Carbon Dioxide and Methane Dynamics in Estuaries

Borges, Alberto; Abril, Gwénaël

doi:10.1016/b978-0-12-374711-2.00504-0

Cited by 225 publications

(390 citation statements)

References 249 publications

(213 reference statements)

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“…A worldwide comparison of riverine and aquatic methane emissions, presented by Stanley et al (2016) and Ortiz-Llorente and Alvarez-Cobelas (2012), revealed no correlation between methane emissions and latitude. This finding contrasts with the review by Borges and Abril (2012) comparing worldwide estuaries, where an increase in methane emissions was evident from estuaries at high latitudes, as well as from tidal systems. (Notably, the Lena Delta matches both of these classifications.)…”

Section: Diffusive Methane Fluxcontrasting

confidence: 55%

“…7), in agreement with our previous findings (Bussmann, 2013). For other estuaries, a complex pattern of increasing/decreasing methane concentrations vs. salinity has been presented (Borges and Abril, 2012). However, none of the currently proposed schemes seems applicable to our data.…”

Section: Methane Concentrationscontrasting

confidence: 40%

“…No current method is totally satisfactory for quantifying k in estuaries, and its calculation remains a matter of debate (Borges and Abril, 2012). In their review, Borges and Abril (2012) report an approximate range for k 600 of < 10 up to 30 cm h −1 (< 2.4-7.2 m d −1 ). For the North Sea in winter, much higher values were obtained (7-62 cm h −1 = 17-150 m d −1 ) (Nightingale et al, 2000).…”

Section: Diffusive Methane Fluxmentioning

confidence: 99%

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Methane distribution and oxidation around the Lena Delta in summer 2013

et al. 2017

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Abstract. The Lena River is one of the largest Russian rivers draining into the Laptev Sea. The predicted increases in global temperatures are expected to cause the permafrost areas surrounding the Lena Delta to melt at increasing rates. This melting will result in high amounts of methane reaching the waters of the Lena and the adjacent Laptev Sea. The only biological sink that can lower methane concentrations within this system is methane oxidation by methanotrophic bacteria. However, the polar estuary of the Lena River, due to its strong fluctuations in salinity and temperature, is a challenging environment for bacteria. We determined the activity and abundance of aerobic methanotrophic bacteria by a tracer method and by the quantitative polymerase chain reaction. We described the methanotrophic population with a molecular fingerprinting method (monooxygenase intergenic spacer analysis), as well as the methane distribution (via a headspace method) and other abiotic parameters, in the Lena Delta in September 2013.The median methane concentrations were 22 nmol L −1 for riverine water (salinity (S) < 5), 19 nmol L −1 for mixed water (5 < S < 20) and 28 nmol L −1 for polar water (S > 20). The Lena River was not the source of methane in surface water, and the methane concentrations of the bottom water were mainly influenced by the methane concentration in surface sediments. However, the bacterial populations of the riverine and polar waters showed similar methane oxidation rates (0.419 and 0.400 nmol L −1 d −1 ), despite a higher relative abundance of methanotrophs and a higher estimated diversity in the riverine water than in the polar water. The methane turnover times ranged from 167 days in mixed water and 91 days in riverine water to only 36 days in polar water. The environmental parameters influencing the methane oxidation rate and the methanotrophic population also differed between the water masses. We postulate the presence of a riverine methanotrophic population that is limited by sub-optimal temperatures and substrate concentrations and a polar methanotrophic population that is well adapted to the cold and methane-poor polar environment but limited by a lack of nitrogen. The diffusive methane flux into the atmosphere ranged from 4 to 163 µmol m 2 d −1 (median 24). The diffusive methane flux accounted for a loss of 8 % of the total methane inventory of the investigated area, whereas the methanotrophic bacteria consumed only 1 % of this methane inventory. Our results underscore the importance of measuring the methane oxidation activities in polar estuaries, and they indicate a population-level differentiation between riverine and polar water methanotrophs.

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Section: Diffusive Methane Fluxcontrasting

confidence: 55%

Section: Methane Concentrationscontrasting

confidence: 40%

Section: Diffusive Methane Fluxmentioning

confidence: 99%

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Methane distribution and oxidation around the Lena Delta in summer 2013

et al. 2017

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“…The tidal variability of CH 4 (and N 2 O in the wet season) can also be interpreted as an indication of the contribution of intertidal sediments and tidal creeks to the CH 4 concentrations in these estuaries. The importance of tidal creeks (Middelburg et al, 2002) and tidal pumping Borges and Abril, 2011) for CH 4 concentrations in estuaries is widely recognized. flux densities between 0.7 and 49 mmol m −2 yr −1 in the estuaries of the Sundarban mangrove ecosystem.…”

