Studying Coastal Acidification Effect on the Atlantic Surfclam, Spisula solidissima through an Experimental and Modeling Survey

Surfclam fisheries rely on wild-caught populations that currently are sustainably managed and responsibly harvested. This species, however, is sensitive to physicochemical changes in its habitat, including temperature and salinity changes. Yet very little is known how this species may respond to ocean acidification, even though it has been identified as a highly susceptible to ocean acidification. A 3-month laboratory experiment, measuring physiological responses was carried out to investigate the effects of ocean acidification on juvenile surfclams. Surfclams (n=198 each treatment) were exposed to one of the three pCO₂ levels (576, 1405, 2203 ppm) and were either fed or unfed. Every other week, growth, as well as physiological rates (feeding rate, respiration rate, ammonia excretion), were measured. Results revealed an appreciable decline in shell length and mass growth proportional to pCO₂ concentrations. This decline can be attributed to reduced feeding rates (clearance rate, assimilation efficiency) and/or increased in metabolism activity (respiration, ammonia excretion).

The data was used to calibrate two individual-based models describing energetic fluxes within an individual and with this individual and the environment. Both models, Dynamic Energy Budget (DEB) and the surfclam model described by Hofmann will be adapted and compared on the basis of ability to reproduce surfclam growth exposed to different pCO₂. The development of these models will enable projections on stock dynamics and economic impacts related to ocean acidification.