Carryover effects and feeding behavior of Atlantic surfclams in response to climate change

Temperature and food availability play large roles in bivalve energetics. Understanding bivalve responses to variability in temperature and food availability (i.e., phytoplankton), is important as climate change leads to ocean warming and changes in phytoplankton production. However, few studies address how changes in seasonal temperature regimes, such as an elevated fall or accelerated spring temperature regime affect bivalves via carryover effects, whereby response signals are detected months following temperature regime exposure. Few studies also address how bivalve feeding preferences may respond to variability in temperature and food availability. Here, controlled laboratory experiments simulated climate changed-induced fall and spring temperature regimes for Atlantic surfclams, Spisula solidissima solidissima. A variety of physiological responses were measured, including scope for growth, gonad development and feeding behavior, plus preferences for different phytoplankton groups. Carryover effects were observed where surfclams that experienced an elevated (+ 3.0 °C) fall temperature regime yielded enhanced gonad development the following spring (i.e., > 6 months later). An accelerated spring temperature regime (a more rapid temperature increase to 17 °C from 7 °C) also impacted surfclam scope for growth. Temperature was the primary driver of surfclam clearance rates, but food concentration was the primary driver of surfclam feeding preferences. Surfclams displayed preferential selection of diatoms and chlorophytes over cryptophytes and cyanobacteria, but increased food availability led to decreased selection of diatoms and a relative increase in the uptake of cyanobacteria. These results suggest that climate change induced alterations in food availability and seasonal temperature regimes may affect surfclam metabolism, reproduction and feeding preferences.