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Variations in δ13CDIC and influencing factors in a shallow macrophytic lake on the Qinghai-Tibetan Plateau: implications for the lake carbon cycle
  • Yanxiang Jin,
  • Xin Jin
Yanxiang Jin
Qinghai Normal University
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Xin Jin
Qinghai Normal University
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Abstract

The primary sources of dissolved inorganic carbon (DIC) in water are carbonate materials and CO2 produced during the biological processing of organic matter. The application of carbon isotope techniques to terrestrial and aquatic ecosystems can accurately elucidate carbon fluxes and other carbon cycle processes in these systems. Lake ecosystems on the Qinghai-Tibetan Plateau are fragile and sensitive to changes in climate and environment. This study explored the relationship between the carbon isotopic composition (δ13C) of the DIC (δ13CDIC) in the Genggahai Lake, the lake environment, and the climate of the watershed based on the observed physicochemical parameters of water in areas with different types of submerged macrophyte communities, combined with changes in the temperature and precipitation during the same period. Overall, the δ13CDIC of the Genggahai Basin exhibited a large range of values, with an average δ13CDIC for inflowing spring water (δ13CDIC-I) of –11.1 ‰, which was the most negative, followed by an average δ13CDIC value of –10.8 ‰ for that from the Shazhuyu River (δ13CDIC-R) and an averageδ13CDIC value of –6.91 ‰ for lake water (δ13CDIC-L). Variations in the photosynthetic activity intensity of different aquatic plants yield significantly changing δ13CDIC-L values in areas with varied aquatic plant communities. Hydrochemical observations revealed that δ13CDIC-I and aquatic plant photosynthesis primarily affected the differences in the δ13CDIC-L values of the Genggahai Lake, thereby identifying them as the key components of the lake carbon cycle.