Highest rates of gross primary productivity maintained despite <scp>CO<sub>2</sub></scp> depletion in a temperate river network
Kelly S. Aho, Jacob D. Hosen, Laura Logozzo, Wade R. McGillis, Peter A. Raymond
Abstract
Abstract Aquatic primary productivity produces oxygen (O 2 ) and consumes carbon dioxide (CO 2 ) in a ratio of ~1.2. However, in aquatic ecosystems, dissolved CO 2 concentrations can be low, potentially limiting primary productivity. Here, results show that a large drainage basin maintains its highest levels of gross primary productivity (GPP) when dissolved CO 2 is diminished or undetectable due to photosynthetic uptake. Data show that, after CO 2 is depleted, bicarbonate, an ionized form of inorganic carbon, supports these high levels of productivity. In fact, outputs from a process‐based model suggest that bicarbonate can support up to ~58% of GPP under the most productive conditions. This is the first evidence that high levels of aquatic GPP are sustained in a riverine drainage network despite CO 2 depletion, which has implications for freshwater ecology, biogeochemistry, and isotopic analysis.