Dissolved organic matter in abyssal sediments: Core recovery artifacts

Hall, Per; Brunnegård, Jenny; Hulthe, Gustaf; Martin, William R.; Ståhl, Henrik; Tengberg, Anders

doi:10.4319/lo.2007.52.1.0019

Cited by 45 publications

(38 citation statements)

References 66 publications

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“…Maintenance respiration of all faunal compartments was defined as 0.01 d 21 at 20uC (Van Oevelen et al 2006) and is corrected with a temperature limitation factor (Tlim) based on the Q 10 formulation with a doubling of rates for every 10uC increase in temperature. Bottom-water temperature at PAP is 2.6uC (Hall et al 2007). Net growth efficiencies were constrained based on Van Oevelen et al (2006) and Hendriks (1999).…”

Section: Methodsmentioning

confidence: 99%

Carbon flows in the benthic food web of the Porcupine Abyssal Plain: The (un)importance of labile detritus in supporting microbial and faunal carbon demands

Oevelen

Soetaert

Heip

2012

Limnology & Oceanography

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Carbon flows in the benthic food web of the Porcupine Abyssal Plain (4850 m, northeast Atlantic) were reconstructed using linear inverse modeling based on mass balances of the various compartments, biomass data, carbon flux measurements, physiological constraints, and data from a previously published 13 C-phytodetritus pulse-chase experiment. Food web compartments consisted of bacteria, Foraminifera, three feeding types of nematodes and of macrofauna, and four feeding types of megafauna. Three lability classes of detritus were defined to clarify especially the possible role of labile detritus in this abyssal plain food web. Total detritus inputs to the food web were 0.56 mmol C m 22 d 21 , with only a minor (3.8%) contribution of labile detritus. The dominant pathway in the food web was dissolution of more refractory detritus, uptake by bacteria, and subsequent respiration (0.36 mmol C m 22 d 21 , 80% of the community respiration). Lower contributions to community respiration were found for surface-deposit-feeding macrobenthos (5.6%), Foraminifera (4.9%), predatory macrobenthos (3.8%), and other deposit-feeding macrobenthos (3.1%). Contributions by other benthic compartments were , 1%. 13 C-phytodetritus transfer data strongly constrained the carbon source for bacteria, Foraminifera, and the nematode and macrobenthic compartments. Surprisingly, labile detritus contributed , 5% of the total carbon requirements for all these compartments. Carbon sources were much less constrained for the megabenthic compartments because for these compartments no 13 C pulse-chase data were available. The carbon flow model evidently shows a limited role of labile detritus in the food web.

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Section: Methodsmentioning

confidence: 99%

Carbon flows in the benthic food web of the Porcupine Abyssal Plain: The (un)importance of labile detritus in supporting microbial and faunal carbon demands

Oevelen

Soetaert

Heip

2012

Limnology & Oceanography

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“…Hall et al, 2007). In the Whittard Canyon, stable-isotope labelling experiments were conducted in situ at ∼ 3500 m, minimizing sedimentrecovery artefacts upon macrofaunal and bacterial activity.…”

Section: Methodological Considerationsmentioning

confidence: 99%

“…Witte et al, 2003a, b). These in situ methods overcome the practical challenges of experimental work in deep-sea sediments, mitigating potential artefacts of changing pressure and temperature associated with shipboard and in vitro studies (Hall et al, 2007). At the ecosystem-scale, carbon processing is linked to the availability of organic nitrogen as a limiting nutrient (Vitousek and Howarth, 1991).…”

Section: Introductionmentioning

confidence: 99%

Sediment community responses to marine vs. terrigenous organic matter in a submarine canyon

