Water Conveyance-Type Lake Systems Shift toward Carbon Sources under Regulatory Balanced Water Level Metabolic Processes

Abstract

The water−air interface is the juncture whereby lake carbon (C) emissions are most active. However, the metabolic regulation of lake C exchange rates at the water−air interface remains unclear, especially for water conveyance-type lake systems that undergo dramatic alterations in water regimes. For the first time, underwater regime fluctuations. Findings show that the C exchange status at the water−air interface is regulated by the coupled connective effect of the water regime−water quality−GPP−pCO 2 effect. Compared to high-and low-water level periods, C emissions at the water−air interface were highest during the intermediate-water-level period. Moreover, this intermediate period was when this water conveyance-type lake system primarily converted basin-derived C inputs and discharged them into the atmosphere. This study also found that C emissions were most active when net ecosystem production (NEP) was close to 0. If NEP is too high (i.e., >6 g O 2 m −2 d −1 ) or too low (i.e., < −6 g O 2 m −2 d −1 ), the partial pressure of carbon dioxide (pCO 2 ) in water will be constrained either below or close to that of atmospheric pCO 2 .

Real-time and dynamic estimation of CO₂ emissions from China��s lakes and reservoirs

“…29,34 For eutrophic lakes within the Yangtze River basin (e.g., Taihu Lake), CO 2 emissions are driven by eutrophication and temperature. 28,35 For floodplain lakes (e.g., Poyang Lake), CO 2 exchange has been shown to be driven by hydrological processes associated with water level fluctuation. 30,36 Driving mechanisms associated with CO 2 exchange in China's inland lakes and reservoirs are known to be both complex and variable.…”