Dispersal and deposition of suspended sediment on the shelf off the Tagus and Sado estuaries, S.W. Portugal

Jouanneau, Jean-Marie; Garcia, Catarina; Oliveira, Anabela; Rodrigues, Armanda; Dias, João Alveirinho; Weber, O.

doi:10.1016/s0079-6611(98)00036-6

Cited by 79 publications

(73 citation statements)

References 9 publications

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“…8g). Jouanneau et al (1998), who studied the OC contents in marine sediments of this area in more detail, also showed that the OC content was low close to the river estuary. This is because the OC content was closely related to the sediment grain size, and the average grain size of the surface sediments was larger close to the river estuary.…”

Section: Characteristics Of the Bulk Organic Mattermentioning

confidence: 85%

“…2 km width). An estimated amount of 0.4-1 million tons of suspended material is exported to the adjacent continental shelf annually (Jouanneau et al, 1998). The suspended matter carried by the Tagus River outflow forms a nepheloid layer that is subject to seasonal variations.…”

Section: Study Areamentioning

confidence: 99%

“…The suspended matter carried by the Tagus River outflow forms a nepheloid layer that is subject to seasonal variations. During summer the surface nepheloid layer is more pronounced and extends up to 14 km offshore, while during winter the bottom nepheloid layer is more pronounced and stretches over the shelf break (Jouanneau et al, 1998). This is related with the summer upwelling season (May to September) during which the Portugal Coastal Current (PCC) flows southward, induced by the northerly Portuguese trade winds blowing nearly parallel to the coast (e.g., Fiúza et al, 1982;Martins et al, 2002).…”

Section: Study Areamentioning

confidence: 99%

“…The inner shelf is characterized by sands representing the river delta front, with bottom currents strong enough to avoid the deposition of fine-grained particles (Paiva et al, 1997). The decrease of velocity, together with increasing water depth unaffected by waves and storms, allow the deposition of fine particles forming a large muddy shelf sediment body (i.e., the Tagus mud belt) between 50 and 130 m in depth (Jouanneau et al, 1998). The suspended matter carried by the Tagus River outflow can be transported as far as the Lisbon Canyon (Jouanneau et al, 1998).…”

Section: Study Areamentioning

confidence: 99%

“…Even in the estuary, only 50 to 65 % of OC content is estimated to be of terrestrial origin (Alt-Epping et al, 2007). The Tagus River acts mainly as a supplier of terrigenous lithogenic particles to the coastal ocean, while the majority of the terrestrial organic matter is retained inside the estuary (Jouanneau et al, 1998).…”

Section: Characteristics Of the Bulk Organic Mattermentioning

confidence: 99%

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Transport of branched tetraether lipids from the Tagus River basin to the coastal ocean of the Portuguese margin: consequences for the interpretation of the MBT'/CBT paleothermometer

Zell

Kim

Balsinha³

et al. 2014

Biogeosciences

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Abstract. Branched glycerol dialkyl glycerol tetraethers (brGDGTs), which are thought to be transported from soil to marine sediment by rivers, have been used to reconstruct the mean annual air temperature (MAAT) and soil pH of the drainage basin using the methylation index of branched tetraethers (MBT, recently refined as MBT') and cyclization index of branched tetraethers (CBT) from coastal marine sediment records. In this study, we trace the brGDGTs from source to sink in the Tagus River basin, the longest river system on the Iberian Peninsula, by determining their concentration and distribution in soils, river suspended particulate matter (SPM), riverbank sediments, marine SPM, and marine surface sediments. The concentrations of brGDGTs in river SPM were substantially higher and their distributions were different compared to those of the drainage basin soils. This indicates that brGDGTs are mainly produced in the river itself. In the marine environment, the brGDGT concentrations rapidly decreased with increasing distance from the Tagus estuary. At the same time, the brGDGT distributions in marine sediments also changed, indicating that marine in situ production also takes place. These results show that there are various problems that complicate the use of the MBT'/CBT for paleoreconstructions using coastal marine sediments in the vicinity of a river. However, if the majority of brGDGTs are produced in the river, it might be possible to reconstruct the environmental (temperature and pH) conditions of the river water using appropriate aquatic calibrations, provided that marine core locations are chosen in such a way that the brGDGTs in their sediments are predominantly derived from riverine in situ production.

