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Dehairs, Frank; Rao, R. G.; Mohan, P. Chandra; Raman, A. V.; Marguillier, S.; Hellings, L.

doi:10.1023/a:1004072310525

Cited by 71 publications

(7 citation statements)

References 35 publications

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“…The aforementioned mixing models are based on assumptions that d 13 C values of plant canopy, SOM, root, and litter may approximate those of each component of E c and E s . The assumptions lie in the fact that: (1) there is no C isotopic fractionation during heterotrophic microbial respiration (Lin and Ehleringer 1997); (2) there is little C isotopic fractionation during the early decomposing stage of fallen plant substances (Balesdent et al 1993;Dehairs et al 2000). Based on published litter turnover times, we limited the study period to 2-3 months such that only the first litterfall contributes to E l , and afterwards there was little new litter formation and decay in the chamber; and (3) there was a negligible difference between d 13 C values of sediment organic C in the surface layer and that of sediment released CO 2 , and little difference of d 13 C values among different soil size fractions as suggested by Bird et al (1996).…”

Section: Sample Collection and Analysismentioning

confidence: 99%

Using isotope labeling to partition sources of CO₂ efflux in newly established mangrove seedlings

Ouyang

Lee

Connolly

2017

Limnology & Oceanography

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Carbon dioxide (CO 2 ) flux is a critical component of the global C budget. While CO 2 flux has been increasingly studied in mangroves, better partitioning of components contributing to the overall flux will be useful in constraining C budgets. Little information is available on how CO 2 flux may vary with forest age and conditions. We used a combination of 13 C stable isotope labeling and closed chambers to partition CO 2 efflux from the seedlings of the widespread mangrove Avicennia marina in laboratory microcosms, with a focus on sediment CO 2 efflux in establishing forests. We showed that (1) above-ground part of plants were the chief component of overall CO 2 efflux; and (2) the degradation of sediment organic matter was the major component of sediment CO 2 efflux, followed by root respiration and litter decomposition, as determined using isotope mixing models. There was a significant relationship between C isotope values of CO 2 released at the sediment-air interface and both root respiration and sediment organic matter decomposition. These relative contributions of different components to overall and sediment CO 2 efflux can be used in partitioning of the sources of overall respiration and sediment C mineralization in establishing mangroves.Mangroves contain variably thick organic sediments and are the most carbon (C) rich forests (Donato et al. 2011;Sanders et al. 2016). The high C accumulation capacity of mangroves has been recognized, and termed "blue C," along with saltmarsh and seagrasses (Mcleod et al. 2011;Duarte et al. 2013;Ouyang and Lee 2014). However, studies of mangrove carbon dioxide (CO 2 ) flux vary in the precision of their partitioning. CO 2 flux in mangroves may originate from the canopy, woody debris, root, litter and sediment organic matter (SOM), and is collectively called ecosystem respiration (E e ), which has been usually studied separately as canopy (above-ground parts, E c ) and sediment respiration (the other components, E s ).Mangrove organic material such as leaf litter, if not exported, becomes incorporated in the sediment through decay and chemically modified by microbes inhabiting the mangrove forest floor (Kristensen et al. 2008). In contrast to the intensively studied and relatively established pattern of C exchange between mangroves and nearshore ecosystems (Lee 1995), the pattern of C gas flux released from mangrove sediment is less clear, although there is an increasing interest in this topic and C gas flux at the ecosystem scale (Lovelock 2008;Barr et al. 2010;Chen et al. 2010Chen et al. , 2012Livesley and Andrusiak 2012;Barr 2013;Leopold et al. 2013Leopold et al. , 2015Leopold et al. , 2016Bulmer et al. 2015). A key but poorly known aspect is the partitioning of E s attributable to various components, i.e., root, litter, and SOM (including the microphytobenthos).Laboratory microcosms have been used effectively in studies of mangrove energy pathways. For example, Bui and Lee (2014) evaluated relative contributions of organic matter from mangrove leaf litter an...

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Section: Sample Collection and Analysismentioning

confidence: 99%

Using isotope labeling to partition sources of CO₂ efflux in newly established mangrove seedlings

Ouyang

Lee

Connolly

2017

Limnology & Oceanography

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“…Wide range for δ CPOC (rivers ~ -25 to -28‰; marine plankton ~ -18 to -22‰; C3 plant ~ -23 to -34‰; C4 plants ~ -9 to -17‰) have been reported by several researchers in different environments (Hedges et al, 1997, Bouillon et al, 2002, Zhang et al, 1997, Smith and Epstein, 1971, Dehairs et al, 2000. On an average, δ 13 CPOC at the Hooghly (-24.87 ± 0.89‰) was relatively lower compared to that of Sundarbans (-23.36 ± 0.32‰) suggesting relatively higher influence of terrestrial inputs in the Hooghly.…”

Section: Particulate Organic Matter In the Hooghly -Sundarbans Systemmentioning

confidence: 95%

The postmonsoon carbon biogeochemistry of estuaries under different levels of anthropogenic impacts

