BIO-02 Key changes in ocean variability and the effects of climate change
Effects of temperature on growth and feeding on the mixotrophic dinoflagellate Lepidodinium sp.
Jiaqi Lei* , Guangzhou Key Laboratory of Subtropical Biodiversity and Biomonitoring, Guangdong Provincial Key Laboratory of Healthy and Safe Aquaculture, School of Life Science, South China Normal University, Guangzhou, China
Guiling Liu, Guangzhou Key Laboratory of Subtropical Biodiversity and Biomonitoring, Guangdong Provincial Key Laboratory of Healthy and Safe Aquaculture, School of Life Science, South China Normal University, Guangzhou, China
Yuting Zeng,
Shuwen Zhang, Guangzhou Key Laboratory of Subtropical Biodiversity and Biomonitoring, Guangdong Provincial Key Laboratory of Healthy and Safe Aquaculture, School of Life Science, South China Normal University, Guangzhou, China

Mixotrophic dinoflagellates are widely distributed in aquatic ecosystems and play an important role in the planktonic food web. However, it is yet unclear how mixotrophic dinoflagellates will respond to the future warming climate and what role they will play in the carbon cycle in the context of global warming. Therefore, in this study, we conducted laboratory experiments to examine the impacts of temperature on the physiological traits of a coastal mixotrophic dinoflagellate Lepidodinium sp. which evolved from the secondary endosymbiosis of green algae. According to our findings, Lepidodinium sp. is a facultative mixotroph with an obligate phototrophic lifestyle and can survive and reproduce in both purely autotrophic and heterotrophic conditions. The thermal sensitivity of Lepidodinium sp., expressed as activation energy (Ea, eV), was dependent on their nutrition history and was substantially higher for Lepidodinium sp. grown under mixotrophic conditions (with sufficient prey, 0.99 eV; without prey, 1.21 eV) than under autotrophic conditions (with nutrients, 0.32 eV). This supports the finding that mixotrophs shift towards more heterotrophy as temperatures increase. Warming would promote a higher growth rate of Lepidodinium sp. cultivated under mixotrophic conditions with sufficient prey than under autotrophic conditions, demonstrating that mixotrophic dinoflagellates may profit significantly from mixotrophy when the temperature rises and prey are abundant. Moreover, the impact of temperature on the ingestion of Lepidodinium sp. depended on the prey concentration; its ingestion rose only when the prey concentration was sufficient and the temperature was below 25 â„? Our results suggested that prey concentration is an important factor for predicting the response of mixotrophic dinoflagellate to the warming climate; if sufficient prey is available, they will have higher growth rates and ingestion rates in warming oceans and their functional roles in marine ecosystem food webs will shift from primary producers to consumers.