RESPONSES OF MIXOTROPHIC PROTISTS TO RESOURCE AVAILABILITY – FROM PHENOTYPIC PLASTICITY TO POPULATION DYNAMICS

Their access to alternative resources allows mixotrophic protists to thrive under conditions that are limiting the growth of specialist photoautotrophic or phago-heterotrophic competitors. The relative availability of light, nutrients and prey therefore shape their success in plankton communities. Yet nutritional strategies among mixotrophic protists are diverse, with different species profiting from different ratios of resource availability, and some adjusting their strategies strongly via phenotypic plasticity. Here, we assessed the impact of resource availability on mixotrophic protists using a range of approaches. First, the subcellular rearrangements made by the model mixotroph Ochromonas in response to varying prey availability have been assessed by transcriptome analysis. This obligate mixotroph invests into prey capture when prey abundance is low, but activates machinery for prey digestion only upon ingestion of prey. We further assessed the response of mixotrophic protists to resource availability within natural communities of the subalpine oligotrophic lake Lunz. Here we found cryptophytes to feed under nutrient limitation at high light intensities, while decreasing their ingestion rates at low light intensity or upon increased nutrient availability. In contrast dictyochophytes were found to feed at high rates regardless of nutrient and light availability. Such functional diversity is reflected in differences in their population dynamics both in response to light availability in a mesocosm experiment and over their seasonal succession.

Presentation Preference: Oral

Primary Presenter: Susanne Wilken, University of Amsterdam (s.wilken@uva.nl)

Authors:

Susanne Wilken, University of Amsterdam  (s.wilken@uva.nl)