The sub-project on Planktothrix rubescens has yielded more optimistic results. In Lake Zurich, for example, the increased water temperatures due to climate change have led to cyanobacteria appearing in masses in some areas. At Lake Constance, however, a blue-green algae plague of this magnitude is considered unlikely in the near future.
It is equally encouraging that some groups of organisms have proven surprisingly resilient to the environmental changes in Lake Constance. For example, using sediment cores, the researchers were able to show that new diatom species that are adapted to nutrient-rich conditions appeared during the period of over-fertilisation. However, after the measures to contain nutrient levels (re-oligothrophication), this development was reversed, so species adapted to nutrient-poor conditions once again dominate today’s Lake Constance. A similar trend can be observed in aquatic plants: Growth and expansion in the shore zones have increased significantly again after re-oligothrophication, even if the species composition and abundance have changed somewhat.
However, Piet Spaak fears that this recovery will be short-lived: "I expect the ecosystem of Lake Constance to change more in future than in recent decades as a result of climate change and invasive species such as the quagga mussel and stickleback. As a countermeasure, we recommend preventing the introduction of further alien species."