ABSTRACT Mixotrophic chrysophytes are known for significant contributions to primary productivity and grazing within microbial loops in aquatic systems. Understanding how projected changes in a warming environment might alter physiological responses in mixotrophs is crucial. In this study, we investigated mixotrophic responses of the freshwater chrysophyte, Chrysolepidomonas dendrolepidota, under an array of temperatures (14–20°C) and inorganic nutrient conditions (1%–50% DY-IV nutrient media). Photosynthetic rates of C. dendrolepidota were reduced in lower inorganic nutrient concentrations and increased with rising temperature. Bacterivory rates were not significantly different across inorganic nutrient regimes but decreased with rising temperature, and in some measure with decreasing bacterial abundance. The highest temperature tested promoted rapid initial growth in higher inorganic nutrient condition, with slower more continuous growth observed at lower temperatures. Our results indicate phototrophy and phagotrophy by C. dendrolepidota are strongly affected by temperature, shifting toward more phototrophic nutritional mode as temperature increased. While some mixotrophs have been shown to be more heterotrophic with increasing temperature, photosynthesis contributes more to C. dendrolepidota’s carbon budget with increasing temperature. These findings demonstrate environmental factors can induce different physiological responses along gradient of photo-osmo-phago-mixotrophic abilities, which should be taken into consideration in future works involving models of climate-change impacts on phagotrophic phytoplankton.
Chang et al. (Sat,) studied this question.