Abstract:The restoration of oyster reefs is a hot issue and has being attracting the attention of researchers worldwide. Crassostrea gigas and C. ariakensis are two important species that build up oyster reefs; however, the population dynamics of these two species in low-salinity estuaries are not the same. We used experimental ecology methods to study the effects of acute lowered salinity (10 and 20, with natural seawater about 29 as a control) on the variations in the physiological metabolism of C. gigas and C. ariakensis. The results showed that acute lowered-salinity incubation significantly affected the oxygen consumption rate, ammonia excretion rate, and feces production rate of these two oysters (P < 0.05), but the responses of these two species were also different. The highest oxygen consumption rate, ammonia excretion rate, feeding rate and feces production rate of C. gigas were found in the control group, which indicated that a decrease in salinity impacted the metabolism of this species. However, C. ariakensis showed better metabolic parameters at salinity 20 than that in the other two groups. To normalize the metabolic rate of oysters with a broad range of wet weights, a regression equation for the metabolic rate to wet weight was established: Y=aWb. The wet weight (20 g) was used for the comparison after normalization. At salinity 20, the respiration rate of C. ariakensis was strong, and the respiration energy accounted for 16.1% of the total energy consumption, while C. gigas showed a stronger oxygen consumption rate in natural seawater (respiratory energy accounted for 7.8% of the total energy consumption), and a lower oxygen consumption rate at salinity 10 (respiratory energy accounted for 0.7% of the total energy consumption). Our results indicated that the acute lowered-salinity incubation had a more significant influence on C. gigas than C. ariakensis, and a low-level reduction in salinity can even promote the energy metabolism of C. ariakensis. From the perspective of energy metabolism, this study explored the response of C. gigas and C. ariakensis to acute reductions in salinities, and provided references for oyster reef restoration, selective breeding, and aquaculture.
