Carbon storage in mollusk shells: An overlooked yet significant carbon sink in terrestrial ecosystems.

Mollusks, the second largest animal family, are found in a variety of ecosystems. As they grow, their shells absorb carbon and form calcium carbonate, making them an important storage place for carbon. However, the amount of carbon deposited in the carbonate shells of terrestrial mollusks throughout modern and geological history has not been quantified. In this study, we first conducted an investigation of carbon deposits in shells from various mollusk species at 470 modern surface soil sample sites across diverse terrestrial ecosystems in China. The deciduous broadleaf forest and shrublands exhibited a higher carbon deposition rate of ∼1.37 ± 2.15 and ∼1.56 ± 2.92 g C m-2/yr-1, while croplands and grasslands displayed a rate of ∼1.11 ± 1.95 and 1.07 ± 1.78 g C m-2/yr-1, respectively. Using geostatistical methods, we estimated the total shell carbon deposition of grassland, forest, shrublands, and croplands in China to be ∼3.39-5.45 × 106 t C yr-1, constituting ∼1.68-2.71 % of China's terrestrial carbon sink, an overlooked portion in previous studies. Additionally, we provided quantitative data on shell carbon fluxes spanning a remarkable 20,000-year period through over ten fossil sequences from loess deposits. The results underscore the continuous and abundant carbon deposition in mollusk shells across various locations for at least 20,000 years, highlighting the persistence and substantial accumulation of shell carbon deposits over time. Remarkably, we estimated that the total shell carbon deposition of loess sediments in China and the world over the past 20,000 years may reach 1.10 × 108 t C and 1.29 × 109 t C, roughly equivalent to an afforestation area of 2.32 × 106 km2 and 2.72 × 107 km2, respectively.

[Effect of Salvia miltiorrhiza on autocrining growth factor by fibroblasts cultured in vitro].

OBJECTIVE: To investigate the mechanism of overhealing alleviation by salvia miltiorrhiza (SM) in wound healing. METHODS: Fibroblasts were cultured in vitro, and SM was applied with different concentrations (40, 80, 160 and 320 micrograms/ml) and time(the 1st, 2nd, 3rd, 4th and 5th days) to influence their autocrine. The levels of transforming growth factor-beta 1 (TGF-beta 1) and epidermal growth factor (EGF) were determined by ELIAS and radioimmunoassay respectively. RESULTS: The SM could inhibit autocrine of TGF-beta 1 by fibroblasts (P < 0.05). However, it did not affect autocrine of EGF (P > 0.05). CONCLUSION: The above results indicate that SM reduces overhealing by inhibiting the autocrine of TGF-beta 1 selectively.