Dutta

Kumar

Mukherjee

et al. 2018

Preprint

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Abstract. The different aspects of carbon biogeochemistry were studied during the postmonsoon at the Hooghly-Sundarbans estuarine system, a part of the Ganga-Brahmaputra river system located in the northeastern India. The study focused on understanding the differences in carbon biogeochemistry of estuaries undergoing different levels of anthropogenic stress by investigating anthropogenically influenced Hooghly estuary and mangrove-dominated estuaries of the Sundarbans. The salinity of well oxygenated (%DO: 91&#8211;104&#8201;%) estuaries of the Sundarbans varied over a narrow range (12.74&#8211;16.69) during postmonsoon relative to the Hooghly (0.04&#8211;10.37). Phytoplankton productivity and carbonate precipitation and/or dissolution were dominant processes controlling DIC dynamics in different parts of the Hooghly, whereas signal for mangrove derived DIC removal was observed in the Sundarbans. Influence of groundwater on estuarine DIC biogeochemistry was also observed in both the estuaries with relatively higher influence at the Hooghly than Sundarbans. In both estuarine systems, DOC behaved non-conservatively with ~&#8201;40&#8201;% higher DOC level in the Hooghly compared to the Sundarbans. No significant evidence of phytoplankton production on DOC level was found in these estuaries, however signal of DOC input through pore-water exchange at the Sundarbans was observed. Relatively lower &#948;13CPOC at the Hooghly compared to the Sundarbans suggest relatively higher terrestrial influence at the Hooghly with a possibility of in situ biogeochemical modifications of POC at the Sundarbans. The freshwater run-off coupled with in situ aerobic OC mineralization controlled estuarine pCO2 level at the Hooghly, whereas the same was principally exogenous for the Sundarbans. The entire Hooghly-Sundarbans system acted as source of CO2 to the regional atmosphere with ~&#8201;17 times higher emission from the Hooghly compared to Sundarbans. The present study clearly establishes the dominance of anthropogenically influenced estuary over relatively pristine mangrove dominated one in the regional greenhouse gas budget and climate change perspective.

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“…Relatively depleted δ 13 C and δ 15 N of phytoplankton in the frontal regions (À25.1 ± 0.5‰ and 4.2 ± 0.3‰, respectively) than the typical δ 13 C and δ 15 N of marine phytoplankton (À23 to À21‰ and 5-7‰, respectively) (Altabet, 1996;Brandes & Devol, 2002;Dehairs et al, 2000;Lamb et al, 2006) suggest that the primary production within the frontal zones is supported by the upwelling of subsurface nutrients. This is because the mineralization of organic matter by heterotrophic activity in the water column releases 13 C-depleted DIC and 15 N-depleted dissolved inorganic nitrogen (DIN) due to the preferential release of 12 C and 14 N, respectively.…”

Section: Potential Sources Of Poc In the Frontal Regionmentioning

confidence: 99%

Particulate Organic Carbon Composition in Temperature Fronts of the Northeastern Arabian Sea during Winter

et al. 2018

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In order to understand the major sources of particulate organic carbon (POC) in the frontal zones and to examine their variability with space and time, a total of five temperature fronts of different ages was sampled in the northeastern Arabian Sea during winter. Compared to the nonfrontal regions, POC and chlorophyll‐a were higher within the coastal fronts, whereas chlorophyll‐a was lower within the open ocean front (T1). The variation of POC between coastal and open ocean fronts is attributed to the combined influence of variable vertical mixing, heterotrophic transformation and age of the front. Relatively depleted δ13CPOC and δ15NPN were observed within the fronts, suggesting that POC pool is contributed by in situ production supported by upwelling of nutrient‐rich water and zooplankton biomass. Elemental C:N ratios, POC:Chl‐a, δ13CPOC, and δ15NPN suggest that POC is mainly contributed from primary producers and heterotrophs in the study region. However, relative contributions from these two sources vary spatially from coastal to open ocean and with the age of the front. Stable Isotope Analysis in R (SIAR) model revealed that zooplankton biomass largely contributed to POC in the open ocean (60–80%) than phytoplankton (20–40%) and nearly equal contribution was observed in the coastal fronts (50–60% and 40–50%, respectively). This study, thus, demonstrates that dominant heterotrophy and autotrophy in the open ocean and coastal fronts and it is consistent with their biomasses. Predominant heterotrophy in the open ocean is attributed to deeper mixed layer resulting in upwelling of bacteria‐rich and phytoplankton‐poor water to surface leading to existence of microbial loop.

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Untitled

Cited by 71 publications

References 35 publications

Using isotope labeling to partition sources of CO₂ efflux in newly established mangrove seedlings

Using isotope labeling to partition sources of CO₂ efflux in newly established mangrove seedlings

The postmonsoon carbon biogeochemistry of estuaries under different levels of anthropogenic impacts

Particulate Organic Carbon Composition in Temperature Fronts of the Northeastern Arabian Sea during Winter

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Untitled

Cited by 71 publications

References 35 publications

Using isotope labeling to partition sources of CO2 efflux in newly established mangrove seedlings

Using isotope labeling to partition sources of CO2 efflux in newly established mangrove seedlings

The postmonsoon carbon biogeochemistry of estuaries under different levels of anthropogenic impacts

Particulate Organic Carbon Composition in Temperature Fronts of the Northeastern Arabian Sea during Winter

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Using isotope labeling to partition sources of CO₂ efflux in newly established mangrove seedlings

Using isotope labeling to partition sources of CO₂ efflux in newly established mangrove seedlings