Seasonal and temporal CO2 dynamics in three tropical mangrove creeks – A revision of global mangrove CO2 emissions

Rosentreter, Judith A.; Maher, Damien T.; Erler, Dirk V.; Murray, Rachel; Eyre, Bradley D.

doi:10.1016/j.gca.2017.11.026

Cited by 77 publications

(64 citation statements)

References 90 publications

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“…Indeed, the average salinity in the Pearl River inner estuary was 17 (Guo et al, 2009), higher than the average salinity of 4 in the Mekong inner estuarine branches during our cruises. The average F CO 2 in the Ca Mau mangrove creeks (89 mmol m −2 d −1 ) was well within the range (−8-862 mmol m −2 d −1 ) and close to the average (63 mmol m −2 d −1 ) of CO 2 fluxes in mangrove estuarine creeks compiled globally by Rosentreter et al (2018).…”

Section: Co 2 and Ch 4 Emissions To The Atmospheresupporting

confidence: 73%

Carbon dynamics and CO2 and CH4 outgassing in the Mekong delta

2018

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Abstract. We report a data set of biogeochemical variables related to carbon cycling obtained in the three branches (M y Tho, Hàm Luông, Có Chiên) of the Mekong delta (Bén Tre province, Vietnam) in December 2003, April 2004, and October 2004. Both the inner estuary (upstream of the mouth) and the outer estuary (river plume) were sampled, as well as side channels. The values of the partial pressure of CO 2 (pCO 2 ) ranged between 232 and 4085 ppm, O 2 saturation level (%O 2 ) between 63 and 114 %, and CH 4 between 2 and 2217 nmol L −1 , within the ranges of values previously reported in temperate and tropical meso-and macro-tidal estuaries. Strong seasonal variations were observed. In the upper oligohaline estuary, low pCO 2 (479-753 ppm) and high %O 2 (98-106 %) values were observed in April 2004 most probably related to freshwater phytoplankton growth owing to low freshwater discharge (1400 m 3 s −1 ) and increase in water residence time; during the two other sampling periods with a higher freshwater discharge (9300-17 900 m 3 s −1 ), higher pCO 2 (1895-2664 ppm) and lower %O 2 (69-84 %) values were observed in the oligohaline part of the estuary. In October 2004, important phytoplankton growth occurred in the offshore part of the river plume as attested by changes in the contribution of particulate organic carbon (POC) to total suspended matter (TSM) (%POC) and the stable isotope composition of POC (δ 13 C-POC), possibly related to low TSM values (improvement of light conditions for phytoplankton development), leading to low pCO 2 (232 ppm) and high %O 2 (114 %) values. Water in the side channels in the Mekong delta was strongly impacted by inputs from the extensive shrimp farming ponds. The values of pCO 2 , CH 4 , %O 2 , and the stable isotope composition of dissolved inorganic carbon (δ 13 C-DIC) indicated intense organic matter degradation that was partly mediated by sulfate reduction in sediments, as revealed by the slope of total alkalinity (TA) and DIC covariations. The δ 13 C-POC variations also indicated intense phytoplankton growth in the side channels, presumably due to nutrient enrichment related to the shrimp farming ponds. A data set in the mangrove creeks of the Ca Mau province (part of the Mekong delta) was also acquired in April and October 2004. These data extended the range of variability in pCO 2 and %O 2 with more extreme values than in the Mekong delta (Bén Tre), with maxima and minima of 6912 ppm and 37 %, respectively. Similarly, the maximum CH 4 concentration (686 nmol L −1 ) was higher in the Ca Mau province mangrove creeks than in the Mekong delta (Bén Tre, maximum 222 nmol L −1 ) during the October 2004 cruise (rainy season and high freshwater discharge period). In April 2004 (dry season and low freshwater discharge period), the CH 4 values were much lower than in October 2004 (average 19 ± 13 and 210 ± 158 nmol L −1 , respectively) in the Ca Mau province mangrove creeks, owing to the higher salinity (average 33.2 ± 0.6 and 14.1 ± 1.2, respectively) that probably led to higher sedim...

