it might even upgrade the poor food quality of cyanobacteria for higher trophic levels like daphnids and rotifers by degrading the microcystins. However, as a mixotroph Ochromonas has a different role in the food web than a purely heterotrophic predator, because it simultaneously acts as predator and competitor of Microcystis. Furthermore the relative contribution of autotrophy and heterotrophy to the metabolism of Ochromonas can be adapted in response to environmental parameters like light intensity and nutrient availability.
In this project both physiological and ecological aspects will be investigated including the nutritional flexibility of Ochromonas in response to resource or prey availability, and the effect of this mixotrophic behavior on food web dynamics.
Selected Publications
Wilken, S., Hoffmann, B., Hersch, N., Kirchgessner, N., Dieluweit, S., Rubner, W., Hoffmann, L.J., Merkel, R., Peeken, I. 2011. Diatom frustules show increased mechanical strength and altered valve morphology under iron limitation. Limnology and Oceanography 56, 1399-1410.
Wilken, S., Wiezer, S., Huisman, J., Van Donk, E. 2010. Microcystins do not provide anti-herbivore defence against mixotrophic flagellates. Aquatic Microbial Ecology 59, 207-216.
Van Donk, E., Cerbin, S., Wilken, S., Helmsing, N.R., Ptacnik, R. and Verschoor, A. 2009. The effect of a mixotrophic chrysophyte on toxic and colony-forming cyanobacteria. Freshwater Biology 54, 1843-1855.
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