Temperature is a better predictor of stable carbon isotopic compositions in marine particulates than dissolved CO2 concentration
Qianqian Liu, K. Selvaraj, Weidong Zhai, Huawei Wang, Yoganandan Veeran, Aiguo Gao, Chen‐Tung Arthur Chen
Abstract
Abstract The stable carbon isotopic composition of marine particulate organic matter (δ 13 C POM ) varies with source and environmental conditions. Dissolved carbon dioxide (CO 2 ) concentration is thought to influence δ 13 C POM more than temperature, but this relationship is poorly constrained in marginal seas. Here we present δ 13 C POM , hydrographic and carbonate system variables at the deep chlorophyll maxima of the southern Yellow Sea in late summer 2017. We find δ 13 C POM values varied between stable and cyclonic gyre regions, but indicated autochthonous organic matter production and were more strongly correlated with temperature than dissolved CO 2 concentration throughout. We find that the relationship between temperature and δ 13 C POM was independent of CO 2 concentration, whereas the relationship between δ 13 C POM and CO 2 concentration was dependent on temperature also being correlated with CO 2 concentration. We suggest that temperature is the primary determinant of marine δ 13 C POM due to temperature-dependent metabolism in phytoplankton, irrespective of inorganic carbon acquisition mode.