Beyond the mean: phytoplankton responses to fluctuating resource and energy supply

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Environmental changes do not only alter mean conditions but also the temporal and spatial variance around these conditions (e.g., temperature variance, nutrient pulses). Concerning the combined effects of resource and temperature fluctuations, some fundamental studies exist on how pulsed (versus constant) resource supply alters community composition and performance. However, these considerations have rarely – if ever – been placed in a warming-resource context, and none of the studies are explicitly addressing fluctuations in more than one dimension. This proposal addresses the consequence of fluctuations in temperature, light and nutrients for monocultures and communities of freshwater phytoplankton. The species-specific information serves to make predictions at the community level, allowing us to test how fluctuation effects might be buffered in multispecies communities. The originality of the project lies in our approach to assess the interactive effect of fluctuating resources (nutrients and light) and fluctuating temperature on freshwater phytoplankton. To understand the underlying mechanisms, we will manipulate both the frequency and the amplitude of fluctuations. Thereby we address the knowledge gap how simultaneous fluctuations in resources and energy will alter phytoplankton growth, resource use and biomass yield.