To B12 or not to B12: Investigating the effects of vitamin B12 and symbiotic bacteria on the thermal performance of phytoplankton

Phytoplankton are closely linked to symbiotic relationships with their bacteria, impacting each partner’s physiology, the environmental chemistry, and species diversity in the ecosystem. Yet phytoplankton and bacteria interactions are highly impacted by the environment, influencing both the strength and type of interactions. With climate change altering the environmental landscape, it is crucial to understand how changes in temperature will impact symbiotic interactions now and in the future. In this study, we examined how the mutualism between a vitamin B12 producing bacteria in exchange for algal carbohydrates from a phytoplankton is impacted across a temperature range. More specifically, we examined how vitamin B12 (presence/absence) and bacteria (no bacteria, with a vitamin B12 producer, with a non-vitamin B12 producer, and a mixed community) affects the growth rate of the cosmopolitan diatom, Phaeodactylum tricornutum, across its thermal range. Our results suggest that vitamin B12 and vitamin B12 producing bacteria increases phytoplankton growth rate near the thermal optimum compared to no vitamin B12 in the environment. Yet, neither vitamin B12 nor bacteria increase the thermal optimum or maximum of P. tricornutum. These results indicate that mutualistic interactions between phytoplankton and bacteria may not allow phytoplankton to persist when exposed to warmer temperatures, which may negatively impact the aquatic environment and ecosystem in a warming world.

Presentation Preference: Oral

Primary Presenter: Brandon Chan, University of Connecticut (brandon.w.chan@uconn.edu)

Authors:

Brandon Chan, University of Connecticut  (brandon.w.chan@uconn.edu)

Sara Jackrel, University of California San Diego  (sjackrel@ucsd.edu)

Colin Kremer, University of Connecticut  (colin.kremer@uconn.edu)