Effects of calcification on respiratory quotient of cultured oyster Crassostrea gigas and its fouling animals

Respiratory quotient (RQ) is one of the basic indices in physiology and energy metabolism of animals. When RQ is calculated, the amount of released CO2 is typically used directly. But for calcifying marine organisms, calcification which can affect dissolved inorganic carbon (DIC) content in the water may cause methodological error to some extent, if it is ignored. In this paper, RQ and O/N of cultured oyster Crassostrea gigas and 3 marine fouling animal species (Mytilus edulis, Ciona intestinalis, Styela clava) were measured in the respiratory chamber to discuss the effect of calcification in RQ determination. The results demonstrated that calcification rates of C. gigas and M. edulis were (56.37 +/- 14.85) and (17.95 +/- 7.21) micromol x g(-1) x h(-1), respectively. (3.72 +/- 0.80) and (1.48 +/- 0.14) mg x L(-1) DIC in the water were correspondingly decreased, which occupied about (60.9 +/- 7.6)% and (39.9 +/- 5.7)% of respired CO2, respectively. RQ values of 4 animals were C. gigas 1.38 +0.19, M. edulis 1.1