Dr. Karla Heidelberg, Professor, USC Department of Biology Teaching and Director, USC Program in Environmental Studies
Exploring the microbial mixotrophic mediators of marine planktonic communities
Biological oceanographers have traditionally categorized plankton as either ‘plant-like’ phytoplankton or ‘animal-like’ zooplankton. However, animals and plants are just two branches on a complex eukaryotic phylogenetic tree. Mixotrophy, the combination of autotrophic and heterotrophic nutrition in the same organism, is widespread in planktonic algae. Modes of mixotrophy are on a spectrum from species that contain their own, reproducing "constitutive" chloroplasts but also ingest particles for nutrition, to those that retain and temporarily use functional chloroplasts from ingested food, and those that harbor functionally independent symbionts. Mixotrophs are not only widespread, but modeling has indicated that mixotrophy has a profound impact on marine planktonic ecosystems and may enhance primary production, biomass transfer to higher trophic levels, and the functioning of the biological carbon pump. In this talk, I will discuss recent insights from laboratory and field studies evaluating the functioning and potential role of mixotrophs in marine environments.