Mechanisms and consequences of change in aquatic protist communities

• Applicant: Professorin Dr. Jana Petermann
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions ; Ecology and Biodiversity of Plants and Ecosystems
• Term: from 2013 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 244513958

Change is ubiquitous in nature. However, rates of environmental change have accelerated strongly over the last few decades as a result of anthropogenic impacts. We know relatively little about how this rapid change affects complex natural communities, and in particular what the actual mechanisms behind community-level responses are. For example, does abiotic change have a direct community impact or do effects operate indirectly via certain species or trophic levels in multitrophic food webs? The resulting differences in community structure potentially affect ecological dynamics and stability. Communities might also show evolutionary responses to environmental change, even over short time frames. Ultimately, these changes could have strong impacts on community functions. However, our limited understanding of these processes precludes robust predictions of consequences of change for natural ecosystems.Here, we propose to use multitrophic protist communities as a model system to study the effects of environmental change on natural communities. These complex assemblages occur in small aquatic habitats in bromeliad plants along strong natural gradients of environmental change on tropical mountain slopes. They are ideally suited for the proposed project because they can be replicated and manipulated in the field but also simplified for lab experiments under controlled conditions.In this project, we will first identify those factors in a field survey that drive changes in bromeliad protist community structure along elevational gradients in Northern Costa Rica. We will subsequently use a field experiment specifically designed to test and quantify effects of those factors on natural communities and their functions. In this experiment, we will examine direct abiotic and indirect biotic (top-down and bottom-up) drivers by manipulating them both in isolation and in certain combinations.We will directly link these field studies with lab experiments using bromeliad protist species that we have in culture at the Institute of Biology, Freie Universität Berlin. The first lab experiment will address mechanisms of ecological change as a result of multiple changing environmental factors, explicitly considering community dynamics and stability. The second lab experiment focuses on evolutionary dynamics in response to environmental change. We will measure plasticity and rapid evolution in certain lines of protists, and determine effects of these processes on coexistence, community structure and ecosystem function.With this project, we aim to identify and test key aspects of environmental change affecting natural communities and reveal mechanisms by which they operate. Ultimately, this knowledge will put us in the position to predict consequences of change for ecosystems and their functions.

• DFG Programme: Research Grants
• International Connection: Austria