Towards a classification of organic enrichment in marine sediments based on biogeochemical indicators

Hargrave, B. T.; Holmer, Marianne; Newcombe, Curtis L.

doi:10.1016/j.marpolbul.2008.02.006

Cited by 220 publications

(207 citation statements)

References 96 publications

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“…This is also visible in our sulfate profiles: the most significant consumption (and likely the highest sulfate reduction rates) occurs in stations with maximal accumulation rate. Hargrave et al (2008) also evidenced an enhancement of microbial sulfate reduction under conditions of high organic matter sedimentation and the progressive formation of suboxic-anoxic conditions. Our results thus suggest that the amount of POC vertically exported, and reaching the coastal seafloor, directly controls the anaerobic mineralization activity and carbon preservation of oceanic sediments (Henrichs and Reeburgh, 1987;Canfield, 1994).…”

Section: Mineralization Processesmentioning

confidence: 90%

“…In the case of the highly reduced sediments of the Rhône River prodelta, this retention is thus likely to be very efficient with values higher than 77 %. Hedges and Keil (1995) already pointed out that the introduction of greater amounts of labile marine OM could drive the redox environments of deltaic and slope sediments on to sulfate reduction, halting then the iron and manganese-based degradation when these metals are precipitated as insoluble, reduced sulfides. Our results suggest that the terrestrial OM delivered by the Rhône River, constituted of a reactive fraction, also pushes the diagenetic system towards the burial of major reduced products.…”

Section: Insights On Iron and Sulfur Cyclesmentioning

confidence: 99%

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Modeling biogeochemical processes in sediments from the Rhône River prodelta area (NW Mediterranean Sea)

et al. 2011

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Abstract. In situ oxygen microprofiles, sediment organic carbon content, and pore-water concentrations of nitrate, ammonium, iron, manganese, and sulfides obtained in sediments from the Rhône River prodelta and its adjacent continental shelf were used to constrain a numerical diagenetic model. Results showed that (1) the organic matter from the Rhône River is composed of a fraction of fresh material associated to high first-order degradation rate constants (11-33 yr −1 ); (2) the burial efficiency (burial/input ratio) in the Rhône prodelta (within 3 km of the river outlet) can be up to 80 %, and decreases to ∼20 % on the adjacent continental shelf 10-15 km further offshore; (3) there is a large contribution of anoxic processes to total mineralization in sediments near the river mouth, certainly due to large inputs of fresh organic material combined with high sedimentation rates; (4) diagenetic by-products originally produced during anoxic organic matter mineralization are almost entirely precipitated (> 97 %) and buried in the sediment, which leads to (5) a low contribution of the re-oxidation of reduced products to total oxygen consumption. Consequently, total carbon mineralization rates as based on oxygen consumption rates and using Redfield stoichiometry can be largely underestimated in such River-dominated Ocean Margins (RiOMar) environments.

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Section: Mineralization Processesmentioning

confidence: 90%

Section: Insights On Iron and Sulfur Cyclesmentioning

confidence: 99%

Modeling biogeochemical processes in sediments from the Rhône River prodelta area (NW Mediterranean Sea)

et al. 2011

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“…Yet, the term "organic 320 enrichment" is often used in a relative or conceptual manner, while there is an increasing need for a quantitative and broadly applicable classification of organic enrichment in marine sediments in order to assess changes in the benthos (Hargrave et al, 2008). This study now provides a quantitative framework for evaluating the biological significance of "organic enrichment" in Mediterranean coastal lagoons, as related to an increasing risk of benthic impact.…”

Section: Organic Enrichment Toc Thresholds and Data Uncertaintymentioning

confidence: 99%

Animal-sediment relationships: Evaluating the ‘Pearson–Rosenberg paradigm’ in Mediterranean coastal lagoons

Magni

Tagliapietra

Lardicci

et al. 2009

Marine Pollution Bulletin

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In the present study, we investigated the applicability of the Pearson-Rosenberg (P-R) conceptual model describing a generalized pattern of response of benthic communities in relation to organic 25 enrichment to a specific typology of marine systems, i.e. coastal lagoons. The study was performed with independent matching data on the structure of macrobenthic communities and total organic carbon (TOC) content of sediments obtained from 349 stations representing three of the most ecologically and economically relevant coastal lagoons in the Mediterranean Sea, i.e. the lagoons of Cabras, Orbetello, and Venice (Italy). Consistent with P-R model predictions, we 30 found two different peaks in benthic diversity and abundance at low (> 2.5-5 mg g -1 ) and high (> 25-30 mg g -1 ) TOC ranges, respectively. We identified TOC thresholds indicating that risks of reduced benthic diversity from organic loading and other associated stressors in sediments should be relatively low at TOC values < about 10 mg g -1 , high at TOC values > about 28 mg g -1 , andintermediate at values in-between. Predictive ability within these ranges was high based on 35 results of re-sampling simulation. Our results validate and support a prior independent study that identified similar TOC thresholds for assessing risks of benthic impacts in samples from seven coastal regions of the world. While not a measure of causality, it is anticipated that these TOC thresholds should serve as a general screening-level indicator for evaluating the likelihood of reduced sediment quality and associated bioeffects in such eutrophic systems of the 40 Mediterranean Sea, which also are exposed to a variety of stressors from multiple human uses.

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“…Some studies have focused on predicting the reach of aquaculture particulate wastes by means of particulate waste dispersion modelling, while others have directly assessed the benthic impact of aquaculture by studying chemical and biological changes in the seabed. However, many of the studies carried out to date, with some exceptions (e. g. Pusceddu et al 2007, Díaz-Almela et al 2008, Kutti et al 2008, Hargrave et al 2008, cannot be considered integrative since they study isolated processes (i.e. either the benthic impact or the aquaculture particulate wastes in the water column) and make no attempt to merge them.…”

Section: Introductionmentioning

confidence: 99%

Relationship between sedimentation rates and benthic impact on Maërl beds derived from fish farming in the Mediterranean

Sanz‐Lázaro

Belando

Marín-Guirao

et al. 2011

Marine Environmental Research

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The aim of this work was to study the dispersion of particulate wastes derived from marine fish farming and correlate the data with the impact on the seabed. Carbon and nutrients were correlated with the physico-chemical parameters of the sediment and the benthic community structure. The sedimentation rates in the benthic system were 1.09, 0.09 and 0.13 g m Therefore, the level of fish farm impact on the benthic community might be underestimated if it is assessed by merely taking into account data obtained from waste dispersion rates. The benthic habitat beneath the fish farm, Maërl bed, was seen to be very sensitive to aquaculture impact compared with other unvegetated benthic habitats, with an estimated POC-carrying capacity to maintain current diversity of 0.087 g C m -2 day -1 (only 36% greater than the basal POC input). Environmental protection agencies should define different aquaculture waste load thresholds for different benthic communities affected by finfish farming, according to their particular degree of sensitivity, in order to maintain natural ecosystem functions.

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Towards a classification of organic enrichment in marine sediments based on biogeochemical indicators

Cited by 220 publications

References 96 publications

Modeling biogeochemical processes in sediments from the Rhône River prodelta area (NW Mediterranean Sea)

Modeling biogeochemical processes in sediments from the Rhône River prodelta area (NW Mediterranean Sea)

Animal-sediment relationships: Evaluating the ‘Pearson–Rosenberg paradigm’ in Mediterranean coastal lagoons

Relationship between sedimentation rates and benthic impact on Maërl beds derived from fish farming in the Mediterranean

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