The Role of Cell Morphotype in Protist Grazing on the Model Diatom Phaeodactylum tricornutum
David Beaudoin1, Matthew D Johnson1, Leila Tirichine2, Achal Rastogi2 and Chris Bowler3, (1)Woods Hole Oceanographic Institution, Biology, Woods Hole, MA, United States, (2)Institut de Biologie de l’Ecole Normale Supérieure (IBENS), Environmental and Evolutionary Genomics Section, Paris, France, (3)Institut de Biologie de l’Ecole Normale Supérieure (IBENS), Ecology and Evolutionary Biology, Paris, France
Abstract:
Microzooplankton grazing is the single greatest loss to daily primary production in the oceans. Factors such as prey quality, chemical defense, and morphology are known to play important roles in mediating interactions with protist grazers. However, for most phytoplankton species we lack a mechanistic understanding of variables that modulate grazing and their relative importance. Here we test the hypothesis that morphological complexity acts to decrease grazing rates of microzooplankton predators, using strains of
Phaeodactylum tricornutum with distinct morphotypes (oval, fusiform, and triradiate). Specifically we expected to find lower grazing on the triradiate morphotype.
In experiments with predominantly uniform morphotypes, our results demonstrate that grazing by the heterotrophic dinoflagellate Oxyrrhis marina was surprisingly greatest on triradiate P. tricornutum, while oval and fusiform morphotypes revealed lower rates. Furthermore, the triradiate morphotype also supported higher growth rates of O. marina. We are currently investigating the role of grazing on morphotype frequency in P. tricornutum strains with mixed phenotypes. Chemical factors, such as prey nutritional content, and oxylipin profiles are also being investigated. Collectively, these experiments will help to determine the role of intraspecific phenotypes in predator-prey interactions, and how grazing helps to shape morphotype frequency in prey populations.
