Lake Morphometry and River Network Controls on Evasion of Terrestrially Sourced Headwater CO2

Lakes are central components of the inland water system distinct from, yet inextricably connected to, river networks. Currently, existing network-scale biogeochemistry research, although robust, typically treats each of these components separately or reductively. Here, we incorporate lake morphometry into a fully connected stream/lake network for the Connecticut River watershed and model potential evasion of terrestrially sourced headwater CO2 as transported through the network, ignoring in-stream production. We found that approximately 25%-30% of total potential soil CO2 evasion occurs in lakes, and percent evasion is inversely related to streamflow. A lake's ability to evade CO2 is controlled by residence time and size: most lakes with residence time over 7 days or surface area greater than 0.004 km(2) evade functionally all terrestrial CO2 entering from upstream, precluding further downstream transport. We conclude that lakes are important for soil CO2 degassing and that this coupled river/lake approach is promising for CO2 studies henceforth.

Automated summary

Lakes are key components of the inland water system and play a significant role in the degassing of soil CO2. The ability of lakes to evade CO2 is influenced by factors such as size and residence time, which in turn affect downstream CO2 transport.