The laboratory of microbial ecology focuses on biodiversity of microbial life in lakes, with a strong emphasis on phytoplankton, i.e. microscopic sized algae and cyanobacteria. Phytoplankton is at the base of the lacustrine foodweb and thus supports other life forms in lake ecosystems. Freshwater ecosystems have an extraordinarily high biodiversity, but are also under great pressure due to human activities (intensive agriculture, climate change, industrial pollution, etc.). Lakes integrate environmental stressors in their catchment and act as sentinels of change, like canaries in a mine. To better protect biodiversity in lakes, we must truly understand the mechanisms that control biodiversity. In our laboratory we study biodiversity at different levels:

1. the evolutionary origin of biodiversity - how do new species appear?
2. biodiversity at the population level – in particular how do parasitism and temporally and spatially variable lake environments contribute to genetic diversity?
3. biodiversity at the community level - how are populations assembled to establish communities?
4. the role of microbial biodiversity in the provision of lake ecosystem service and what happens when biodiversity brakes down?

Our work on the biodiversity of the phytoplankton is inspired by a 1961 publication: "The paradox of the plankton. How is it that dozens of species of phytoplankton can co-exist in the apparently homogeneous environment of a well-mixed Lake? One would expect that only the best adapted species survive and out-compete all others. In our journey to find solutions to this paradox, we come across fascinating areas of scientific research. Limnology for example: lakes are not as homogeneous as one might think, but are highly dynamic in time and space. How does climate change affect this spatial structure and temporal patterns in lakes? Or the discussion of niche versus neutrality: does each of the dozens of phytoplankton species in a lake really have its own niche or are many species of phytoplankton interchangeable? What about the importance of trade-offs: what if the strongest competitors are more vulnerable to parasites or predators, does this promote co-existence and diversity? In the group we have a particular interest in the role of complexity of the environment for the evolution and maintenance of diversity. A fascinating question here is, where does complexity come from? Does life itself contribute to complexity on which biodiversity depends?

Hutchinson`s famous 1961 paper on the paradox of the plankton

We see tree paintings, Monet`s waterlilies, Malevich`s black square and Mondriaan`s Victory boogie woogie. If the goal of ecology is to understand Monet, nature in all of its complexity, then in order to make progress we need to understand diversity in more simple (experimental) systems. If nature looked like Malevich black square – a single homogenous niche- biodiversity would be limited. If, however, complexity is increased to the level shown in Victory boogie woogie, several niches exist and a larger degree of diversity could be maintained.

Work in the group is equally divided between laboratory, field and computational studies, and a wide array of tools and techniques are being used, which may vary from molecular markers for population genetics, or PAM fluorometry for photosynthesis to lake monitoring using remote sensing and automated in situ flowcytometry. From experiments in chemostats or in- and outdoor mesocosms to experimental evolution using photo- and heterotrophic microorganisms. Or from (fuzzy logic) modeling to genomics (transcriptomics).