Postdoctoral Fellowship: OCE-PRF: Climate change impacts on cycling of reactive oxygen species and interactions between phytoplankton and "helper" bacteria

Phytoplankton provide essential services such as oxygen production, but they are threatened by environmental perturbations including elevated light stress, warming temperatures, and ocean acidification. Less is known about how these changes will impact microscale interactions within the marine microbial community. These interactions warrant investigation as they influence key global biogeochemical processes. This research will test how climate change may shift cycling of extracellular reactive oxygen species (ROS) such as hydrogen peroxide. ROS production is projected to increase due to changing environmental conditions. Because ROS influence biogeochemical cycling and microbial interactions, changes in ROS production could have broad implications in future oceans. These efforts will advance current understanding of phytoplankton-bacteria relationships under current and future ocean conditions and how these microscale interactions will impact global processes. Through this project, educational resources will also be developed to provide hands-on research experiences and training in computational skills for undergraduate students.

The goals of the proposed research are to 1) determine shifts in ROS dynamics and 2) assess plastic and evolutionary responses of co-cultures due to warming temperatures, elevated light stress, and ocean acidification. To address these goals, the postdoctoral fellow leading this project will conduct an evolution experiment wherein representative phytoplankton and heterotrophic bacteria are coevolved using a “scenario-based approach” consisting of a combination of climate change perturbations while tracking responses and resulting biogeochemistry. Phytoplankton used in the experiment will be a prokaryotic representative Prochlorococcus marinus and a eukaryotic representative Thalassiosira oceanica. Each phytoplankton will be paired with Alteromonas macleodii, which is widespread throughout temperate and tropical oceans. The experiments will be maintained for at least one year. In the first three weeks of the experiment, a factorial design approach will be used to help disentangle plastic responses to specific stressors. Throughout the experiment, changes in fitness, ROS, and culture conditions will be measured routinely. At specific points during the experiment, the investigator will also assess the metatranscriptome, metagenome, and metabolome of the model phytoplankton and heterotrophic bacteria community. Finally, a reciprocal transplant experiment will be conducted, wherein ancestral and evolved cultures will be exposed to control and climate change conditions while measuring fitness, ROS, culture conditions, as well as the metatranscriptome of co-cultures.

This project is jointly funded by the Ocean Sciences Postdoctoral Research Fellowships Program and the Established Program to Stimulate Competitive Research (EPSCoR).

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Award Number: 2511947
Principal Investigator: Sydney Plummer
Funds Obligated: $329,635
State: AL