Winter dynamics on the northern Portuguese shelf. Part 1: physical processes

Vitorino, J.; Oliveira, Anabela; Jouanneau, Jean-Marie; Drago, Teresa

doi:10.1016/s0079-6611(02)00003-4

Cited by 128 publications

(65 citation statements)

References 17 publications

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“…Such higher values of primary production compared to the Gulf of Lion are the result of the prevailing summer upwelling regime characterizing the Portuguese margin (Vitorino et al, 2002). This was also confirmed by values of net photosynthetic primary production extracted from the ocean productivity database …”

Section: Study Areas and Sampling Strategysupporting

confidence: 64%

Trophic state of benthic deep-sea ecosystems from two different continental margins off Iberia

et al. 2013

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The bioavailability of organic matter in benthic deep-sea ecosystems, commonly used to define their trophic state, can greatly influence key ecological processes such as biomass production and nutrient cycling. Here, we assess the trophic state of deep-sea sediments from open slopes and canyons of the Catalan (NW Mediterranean) and Portuguese (NE Atlantic) continental margins, offshore east and west Iberia, respectively, by using a biomimetic approach based on enzymatic digestion of protein and carbohydrate pools. Patterns of sediment trophic state were analyzed in relation to increasing water depth, including repeated samplings over a 3 yr period in the Catalan margin. Two out of the three sam- pling periods occurred a few months after dense shelf water cascading events. The benthic deep-sea ecosystems investi- gated in this study were characterized by high amounts of bioavailable organic matter when compared to other deep- sea sediments. Bioavailable organic matter and its nutritional value were significantly higher in the Portuguese margin than in the Catalan margin, thus reflecting differences in pri- mary productivity of surface waters reported for the two re- gions. Similarly, sediments of the Catalan margin were char- acterized by significantly higher food quantity and quality in spring, when the phytoplankton bloom occurs in surface wa- ters, than in summer and autumn. Differences in the benthic trophic state of canyons against open slopes were more ev- ident in the Portuguese than in the Catalan margin. In both continental margins, bioavailable organic C concentrations did not vary or increase with increasing water depth. Overall our findings suggest that the intensity of primary production processes along with the lateral transfer of organic particles, even amplified by episodic events, can have a role in controlling the quantity and distribution of bioavailable organic detritus and its nutritional value along these continental margin ecosystems

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Section: Study Areas and Sampling Strategysupporting

confidence: 64%

Trophic state of benthic deep-sea ecosystems from two different continental margins off Iberia

et al. 2013

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“…The hydrography of the shelf is dominated by a poleward current in winter and an equatorward current during summer (Vitorino et al 2002, Coelho et al 2003). The poleward current favours downwelling, while the equatorward current is generally associated with coastal upwelling, which triggers high primary production along the Iberian Margin (Vitorino et al 2002).…”

Section: Methodsmentioning

confidence: 99%

“…Inside the canyon there is a strong internal tide circulation of water, with velocities of up to 15 cm s -1 (Coelho et al 2003). Sediment transported over the shelf and upper slope by alongshore currents is temporarily deposited in the very narrow upper and middle part of the canyon, until it is further transported to the deep sea in nepheloid layers or flushed down canyon by turbidite currents (Van Weering et al 2002, Garcia et al 2003.The hydrography of the shelf is dominated by a poleward current in winter and an equatorward current during summer (Vitorino et al 2002, Coelho et al 2003). The poleward current favours downwelling, while the equatorward current is generally associated with coastal upwelling, which triggers high primary production along the Iberian Margin (Vitorino et al 2002).…”

mentioning

confidence: 99%

Distribution of meiobenthos in the Nazaré canyon and adjacent slope (western Iberian Margin) in relation to sedimentary composition

García¹,

Koho²,

Stigter³

et al. 2007

Mar. Ecol. Prog. Ser.