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Section: Characteristics Of the Bulk Organic Mattermentioning

confidence: 85%

Section: Study Areamentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Characteristics Of the Bulk Organic Mattermentioning

confidence: 99%

See 3 more Smart Citations

Transport of branched tetraether lipids from the Tagus River basin to the coastal ocean of the Portuguese margin: consequences for the interpretation of the MBT'/CBT paleothermometer

Zell

Kim

Balsinha³

et al. 2014

Biogeosciences

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Impact of organic matter source and quality on living benthic foraminiferal distribution on a river‐dominated continental margin: A study of the Portuguese margin

et al. 2016

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Living (rose Bengal stained) benthic foraminifera were investigated on surface sediments from 23 stations from the river-dominated northwestern Portuguese margin. Samples were collected in March 2011, following the period of the maximum rainfall over the Iberian Peninsula, between 20 and 2000 m water depth along five cross-margin transects. Four of them are located off the Douro, Mondego, Tagus, and Sado Rivers and one off the Estremadura coast. The major objectives of this study are (1) to assess the impact of organic matter of various origin and quality on the benthic foraminifera and (2) to investigate the spatial differences of faunal distribution from coastal waters to the deep sea under river influences. To do this, sedimentological and biogeochemical characteristics of the sediments were identified by measuring grain size, oxygen penetration depth, total organic carbon (TOC) content, stable carbon isotopic composition of TOC (δ 13 C TOC ) and concentration of pigments and amino acids. Based on the principal component and cluster analyses of the environmental data, three major geographical groups are identified: (1) deep stations, (2) coastal and middle slope stations, and (3) shelf stations under river influence. At the deepest stations, species are associated with high organic matter (OM) quantity but low OM quality, where Uvigerina mediterranea, Hoeglundina elegans, and agglutinated species such as Reophax scorpiurus or Bigenerina nodosaria are dominant. All stations off the Sado River, which is the most affected area by the anthropogenic influence, are also characterized by high quantity but low quality of OM with the minimum faunal density and diversity within the study area. Middle slope stations are associated with low OM content and coarse sediments (Q 50 ) with the predominance of N. scaphum. Shallow shelf stations close to the Douro and Tagus River mouths show a dominance of taxa (e.g., Ammonia beccarii, Bulimina aculeata, Eggerelloides scaber, Nonion scaphum, Cancris auriculus, and Quinqueloculina seminula) adapted to environments characterized by high OM quality (high fresh chlorophyll (Chl a/Phaeo)) and available amino acids (enzymatically hydrolyzable amino acid (EHAA)/total enzymatically hydrolyzable amino acid (THAA)). The Biotic and Environmental linking analysis suggests that the benthic foraminiferal distribution is mostly controlled by three environmental parameters, i.e., TOC (quantity), EHAA/THAA (quality), and δ 13 C TOC (source). Hence, this study clearly highlights that the quantitative and qualitative inputs of OM and its source are the most important factors controlling the living benthic foraminiferal distribution with clear influences between the different rivers. This study also suggests a good tolerance of several species for river discharges where the OM quality is high.

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The Iberian Atlantic Margin

Moura

Gomes

Horta

2017

Submerged Landscapes of the European Continental Shelf

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Dispersal and deposition of suspended sediment on the shelf off the Tagus and Sado estuaries, S.W. Portugal

Cited by 79 publications

References 9 publications

Transport of branched tetraether lipids from the Tagus River basin to the coastal ocean of the Portuguese margin: consequences for the interpretation of the MBT'/CBT paleothermometer

Transport of branched tetraether lipids from the Tagus River basin to the coastal ocean of the Portuguese margin: consequences for the interpretation of the MBT'/CBT paleothermometer

Impact of organic matter source and quality on living benthic foraminiferal distribution on a river‐dominated continental margin: A study of the Portuguese margin

The Iberian Atlantic Margin

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