The effects of warming on populations and communities are currently central research topics in ecology and evolution. However, warming will not occur in isolation from other abiotic environmental changes. Therefore, it is important to consider how these factors may interact with warming. There is a lack of a mechanistic understanding of how temperature and resource availability interact and shape communities. Using phytoplankton, a key component of all aquatic ecosystems, I aim to investigate if the temperature-sensitivities of resource-use traits are conserved across the tree of life or if they differ systematically among taxonomic or functional groups. Furthermore, I will evaluate if the temperature dependence of resource-use traits is fixed for individual species. For this purpose, 20 phytoplankton species from four Swiss lakes were isolated. I then performed resource requirement experiments according to Tilman's framework (<em>R*</em> experiments), growing these species in 48 different conditions in which we manipulated one of three resources - nitrogen, phosphorus, and light, and temperatures – from 15°C to 35°C. The preliminary results show for every species, a temperature dependence on resource-use, usually, it is an increase of the resource requirements with temperature. However, these results do not show a general pattern that we can associate with functional groups for example. The change in resource requirements caused by warming may lead to modified competitive hierarchies, and thereby alter the outcome of competition in phytoplankton communities.

Primary Presenter: Sarah Levasseur, Eawag - Swiss Federal Institute of Aquatic Science and Technology (sarah.levasseur@eawag.ch)

Authors:

Sarah Levasseur, Eawag -Swiss Federal Institute of Aquatic Science and Technology- & ETH Zürich  (sarah.levasseur@eawag.ch)

Vanessa Weber de Melo, Eawag -Swiss Federal Institute of Aquatic Science and Technology.  (vanessa.weberdemelo@eawag.ch)

Anita Narwani, Eawag -Swiss Federal Institute of Aquatic Science and Technology.  (anita.narwani@eawag.ch)