Importance of humic substances for carbon and nitrogen transport into southeastern United States estuaries

Alberts, James J.; Takács, Monika

doi:10.1016/s0146-6380(99)00024-8

Cited by 50 publications

(25 citation statements)

References 11 publications

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“…This concentration was selected as it is consistent with OC concentrations in Georgia coastal estuarine systems from which the microbial community inoculum was derived (400-3000 µMC) (Alberts and Takács, 1999). BSA was selected as a representative protein source due to its well-defined chemcial character and because it has frequently been used as a model protein in aquatic biogeochemical research.…”

Section: Microcosm Incubationsmentioning

confidence: 99%

Evidence for the Priming Effect in a Planktonic Estuarine Microbial Community

2016

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The "priming effect," in which addition of labile substances changes the remineralization rate of recalcitrant organic matter, has been intensively studied in soils, but is less well-documented in aquatic systems. We investigated the extent to which additions of nutrients or labile organic carbon could influence remineralization rates of 14 C-labeled, microbially-degraded, phytoplankton-derived organic matter (OM) in microcosms inoculated with microbial communities drawn from Grove Creek Estuary in coastal Georgia, USA. We found that amendment with labile protein plus phosphorus increased remineralization rates of degraded, phytoplankton-derived OM by up to 100%, whereas acetate slightly decreased remineralization rates relative to an unamended control. Addition of ammonium and phosphate induced a smaller effect, whereas addition of ammonium alone had no effect. Counterintuitively, alkaline phosphatase activities increased in response to the addition of protein under P-replete conditions, indicating that production of enzymes unrelated to the labile priming compound may be a mechanism for the priming effect. The observed priming effect was transient: after 36 days of incubation roughly the same quantity of organic carbon had been mineralized in all treatments including no-addition controls. This timescale is on the order of the typical hydrologic residence times of well-flushed estuaries suggesting that priming in estuaries has the potential to influence whether OC is remineralized in situ or exported to the coastal ocean.

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Section: Microcosm Incubationsmentioning

confidence: 99%

Evidence for the Priming Effect in a Planktonic Estuarine Microbial Community

2016

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“…As a result, the input of terrestrial DIC plays a critical role in elevating CO 2 concentrations in continental shelf waters. Terrestrial sources increase nearshore pCO 2 directly through input of inorganic carbon from rivers (Cai and Wang, 1998;Cai et al, 1999;Jiang et al, 2008b) and salt marshes (Wang and Cai, 2004), and indirectly by input of organic carbon (Moran et al, 1991;Alberts and Takács, 1999;DeAlteris, 2007) that is later remineralized to varying extents on the shelf as part of the shelf NEM.…”

Section: Impact Of Terrestrial Carbon On Continental Shelf Comentioning

confidence: 99%

Influence of terrestrial inputs on continental shelf carbon dioxide

et al. 2013

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Abstract. The US South Atlantic Bight (SAB) is a low-latitude shallow continental shelf bordered landward by abundant salt marshes and rivers. Based on previously published data on sea surface partial pressure of carbon dioxide (pCO2) and new dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) data, a model analysis is presented to identify and quantify the contributions of various terrestrial carbon inputs on SAB sea surface pCO2. After removal of pCO2 variations due to annual temperature variability and air–sea gas exchange from the in situ pCO2, the temperature- and gas-exchange-corrected pCO2 (TG-corrected pCO2) is derived. Contributions from rivers, salt marshes, and the continental shelf to the TG-corrected pCO2 are then calculated. Our findings demonstrate that although additions of CO2 from within shelf waters (i.e., ΔpCO2(shelf)) were the greatest of the three components and underwent the largest seasonal changes, ΔpCO2(shelf) showed smaller onshore–offshore gradients than rivers and marshes. In contrast, CO2 contributions from river (ΔpCO2(river)) and salt marsh (ΔpCO2(marsh)) components were greatest closest to the coast and decreased with distance offshore. In addition, the magnitude of ΔpCO2(marsh) was about three-fold greater than ΔpCO2(river). Our findings also revealed that decomposition of terrestrial organic carbon was an important factor regulating the seasonal pattern of pCO2 on the inner shelf. Despite large uncertainties, this study demonstrates the importance of terrestrial inputs, in particular those from coastal wetlands, on coastal ocean CO2 distributions.

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“…Using Cai's (2011) values for comparison, photochemical production of inorganic carbon products in this system could contribute between 6.4 % to 7.3 % of the total inorganic carbon signal annually. Based on numbers from Hopkinson (1988), Alberts and Takacs (1999); Moran et al (1999), the total DOC input to the entire South Atlantic Bight annually is 5.1×10 12 g C yr −1 (Cai, 2011), with the majority (∼86 %) of this carbon being marsh-derived DOC. A significant portion of this organic carbon is transformed, presumably by heterotrophic bacteria, to inorganic carbon during its transit from marsh and river to the open ocean (Cauwet, 2002).…”

Section: Contribution Of Photochemistry To the Coastal Systemmentioning

confidence: 99%

Variability of carbon monoxide and carbon dioxide apparent quantum yield spectra in three coastal estuaries of the South Atlantic Bight

Reader

Miller

2012

Biogeosciences

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Abstract. The photochemical oxidation of oceanic dissolved organic carbon (DOC) to carbon monoxide (CO) and carbon dioxide (CO 2 ) has been estimated to be a significant process with global photoproduction transforming petagrams of DOC to inorganic carbon annually. To further quantify the importance of these two photoproducts in coastal DOC cycling, 38 paired apparent quantum yield (AQY) spectra for CO and CO 2 were determined at three locations along the coast of Georgia, USA over the course of one year. The AQY spectra for CO 2 were considerably more varied than CO. CO AQY spectra exhibited a seasonal shift in spectrally integrated (260 nm-490 nm) AQY from higher efficiencies in the autumn to less efficient photoproduction in the summer. While full-spectrum photoproduction rates for both products showed positive correlation with pre-irradiation UV-B sample absorption (i.e. chromophoric dissolved organic matter, CDOM) as expected, we found no correlation between AQY and CDOM for either product at any site. Molecular size, approximated with pre-irradiation spectral slope coefficients, and aromatic content, approximated by the specific ultraviolet absorption of the pre-irradiated samples, were also not correlated with AQY in either data set. The ratios of CO 2 to CO photoproduction determined using both an AQY model and direct production comparisons were 23.2 ± 12.5 and 22.5 ± 9.0, respectively. Combined, both products represent a loss of 2.9 to 3.2 % of the DOC delivered to the estuaries and inner shelf of the South Atlantic Bight yearly, and 6.4 to 7.3 % of the total annual degassing of CO 2 to the atmosphere. This result suggests that direct photochemical production of CO and CO 2 is a small, yet significant contributor to both DOC cycling and CO 2 gas exchange in this coastal system.

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Importance of humic substances for carbon and nitrogen transport into southeastern United States estuaries

Cited by 50 publications

References 11 publications

Evidence for the Priming Effect in a Planktonic Estuarine Microbial Community

Evidence for the Priming Effect in a Planktonic Estuarine Microbial Community

Influence of terrestrial inputs on continental shelf carbon dioxide

Variability of carbon monoxide and carbon dioxide apparent quantum yield spectra in three coastal estuaries of the South Atlantic Bight

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