Seagrass and macrophyte mediated CO2 and CH4 dynamics in shallow coastal waters

Banerjee, Kakolee; Paneerselvam, A.; Ramachandran, Ramesh; Ganguly, Dipnarayan; Singh, Gurmeet

doi:10.1371/journal.pone.0203922

Cited by 36 publications

(17 citation statements)

References 49 publications

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“…Abundant OM in the sediments can reduce competition between sulfate reducers and methanogens by providing more competitive substrate and/or providing more noncompetitive substrate for methanogenesis (King, 1984; Reeburgh, 2007; Zhuang et al, 2018). Vegetated habitats typically have higher sediment OM concentrations compared to sediments without vegetation (e.g., Banerjee et al, 2018; Marinho, Campos, Guimarães, & Esteves, 2012; Yuan et al, 2015). Generally, there is a reported increase in CH 4 emissions in vegetated compared to nonvegetated areas (e.g., Bahlmann et al, 2015; Wang et al, 2016).…”

Section: Driversmentioning

confidence: 99%

“…NEP is considered a better predictor of productivity as it captures biomass production and consumption over a longer time period (i.e., is a reflection of the metabolism of an ecosystem) through CO 2 or O 2 flux while biomass is a static measurement. Of the studies that reported net ecosystem exchange or NEP, most did not test the relationship between CH 4 flux and NEP and the four studies that did reported mixed results (Bahlmann et al, 2015; Banerjee et al, 2018; Wilson, Mortazavi, & Kiene, 2015; Yuan et al, 2015). Not surprisingly then, when combining data across systems we found no relationship between NEP and CH 4 flux (Table 2).…”

Section: Driversmentioning

confidence: 99%

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A synthesis of methane emissions from shallow vegetated coastal ecosystems

Al‐Haj

Fulweiler

2020

Global Change Biology

145

132

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Vegetated coastal ecosystems (VCEs; i.e., mangroves, salt marshes, and seagrasses) play a critical role in global carbon (C) cycling, storing 10× more C than temperate forests. Methane (CH 4 ), a potent greenhouse gas, can form in the sediments of these ecosystems. Currently, CH 4 emissions are a missing component of VCE C budgets. This review summarizes 97 studies describing CH 4 fluxes from mangrove, salt marsh, and seagrass ecosystems and discusses factors controlling CH 4 flux in these systems. CH 4 fluxes from these ecosystems were highly variable yet they all act as net methane sources (median, range; mangrove: 279.17, −67.33 to 72,867.83; salt marsh: 224.44, −92.60 to 94,129.68; seagrass: 64.80, 1.25-401.50 µmol CH 4 m −2 day −1 ). Together CH 4 emissions from mangrove, salt marsh, and seagrass ecosystems are about 0.33-0.39 Tmol CH 4 -C/year-an addition that increases the current global marine CH 4 budget by more than 60%. The majority (~45%) of this increase is driven by mangrove CH 4 fluxes. While organic matter content and quality were commonly reported in individual studies as the most important environmental factors driving CH 4 flux, they were not significant predictors of CH 4 flux when data were combined across studies. Salinity was negatively correlated with CH 4 emissions from salt marshes, but not seagrasses and mangroves. Thus the available data suggest that other environmental drivers are important for predicting CH 4 emissions in vegetated coastal systems. Finally, we examine stressor effects on CH 4 emissions from VCEs and we hypothesize that future changes in temperature and other anthropogenic activites (e.g., nitrogen loading) will likely increase CH 4 emissions from these ecosystems. Overall, this review highlights the current and growing importance of VCEs in the global marine CH 4 budget. K E Y W O R D S global carbon budget, mangrove, methanogenesis, methanotrophy, salt marsh, seagrass, synthesis | 2989 AL-HAJ And FULWEILER About two-thirds of the total global CH 4 emissions can be attributed to human activity (e.g., agriculture, sewage and landfill waste, fossil fuel consumption; Saunois et al., 2016). Vegetated coastal ecosystems (VCEs; i.e., mangroves, salt marshes, and seagrasses) play a critical role in global carbon (C) cy-S U PP O RTI N G I N FO R M ATI O N Additional supporting information may be found online in the Supporting Information section. How to cite this article: Al-Haj AN, Fulweiler RW. A synthesis of methane emissions from shallow vegetated coastal ecosystems. Glob Change Biol. 2020;26:2988-3005. https://

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Section: Driversmentioning

confidence: 99%

Section: Driversmentioning

confidence: 99%

A synthesis of methane emissions from shallow vegetated coastal ecosystems

Al‐Haj

Fulweiler

2020

Global Change Biology

145

132

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“…The seagrass meadows are known to serve as antacid to contain ocean acidification as they can sequester dissolved CO 2 and enrich the lagoon with oxygen through canopy photosynthesis and storage of blue carbon (12%) in their underground shoot and root systems. Banerjee et al (2018) studied a combined air-water flux of CO 2 and CH 4 from the seagrass meadows of brackishwater Chilika Lake. Growing coastal populations and increasing coastal developments threaten seagrass habitats globally and the decline of seagrass meadows is taking place very rapidly (Waycott et al, 2009;Fourqurean et al, 2012;Kaladharan and Anasukoya, 2019).…”

