Effects of temperature and salinity on carbon budget of Crassostrea hongkongensis

【Objective】To clarify the effects of temperature and salinity on the physiology metabolism and carbon budget of the Crassostrea hongkongensis，and providing reference for the mechanism of carbon budget of C. hongkongensis，as well as to lay theoretical foundation for the subsequent exploration of the carbon sequestration function of oysters and the development of blue and low-carbon emerging economic industries.【Method】The oxygen consumption rate，ammonia excretion rate，feeding rate and fecal excretion rate of the C. hongkongensis were determined at different temperatures （12，19，26 and 33 ℃）and salinities（6‰，15‰，24‰ and 33‰）using hydrostatic method，and carbon balance equations were established.【Result】The oxygen consumption rate of C. hongkongensis increased gradually with increasing temperature，reaching a maximum value［1.87 mg/ （g·h）］at the highest temperature tested（33 ℃）；the ammonia excretion rate first decreased and then increased with increasing temperature，according to the fitted equation，the minimum ammonia excretion rate occurred at 17.70 ℃［0.02 mg/ （g·h）］；the feeding rate showed an increasing and then decreasing trend with increasing temperature，according to the fitted equation，the maximum feeding rate occurred at 21.99° C ［17.54mg/ （g·h）］；the fecal excretion rate did not show any obvious regularity under different temperatures. Under different salinity conditions，the feeding rate and oxygen consumption rate of the C. hongkongensis showed an increasing and then decreasing trend，according to the fitted equation，the oxygen consumption rate reached the maximum value at salinity 21.54‰［1.29 mg/ （g·h）］，and the feeding rate reached the maximum value at salinity 18.88‰［28.48 mg/ （g·h）］. The ammonia excretion rate and fecal excretion rate showed a decreasing trend with the increasing salinity，and both reached the minimum value at the maximum salinity set by the test（33‰）. Temperature and salinity had obvious effects on the carbon budget of C. hongkongensis，under the conditions of temperature 19-26 ℃ and salinity 15‰-24‰，most of the carbon ingested by C. hongkongensis was used for growth. Under different temperature and salinity conditions，the carbon budget of C. hongkongensis exhibited the following pattern：the proportion of growth carbon accounted for the largest part of the ingested carbon，followed by fecal carbon and respiratory carbon，while the proportion of excreted carbon was the smallest.【Conclusion】Both temperature and salinity have effects on the physiological metabolism and carbon budget of C. hongkongensis，especially under the conditions of temperature 19-26 ℃ and salinity 15‰-24‰，the proportion of growth carbon to feeding carbon is higher，which is more suitable for growth and has higher carbon sequestration ability.