Current projects

The temperature dependence of competition in phytoplankton

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​The effects of warming on populations, communities and ecosystems are currently central topics of research in ecology and evolution, due to predicted climate change. However, warming will not occur in isolation to other types of abiotic environmental change. It is therefore important to consider how other gradients of environmental change may interact with warming. In aquatic environments, resource limitation and warming may increasingly occur together, because as waters warm they become increasingly stratified, preventing the mixing and resuspension of resources from the sediment. Resources and environmental temperature are both important drivers of metabolic processes, which have impacts across all scales of biological organization, from cells to ecosystems. The overarching goal of this project is to determine the extent to which warming alters essential resource requirements and elemental stoichiometry in freshwater phytoplankton, and in turn how such changes may influence competitive species interactions, community assembly and ecosystem functioning under warming. I aim to understand these impacts from a mechanistic perspective, addressing multiple levels of biological organization, from molecular to population, and community-level differences.​

This project is funded by the SNSF for 4 years and will begin in the summer of 2021. We will soon welcome Sarah Levasseur as the PhD student leading the ecological compoent of this project. We are very excited that she is joining us and look forward to getting started with this work.

The impact of warming and resource limitation on phytoplankton metabolism –
leveraging high-throughput metabolomics

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​Resource availability and temperature are both independently among the most important drivers of biological processes across all scales of biological organization, from cellular metabolism, to population-level growth rates, community assembly, and even ecosystem-level fluxes of material and energy. We have separate mechanistic understandings of the influences of both temperature and resource availability on processes at all biological scales, but much less is known about how these two drivers interact. How does temperature influence different sub-cellular processes? Are all metabolic processes affected equally by warming or do some show greater temperature-sensitivity than others? If so, can we identify general rules about how particular metabolic pathways and their respective resource requirements are sensitive to temperature due to the activation energy of their metabolism? This project represents a first attempt at a comprehensive investigation of the interactive influences of temperature and resource availability on phytoplankton metabolism, and how this metabolic variation scales up to population-level dynamics. 

This project is funded by Eawag and is led by Dr. Vanessa Weber de Melo (vanessa.weberdemelo@eawag.ch)
Figure adapted from Steuer et al. 2019, Frontiers in Chemistry. 

Warming-related community turnover in freshwater and terrestrial ecosystems

In this Blue-Green-Biodiversity project, funded by the ETH Domain, we are quantifying and comparing the rates of warming-related comunity turnover occuring in freshwater and terrestrial communities. In this project we are analyzing existing data from biodiversity monitoring projects, where the same sites are sampled repeatedly over time. This includes Swiss Biodiversity Monitoring data (BDM), National Lakes Assessment Survey Data (USA EPA), Alberta Biodiversity Monitoring data (ABMI), RivFishTime, BioTime, and other published time-series. We hope to understand whether cold-loving taxa are being replaced by warm-loving (thermophilic) taxa, or whether warm-loving taxa are simply addiing up. Additionally we hope to elucidate both environmental and biological drivers of this signal of "thermophilisation". Does body size determine the rate of turnover? Or are thermal niches and environmental variation inmportant drivers? 

This project is a collaboration with Christian Rixen, and is led by Dr. Imran Khaliq (imran.khaliq@eawag.ch).