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Section: Co 2 and Ch 4 Emissions To The Atmospheresupporting

confidence: 73%

Carbon dynamics and CO2 and CH4 outgassing in the Mekong delta

2018

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“…This was two orders of magnitude lower than the average carbon dioxide atmospheric emissions (Table ). Carbon dioxide emissions have recently been reviewed for mangrove‐dominated systems (Call et al ; Rosentreter et al ), so here we focus on the methane contribution. Overall, the CH 4 concentrations and emissions were within the broad range observed in other similar systems.…”

Section: Discussionmentioning

confidence: 99%

“…Aquatic carbon flux investigations in mangroves and saltmarshes have focused primarily on organic carbon (Duarte et al ; Dittmar et al ; Adame and Lovelock ) and carbon dioxide fluxes at the air–water interface (Borges et al ; Linto et al ; Rosentreter et al ). For example, mangrove outwelling has been estimated to contribute ~ 10% of the terrestrially derived dissolved organic carbon (DOC) to the oceans (Dittmar et al ; Sippo et al ).…”

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confidence: 99%

Carbon outwelling and outgassing vs. burial in an estuarine tidal creek surrounded by mangrove and saltmarsh wetlands

Santos

Maher

Larkin

et al. 2019

Limnology & Oceanography

147

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Mangrove-and saltmarsh-dominated estuaries have high rates of organic carbon burial. Here, we estimate soil, pore water, and surface-water carbon fluxes in an Australian estuarine tidal creek to assess whether (1) advective pore water exchange releases some of the soil carbon, (2) outwelling (lateral exports) represents a major carbon sequestration mechanism, and (3) methane emissions offset soil carbon sequestration. A radon ( 222 Rn) mass balance implied tidally driven pore-water exchange rates ranging from 5.5 AE 3.6 to 15.6 AE 8.1 cm d −1 . Pore water exchange explained most of the dissolved organic carbon (DOC) and methane surface-water fluxes but not dissolved inorganic carbon (DIC) and alkalinity. Organic carbon burial in soils derived from 239 + 240 Pu dating was 11-63 g C m −2 yr −1 . Methane and carbon dioxide emissions at the water-air interface were 0.27 AE 0.03 and 63 AE 166 mmol m −2 d −1 , respectively. When calculated as CO 2 -equivalents, aquatic CH 4 emissions converted to 19-94 g C-CO 2 m −2 yr −1 . Upscaling methane and soil carbon fluxes to representative areas revealed that CH 4 emissions could offset < 5% of soil carbon burial. DIC outwelling (12 AE 6 mmol m −2 catchment d −1 ) was less than five-fold greater than DOC and particulate organic carbon (POC) outwelling and four-fold greater than catchment-wide carbon burial. Because much of this DIC remains in the ocean after airwater equilibration, lateral DIC exports may represent an important long-term carbon sink. Recent research has focused on quantifying carbon burial rates in blue carbon habitats such as saltmarshes and mangroves. We suggest that DIC outwelling and methane outgassing should also be considered when assessing the carbon sequestration capacity of these coastal vegetated habitats.

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“…Part or all parameters of the CO 2 system of mangrove forest waters have been characterized in several studies (e.g., Borges et al, 2003;Bouillon et al, 2007;Call et al, 2015;Camp et al, 2016;Ray et al, 2018;Rosentreter et al, 2018;Sippo et al, 2016;Yates et al, 2014), but, to our knowledge, this is the first study to report a year-round survey of the CO 2 system of mangrove forest waters. All studies are pointing at large day-night and tidal variations of the CO 2 system, with pCO 2 variations of several thousand μatm and pH variations of more than one unit (e.g., Bouillon et al, 2007;Rosentreter et al, 2018;Sippo et al, 2016). As an example, daily mean pH of 6.30 to 6.91 with diel variations up to 1.12 were found in Queensland (Australia) mangrove systems with salinities above 30 (Rosentreter et al, 2018).…”

