Carbon source/sink function of a subtropical, eutrophic lake determined from an overall mass balance and a gas exchange and carbon burial balance

Yang, Hong; Xing, Yangping; Xie, Ping; Ni, Leyi; Kewen, Rong

doi:10.1016/j.envpol.2007.04.006

Cited by 58 publications

(29 citation statements)

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“…Annual rate of CO 2 effluxes calculated in this study are probably underestimates of true values as chemical enhancement factors were not included in calculations (Wanninkhof and Knox 1996). Rates of CO 2 evasion from Middle Lake are lower than those reported for fluvial ecosystems characterized by slow water flow (e.g., 5.8-13.5 mol m -2 y -1 , Raymond et al 1997;69.2 ± 20.0 mol m -2 y -1 , Richey et al 2002;69.2-130.0 mol m -2 y -1 , Yao et al 2007), but comparable or higher than those reported for lentic ecosystems (e.g., 1.14-2.75 mol m -2 y -1 , Xing et al 2005; 1.96 mol m -2 y -1 , Yang et al 2008). In this study, we demonstrated that CO 2 degassing from Middle Lake came from chemical and hydrological conditions and that it was not sufficient to characterize Middle Lake as net heterotrophic (Raymond et al 1997;Dubois et al 2009;Stets et al 2009).…”

Section: Metabolism and Internal Processes In Middle Lakementioning

confidence: 84%

Net autotrophy in a fluvial lake: the relative role of phytoplankton and floating-leaved macrophytes

et al. 2011

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This study combined water-and sediment flux measurements with mass balances of dissolved gas and inorganic matter to determine the importance of pelagic and benthic processes for whole-system metabolism in a eutrophic fluvial lake. Mass balances of dissolved O 2 , inorganic carbon (DIC), nitrogen (DIN), phosphorous (SRP), particulate N (PN) and P (PP) and Chl a were calculated at a nearly monthly frequency by means of repeated sampling at the lake inlet and outlet. Simultaneously, benthic fluxes of gas and nutrients, including denitrification rates, and the biomass of the dominant pleustophyte (Trapa natans) were measured, and fluxes of O 2 and CO 2 across the water-atmosphere interface were estimated from diel changes in outlet concentrations. On an annual scale, Middle Lake exhibited CO 2 supersaturation, averaging 313% (range 86-562%), but was autotrophic with a net O 2 production (6.35 ± 2.05 mol m -2 y -1 ), DIC consumption (-31.18 ± 18.77 mol m -2 y -1 ) and net export of Chl a downstream (8.38 ± 0.95 mol C m -2 y -1 ). Phytoplankton was the main driver of Middle Lake metabolism, with a net primary production estimated at 33.24 mol O 2 m -2 y -1 , corresponding to a sequestration of 4.18 and 0.26 mol m -2 y -1 of N and P, respectively. At peak biomass, T. natans covered about 18% of Middle Lake's surface and fixed 2.46, 0.17 and 0.02 mol m -2 of C, N and P, respectively. Surficial sediments were a sink for O 2 (-14.47 ± 0.65 mol O 2 m -2 y -1 ) and a source of DIC and NH 4 ? (18.84 ± 2.80 mol DIC m -2 y -1 and 0.83 ± 0.16 mol NH 4 ? m -2 y -1 ), and dissipated nitrate via denitrification (1.44 ± 0.11 mol NO 3 -m -2 y -1 ). Overall, nutrient uptake by primary producers and regeneration from sediments were a minor fraction of external loads. This work suggests that the creation of fluvial lakes can produce net autotrophic systems, with elevated rates of phytoplanktonic primary production, largely sustained by allochtonous nutrient inputs. These hypereutrophic aquatic bodies are net C sinks, although they simultaneously release CO 2 to the atmosphere.

