Intertidal foraminifera and stable isotope geochemistry from world's largest mangrove, Sundarbans: Assessing a multiproxy approach for studying changes in sea-level

Sen, Areen; Bhadury, Punyasloke

doi:10.1016/j.ecss.2017.05.010

Cited by 12 publications

(3 citation statements)

References 45 publications

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“…The δ 13 C values collected as part of the radiocarbon measurements indicate that both bulk and organic concentrate samples are likely sampling a mangrove organic carbon pool (Figure 7), as values are consistent with those measured in other mangrove sediments (Kemp et al, 2019; Khan et al, 2019; McKee et al, 2002; Sen and Bhadury, 2017). Fine root material (of the size 10–63 µm) and/or degraded root material may still be present in relatively large amounts in the organic concentrates at Grand Anse.…”

Section: Discussionsupporting

confidence: 74%

Reliability of mangrove radiocarbon chronologies: A case study from Mahé, Seychelles

et al. 2022

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Mangrove sediments are valuable archives of paleoenvironmental and relative sea-level changes. The most widely applied method to obtaining chronologies of past changes in mangrove sediments is radiocarbon dating, because mangroves produce large amounts of organic matter in situ. However, there are many challenges to obtaining reliable radiocarbon chronologies because bioturbation processes from roots and crabs can rework mangrove sediments, resulting in ages that are not in stratigraphic order. Previous studies have suggested that methods that isolate specific sediment size fractions may yield ages closer to the age of the paleo depositional surface by removing younger carbon contamination from fine roots. This study examines which sample types are more likely to yield reliable radiocarbon ages using shallow cores from a mangrove environment on Mahé, Seychelles, in the Indian Ocean. We compare radiocarbon ages from bulk sediment, sieved organic concentrates and above-ground macrofossils collected from the same stratigraphic depths. Bulk sediment and organic concentrate ages are comparable, which suggests that methods that separate out different size fractions do not sample different carbon sources in Seychelles mangrove cores. Identifiable above-ground macrofossils are rare in Seychelles mangrove cores, but yield older radiocarbon ages than comparable bulk sediment or organic concentrate ages. We suggest that in Seychelles, limited accommodation space over the late-Holocene, determined by relatively stable relative sea levels, has resulted in poor preservation of above-ground macrofossils for radiocarbon dating due to low rates of burial and sediment accretion. Low accretion rates have likely resulted in a mangrove sediment sequence that is highly bioturbated and degraded, meaning both bulk sediment and organic concentrate samples are impacted by contamination from younger roots. We argue that the availability of accommodation space and sediment composition controls the reliability of mangrove radiocarbon chronologies, which has implications for sample choice and site selection.

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Section: Discussionsupporting

confidence: 74%

Reliability of mangrove radiocarbon chronologies: A case study from Mahé, Seychelles

et al. 2022

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“…In addition, the 13 C‐depleted DIC (−10‰ to −16‰) accumulates in the recharge zone, which was generally consistent with plant distribution (Figure 1c) and salinity (Figure 3) in the study area. This further proves that the recharge zone has received vertical infiltration of plant organic matter, because the 13 C range of C4 plants is approximately −12–16‰ in the mangrove intertidal zone (Sen & Bhadury, 2017). The deep mangrove groundwater had higher FI, HIX, and BIX values than shallow groundwater ( p < 0.05; Table 1), suggesting new microbially derived humic‐like DOM in the deeper aquifer (Figure 5 and Figure S5 in Supporting Information ).…”

Section: Discussionmentioning

confidence: 70%

Tidal Pumping Controls Dissolved Organic Matter Properties and Outwelling From Mangrove Groundwater to Coastal Water

Xiao

Zhang

Santos

et al. 2023

Water Resources Research

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Dissolved organic matter (DOM) in highly productive intertidal mangroves is an important carbon and nutrient source to the coastal ocean. In highly dynamic mangrove intertidal systems, both tidal pumping or geochemical factors can control DOM characteristics. The influence of groundwater flow on DOM properties and fluxes remains poorly understood. Here, we compared the concentrations, sources, and spectroscopic characteristics of DOM across a recharge‐discharge gradient. We used a three‐dimensional array sampling strategy to reduce spatial biases, groundwater monitoring to quantify tidally driven exchange, and spectrofluoroscopy to quantify DOM fluorescent components. The results showed that tidal hydrology played the key role driving groundwater DOM properties in both horizontal (i.e., from the mangrove to the sea) and vertical directions. Due to the high spatial heterogeneity of dissolved inorganic (DIC) and organic (DOC) carbon concentrations in mangrove groundwater, carbon outwelling showed a high degree of variability at the intertidal scale (54.8–234.8 μmol m−2 d−1 for DIC and 2.5–12.4 μmol m−2 d−1 for DOC). The contribution of terrestrial DOM gradually decreased toward the ocean, but the microbial contributions for recently produced autochthonous DOM increased. Deep groundwater received less terrestrial DOM and experienced anaerobic microbial mineralization, resulting in lower organic carbon than shallow groundwater. Greater variations in spectroscopic characteristics were found in shallow groundwater than in deep groundwater. Overall, tidally driven surface water‐groundwater interactions control the variability in DOM properties and how DOM contributes to carbon budgets and sequestration in mangrove groundwater.

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“…Holocene paleoenvironments have been comprehensively reconstructed using a multiproxy approach (e.g., Barnett et al, 2017;Di Rita et al, 2011;Sen and Bhadury, 2017).…”

Section: Introductionmentioning

confidence: 99%

Early and late Holocene paleoenvironmental reconstruction of the Pearl River estuary, South China Sea using foraminiferal assemblages and stable carbon isotopes

Chen

Wang

Khan

et al. 2019

Estuarine, Coastal and Shelf Science

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Intertidal foraminifera and stable isotope geochemistry from world's largest mangrove, Sundarbans: Assessing a multiproxy approach for studying changes in sea-level

Cited by 12 publications

References 45 publications

Reliability of mangrove radiocarbon chronologies: A case study from Mahé, Seychelles

Reliability of mangrove radiocarbon chronologies: A case study from Mahé, Seychelles

Tidal Pumping Controls Dissolved Organic Matter Properties and Outwelling From Mangrove Groundwater to Coastal Water

Early and late Holocene paleoenvironmental reconstruction of the Pearl River estuary, South China Sea using foraminiferal assemblages and stable carbon isotopes

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