Impacts of acidification and warming on carbon sequestration capacity in Pacific oysters: Roles of biosynthesis and biodeposition

Abstract

Bivalve aquaculture shows promise as a carbon sink, but its sensitivity to temperature and pH fluctuations highlights the need to study the effects of ocean acidification (OA) and ocean warming (OW) on carbon sequestration. This study investigates the effects of OA and OW on physiological processes and carbon sequestration mediated by biosynthesis and biodeposition in Crassostrea gigas. OA significantly enhances carbon ingestion, reduces respiratory carbon, increases carbon allocation to growth, improves digestive efficiency, and promotes TOC accumulation in soft tissues (all p < 0.05). While OW significantly increases excreted and fecal carbon (p < 0.05), but enhanced digestion compensates for energy loss, sustaining TOC accumulation. Combined OA and OW significantly altered soft tissue carbon sequestration, with values between OA and OW alone (p < 0.05). Notably, their interaction increases biodeposit density and sinking velocity (p < 0.05), potentially enhancing carbon burial. Tissue-specific metabolic responses reveal that muscle tissue prioritizes energy production, whereas the digestive gland follows an opposite trend, resulting in uneven energy distribution. Furthermore, functional predictions based on KEGG pathway analysis and correlation patterns suggest that SCFAs production via tryptophan metabolism might be a potential mechanism through which probiotics modulate host metabolism and contribute to biosynthesis-mediated carbon sequestration. However, disruptions in microbial homeostasis due to an imbalance between probiotics and pathogens in the digestive gland may threaten the long-term sustainability of this sequestration process. These findings provide insights into the complex physiological and microbial responses of oysters under climate change, highlighting potential mechanisms for carbon sequestration in marine ecosystems.