Pacific oyster (Crassostrea gigas) shell growth duration in a year in Bohai Bay and implication for its carbon sink potential

Oyster is a bivalve mollusk widely distributed in estuarine and shallow sea environments. Its growth and burial process is a carbon sequestration and storage process. Oyster shell may stop growing due to suffer from freeze shock during the winter season within a temperate climate, therefore, in order to study the carbon sequestration capacity of oysters we need to know the water temperature at which the shell suffer from winter freeze shock. This study examines δ¹⁸O profiles across consecutive micro-growth layers found in three modern Pacific oyster shells from the northwest coast of Bohai Bay. A total of 165 oxygen isotope values from sequential samples of their left shells showed periodically varying values, and the variation fluctuation of oxygen isotope values was 4.97‰ on average. According to the variation range of the oxygen isotope value of the shell, combined with the sea surface temperature and the sea surface salinity data of the water in which the oysters grew, the water temperature that suffer from winter freeze shock and stops or retards the growth of Pacific oysters in Bohai Bay is about 8.3°C, and the corresponding period is from December to March of the following year. The calcification time of oysters within one year is nearly a month longer than previously thought, therefore, its carbon sink potential is also improved.