Environmental Chemistry of Biomolecules
The overall aim is to determine production dynamics and environmental transformation processes of toxins and other NRPs that define cyanoHABs. First, we will assess seasonal and annual variations in the natural lake system and compare NRP profiles and intracellular and extracellular cell quotas with other monitoring parameters. To further promote the predictability of NRPs in surface waters, we will delineate production dynamics in response to fitness dis-/advantages of toxin-producers and for a varying degrees of community complexity in laboratory setups. Finally, we will study biodegradation of toxins/NRPs in surfaces waters and determine the contribution of extracellular aquatic enzymes.
Synthetic Microbial Ecology
The aim is to understand when (and under what conditions) cyanoHAB taxa have a growth advantage over competitors, and thus when cyanoHAB taxa are likely to proliferate. The main goal is to measure the relative fitness of cyanoHAB taxa relative to a range of competitors under different abiotic and biotic conditions and when in the presence of predators and potential facilitators using a synthetic microbial ecology approach.
Theoretical ecology and evolution
The aim of this project is to integrate and consolidate the information acquired by the work of the phytoplankton ecology group, synthesising it into conceptual and theoretical models about how cyanoHABs occur in nature. This synthesis, based on both data-driven and theoretical models, will allow to formalise mechanisms and test general hypotheses of the overall behaviour of the system (a network of interacting plankton taxa), and make predictions about how environmental changes will influence the probability of occurrence of cyanoHABs. The conceptual model will also lay the foundation for re-designing both sampling efforts and data-driven models to monitor and forecast toxic blooms.
The general aims to study the eco-evolutionary mechanisms that trigger cyanobacterial blooms, based on high frequency data of plankton communities and their growth environment. We want to establish the chain of events that lead to cyanoHABs, and how cyanoHAB taxa respond to environmental conditions in nature. We will model cyanobacterial dynamics and trait changes (NRP gene prevalence and expression, and size), to infer drivers of turnover in taxa, genes and traits. This will restrict the range of mechanisms to test in experiments, informing theory development.
Greifensee is an eutrophic, dimictic lake in the north of Switzerland (47.3525°N, 8.6748°E), about 12 km from Zurich. It covers a surface area of 8.45 km2 and has a mean depth of 17.6 m, while the maximum depth is 32.3 m. Its mean water retention time is 420 days. Naturally, Greifensee used to be an oligotrophic lake. In the second half of the 20th century, Greifensee suffered a period of heavy eutrophication due to a rapid increase in population in the catchment area. Thanks to stricter wastewater treatment, emission and fertiliser regulations, the nutrient input into Greifensee has again been reduced since the 1980s. Due to strong phytoplankton growth in late summer, there is often not enough oxygen for fish in depths below 6m. Therefore, a ventilation system was installed in 2009 which produces a local fish refuge in the critical summer months.
Source: AWEL, Bürgi et al. (2003)