Coupled action of rock weathering and aquatic photosynthesis: Influence of the biological carbon pump effect on the sources and deposition of organic matter in Ngoring Lake, Qinghai-Tibet Plateau, China

A critical problem in the study of global climate change is how to identify "missing" carbon sinks. The carbon sink resulting from the weathering of carbonate and silicate minerals may make a major contribution, and it is often coupled with aquatic photosynthesis (the biological carbon pump effect - 'BCP'). However, the lack of relevant field studies hinders our understanding of rock weathering and the carbon cycle. To address this issue, we analyzed the pH, [HCO3-], carbon isotopic composition of dissolved inorganic carbon (delta C-13(DIC)), total organic carbon (TOC), total nitrogen (TN), TOC/TN, and the stable carbon isotopic composition of TOC (delta C-13(org)) and CaCO3 (delta C-13(carb)) in the modern surface sediments of Ngoring Lake, in the northeastern Qinghai-Tibet Plateau (QTP), China. The results show that the efficiency of aquatic photosynthesis may be an important factor affecting the delta C-13(DIC) in Ngoring Lake. delta C-13(org) in the surface sediments is positively correlated with the delta C-13(carb) of inorganic carbon produced within the lake, especially in shallow water (