Project: Ocean Acidification: Influence of Ocean Acidification on Biotic Controls of DMS Emissions

NSF Award Abstract:

To date, investigations into the biogeochemical consequences of predicted increases in pCO2 and reduced pH in the oceans (ocean acidification, OA) over the next century have largely focused on the production and fate of carbon. Considerably less is known about how OA will influence other biogeochemical cycles or the exchange of reactive trace gases between ocean and atmosphere. Variations in trace gas exchange will alter atmospheric chemistry, including aerosol formation and growth, and potentially feedback on climate change.

In this project, a research team at the Bigelow Laboratory for Ocean Sciences will study the influence of OA on the biological processes that govern the concentrations and hence emission, of dimethyl sulfide (DMS) in the surface oceans. The team will study OA effects on the DMS-cycle in three natural-water mesocosm experiments designed to encompass natural community responses to predicted changes in pCO2 of varying degrees. They will exploit the opportunity to participate in a major experiment in sub-tropical oceanic waters involving the deployment of nine large scale (~60 m3) free floating, pelagic mesocosms, as part of the German-funded BIOACID Program. Two replicate experiments conducted using the new mesocosm facilities at Bigelow will further expand the environmental range of DMS-OA studies. Through a combination of standard analytical approaches, recently developed cutting-edge tracer approaches to determine process rates, as well as the underlying organism diversity and genetic response of microbes involved with biogenic sulfur cycling, they will determine how altered pH influences key biological pathways governing DMS concentrations and the organisms responsible during the experiments.

Broader Impacts: The information generated will be used to inform on-going development of global ocean-atmosphere coupled models, able to examine the influence of ocean acidification on climate change. The information will also be used to further develop physiology-based mechanistic approaches to biogeochemical ecosystem models. A Postdoctoral Research Scientist will be trained in the experimental approaches, will gain modeling experience by working with European scientists, and will develop international and US collaborations, with a common aim to increase our understanding of ocean acidification on ecosystem function. Four undergraduates, two interns and two REU-students, will gain valuable experience by participating in the Bigelow experiments. An additional undergraduate with a mathematical background will be mentored in and participate in the interpretation and modeling aspects. Extensive outreach to K-12 students and teachers as well as the general public will be pursued as part of established Bigelow programs in which all PIs will participate (BLOOM, Cafe Scientifique). Joint programs with Colby College (Changing Oceans semester) and Island Institute will reach undergraduates and Maine island K-8 schools, respectively.