et al. 2013

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Abstract. The Whittard Canyon is a branching submarine canyon on the Celtic continental margin, which may act as a conduit for sediment and organic matter (OM) transport from the European continental slope to the abyssal sea floor. In situ stable-isotope labelling experiments were conducted in the eastern and western branches of the Whittard Canyon, testing short-term (3-7 days) responses of sediment communities to deposition of nitrogen-rich marine (Thalassiosira weissflogii) and nitrogen-poor terrigenous (Triticum aestivum) phytodetritus. 13 C and 15 N labels were traced into faunal biomass and bulk sediments, and the 13 C label traced into bacterial polar lipid fatty acids (PLFAs). Isotopic labels penetrated to 5 cm sediment depth, with no differences between stations or experimental treatments (substrate or time). Macrofaunal assemblage structure differed between the eastern and western canyon branches. Following deposition of marine phytodetritus, no changes in macrofaunal feeding activity were observed between the eastern and western branches, with little change between 3 and 7 days. Macrofaunal C and N uptake was substantially lower following deposition of terrigenous phytodetritus with feeding activity governed by a strong N demand. Bacterial C uptake was greatest in the western branch of the Whittard Canyon, but feeding activity decreased between 3 and 7 days. Bacterial processing of marine and terrigenous OM were similar to the macrofauna in surficial (0-1 cm) sediments. However, in deeper sediments bacteria utilised greater proportions of terrigenous OM. Bacterial biomass decreased following phytodetritus deposition and was negatively correlated to macrofaunal feeding activity. Consequently, this study suggests that macrofaunal-bacterial interactions influence benthic C cycling in the Whittard Canyon, resulting in differential fates for marine and terrigenous OM.

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“…A similar approach was used in previous work (Martin and McCorkle, 1993;Lahajnar et al, 2005;Hall et al, 2007). Bottom water temperatures ranged from 3 to 5 • C, and the porosity of the surface sedi- and molecular weight (MW; at 25 • C in distilled water) reported by Burdige et al (1992), assuming a fixed average MW of 2500 daltons for both DON and DOC.…”

Section: Doc and Don Benthic Fluxesmentioning

confidence: 99%

Benthic fluxes of dissolved organic nitrogen in the lower St. Lawrence estuary and implications for selective organic matter degradation

et al. 2013

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Abstract. The distribution of dissolved organic nitrogen (DON) and carbon (DOC) in sediment porewaters was determined at nine locations along the St. Lawrence estuary and in the gulf of St. Lawrence. In a previous manuscript (Alkhatib et al., 2012a), we have shown that this study area is characterized by gradients in the sedimentary particulate organic matter (POM) reactivity, bottom water oxygen concentrations, and benthic respiration rates. Based on the porewater profiles, we estimated the benthic diffusive fluxes of DON and DOC in the same area. Our results show that DON fluxed out of the sediments at significant rates (110 to 430 µmol m −2 d −1 ). DON fluxes were positively correlated with sedimentary POM reactivity and varied inversely with sediment oxygen exposure time (OET), suggesting direct links between POM quality, aerobic remineralization and the release of DON to the water column. DON fluxes were on the order of 30 to 64 % of the total benthic inorganic fixed N loss due to denitrification, and often exceeded the diffusive nitrate fluxes into the sediments. Hence they represented a large fraction of the total benthic N exchange, a result that is particularly important in light of the fact that DON fluxes are usually not accounted for in estuarine and coastal zone nutrient budgets. In contrast to DON, DOC fluxes out of the sediments did not show any significant spatial variation along the Laurentian Channel (LC) between the estuary and the gulf (2100 ± 100 µmol m −2 d −1 ). The molar C / N ratio of dissolved organic matter (DOM) in porewater and the overlying bottom water varied significantly along the transect, with lowest C / N in the lower estuary (5-6) and highest C / N (> 10) in the gulf. Large differences between the C / N ratios of porewater DOM and POM are mainly attributed to a combination of selective POM hydrolysis and elemental fractionation during subsequent DOM mineralization, but selective adsorption of DOM to mineral phases could not be excluded as a potential C / N fractionating process. The extent of this C-versus N-element partitioning seems to be linked to POM reactivity and redox conditions in the sediment porewaters. Our results thus highlight the variable effects selective organic matter (OM) preservation can have on bulk sedimentary C / N ratios, decoupling the primary source C / N signatures from those in sedimentary paleoenvironmental archives. Our study further underscores that the role of estuarine sediments as efficient sinks of bioavailable nitrogen is strongly influenced by the release of DON during early diagenetic reactions, and that DON fluxes from continental margin sediments represent an important internal source of N to the ocean.

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Dissolved organic matter in abyssal sediments: Core recovery artifacts

Cited by 45 publications

References 66 publications

Carbon flows in the benthic food web of the Porcupine Abyssal Plain: The (un)importance of labile detritus in supporting microbial and faunal carbon demands

Carbon flows in the benthic food web of the Porcupine Abyssal Plain: The (un)importance of labile detritus in supporting microbial and faunal carbon demands

Sediment community responses to marine vs. terrigenous organic matter in a submarine canyon

Benthic fluxes of dissolved organic nitrogen in the lower St. Lawrence estuary and implications for selective organic matter degradation

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