Dissolved inorganic carbon (DIC) is a primary constituent of the aquatic geochemistry of terrestrial ecosystems. Changes in DIC concentration and its isotopic composition are closely associated with environmental changes in the drainage basin. Thus, a better understanding of DIC may lead to improved characterization of environmental changes. Corbicula fluminea (Müller 1774), a bivalve native to southeast Asia and a dominant invasive species in many aquatic environments around the world, has the poten-tial to record DIC information, particularly because of its sequential skeletal deposition. Analysis of the stable carbon isotope composition (δ 13C) of the shell and the aquatic DIC in the Xijiang River drainage basins in southern and western China allowed us to determine that changes in δ 13C in the skeleton significantly correlated with those of DIC (P < 0.01, r = 0.63). These results indicate that the isotopic signature of the shell reflects that δ 13C of the DIC in ambient water. The temporal resolution was at the seasonal scale. Metabolic effect does not change the co-variation, even though it makes the shell δ 13C 1.4‰ lower statistically than that of DIC. δ 13C of DIC in creeks of some watershed areas may experience large temporal changes characterization of these changes requires high sampling resolution of the shell. This problem makes the clams in these areas less preferable for reconstruc-tion of environmental changes. The present findings provide the basis for recovering paleoenvironmental changes and carbon cycles in a watershed through analysis of fossil shells of C. fluminea, which are common in some lacustrine and/or riverine sedi-ment sequences. Dissolved inorganic carbon (DIC) is a primary constituent of the aquatic geochemistry of terrestrial ecosystems. Changes in DIC concentration and its isotopic composition are closely associated with environmental changes in the drainage basin. Thus, a better understanding of DIC may lead to improved characterization of environmental changes. Corbicula fluminea (Müller 1774), a bivalve native to southeast Asia and a dominant invasive species in many aquatic environments around the world, has the poten- tial to record DIC information, particularly because of its sequential skeletal deposition. Analysis of the stable carbon isotope composition (δ 13C) of the shell and the aquatic DIC in the Xijiang River drainage basins in southern and western China allowed us to determine that changes in δ 13C in the skeleton significantly correlated with those of DIC (P <0.01, r = 0.63). These results indicate that the isotopic signature of the shell says that δ 13C of the DIC in ambient water. The temporal resolution was at the seasonal scale. Metabolic effect does not change the co-variation, even though it makes the shell δ 13C 1.4 ‰ lower statistically than that of DIC. Δ 13C of DIC in creeks of some watershed areas may experience large temporal changes characterization of these changes requires high sampling resolution of the shell. The problem makes the clams in these areas less preferable for reconstruc- tion of environmental changes. The present findings provide the basis for recovering paleoenvironmental changes and carbon cycles in a watershed through analysis of fossil shells of C. fluminea, which are common in some lacustrine and / or riverine sediment ment sequences.