Pulsed, cross‐shelf export of terrigenous dissolved organic carbon to the Gulf of Mexico

Fichot, Cédric G.; Lohrenz, Steven E.; Benner, Ronald

doi:10.1002/2013jc009424

Cited by 61 publications

(66 citation statements)

References 63 publications

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“…Nevertheless, it should be kept in mind that DOM optical properties during estuarine mixing might also change without changes (losses or gains) in their quantities. In addition, DOM optical properties can be affected not only by DOM concentration and composition but also by the interactions of DOM with trace metals (Sharpless & Blough, ; Xu et al, ; Yan et al, ), and estuarine mixing zones are known for supporting losses of both trace elements and DOM (Chupakova et al, ; Fichot et al, ; Hedges et al, ; Opsahl & Benner, ). The different environmental factors in different same‐salinity patches, such as pH, may also influence the DOM abundance and chemical properties (Xu et al, ) and, consequently, have a potential influence on the fate of DOM during the estuarine mixing and offshore transport.…”

Section: Discussionmentioning

confidence: 99%

“…Dissolved organic matter (DOM) is heterogeneous and its changes in composition and mixing behavior at the land‐ocean interface are complex and dynamic (D'Sa et al, ; Fichot et al, ; Giraud et al, ; Seitzinger et al, ; Singh et al, ; Xu & Guo, ). Within the bulk DOM pool, individual organic components or molecular‐sized fractions have been shown to have different extents of removal or addition during estuarine mixing (Wang et al, ; Zhou et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Elucidating the Hidden Nonconservative Behavior of DOM in Large River‐Dominated Estuarine and Coastal Environments

Gao

Zong

et al. 2019

JGR Oceans

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Understanding the mixing behavior and biogeochemical cycling of heterogeneous dissolved organic matter (DOM) at the land‐ocean interface has been a major challenge, especially in large river‐dominated estuarine and coastal environments with multiple and complex end‐members of riverwater and seawater. Significant correlations and thus an “apparent” conservative behavior are generally observed for the bulk DOM when plotting concentration‐salinity relationships, but the relatively small deviations from the apparent conservative behavior are difficult to be quantified. In July 2016, the flood in the Changjiang River basin caused the Changjiang Diluted Water extended widely to the western East China Sea, making it a natural laboratory to examine the river‐sea mixing behavior of riverine DOM and other optical properties. Here a new biogeochemical approach was established to elucidate their hidden nonconservative behavior in the study area. Comparisons in the bulk dissolved organic carbon and the three chromophoric DOM properties among 13 pairs of same‐salinity patches (with similar salinities but quite different distances from the river mouth) revealed that the East China Sea shelf was a significant sink for all the three chromophoric DOM properties. The Changjiang Diluted Water surface branches transporting southward tended to serve as a sink for the bulk dissolved organic carbon while the ones transporting northward were less a sink or even a source. The different removal extents of various biogeochemical constituents can also be calculated from the same‐salinity patch comparisons. Our results obtained by the new approach provide detailed magnitudes of sink or source for different DOM properties and their in situ removal/production extents, giving new insights into biogeochemical processes in large river‐dominated estuarine and coastal environments.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Elucidating the Hidden Nonconservative Behavior of DOM in Large River‐Dominated Estuarine and Coastal Environments

Gao

Zong

et al. 2019

JGR Oceans

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“…Indeed, estimates from in situ measurements, satellite observations, and numerical models have been shown to be influenced by these physical factors [ Ortner et al . ; Ohlmann and Niiler , ; Hu et al ., ; D'Sa et al ., ; Huang et al ., ; Fichot et al ., ; Le et al ., ; Schiller et al ., ; Zhang et al ., ]. Water circulation on the inner shelf is primarily driven by wind [ Cochrane and Kelly , ; Nowlin et al ., ].…”

Section: Discussionmentioning

confidence: 99%

Satellite observation of particulate organic carbon dynamics on the Louisiana continental shelf

