A particularly well studied example of alternative stable states is the development of submerged vegetation in turbid shallow lakes. Submerged plants can greatly reduce turbidity by a suit of mechanisms such as control of excessive phytoplankton development and prevention of wave resuspension of sediments. However, the submerged plants also need low turbidity in order to get sufficient light. As a consequence, there can be situations in which loss of vegetation leads to an increase of turbidity sufficient to prevent recolonization by submerged plants. Another marked shift in lakes happens if the phytoplankton community becomes dominated by cyanobacteria.
We have a long history of studying critical transitions in lakes. With Erik Jeppesen, Sarian Kosten and others we now analyze how the combination of pollution and climatic change affects the resilience of the different states of lakes. Also we study micro-ecosystems with plankton in the lab to test mathematical predictions on early warning signals.