Effects of mixotrophic metabolism on predation risk

This is the authors' abstract. We don't add key points for this paper.

Planktonic mixotrophic nanoflagellates, which combine the capacity for phagotrophy and photosynthesis within the same cell, play a crucial role at the base of marine food webs. Their population dynamics are constrained by resource availability and top-down control from grazers. However, the relationship between mixotroph metabolic strategy and predation risk remains unclear. Mixotrophs vary in their metabolic strategy, both evolutionarily (across lineages) and plastically (within lineages; e.g. in response to resource availability), and different metabolic strategies may produce different predation risks. For example, if mixotroph grazing activity increases hydrodynamic disturbance, predation risk from grazers that respond to this disturbance may increase. Mixotroph chemical cues and toxin production may also vary with diet. Here, we tested for relationships between metabolism and predation risk by offering 8 members of the cosmopolitan mixotroph genus Ochromonas to the generalist grazer Oxyrrhis marina . We found that well-fed, more metabolically active Ochromonas triggered greater O. marina clearance rates. Strains also varied in their impact on the grazer’s growth, suggesting that these mixotrophs may use modified grazing behaviors to alter their predation risk.