Sediment organic carbon burial in agriculturally eutrophic impoundments over the last century

Abstract

[1] We estimated organic carbon (OC) burial over the past century in 40 impoundments in one of the most intensively agricultural regions of the world. The volume of sediment deposited per unit time varied as a function of lake and watershed size, but smaller impoundments had greater deposition and accumulation rates per unit area. Annual water storage losses varied from 0.1-20% and were negatively correlated with impoundment size. Estimated sediment OC content was greatest in lakes with low ratios of watershed to impoundment area. Sediment OC burial rates were higher than those assumed for fertile impoundments by previous studies and were much higher than those measured in natural lakes. OC burial ranged from a high of 17,000 g C m À2 a À1 to a low of 148 g C m À2 a À1 and was significantly greater in small impoundments than large ones. The OC buried in these lakes originates in both autochthonous and allochthonous production. These analyses suggest that OC sequestration in moderate to large impoundments may be double the rate assumed in previous analyses. Extrapolation suggests that they may bury 4 times as much carbon (C) as the world's oceans. The world's farm ponds alone may bury more OC than the oceans and 33% as much as the world's rivers deliver to the sea.

Drivers of Sediment Accumulation and Nutrient Burial in Coastal Stormwater Detention Ponds, South Carolina, USA

“…Of particular interest is the similarity of stormwater pond sediments to sediments of 46 Minnesota lakes with catchments classified as undisturbed forest or prairie; the mean C concentration was also 12% by dry mass (Dean and others 1993). In contrast to their similarity with natural lakes, stormwater pond sediments show threefold to fourfold greater %C content relative to reservoir sediments from agricultural and mixed land use catchments (Brunskill and others 1971;Gorham and others 1974;Dean and others 1993;Downing and others 2008;Knoll and others 2014). The differences in sediments %C content in pond/lakes and reservoirs are likely ex- The number of sites sampled n is given in ().…”

“…Though lakes account for only 1% of the earth's surface area, conservative estimates predict that lakes and reservoirs bury 0.23 Pg C y -1 , a rate comparable to global C burial in ocean sediments (Cole and others 2007). In the continental USA, small artificial water bodies are estimated to account for 20% of total surface water and have disproportionately high rates of C sequestration (Smith and others 2002;Downing and others 2006;Cole and others 2007;Downing and others 2008;Tranvik and others 2009). These high rates of organic C burial are hypothesized to be the result of increased internal production and deposition of algal biomass (Downing and others 2008;Anderson and others 2014;Clow and others 2015).…”

“…In the continental USA, small artificial water bodies are estimated to account for 20% of total surface water and have disproportionately high rates of C sequestration (Smith and others 2002;Downing and others 2006;Cole and others 2007;Downing and others 2008;Tranvik and others 2009). These high rates of organic C burial are hypothesized to be the result of increased internal production and deposition of algal biomass (Downing and others 2008;Anderson and others 2014;Clow and others 2015). Stormwater ponds, as small, often eutrophic waterbodies (Siegel and others 2011), are hypothesized to follow this trend (Lewitus and others 2008), though they are also exposed to external sources of terrestrial biomass such as leaves and grass clippings (Grimm and others 2008).…”

“…Given previous studies in lakes and reservoirs (Downing and others 2008;Anderson and others 2014), as well as previous observations that stormwater ponds of the Southeast generally promote high concentrations of algal biomass (Lewitus and others 2008), it was hypothesized that internal algal production would be the major source of organic matter to sediments. However, multiple indices showed that terrestrial biomass was the dominant source of sediment organic matter to SC coastal stormwater ponds.…”

Holocene carbon burial by lakes in SW Greenland

“…The potential relevance of lakes to the global carbon (C) budget has received attention recently with the realization that lakes form an important component of the terrestrial C cycle (Algesten et al, 2004;Cole et al, 2007;Downing et al, 2008). Estimates of the rate of global C burial by lakes suggest burial rates ranging from 0.03 to 0.07 Pg C yr −1 (Cole et al, 2007).…”