Specht, Jaclyn A.. Effects of temperature on hard clam (Mercenaria mercenaria) feeding and energetics. Retrieved from https://doi.org/doi:10.7282/T3B85C80
DescriptionTemperature can affect hard clam (Mercenaria mercenaria) health through its influences on metabolism, dissolved oxygen concentration, and suspension feeding. Warming seawater raises the standard metabolic rate by raising the kinetic energy and increasing the rates of biochemical reactions. Warming seawater also reduces the concentration of dissolved oxygen in the seawater. To compensate for the reduced dissolved oxygen concentration, hard clams may increase pumping efforts, raising the active metabolic rate. Higher pumping rates are also associated with higher food uptake rates from suspension feeding. However, it is unknown under what temperature conditions the metabolic gains from feeding can offset the increases in metabolic costs. Warming also decreases seawater viscosity and may affect ingestion rates through temperature-induced changes in viscous forces acting on ciliary beating. I conducted laboratory experiments to quantify the effects of temperature and temperature-induced viscosity change on M. mercenaria feeding and ciliary beat rates. I also quantified the effects of temperature on respiration and ingestion rates, and based on an energetic balance, I determined the net rate of energy change for hard clams over a temperature range of 4 to 36 ˚C. Ingestion and clearance rates varied with temperature but not with viscosity, and unresponsiveness to viscosity was confirmed by separate ciliary beat measurements on isolated gill preparations at different viscosities. The lack of feeding and ciliary response to viscosity indicates that M. mercenaria ingestion rates are driven by the thermal—not viscous—effects of temperature, a result that differs from previous findings for the mussel Mytilus edulis. Respiration and ingestion rates varied with temperature and peaked at 28 and 24 ˚C, respectively. The net rate of energy change peaked at 20 ˚C, 4 ˚C higher than mean New Jersey sea surface temperatures. These results have important implications for hard clams’ ability to survive and grow in a warming ocean and indicate that hard clams may benefit from moderate ocean warming, provided, among other factors, that there is sufficient food available.