Ocean acidification and warming effects on the physiology, skeletal properties, and microbiome of the purple-hinge rock scallop

Abstract

Ocean acidification and increased ocean temperature from elevated atmospheric carbon dioxide can significantly influence the physiology, growth and survival of marine organisms. Despite increasing research efforts, there are still many gaps in our knowledge of how these stressors interact to affect economically and ecologically important species. This project is the first to explore the physiological effects of high pCO₂ and temperature on the acclimation potential of the purple-hinge rock scallop (Crassadoma gigantea), a widely distributed marine bivalve, important reef builder, and potential aquaculture product. Scallops were exposed to two pCO₂ (365 and 1050 μatm) and temperature (14 and 21.5 °C) conditions in a two-factor experimental design. Simultaneous exposure to high temperature and high pCO₂ reduced shell strength, decreased outer shell density and increased total lipid content. Despite identical diets, scallops exposed to high pCO₂ had higher content of saturated fatty acids, and lower content of polyunsaturated fatty acids suggesting reorganization of fatty acid chains to sustain basic metabolic functions under high pCO₂. Metagenomic sequencing of prokaryotes in scallop tissue revealed treatment differences in community composition between treatments and in the presence of genes associated with microbial cell regulation, signaling, and pigmentation. Results from this research highlight the complexity of physiological responses for calcifying species under global change related stress and provide the first insights for understanding the response of a bivalve's microbiome under multiple stressors.

Keywords: Bivalve; CT scan; Fatty acids; Metagenomics; Multiple stressors; Shell strength.