Organic Carbon Cycling and Transformation

Martin, Patrick; Bianchi, Thomas S.

doi:10.1016/b978-0-323-90798-9.00061-5

Cited by 4 publications

(3 citation statements)

References 767 publications

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“…In contrast, Aarnos et al (2012) found that the annual DOC photomineralization exceeds the riverine tDOC supply in the Baltic Sea and concluded that photomineralization is likely an important tDOC sink, although this study could not distinguish photomineralization of tDOC from that of autochthonous DOC. However, for most shelf sea regions we have little understanding of in situ tDOC photomineralization, which limits our ability to predict how anthropogenically driven changes to tDOC fluxes might impact coastal ecosystems (Ciais et al, 2013;Martin & Bianchi, 2023). Although modeling frameworks are being developed to represent the biogeochemistry of tDOC across the land-ocean aquatic continuum (Anderson et al, 2019;Polimene et al, 2022) and to integrate coastal carbon cycling processes in global ocean models (Mathis et al, 2022), appropriate rate constants for tDOC remineralization are still very poorly constrained.…”

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confidence: 99%

Quantifying Photodegradation of Peatland‐Derived Dissolved Organic Carbon in the Coastal Ocean of Southeast Asia

Zhou,

Müller,

Cherukuru

et al. 2023

JGR Oceans

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Southeast Asia's peatlands are a globally significant source of terrigenous dissolved organic carbon (tDOC) to the ocean, and field observations show that this tDOC is extensively remineralized within the shelf sea. Yet the processes that drive this remineralization remain unclear. Here, we combined incubation experiments and model simulations to quantify the rate and extent of photodegradation of tDOC in the Sunda Shelf Sea. During laboratory photodegradation experiments, 26%–74% of the peatland tDOC was photomineralized, but realistic in situ rates of photodegradation have not yet been estimated in this region. Based on spectrally resolved apparent quantum yields for tDOC remineralization calculated from experiments, modeled in situ solar irradiance, and measured in‐water inherent optical properties, we simulated peatland tDOC photomineralization for two coastal regions of the Sunda Shelf Sea. These simulations show that sunlight can directly remineralize 25 ± 9% of the tDOC input over its maximum 2‐year residence time in the Sunda Shelf Sea, accounting for 38% of the total tDOC remineralization. We also found that photobleaching can remove 54 ± 4% of colored dissolved organic matter over this time‐scale. We further derived a simplified photochemical decay constant ∅ref of 0.016 day−1 for Southeast Asia's peatland‐derived tDOC, which can be used to parameterize the recently proposed UniDOM model. We conclude that direct photodegradation may be a greater sink for tDOC in Southeast Asia's coastal ocean compared to higher latitudes, although it is insufficient to account for the total tDOC remineralization observed in the Sunda Shelf Sea.

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confidence: 99%

Quantifying Photodegradation of Peatland‐Derived Dissolved Organic Carbon in the Coastal Ocean of Southeast Asia

Zhou,

Müller,

Cherukuru

et al. 2023

JGR Oceans

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“…The biogeochemical functioning of estuaries and coastal waters is greatly influenced by terrestrial inputs as well as by biogeochemical transformations taking place along the land-ocean aquatic continuum (Bianchi and Morrison, 2023;Martin and Bianchi, 2023;Voss et al 2011). These fluxes and biogeochemical processes can be greatly affected by increasing coastal development, changing land-use practices, and climatic changes.…”

Section: Introduction 30mentioning

confidence: 99%

“…Estuaries also receive large fluxes of terrestrial organic carbon, partly as a result of human activities (Regnier et al, 2022;Martin and Bianchi, 2023). Tropical rivers are particularly significant sources of dissolved organic carbon (DOC) to the ocean (Dai et al, 2012), with mangroves thought to be a disproportionally large source of terrigenous DOC (Dittmar et al, 2006).…”

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Distribution of nutrients and dissolved organic matter in a eutrophic equatorial estuary, the Johor River and East Johor Strait

Cheong,

Annammala,

Yong

et al. 2023

Preprint

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Abstract. Estuaries have strong physicochemical gradients that lead to complex variability and often high rates of biogeochemical processes. The biogeochemistry of many estuaries is also increasingly impacted by human activities. Yet our understanding of estuarine biogeochemistry remains skewed towards temperate systems in the northern hemisphere, with far less research from tropical estuaries. This study examined seasonal and spatial variability in dissolved organic matter (DOM) and nutrient biogeochemistry along a partly eutrophic, mixed agricultural/urban estuary system in Southeast Asia, the Johor River and the East Johor Strait. Dissolved organic carbon (DOC) and chromophoric DOM (CDOM) properties showed non-conservative mixing, indicating significant DOM inputs along the estuary. The CDOM spectral slopes and CDOM:DOC ratios suggest that these inputs are dominated by terrigenous, soil-derived DOM along the Johor River, but that phytoplankton production and microbial recycling are more important DOM sources in the Johor Strait. Nitrate consistently showed conservative mixing, while nitrite concentrations peaked at intermediate salinities of 10–25. Ammonia decreased with salinity in the Johor River. In the Johor Strait, however, ammonia increased up to 50 µmol l-1, often dominating the dissolved inorganic nitrogen (DIN) pool. Phosphate was low (<0.5 µmol l-1) throughout the Johor River, but increased in the Johor Strait, where DIN:phosphate ratios were typically at or above 16:1. This suggests that phytoplankton in the Johor Strait may sometimes experience phosphorus limitation. Moreover, internal recycling is likely important for maintaining high nutrient concentrations in the Johor Strait.

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