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confidence: 99%

Blue carbon stock of the seagrass meadows of Gulf of Mannar and Palk Bay off Coromandel Coast, south India

et al. 2020

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Blue carbon stock of the seagrass meadows of Gulf of Mannar and Palk Bay, off Coromandel Coast, south India, were computed from the organic carbon content and dry bulk densities of sediment core taken from the seagrass meadows of these two ecosystems. The Gulf of Mannar (GoM) and Palk Bay (PB) harbour 13 seagrass species dominated by Cymodocea serrulata and Syringodium isoetifolium. The soil carbon density of both GoM and PB were higher in subsurface cores. The blue carbon stock of seagrass meadows of the GoM was estimated as 0.001782 Tg and that of PB as 0.043996 Tg. The estimated value of blue carbon stored in seagrass meadows of GoM was 17820 US$ and that of PB was 43,99,682 US$. The results of this study are discussed in the light of climate change mitigation, emphasising the need to conserve these underwater meadows.

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“…Reports on greenhouse gas fluxes by seagrass ecosystems are limited (Oremland, 1975;Barber and Carlson, 1993;Alongi et al, 2008;Deborde et al, 2010;Bahlmann et al, 2015;Garcias-Bonet and Duarte, 2017;Banerjee et al, 2018;Lyimo et al, 2018), and no reports had been previously published on how increasing seawater temperatures might affect greenhouse gas fluxes by seagrass ecosystems. Blue carbon ecosystems have shown to turn into C sources when disturbances led to 25 mortality (Macreadie et al, 2015;Lovelock et al, 2017;Arias-Ortiz et al, 2018), consistent with the very large CO2 and CH4 fluxes observed in one vegetated sediment where the seagrass died when warmed to 33 ˚C.…”

Section: Discussionmentioning

confidence: 99%

Warming enhances carbon dioxide and methane fluxes from Red Sea seagrass (Halophila stipulacea) sediments

Burkholz¹,

Garcías-Bonet²,

Duarte³

2019

Preprint

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Abstract. Seagrass meadows are autotrophic ecosystems storing carbon in their biomass and sediments, but they have also been shown to be sources of carbon dioxide (CO2) and methane (CH4). Seagrasses can be negatively affected by increasing seawater temperatures, but the effects of warming on CO2 and CH4 fluxes in seagrass meadows have not yet been reported. Here, we examine the effect of two disturbances on air-seawater fluxes of CO2 and CH4 in Red Sea Halophila stipulacea communities compared to adjacent unvegetated sediments using cavity ring-down spectroscopy. We first characterized CO2 and CH4 fluxes in vegetated and adjacent unvegetated sediments, and then experimentally examined their response, along with that of the C isotopic signature of CO2 and CH4, to gradual warming from 25&#8201;&#176;C (winter seawater temperature) to 37&#8201;&#176;C, 2&#8201;&#176;C above current maximum temperature. In addition, we assessed the response to prolonged darkness, thereby providing insights into the possible role of suppressing plant photosynthesis in supporting CO2 and CH4 fluxes. We detected distinct differences between vegetated and unvegetated sediments, with the vegetated sediments supporting 6-fold higher CO2 fluxes, and 10- to 100-fold higher CH4 fluxes. Warming led to an increase in net CO2 and CH4 fluxes, reaching average fluxes of 10,422.18&#8201;&#177;&#8201;2,570.12&#8201;&#181;mol CO2&#8201;m&#8722;2&#8201;d&#8722;1 and 88.11&#8201;&#177;&#8201;15.19&#8201;&#181;mol CH4&#8201;m&#8722;2&#8201;d&#8722;1, while CO2 and CH4 fluxes decreased over time in sediments maintained at 25&#8201;&#176;C. Prolonged darkness led to an increase in CO2 fluxes but a decrease in CH4 fluxes in vegetated sediments. These results add to previous research identifying Red Sea seagrass meadows as a significant source of CH4, while also indicating that sublethal warming may lead to increased emissions of greenhouse gases from seagrass meadows, providing a feedback mechanism that may contribute to further enhance global warming.

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Seagrass and macrophyte mediated CO2 and CH4 dynamics in shallow coastal waters

Cited by 36 publications

References 49 publications

A synthesis of methane emissions from shallow vegetated coastal ecosystems

A synthesis of methane emissions from shallow vegetated coastal ecosystems

Blue carbon stock of the seagrass meadows of Gulf of Mannar and Palk Bay off Coromandel Coast, south India

Warming enhances carbon dioxide and methane fluxes from Red Sea seagrass (<i>Halophila stipulacea</i>) sediments

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Seagrass and macrophyte mediated CO2 and CH4 dynamics in shallow coastal waters

Cited by 36 publications

References 49 publications

A synthesis of methane emissions from shallow vegetated coastal ecosystems

A synthesis of methane emissions from shallow vegetated coastal ecosystems

Blue carbon stock of the seagrass meadows of Gulf of Mannar and Palk Bay off Coromandel Coast, south India

Warming enhances carbon dioxide and methane fluxes from Red Sea seagrass (&lt;i&gt;Halophila stipulacea&lt;/i&gt;) sediments

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Warming enhances carbon dioxide and methane fluxes from Red Sea seagrass (<i>Halophila stipulacea</i>) sediments