Lehrter

et al. 2017

JGR Oceans

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Particulate organic carbon (POC) plays an important role in coastal carbon cycling and the formation of hypoxia. Yet, coastal POC dynamics are often poorly understood due to a lack of long‐term POC observations and the complexity of coastal hydrodynamic and biogeochemical processes that influence POC sources and sinks. Using field observations and satellite ocean color products, we developed a new multiple regression algorithm to estimate POC on the Louisiana Continental Shelf (LCS) from satellite observations. The algorithm had reliable performance with mean relative error (MRE) of ∼40% and root mean square error (RMSE) of ∼50% for MODIS and SeaWiFS images for POC ranging between ∼80 and ∼1200 mg m−3, and showed similar performance for a large estuary (Mobile Bay). Substantial spatiotemporal variability in the satellite‐derived POC was observed on the LCS, with high POC found on the inner shelf (<10 m depth) and lower POC on the middle (10–50 m depth) and outer shelf (50–200 m depth), and with high POC found in winter (January–March) and lower POC in summer to fall (August–October). Correlation analysis between long‐term POC time series and several potential influencing factors indicated that river discharge played a dominant role in POC dynamics on the LCS, while wind and surface currents also affected POC spatial patterns on short time scales. This study adds another example where satellite data with carefully developed algorithms can greatly increase the spatial and temporal observations of important biogeochemical variables on continental shelf and estuaries.

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“…The semi‐labile nature of mDOC acc facilitates its transport by eddies and wind‐driven currents. Easterly winds are usually prevalent in all seasons but summer, when wind direction shifts to the south and triggers Ekman transport of shelf waters eastward toward the shelf break, promoting cross‐shelf transport of shelf waters (Morey et al ; Fichot et al ). An impressive cross‐shelf export of mDOC acc occurred during summer 2009.…”

Section: Discussionmentioning

confidence: 99%

Biological hot spots and the accumulation of marine dissolved organic matter in a highly productive ocean margin

Shen

Fichot

Liang

et al. 2016

Limnology & Oceanography

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Concentrations of dissolved organic carbon (DOC) and major biochemicals (amino acids and carbohydrates) were measured during five cruises (2009)(2010) to the Louisiana margin in the northern Gulf of Mexico. Concentrations of amino acids and carbohydrates were elevated at mid-salinities and were indicative of plankton production of dissolved organic matter (DOM) in surface waters. Hot spots of two compositionally distinct types of labile DOM were identified based on the relative abundances of amino acids and carbohydrates. Amino acidrich hot spots occurred sporadically in regions of high phytoplankton biomass and were mostly observed between dusk and dawn, reflecting a grazing source. In contrast, carbohydrate-rich hot spots were more widespread and were often found in nutrient-poor waters, indicating the production of carbon-rich DOM associated with nutrient limitation. Major biochemical indicators and bioassay experiments indicated labile DOM comprised a relatively small fraction of the DOC. Most DOM was degraded and had a semi-labile nature. Substantial accumulations of marine (plankton-derived) DOC were observed in surface waters, particularly at mid-salinities during the summer. Microbial alteration of marine DOC and nutrient limitation of microbial utilization of carbon-rich DOM appeared largely responsible for the accumulation of DOC. The reservoir of accumulated marine DOC in the shelf surface mixed layer ranged from 0.11 Tg C to 0.23 Tg C, with the lowest and highest values occurring during winter and summer. Substantial cross-shelf export of semi-labile marine DOM occurred during the summer and provided a major carbon and energy subsidy to microbial food webs in offshore waters.

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Pulsed, cross‐shelf export of terrigenous dissolved organic carbon to the Gulf of Mexico

Cited by 61 publications

References 63 publications

Elucidating the Hidden Nonconservative Behavior of DOM in Large River‐Dominated Estuarine and Coastal Environments

Elucidating the Hidden Nonconservative Behavior of DOM in Large River‐Dominated Estuarine and Coastal Environments

Satellite observation of particulate organic carbon dynamics on the Louisiana continental shelf

Biological hot spots and the accumulation of marine dissolved organic matter in a highly productive ocean margin

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