Section: Mangrove Forestmentioning

confidence: 99%

Characterization of the CO₂ System in a Coral Reef, a Seagrass Meadow, and a Mangrove Forest in the Central Red Sea

et al. 2019

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The Red Sea is characterized by its high seawater temperature and salinity, and the resilience of its coastal ecosystems to global warming is of growing interest. This high salinity and temperature might also render the Red Sea a favorable ecosystem for calcification and therefore resistant to ocean acidification. However, there is a lack of survey data on the CO 2 system of Red Sea coastal ecosystems. A 1-year survey of the CO 2 system was performed in a seagrass lagoon, a mangrove forest, and a coral reef in the central Red Sea, including fortnight seawater sampling and high-frequency pH T monitoring. In the coral reef, the CO 2 system mean and variability over the measurement period are within the range of other world's reefs with pH T , dissolved inorganic carbon (DIC), total alkalinity (TA), pCO 2, and Ω arag of 8.016±0.077, 2061±58 μmol/kg, 2415±34 μmol/kg, 461±39 μatm, and 3.9±0.4, respectively. Here, comparisons with an offshore site highlight dominance of calcification and photosynthesis in summer-autumn, and dissolution and heterotrophy in winter-spring. In the seagrass meadow, the pH T , DIC, TA, pCO 2 , and Ω arag were 8.00±0.09, 1986±68 μmol/kg, 2352±49 μmol/kg, 411±66 μatm, and 4.0±0.3, respectively. The seagrass meadow TA and DIC were consistently lower than offshore water. The mangrove forest showed the highest amplitudes of variation, with pH T , DIC, TA, pCO 2 , and Ω arag , were 7.95±0.26, 2069±132 μmol/kg, 2438±91 μmol/kg, 493 ±178 μatm, and 4.1±0.6, respectively. We highlight the need for more research on sources and sinks of DIC and TA in coastal ecosystems.Plain Language Summary Global warming and ocean acidification are consequences of increased CO 2 emissions to the atmosphere by humankind and are major threats to marine ecosystems. The Red Sea waters are naturally warm and saline. The resilience of its coral reefs, mangrove forests, and seagrass meadows is of growing interest for the scientific community in the context of global warming. The high temperature and salinity might render the Red Sea quite resistant to ocean acidification as well as an environment chemically very favorable for calcification, notably by corals. Calcification is a process dampened by the acidity (pH) of water, which depends on the chemistry of CO 2 in seawater. Warm and saline water naturally tend to have a more basic pH and then be less corrosive to calcareous skeletons. However, the chemistry of the CO 2 and acidity baselines and variability in the Red Sea are poorly documented. We conducted a year-round survey of the CO 2 chemistry of seawater in a seagrass meadow, mangrove forest, and coral reef ecosystem, involving discrete water sampling and highfrequency measurements.

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Seasonal and temporal CO2 dynamics in three tropical mangrove creeks – A revision of global mangrove CO2 emissions

Cited by 77 publications

References 90 publications

Carbon dynamics and CO<sub>2</sub> and CH<sub>4</sub> outgassing in the Mekong delta

Carbon dynamics and CO<sub>2</sub> and CH<sub>4</sub> outgassing in the Mekong delta

Carbon outwelling and outgassing vs. burial in an estuarine tidal creek surrounded by mangrove and saltmarsh wetlands

Characterization of the CO₂ System in a Coral Reef, a Seagrass Meadow, and a Mangrove Forest in the Central Red Sea

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Seasonal and temporal CO2 dynamics in three tropical mangrove creeks – A revision of global mangrove CO2 emissions

Cited by 77 publications

References 90 publications

Carbon dynamics and CO&lt;sub&gt;2&lt;/sub&gt; and CH&lt;sub&gt;4&lt;/sub&gt; outgassing in the Mekong delta

Carbon dynamics and CO&lt;sub&gt;2&lt;/sub&gt; and CH&lt;sub&gt;4&lt;/sub&gt; outgassing in the Mekong delta

Carbon outwelling and outgassing vs. burial in an estuarine tidal creek surrounded by mangrove and saltmarsh wetlands

Characterization of the CO2 System in a Coral Reef, a Seagrass Meadow, and a Mangrove Forest in the Central Red Sea

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Carbon dynamics and CO<sub>2</sub> and CH<sub>4</sub> outgassing in the Mekong delta

Carbon dynamics and CO<sub>2</sub> and CH<sub>4</sub> outgassing in the Mekong delta

Characterization of the CO₂ System in a Coral Reef, a Seagrass Meadow, and a Mangrove Forest in the Central Red Sea