Source and distribution of organic matter in sediments in the SE Brazilian continental shelf influenced by river discharges: An approach using stable isotopes and molecular markers

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) 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) 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 Ocean dominated Margins (RiOMar) environments.

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Impact of anthropogenic organic matter on bacterial community distribution in the continental shelf sediments of southeastern Arabian Sea

Marine Pollution Bulletin ◽

10.1016/j.marpolbul.2021.113227 ◽

2022 ◽

Vol 174 ◽

pp. 113227

Author(s):

P.V. Vipindas ◽

T. Jabir ◽

K.M. Mujeeb Rahiman ◽

T.V. Rehitha ◽

V. Sudheesh ◽

...

Keyword(s):

Organic Matter ◽

Bacterial Community ◽

Continental Shelf ◽

Arabian Sea ◽

Southeastern Arabian Sea ◽

Shelf Sediments

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The offshore environmental impact by Sarno river in Naples bay (South-West Italy)

Proceedings e report - Eighth International Symposium “Monitoring of Mediterranean Coastal Areas. Problems and Measurement Techniques” ◽

10.36253/978-88-5518-147-1.39 ◽

2020 ◽

pp. 392-401

Author(s):

Antonella Di Leo ◽

Santina Giandomenico ◽

Lucia Spada ◽

Nicola Cardellicchio ◽

Francesco Paolo Buonocunto ◽

...

Keyword(s):

Grain Size ◽

Organic Matter ◽

Organic Carbon ◽

Environmental Impact ◽

Continental Shelf ◽

Metal Content ◽

Spatial Trends ◽

Naples Bay ◽

Sorrento Peninsula ◽

Sarno River

The goal of this work has been to establish the influence of the Sarno river on the present sedimentation in the Naples bay continental shelf by evaluating organic matter contribution and pollution. Sediments samples were collected, by van Veen grab, in 71 stations located offshore the Sarno river between Vesuvian and Sorrento Peninsula coasts. The characteristics of the surface sediments were analysed to highlight spatial trends in the (i) granulometry (grain-size); (ii) total nitrogen, organic carbon and total phosphorus; (iii) metal content (Hg, Cd, Pb, As, Cr, Cu, Ni, Zn, Fe and Mn).

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