INDIVIDUAL AND INTERACTIVE EFFECTS OF OCEAN ACIDIFICATION AND WARMING ON A MIXOTROPHIC PROTIST

Mixotrophic protists, capable of both photosynthesis and phagotrophy of prey, constitute a significant proportion of primary producers and bacterivores in aquatic food webs. They are especially dominant in oligotrophic marine systems, which are only expected to expand in a future climate. Mixotrophs are able to modulate both photosynthesis and phagotrophy in response to changes in the environment, which in turn affects their function in the food web. However, we know very little on how mixotrophic species respond to interactive effects of environmental changes.  We studied the response of a constitutive mixotrophic marine protist of the Ochromonas genus to ocean acidification and warming conditions. We acclimatized cultures of the Ochromonas CCMP 2951 strain to four treatments including high and low CO₂ concentrations and temperature in a factorial design. We show that the strain benefited from higher growth rates under higher temperature and ocean acidification conditions. In addition to individual effects on physiology, we also observed interactions between the two environmental factors on this strain’s mixotrophic balance. For example, a positive effect of ocean acidification conditions on photosynthetic carbon fixation rates was temperature dependent. Physiological responses will be linked to cellular composition measurements to assess the potential impact of observed responses on higher trophic levels. Finally, we will incorporate results from a differential gene expression analysis to identify some of the regulatory mechanisms of the observed physiological responses.

Presentation Preference: Oral

Primary Presenter: Shai Slomka, University of Amsterdam (s.slomkadeoliveira@uva.nl)

Authors:

Shai Slomka, University of Amsterdam  (s.slomkadeoliveira@uva.nl)

Jolanda M.H. Verspagen, University of Amsterdam  (j.m.h.verspagen@uva.nl)

Jef Huisman, University of Amsterdam  (j.huisman@uva.nl)

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