Ocean warming and acidification alter larval development and swimming behavior in the Atlantic sea scallop, Placopecten magellanicus

Emily A. Roberts , Jaquan High, Benjamin Capuano, Raymond Czaja, Madeline Wren, Tessa Houston, Brea Salter, Brian Beal, Daphne Munroe, Tyler Menz, Robert M Cerrato, Kyle Pepperman, Emmanuelle Pales Espinosa, Bassem Allam

Ocean warming (OW) and ocean acidification (OA) are expected to have wide-ranging consequences for populations in marine systems caused by organism-level responses at a range of life history stages, including early larval stages. The Atlantic sea scallop, Placopecten magellanicus, is an economically important bivalve species that may be vulnerable to ocean change, but larval responses remain unclear. While the effects of OW and OA are known to impact adult sea scallops, little is known about the interactive effects of these two factors on early life stages. Larval dispersal is key to population-level patterns (e.g. abundance and distribution), but is contingent on growth rates and vertical swimming behaviors, which are both influenced by environmental conditions. Here, we evaluate the combined effects of OW and OA on larval development and behavior in a factorial lab experiment. We maintained larval sea scallop cultures up to metamorphosis under a range of physico-chemical conditions (17℃ and 14℃, and pH 7.3, 7.6, 7.9). Sea scallop larval development time was temperature dependent (1 vs. 1.5 months). There was an interactive effect of OW and OA on growth, where OA limited gains in growth experienced in warmer conditions. OA limited a decline in distribution late in development, while OW dominated individual vertical swimming behavior in intermediate development. Finally, Ω_Ar growth sensitivity was intermediate compared to that of other bivalve taxa. These results contribute to an improved understanding of developmental and behavioral responses to OW and OA, and provide information necessary for improved larval dispersal models under ocean change.