Seasonal patterns in carbon dioxide in 15 mid-continent (USA) reservoirs

Abstract

Evidence suggests that lakes are important sites for atmospheric CO 2 exchange and so play a substantial role in the global carbon budget. Previous research has 2 weaknesses: (1) most data have been collected only during the open-water or summer seasons, and (2) data are concentrated principally on natural lakes in northern latitudes. Here, we report on the full annual cycle of atmospheric CO 2 exchanges of 15 oligotrophic to eutrophic reservoirs in the Glacial Till Plains of the United States. With one exception, these reservoirs showed an overall loss of CO 2 during the year, with most values within the lower range reported for temperate lakes. There was a strong cross-system seasonal pattern: an average of 70% of total annual CO 2 efflux occurred by the end of spring mixis; some 20% of annual flux was reabsorbed during summer stratification; and the remaining 50% of efflux was lost during autumnal mixing. Net annual flux was negatively correlated with depth and positively correlated with both water residence time and DOC, with the smallest annual CO 2 efflux measured in shallow fertile impoundments. Strong correlations yield relationships allowing regional up-scaling of CO 2 evasion. Understanding lacustrine CO 2 uptake and evasion requires seasonal analyses across the full range of lake trophic states and morphometric attributes.

Biological and land use controls on the isotopic composition of aquatic carbon in the Upper Mississippi River Basin

“…Navigation pools impounded by man-made dams are present on 930 km of the main stem Mississippi River and are common features of large industrialized rivers globally [Bonnerjee et al, 2009]. CO 2 undersaturation attributed to biological uptake has been observed throughout the portion of the Mississippi River impounded by the navigational lock and dam system [Crawford et al, 2016], a phenomenon which is likely a widespread feature of impounded temperate rivers [Deemer et al, 2016;Jones et al, 2016;Ran et al, 2017]. We exploit differences in land use, seasonal environmental conditions, and associated changes in stable and radio-isotope compositions to determine whether organic and inorganic aquatic carbon pools retain the isotopic imprint of terrestrial source materials and how biogeochemical processes modify isotopic composition during downstream transport.…”

Where does the river end? Drivers of spatiotemporal variability in CO2 concentration and flux in the inflow area of a large boreal lake

“…A large source of uncertainty in CO 2 emission from these systems arises from the period of ice‐melt in spring and early summer. Boreal lakes typically experience ice‐cover during substantial parts of the year; and it is anticipated that the sudden release of accumulated CO 2 at ice‐melt accounts for a considerable proportion of the total annual CO 2 flux into the atmosphere (Weyhenmeyer et al ; Karlsson et al ; Jones et al ). However, only a few studies have resolved temporal CO 2 trends under ice and quantified CO 2 emission flux at ice breakup based on direct in situ measurements (Baehr and Degrandpre , ; Denfeld et al ).…”

Large Spatial and Temporal Variability of Carbon Dioxide and Methane in a Eutrophic Lake

“…While this autumnal spike in CO 2 has been well documented in temperate lakes and reservoirs (Ducharme-Riel et al, 2015;Jones et al, 2016), we were surprised by the lack of CO 2 efflux at ice break. On 29 March 2016 (16 days after ice break), CO 2 concentrations were undersaturated ( Figure 2).…”