The relevance of pelagic calcification in the global carbon budget of lakes and reservoirs

Abstract

The relevance of pelagic calcification in the global carbon budget of lakes and reservoirsCalcite precipitation acts as a carbon sink in the sediments and a short-term source of carbon dioxide (CO 2 ) to the atmosphere, as widely acknowledged in marine studies. However, pelagic calcite precipitation has received limited attention in lakes. Here we use the relationship between lake water alkalinity and reported calcification rates to provide the first global estimate of pelagic calcification in lakes. Global gross calcification rates amount to 0.03 Pg C yr -1 (0.01 -0.07) comparable to rates of organic carbon burial, whereas its related CO 2 release is largely buffered by the carbonate equilibria. Calcification occurs at water alkalinity above 1 meq/L corresponding to 57 % of global lake and reservoir surface area. Pelagic calcification therefore is a prevalent process in lakes and reservoirs at the global scale, with a potentially relevant role as a sedimentary inorganic carbon sink, comparable in magnitude to the total calcite accumulation rates in ocean sediments.

Whiting Events in a Large Peri‐Alpine Lake: Evidence of a Catchment‐Scale Process

“…While such evaluation should contribute to verifying the general relevance of our results, the large prevalence of lakes within carbonate‐rich catchments (Marcé et al., 2015) would nevertheless suggest that the identified patterns may hold true in other freshwater systems. Considering that calcite precipitation represents a major inorganic carbon sink in inland waters (Khan et al., 2022) and that whiting events may materialize catalyzed periods of carbon transformations across catchments, a refined perspective on the conditions triggering these phenomena would, thereby, appear essential to accurately constrain lacustrine carbon budgets. Such assessment would, moreover, seem even more relevant in the context of global change, especially in peri‐alpine areas, as the combined effects of increasing temperatures, weathering rates, and altered hydrological regimes are likely to impact the complex balance of mechanisms and processes underlying these events.…”

“…Calcium carbonate (calcite) precipitation (CaCO 3(s) , Equation 1) is a prevalent process in hardwater lakes and reservoirs and represents a relevant term of the global lacustrine carbon budget (Khan et al, 2022).…”

Integrating terrestrial and aquatic ecosystems to constrain estimates of land-atmosphere carbon exchange

“…Current uncertainties in lake carbon storage arise from (1) variable estimates of the number and size distribution of lakes across regions and the globe 12,[151][152][153][154] , (2) different lake basin shapes, (3) sediment heterogeneity and focusing, which may lead to bias when extrapolating site-specific burial rates to the whole lake basin 155,156 , (4) overlooking the role of macrophyterich, lake littoral areas with potentially high carbon accumulation rates, and (5) understudied processes that could increase the storage of carbon in sediments (e.g., calcite precipitation in high alkalinity lakes and reservoirs; ref. 157 ). Beyond overcoming these technical challenges, there is an acute need to improve the upscaling of carbon burial in lakes and reservoirs to the ensemble of systems at the regional and continental scales based on system, watershed and climate properties.…”

Mineralization of autochthonous particulate organic carbon is a fast channel of organic matter turnover in Germany's largest drinking water reservoir

“…In addition, mineralization of OM into DIC has implications for greenhouse gas dynamics as it releases CO 2 into the water, a process that also increases DIC (Sun et al, 2016). In lakes that may also be affected by inorganic carbon sequestration processes such as photosynthesis or calcite precipitation (Khan et al, 2022), increases in DIC concentrations may lead to CO 2 degassing from the water column. From this perspective, lentic water bodies are not only reactors for carbon turnover but also sources of CO 2 (Åberg et al, 2004;Cole et al, 2007).…”