Section: Chmentioning

confidence: 99%

Nitrous oxide and methane in two tropical estuaries in a peat-dominated region of northwestern Borneo

et al. 2016

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Abstract. Estuaries are sources of nitrous oxide (N 2 O) and methane (CH 4 ) to the atmosphere. However, our present knowledge of N 2 O and CH 4 emissions from estuaries in the tropics is very limited because data are scarce. In this study, we present first measurements of dissolved N 2 O and CH 4 from two estuaries in a peat-dominated region of northwestern Borneo. Two campaigns (during the dry season in June 2013 and during the wet season in March 2014) were conducted in the estuaries of the Lupar and Saribas rivers. Median N 2 O concentrations ranged between 7.2 and 12.3 nmol L −1 and were higher in the marine end-member (13.0 ± 7.0 nmol L −1 ). CH 4 concentrations were low in the coastal ocean (3.6 ± 0.2 nmol L −1 ) and higher in the estuaries (medians between 10.6 and 64.0 nmol L −1 ). The respiration of abundant organic matter and presumably anthropogenic input caused slight eutrophication, which did not lead to hypoxia or enhanced N 2 O concentrations, however. Generally, N 2 O concentrations were not related to dissolved inorganic nitrogen concentrations. Thus, the use of an emission factor for the calculation of N 2 O emissions from the inorganic nitrogen load leads to an overestimation of the flux from the Lupar and Saribas estuaries. N 2 O was negatively correlated with salinity during the dry season, which suggests a riverine source. In contrast, N 2 O concentrations during the wet season were not correlated with salinity but locally enhanced within the estuaries, implying that there were additional estuarine sources during the wet (i.e., monsoon) season. Estuarine CH 4 distributions were not driven by freshwater input but rather by tidal variations. Both N 2 O and CH 4 concentrations were more variable during the wet season. We infer that the wet season dominates the variability of the N 2 O and CH 4 concentrations and subsequent emissions from tropical estuaries. Thus, we speculate that any changes in the Southeast Asian monsoon system will lead to changes in the N 2 O and CH 4 emissions from these systems. We also suggest that the ongoing cultivation of peat soil in Borneo is likely to increase N 2 O emissions from these estuaries, while the effect on CH 4 remains uncertain.

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“…Field measurements suggest that 10 % of the total CO 2 emissions from the inner estuary of macrotidal systems is sustained by the ventilation of riverine CO 2 , whereas 90 % is due to local net heterotrophy (Borges et al, 2006) fueled by inputs of terrestrial-and riverine-algae-derived (planktonic) detritus and, in populated areas, sewage (Chen and Borges, 2009). In estuaries with long freshwater residence times, the riverine CO 2 will be fully ventilated to the atmosphere within the estuary, and the total CO 2 emissions can be attributed to net heterotrophy (Borges and Abril, 2011).…”

Section: Introductionmentioning

confidence: 99%

Spatial variability in surface-water <i>p</i>CO<sub>2</sub> and gas exchange in the world's largest semi-enclosed estuarine system: St. Lawrence Estuary (Canada)

Dinauer

Mucci

2017

Biogeosciences

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Abstract. The incomplete spatial coverage of CO 2 partial pressure (pCO 2 ) measurements across estuary types represents a significant knowledge gap in current regional-and global-scale estimates of estuarine CO 2 emissions. Given the limited research on CO 2 dynamics in large estuaries and bay systems, as well as the sources of error in the calculation of pCO 2 (carbonic acid dissociation constants, organic alkalinity), estimates of air-sea CO 2 fluxes in estuaries are subject to large uncertainties. The Estuary and Gulf of St. Lawrence (EGSL) at the lower limit of the subarctic region in eastern Canada is the world's largest estuarine system, and is characterized by an exceptional richness in environmental diversity. It is among the world's most intensively studied estuaries, yet there are no published data on its surface-water pCO 2 distribution. To fill this data gap, a comprehensive dataset was compiled from direct and indirect measurements of carbonate system parameters in the surface waters of the EGSL during the spring or summer of 2003-2016. The calculated surface-water pCO 2 ranged from 435 to 765 µatm in the shallow partially mixed upper estuary, 139-578 µatm in the deep stratified lower estuary, and 207-478 µatm along the Laurentian Channel in the Gulf of St. Lawrence. Overall, at the time of sampling, the St. Lawrence Estuary served as a very weak source of CO 2 to the atmosphere, with an area-averaged CO 2 degassing flux of 0.98 to 2.02 mmol C m −2 d −1 (0.36 to 0.74 mol C m −2 yr −1 ). A preliminary analysis revealed that respiration (upper estuary), photosynthesis (lower estuary), and temperature (Gulf of St. Lawrence) controlled the spatial variability in surface-water pCO 2 . Whereas we used the dissociation constants of Cai and Wang (1998)

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Carbon Dioxide and Methane Dynamics in Estuaries

Cited by 225 publications

References 249 publications

Methane distribution and oxidation around the Lena Delta in summer 2013

Methane distribution and oxidation around the Lena Delta in summer 2013

Nitrous oxide and methane in two tropical estuaries in a peat-dominated region of northwestern Borneo

Spatial variability in surface-water <i>p</i>CO<sub>2</sub> and gas exchange in the world's largest semi-enclosed estuarine system: St. Lawrence Estuary (Canada)

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Carbon Dioxide and Methane Dynamics in Estuaries

Cited by 225 publications

References 249 publications

Methane distribution and oxidation around the Lena Delta in summer 2013

Methane distribution and oxidation around the Lena Delta in summer 2013

Nitrous oxide and methane in two tropical estuaries in a peat-dominated region of northwestern Borneo

Spatial variability in surface-water &lt;i&gt;p&lt;/i&gt;CO&lt;sub&gt;2&lt;/sub&gt; and gas exchange in the world's largest semi-enclosed estuarine system: St. Lawrence Estuary (Canada)

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Spatial variability in surface-water <i>p</i>CO<sub>2</sub> and gas exchange in the world's largest semi-enclosed estuarine system: St. Lawrence Estuary (Canada)