Ocean Acidification Category 1: A mechanistic understanding of the impacts of ocean acidification on the early life stages of marine bivalves

Oregon State University, Corvallis OR

Investigators

Abstract

Intellectual Merit: The shift in the carbonate chemistry of marine waters, as a result of direct anthropogenic CO2 addition and climate-driven changes in circulation, poses a threat to many organisms. A rapidly expanding body of literature has shown that increasing levels of carbonic acid and decreasing carbonate will have deleterious effects on many marine organisms; however little is known about the mode of action of these changes in water chemistry. Many marine organisms, particularly bivalves, depend critically on the production of calcium carbonate mineral, and this material becomes thermodynamically unstable under more acidic conditions. The actual mineral precipitation, however, takes place within interstitial volumes intermittently separated from ambient seawater by biological membranes. Therefore, abiotic relationships between solid phase minerals and seawater thermodynamics are oversimplified representations of the complex interplay among seawater chemistry, bivalve physiology, and shell growth processes. This integrative, multi-disciplinary project will develop and apply novel experimental approaches to elucidate fundamental physiological responses to changes in seawater chemistry associated with ocean acidification. The PIs will: 1) develop a novel experimental approach and system capable of unique combinations of pCO2, pH, and mineral saturation state, 2) conduct short-term exploratory experiments to determine bivalve responses to different carbonate system variables, 3) conduct longer-term directed studies of the integrated effects of different carbonate system variables over early life history of bivalves, and 4) compare these biological responses among a group of bivalve species that differ in shell mineralogy and nativity to the periodically acidified upwelling region of the Pacific Northwest coast of North America. Extensive laboratory experiments will be carried out on three primary taxa (oyster, mussel, clam) having native and non-native species pairs: oysters Ostrea lurida and Crassostrea gigas; mussels Mytilus califonianus and Mytilus galloprovincialis; and clams Macoma nasuta and Ruditapes philippinarum. High precision pCO2 and dissolved inorganic carbon (DIC) instruments will be used in experiments to control and properly constrain the carbonate chemistry. A compliment of response variables will be measured across the early life stages of these species that include tissue acid-base balance, shell mineralogy and chemistry, respiration rate, and behavior. Additionally, an emphasis will be placed on observation of development, growth, and shell structure while directly linking observational data with other measured response data. Short-term experiments will determine the most salient variables in the carbonate system to manipulate in longer-term studies. This approach will also allow the evaluation of acute effects, mimicking diurnal changes to carbonate variables often found in coastal areas, and integrated chronic effects mimicking a more gradual acidification due to the rise in atmospheric CO2. An experimental approach will be developed that will significantly advance understanding of biological responses to ocean acidification. Currently, the confounding effects of pCO2, pH, and Omega in all ocean acidification experiments to date make it extremely difficult to illuminate the underlying physiological mechanisms of organism responses to ocean acidification. Applying this approach across a group of related bivalves with differences in shell structure and nativity to a periodically acidified environment will answer fundamental questions of how vulnerable species will be affected by ocean acidification. Broader Impacts: A significant cross-collaboration can be anticipated with other ocean acidification research groups after the development of the experimental system, as the instrumentation and control circuits are compact and will be highly portable. The principle investigators on this project have and continue to discuss ocean acidification with a broad base of user groups including the aquaculture industry, government officials, student groups, and the general public. The PIs on this project will develop a webpage to provide an approachable yet scientific treatment of ocean acidification, particularly with respect to the coastal oceans and estuaries. Waldbusser has also been corresponding with aquaculture advocacy groups with regard to developing outreach materials. In addition, three graduate students will be supported and trained over the four-year project period.