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Abundance of metazoan meiofauna and foraminifera, and biomass and community structure of nematodes, were investigated in the benthic zone along the Nazaré Canyon and adjacent continental slope in relation to concentration of organic matter and its suitability as a food source for the meiobenthos. The Nazaré canyon sediments were richer in organic carbon (Corg), total nitrogen, and phytopigments than the adjacent open slope. In addition, phytodetritus was fresher in the canyon sediment than on the slope (higher chlorophyll a: phaeopigments). Nevertheless, the abundance of polychaetes, copepods, bivalves, nematodes, total metazoans, and nematode biomass were not always higher in the canyon than on the adjacent open slope. Lower densities occurred in the upper and middle canyon, and living benthic foraminifers were significantly more abundant on the adjacent slope. The stations in the upper and middle canyon contained infinitesimal numbers of foraminifers. Reduced diversity and evenness and high K-dominance of the nematode assemblages in the upper part of the canyon indicated environmental stress, perhaps related to high Corg content and sediment disturbance. Non-selective deposit-feeders dominated the nematode assemblages of the upper and middle parts of the canyon, whereas a more diverse trophic structure was found in the deeper parts and the open slope. Conditions in the upper and middle areas of the Nazaré canyon are harsh, and only opportunistic organisms can survive there. KEY WORDS: Nazaré canyon · Meiobenthos · Foraminifera · Sedimentary organic carbon · Physical disturbanceResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 340: 207-220, 2007 Corg content than in the open continental shelf and slope (Epping et al. 2002, Van Weering et al. 2002. Enhanced remineralisation rates have been shown as a result of enrichment with Corg (Epping et al. 2002).Meiofaunal communities are responsible for a significant amount of sediment remineralisation and support significant trophic pathways (Leguerrier et al. 2003). According to Tietjen (1992), on average, bacteria comprise 86%, macrofauna 7% and meiofauna 5% of living carbon in deep-sea sediments. Hence, despite comprising a relatively minor component of the living carbon compared to bacteria, macro-and meiofauna play an important role in the total carbon turnover of deep-sea environments. The meiofauna communities in the Nazaré canyon have rarely been studied: a few records of metazoan meiobenthos are available for the Western Iberian Margin (see Soltwedel 2000, Flach et al. 2002), while Flach (2003 reported very high densities of meiofauna in the canyon at all depths.Benthic animal communities from canyon systems can reflect the unstable and organically enriched conditions of these systems. Indeed, the fauna communities inhabiting submarine canyons have been found to differ in structure from those on adjacent abyssal plains, continental shelf, or slope. Faunal densities and biomasses in canyon systems have...

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“…[28] The total spectrum at all stations shows similar distribution to the wind stress spectrum obtained by Vitorino et al [2002] at a coastal station in Oporto (41°10 0 N) for 1997-1999 autumn-winter months at timescales larger than 2 days, which correspond to the timescales of the lowpressure systems. At the diurnal band, the winter contribution found by Vitorino et al is larger than the presented in this study.…”

Section: Spectral Analysismentioning

confidence: 53%

“…This situation favors the passage of fronts associated with low-pressure systems centered in the Atlantic at the latitude of Ireland. High interannual variability in the autumn position of the Azores High is observed, and during some autumns it remains in a more northern position [Vitorino et al, 2002;Torres et al, 2003] and induces more frequent upwelling conditions. Autumn transition in 2002 can be considered as typical since winds were variable and weak from early September with some weak downwelling episodes until the strong storm on 9 -11 October.…”

Section: Discussionmentioning

confidence: 97%

Wind forcing of the coastal circulation off north and northwest Iberia: Comparison of atmospheric models

Otero-Tranchero

Ruiz-Villarreal

2008

J. Geophys. Res.

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[1] Comparisons between observed winds and winds from reanalysis (National Centers for Environmental Prediction (NCEP) Reanalysis 1 and 2) and forecast meteorological models (High-Resolution Limited Area Model (HIRLAM)-Agencia Estatal de Meteorologia 0.2°and Atmospheric Research Mesoscale Model version 5-MeteoGalicia with 30 km and 10 km resolution) have been performed for the coastal region around northwest and north Iberia during a typical autumn downwelling period (SeptemberDecember 2002). Observations at buoys and coastal stations and QuikSCAT-derived winds were employed. The analyzed period was dominated by southerly and southwesterly winds associated to the passage of low-pressure systems. Our results show that the westward component is higher on the north coast than on the west coast and that winds are intensified at the western north coast. In this situation, the performance is similar in all model products in general terms, but only HIRLAM represents the reduction of winds in the Cantabrian Sea and NCEP and MM5 overestimate the magnitude of southsouthwest winds. Spatial differences in winds are also obtained for upwelling favorable events, associated either with a high-pressure system north from Iberia at the beginning of the autumn transition (northeasterly winds) or with conditions after the passage of a lowpressure system (northwesterly winds). The existence of sea surface temperature (SST) gradients in the coastal region implies that higher-resolution boundary SST products for meteorological models are necessary. Finally, the effect of these wind products on the coastal circulation was assessed with a 3-D numerical simulation. Differences in the expansion/confinement of river plumes and the surface speed of the slope current are induced by differences in wind patterns over the shelf and slope area among atmospheric models.Citation: Otero, P., and M. Ruiz-Villarreal (2008), Wind forcing of the coastal circulation off north and northwest Iberia: Comparison of atmospheric models,

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Winter dynamics on the northern Portuguese shelf. Part 1: physical processes

Cited by 128 publications

References 17 publications

Trophic state of benthic deep-sea ecosystems from two different continental margins off Iberia

Trophic state of benthic deep-sea ecosystems from two different continental margins off Iberia

Distribution of meiobenthos in the Nazaré canyon and adjacent slope (western Iberian Margin) in relation to sedimentary composition

Wind forcing of the coastal circulation off north and northwest Iberia: Comparison of atmospheric models

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