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Section: Metabolism and Internal Processes In Middle Lakementioning

confidence: 84%

Net autotrophy in a fluvial lake: the relative role of phytoplankton and floating-leaved macrophytes

et al. 2011

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“…During the four field campaigns, the diffusive fluxes of CH 4 and CO 2 across the water-air (Abril et al 2005;Guerin et al 2006;Yang et al 2008). The fluxes correlation coefficient (R 2 ) of the linear regression comes higher than 0.80 (R 2 : 0.95).…”

Section: Measurement Of Ghg Fluxesmentioning

confidence: 98%

Assessment of risk of GHG emissions from Tehri hydropower reservoir, India

Kumar

Sharma

2015

Human and Ecological Risk Assessment: An International Journal

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The hydropower reservoirs, considered as a green source of energy till few decades ago, are now found to emit significant quantities of green house gas (GHG) to the atmosphere. The present paper attempts to predict the vulnerability of Tehri reservoir, India to GHG emissions using the GHG Risk assessment tool (GRAT) and its verified with experimental GHG fluxes. The annual mean CO 2 fluxes from diffusion, bubbling and degassing pathways were found as 425.93±122.50, 4.81±1.33 and 7.01±2.77 mg m -2 d -1 , whereas CH 4 fluxes were found as 23.11±7.08, 4.79±1.08 and 7.41±4.50 mg m -2 d -1 respectively during 2011-12. The model found that Tehri reservoir emit higher CO 2 and CH 4 , i.e. 790 mg m -2 d -1 and 64 mg m -2 d -1 respectively in 2011, which comes within higher vulnerability range to cause more climate change impact. But by the year 2015, it would scale down to medium risks necessitating no further assessment of GHG. Significant difference between predicted and experimental GHG emission are assessed, Downloaded by [University of Sussex Library] at 00:56 19 August 2015 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2which may be due to lack of sufficient data, spatial and temporal variations, decomposition of flooded biomass, limitation of GRAT model and inadequate methodology. The study reveals that, GHG emission from Tehri reservoir is less than predicted by the GRAT.

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“…We then estimated the flux of CO 2 across the air-water interface (CO 2flux ) from the difference between lake pCO 2 and atmospheric pCO 2 (assumed to be 375 µatm), and wind speed (Cole and Caraco 1998). Although eutrophic lakes may be sources of methane (CH 4 ; Yang et al 2008), C exchange as CH 4 was not included in our analyses because these rates are small relative to CO 2 . We assumed atmospheric wet deposition of C (TOC dep ) via precipitation over the lakes to be 2.5 g m −2 yr −1 of C based on data collected in United States (Gill et al 2000).…”

Section: Methodsmentioning

confidence: 99%

Eutrophication reverses whole-lake carbon budgets

2014

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Lakes play a large role in global atmospheric and landscape carbon (C) processes, but their role may change as they become polluted with nutrients. Geographic regions rich in surface waters are also prone to agricultural and urban development and so may become increasingly eutrophic as the population rises. Here we develop C budgets of highly eutrophic lakes. These analyses show that lakes undergoing eutrophication can become atmospheric carbon dioxide (CO 2 ) sinks because of the CO 2 disequilibrium caused by extreme primary production. C budgets of such lakes show they absorb both landscape and atmospheric C, converting it into lake sediments and passing additional dissolved organic C (DOC) downstream. Eutrophication may cause a reversal in the role played by oligotrophic lakes by promoting atmospheric C sequestration as sediment and DOC. This means that as eutrophication increases from agriculture and urbanization, the expected large CO 2 evasion to the atmosphere by natural lakes will decline substantially and inland C sequestration and enrichment of DOC in waters flowing to the sea will be augmented. Thus, we suggest that the global C role of eutrophication is worthy of future consideration because it represents an interface between 2 large, converging environmental problems, whose interaction may reverse the role of lakes in the global C cycle.

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Carbon source/sink function of a subtropical, eutrophic lake determined from an overall mass balance and a gas exchange and carbon burial balance

Cited by 58 publications

References 50 publications

Net autotrophy in a fluvial lake: the relative role of phytoplankton and floating-leaved macrophytes

Net autotrophy in a fluvial lake: the relative role of phytoplankton and floating-leaved macrophytes

Assessment of risk of GHG emissions from Tehri hydropower reservoir, India

Eutrophication reverses whole-lake carbon budgets

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