An Experimental Investigation of the Impact of Ocean Acidification on the Early Life Stages of Surf Clams, and the Interactive Effects of Feeding

Surf clams, Spisula solidissima, are a commercially important fishery species in the United States.  Surf clams have a protracted free swimming larval stage, and form their initial shells out of aragonite, the more soluble form of calcium carbonate.  Thus, larval surf clams may be particularly vulnerable to ocean acidification, impacting recruitment to the fishery.  In 2011, we conducted a series of experiments to investigate the effects of ocean acidification on early development and metamorphic success of surf clams. We observed that (a) elevated pCO2 decreases the 15-day survival of larval surf clams, (b) elevated pCO2 does not have a strong effect on the size of larval surf clams, but may lead to lower calcification rates (thinner shells), and (c) feeding increases overall calcification rates but does not appear to alter the sensitivity of surf clam shell mass to elevated pCO2. We propose to expand upon this work in fiscal year 2012 with a set of ocean acidification culturing experiments that again will be carried out in collaboration with colleagues at the NOAA-NMFS Milford Lab.  We propose to run a 6 day experiment to better constrain the interaction between food availability and growth in early stage larvae of the surf clam.  Measures will include shell height, mass, SEM imaging, and biochemical sampling of clam tissues (protein and lipid class) to investigate the mechanisms underlying the variable responses to different food vs. CO2 concentration combinations.  Additionally we will conduct a short term (48h) experiment to examine fertilization success of surf clams exposed to a range of CO2 concentrations and the viability of their gametes.  Requested CINAR funding for these 2012 projects totals $34,557.