Impacts of an Acidifying Ocean on the Biological Production of Reactive Oxygen Species

Colleen Hansel, Marine Chemistry & Geochemistry
Peter Andeer, Marine Chemistry & Geochemistry


2014 OCCI Funded Project

Fossil-fuel induced ocean acidification, and the ensuing environmental and socioeconomic impacts, is one of the most pressing issues of this generation. Yet, to understand and predict the consequences of acidification on the health and chemistry of the ocean requires a thorough understanding of how biogeochemical processes will be altered under changing temperature and pH. Reactive oxygen species (ROS) are key compounds in the ocean that influence the bioavailability of metals and carbon, allow for communication within and between microbial communities, and induce oxidative stress and subsequent cell death in organisms.

Given that both phytoplankton and bacteria control ROS fluxes, changes in their abundances and activities due to increasing pCO2 and temperature will impact the fluxes and lifetime of ROS as well as subsequent ROS-mediated reactions. Alterations to current ROS flux balances could either help mitigate (e.g., through the consumption of protons during superoxide dismutation or by increasing iron bioavailability for photosynthesis) or exacerbate (e.g., through shifts in microbial community structure and health) ocean acidification. However, there is little information on the environmental controls of microbial ROS production. Accordingly, the goal of this project is to better understand how increases in anthropogenic carbon dioxide concentrations and the associated changes in ocean temperature and pH will impact biological production and decay of the ROS superoxide and hydrogen peroxide in marine waters. We predict that pH, pCO2 and temperature induced shifts in the composition, activity, and stress of microbial populations will significantly alter biological ROS fluxes and subsequently the ROS balance within the ocean.

This research will be guided by two objectives, which are to determine the (1) impact of pCO2 levels and temperature on extracellular ROS fluxes by key marine microorganisms, and (2) influence of increasing pCO2 and temperature on biogenic extracellular ROS fluxes within natural marine waters and associated changes in microbial community structure. Model microbial populations and waters that will be collected from Cape Cod Bay and Massachusetts Bay will be incubated under varying temperature and pCO2 conditions mimicking ocean acidification predictions. Both biological production and decay of superoxide and hydrogen peroxide will be measured to define total ROS fluxes by the various organisms and communities under each condition. Addressing these two objectives will provide critical information into how ROS dynamics, and by extension many other biogeochemical cycles, will respond to climate change. While ROS fluxes are predicted to shift dramatically in response to ocean acidification, the current paucity of data on the controls, fluxes, and mechanisms of biogenic ROS balance is a crippling obstacle in obtaining funding for research on this topic. Accordingly, this research will be the first exploration to address this knowledge gap and provide essential data and justification to help our efforts to secure funding for this critical research.