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.