Highest rates of gross primary productivity maintained despite CO2 depletion in a temperate river network

Aho, K., J.D. Hosen, L.A. Logozzo, W. McGillis, P.A. Raymond
May 2021 · Limnology and Oceanography Letters

Aquatic primary productivity produces oxygen (O₂) and consumes carbon dioxide (CO₂) in a ratio of ~1.2. However, in aquatic ecosystems, dissolved CO₂ 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 CO₂ 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 CO2 depletion, which has implications for freshwater ecology, biogeochemistry, and isotopic analysis. </p> Read more}