ROLE OF PARTICLE-ASSOCIATED BACTERIA IN AGGREGATE FORMATION IN THE CURRENT AND FUTURE OCEAN

The formation of aggregates is an important part of the biological carbon pump as carbon is exported to depth. These particles are composed of cells, minerals, and other sources of organic carbon that can be held together by transparent exopolymeric particles (TEP) acting as a glue-like matrix. Due to anthropogenic impacts, the concentration of carbon dioxide in the atmosphere is steadily increasing, causing an increase in ocean temperature and acidity, and it is essential to understand how carbon export by the biological carbon pump is impacted by future ocean conditions. Using mesocosms and roller tank experiments, we investigated the aggregation potential of natural seawater planktonic communities in the summer in the Sargasso Sea under current and future ocean conditions. Future ocean conditions were simulated at 30 degrees Celsius and 7.9 pH, while ambient conditions were simulated at 27 degrees Celsius and 8.1 pH. Roller tank experiments carried out in both conditions resulted in visible macroaggregates with a clay addition. Significantly more aggregates formed under ambient conditions, but there was no significant difference in aggregate diameter between treatments. We will present 16S sequencing analyses of size-fractionated aggregates to understand how the different conditions influenced microbial communities and show how TEP concentrations differed in the treatments. Our findings expand our understanding of how anthropogenic stressors, including ocean acidification and ocean warming, impact aggregation and carbon sequestration in the ocean. 

Presentation Preference: Oral

Primary Presenter: Britni Livar, Arizona State University (blivar@asu.edu)

Authors:

Britni Livar, Arizona State University  (blivar@asu.edu)

Susanne Neuer, Arizona State University  (susanne.neuer@asu.edu)