Taste and nutritional value of triploid oysters: integrated metabolomic insights into environmental interactions

Oyster aquaculture in China plays a critically important role to meet expected global demand for seafood protein, which is currently accounting almost over 85% global oyster aquaculture production. This coastal industry is aiming to introduce "triploid" oysters of the region for improved growth and enhanced tolerance to multiple stressors. Nevertheless, performance of triploid oysters with respect to flavour chemistry and metabolic adaptability to multiple stressors in real-world culture environments are yet to be studied. This knowledge is critically important for successful introduction of this emerging technology for sustainable farming of oysters, particularly in south China. In this context, we have examined growth, metabolomic profiles, and flavour-related volatiles of diploid and triploid Hong Kong oysters (Crassostrea hongkongensis), deployed in three distinct environmental zones in their culture area. Triploids consistently outperformed diploids, with the greatest advantage at optimal zone B (salinity: 22.1 ppt, pH: 7.8, chlorophyll: 3.06 μg L^-1) yielding 17% longer shells, 40% higher whole weight, and 78% greater meat. Untargeted UHPLC-MS/MS metabolomic analysis revealed lipid dominance (1449 molecules; 53 subclasses), with triploids exhibiting significant enrichment of PUFAs (EPA, ALA, AA) and glycerophospholipids, particularly in low salinity zone A (salinity: 16.08 ppt, pH: 7.6, chlorophyll: 5.38 μg L^-1). Amino acid pools varied by culture zones: nitrogen-rich amino acids (ornithine, histidine and its derivatives) peaked at zone B, while glycine, proline derivatives and sulfur-containing amino acids were abundant in zone A. GC-MS analysis identified 817 volatile compounds, dominated by acids and alcohols; fruity aldehydes were enriched at zone B, while terpenoid-like hydrocarbons prevailed at zone A, reflecting amino acid-driven aroma pathways. Pathway enrichment analysis highlighted lipid metabolism as a core adaptive mechanism for high salinity associated stress tolerence. ICP-MS analysis revealed HK oysters reflect site-driven trace metals distribution, with high nutritional value. These findings underscore the optimal location for triploid deployment and provide metabolomic insights for site-specific management to enhance productivity and flavour quality for sustainable aquaculture of HK oysters across southern China.