Methane sources, sinks and fluxes in a temperate tidal Lagoon: The Arcachon lagoon (SW France)

Deborde, Jonathan; Anschutz, Pierre; Guerin, Frédéric; Poirier, Dominique; Marty, Danielle; Boucher, Guy; Thouzeau, Gérard; Canton, Mathieu; Abril, Gwénaël

doi:10.1016/j.ecss.2010.07.013

Cited by 62 publications

(46 citation statements)

References 61 publications

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“…Altogether, our findings and consistent literature reports suggest that organic exudates from seagrasses are fueling a complex microbial community including methanogenic Archea. Moreover, a trend toward increasing CH 4 production with increasing salinity (Figure 4B) suggests that salinity slightly enhances CH 4 production in the Red Sea, contrary to what has been previously described for estuaries and intertidal systems with freshwater inputs (Bartlett et al, 1987;Middelburg et al, 2002;Deborde et al, 2010). However, this relationship may be spurious, rather than causal, as salinity, increasing from south to north along the Red Sea, is also related to gradients in climate and productivity (Raitsos et al, 2013;Wafar et al, 2016), which may be driving the apparent relationship with salinity.…”

Section: Discussioncontrasting

confidence: 77%

Methane Production by Seagrass Ecosystems in the Red Sea

Garcías-Bonet

Duarte

2017

Front. Mar. Sci.

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Atmospheric methane (CH 4 ) is the second strongest greenhouse gas and it is emitted to the atmosphere naturally by different sources. It is crucial to define the dimension of these natural emissions in order to forecast changes in atmospheric CH 4 mixing ratio in future scenarios. However, CH 4 emissions by seagrass ecosystems in shallow marine coastal systems have been neglected although their global extension. Here we quantify the CH 4 production rates of seagrass ecosystems in the Red Sea. We measured changes in CH 4 concentration and its isotopic signature by cavity ring-down spectroscopy on chambers containing sediment and plants. We detected CH 4 production in all the seagrass stations with an average rate of 85.09 ± 27.80 µmol CH 4 m −2 d −1 . Our results show that there is no seasonal or daily pattern in the CH 4 production rates by seagrass ecosystems in the Red Sea. Taking in account the range of global estimates for seagrass coverage and the average seagrass CH 4 production, the global CH 4 production and emission by seagrass ecosystems could range from 0.09 to 2.7 Tg yr −1 . Because CH 4 emission by seagrass ecosystems had not been included in previous global CH 4 budgets, our estimate would increase the contribution of marine global emissions, hitherto estimated at 9.1 Tg yr −1 , by about 30%. Thus, the potential contribution of seagrass ecosystems to marine CH 4 emissions provides sufficient evidence of the relevance of these fluxes as to include seagrass ecosystems in future assessments of the global CH 4 budgets.

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Section: Discussioncontrasting

confidence: 77%

Methane Production by Seagrass Ecosystems in the Red Sea

Garcías-Bonet

Duarte

2017

Front. Mar. Sci.

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“…When compared to a temperate system, diffusive CH 4 fluxes from sub-tidal sediment of the Saptamukhi estuary were comparable to those found in the Arcachon tidal lagoon (France) (11.97 µmol m −2 d −1 ; Deborde et al, 2010). Similarly, our diffusive CH 4 fluxes were also higher than in the Yangtze temperate estuary, China (1.7-2.2 µmol m −2 d −1 ; Zhang et al, 2008), yet lower than White Oak river estuary, in northern California (17.1 µmol m −2 d −1 ; Kelley et al, 1990).…”

Section: Pore-water Ch 4 Levels and Its Fluxes To The Adjacent Saptamsupporting

confidence: 52%

“…In coastal wetlands, the role of plant-mediated transport is significantly reduced because methanogenesis is largely suppressed by sulfate reduction. However, tidal effects can introduce another pathway of transport whereby during low-tide conditions, CH 4 -rich pore water is transported to adjacent creeks and estuaries through hypsometric gradients (Deborde et al, 2010;Santos et al, 2012;Stieglitz et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Mangrove Methane Biogeochemistry in the Indian Sundarbans: A Proposed Budget

2017

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Biogeochemical cycling of CH 4 was investigated at Lothian Island, one of the relatively pristine islands of Indian Sundarbans and its adjacent Saptamukhi estuary, during June 2010 to December 2012. Intertidal mangrove sediments were highly anoxic and rich in organic carbon. Mean rates of methanogenesis were 3,547 and 48.88 µmol m −3 wet sediment d −1 , for intertidal (up to 25 cm depth) and sub-tidal sediments (first 5 cm depth), respectively. CH 4 in pore-water was 53.4 times more supersaturated than in adjacent estuarine waters. This resulted in significant CH 4 efflux from sediments to estuarine waters-via advective and diffusive transport. About 8.2% of the total CH 4 produced in intertidal mangrove sediments was transported to the adjacent estuary through advective flux, which was 20 times higher than diffusive CH 4 flux. Mean CH 4 concentrations in estuarine surface and sub-surface waters were 69.9 and 56.1 nM, respectively, with a dissolved CH 4 oxidation rate in estuarine surface waters of 20.5 nmol L −1 d −1 . An estimated 0.09 Gg year −1 of CH 4 is released from estuaries of Sundarbans to the regional atmosphere. The mean CH 4 mixing ratio over the forest atmosphere was 2 ppmv. On annual basis, only 2.75% of total supplied CH 4 to the forest atmosphere was transported to the upper atmosphere via biosphere-atmosphere exchange. Mean CH 4 photo-oxidation rate over the forest atmosphere was 3.25 × 10 −9 mg cm −3 d −1 . Using new and previously published data we present for the first time, a CH 4 budget for Sundarbans mangrove ecosystem which in part, revealed the existence of anaerobic CH 4 oxidation in the mangrove sediment column.

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“…Over the one year study period, mean monthly CH 4 fluxes across both grazing treatments varied from 0.01 to 1.27 mg m -2 h -1 in line with fluxes recorded from North American and Australian salt marshes, a temperate tidal lagoon and a European flooded coastal meadow (Priemé, 1994;Deborde et al, 2010;Chmura et al, 2011;Livesley & Andrusiak, 2012) but greater than those recorded from a UK salt marsh (Dausse et al, 2012). Our variable soil CH 4 fluxes support the recent review by Poffenbarger et al (2011), that oligohaline marshes have more temporally and spatially variable emissions than previously thought.…”

Section: Chmentioning

confidence: 83%