Warming effect in a multiple stressor context: role of thermal variability and resource supply shaping phytoplankton communities’ responses to environmental change

• Applicant: Dr. Miriam Gerhard
• Subject Area: Ecology and Biodiversity of Plants and Ecosystems
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 465193586

Freshwater ecosystems provide critical ecosystem services but are threatened by human activities causing modifications in, for example, temperature and nutrients. Changes in mean and variance (i.e. fluctuations) of these factors affect primary producers’ performance. In phytoplankton, responses to temperature are mediated by the nutrient context, and unfavourable nutrient conditions can restrict thermal tolerance or responses to temperature fluctuations. Novel environmental conditions might also interact with community composition according to species-specific traits and biotic interactions shifting the community structure. Since these changes in phytoplankton function and structure are crucial for the maintenance of ecosystem processes and services, as phytoplankton is responsible for almost half of Earth’s primary productivity, it is relevant to understand how phytoplankton communities respond to multiple environmental stressors. Current studies focus mostly on simplified evaluations by either considering changes in temperature mean and variability separately, considering one nutrient concentration but not the balance between multiple nutrients, or are mostly based on single species omitting community interactions. The general aim of this project is to evaluate freshwater natural communities’ responses to expected changes in temperature, considering interactions with local factors, i.e. the nutrient context and thermal history. For that, controlled experiments will be conducted manipulating temperature mean and variance, as well as nutrient availability (concentrations and ratios) using natural phytoplankton communities from different climatic regions, which has not been previously addressed for freshwater systems. This proposal will allow for testing responses to environmental change and the generation of new theoretical concepts for describing and understanding complex processes in natural ecosystems.

• DFG Programme: WBP Fellowship
• International Connection: Uruguay
• Host: Professorin Dr. Mariana Meerhoff