Microbes in the oceans provide essential ecosystem services including primary production (photosynthesis) and organic matter turnover that sustain all higher marine organisms. It remains unclear how marine microorganisms will adapt to the acidification of the oceans (i.e., decrease in seawater pH due to increased atmospheric CO2) and how much their activities will be affected. It is also important to quantify how multiple stressors related to ocean acidification (OA) such as higher temperatures interact with increased acidity to represent the impact of multiple stressors on marine microbial communities. Advancing our understanding of these issues is essential in order to predict the consequences of OA on ocean life and fisheries, identify areas of the ocean that might be more vulnerable to OA, and propose modes of action to counteract potential adverse effects. This collaborative project by Duke University and Georgia Institute of Technology researchers will combine oceanographic and advanced molecular techniques to characterize the adaptive responses of microbial communities to multiple stressors associated with OA. In particular, microbial communities from estuarine and coastal ecosystems as well as open ocean waters will be incubated under conditions of increased acidity or temperature or both, and their activities will be measured and quantified. By integrating multiple types of data, this project will provide a predictive and mechanistic understanding of microbial community responses and feedbacks to OA, including essential ecosystem services. In addition to providing advanced training for undergraduate, graduate and postdoctoral students, results from this research project will be translated to broad public and K-12 education on OA through the development of an interactive museum display and iPAD application.

Preliminary data from time-series observations of a coastal temperate estuary shows that pH, temperature and other stressors vary over multiple space and time scales, and this variability is relatively higher than that observed in open ocean waters. Based on this evidence, the guiding hypothesis of this work is that microbes in coastal ecosystems are better adapted to ocean acidification as well as multiple stressors compared to similar microbes from the open ocean. To quantify the adaptive genetic, physiological and biogeochemical responses of microbes to OA, the team's specific goals are to: (1) characterize complex natural microbial community responses to multiple stressors using factorial mesocosm manipulations, (2) assemble a detailed view of genomic and physiological (including transcriptional) adaptations to OA at the single species level using cultured model marine microbes (e.g. Prochlorococcus, Synechococcus, Vibrio) identified as responsive to stressors in whole community mesocosm experiments, and (3) assess the power of model microbial strains and mesocosm experiments to predict microbial community responses to natural OA variability in a temporally dynamic, temperate estuary and along a trophic/pH gradient from the Neuse-Pamlico Sound to the Sargasso Sea. By comparing an estuarine ecosystem to its open ocean counterpart, this study will assess the sensitivity of microbial structure and function in response to ocean acidification.

National Science Foundation (NSF)
Division of Ocean Sciences (OCE)
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Michael Sieracki
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Georgia Tech Research Corporation
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