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Suspended sediment delivery from small catchments to the Bay of Biscay. What are the controlling factors?

Suspended sediment delivery from small catchments to the Bay of Biscay. What are the controlling factors?

To link to this article : DOI : 10.1002/esp.3957 URL : http://dx.doi.org/10.1002/esp.3957 To cite this version : Zabaleta, Ane and Antiguedad, Inaki and Barrio, Irantzu and Probst, Jean-Luc Suspended sediment delivery from small catchments to the Bay of Biscay. What are the

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The utilization of polysaccharides by heterotrophic bacterioplankton in the Bay of Biscay (North Atlantic Ocean)

The utilization of polysaccharides by heterotrophic bacterioplankton in the Bay of Biscay (North Atlantic Ocean)

lar glucosidase and glucose uptake, respectively (Fig. 4). Therefore, it seems likely that proteins and amino acids were also primary substrates for bacterioplankton pro- duction in the Bay of Biscay during late spring. It appears that the main function of polysaccharides for bacterioplankton growth in the ocean is not to support a high fraction of the bacterial carbon demand. Nevertheless, BBP in the Bay of Biscay was correlated with polysaccharide concentrations. Therefore, it can be assumed that bacterial growth was dependent on the carbon amendment provided by polysaccharide turn- over. Furthermore, it seems likely that carbon derived from polysaccharides flexibly supported other require- ments of bacterial growth such as energy generation and de novo synthesis of proteins to extents that were adjustable to environmental conditions. Polysaccharide turnover times of weeks to months ensured a continuous carbon supply, in contrast to the sporadic availability of labile compounds like amino acids. Hence, carbon derived from polysaccharide turnover complements bac- terial growth in the ocean when more labile substrates are available, but it also provides a reliable long-term carbon source that sustains bacterioplankton commu- nities on time-scales of months.
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Comparison of 0- and 2-group otolith elemental signatures to discriminate Solea solea nurseries in the bay of biscay

Comparison of 0- and 2-group otolith elemental signatures to discriminate Solea solea nurseries in the bay of biscay

The common sole Solea solea (L.) is a commercially important and widely distributed flatfish of the North-East Atlantic. For the Bay of Biscay stock, sole nurseries display differences in terms of quantity and quality. In fine the measure of the quality of a habitat for juveniles of a particular species is expressed by the contribution to the recruitment into the adult population. Understanding this connectivity between juvenile and adult habitats, i.e. evaluating the contribution of each nursery to a single adult stock appears essential in terms of stock management. However, this critical link is still missing for the Bay of Biscay sole stock.
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Assessment of the importance of the carbonate pump in surface waters of the Bay of Biscay

Assessment of the importance of the carbonate pump in surface waters of the Bay of Biscay

2 Unité d'Océanographie Chimique, Université de Liège 3 MiTAC, University of Antwerp During the Belgica BG02/11 cruise (22 April - 11 May 2002) in the northern Bay of Biscay, a slope survey covering transects across the continental margin from the La Chapelle Bank to the Goban Spur area were conducted. The sampling campaign was assisted in addition by remote sensed data from SeaWiFS to locate the coccolithophore blooms, as characterised by white, highly reflective

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Spatial distribution of zooplankton size spectra on the French continental shelf of the Bay of Biscay during spring 2000 and 2001

Spatial distribution of zooplankton size spectra on the French continental shelf of the Bay of Biscay during spring 2000 and 2001

Received 18 May 2005; revised 27 October 2005; accepted 21 November 2005; published 20 May 2006. [ 1 ] During two cruises in springtime (18 March to 13 April 2000 and 27 March to 4 June 2001), the whole French continental shelf of the Bay of Biscay was sampled to obtain an overview on the zooplankton community size structure. A laboratory optical plankton counter (OPC-1L) was used to process plankton net tow samples and estimate abundance, biovolume, and general characteristics of size spectra. In a second step, biomass estimates were extrapolated from size by using a conversion factor. Both biomass and abundance estimates show spatial patterns with a clear coastal-open sea gradient for both years. The coastal area was characterized by the highest biomasses and abundances per volume. A first analysis of the zooplankton community size spectra was made by using the slope of the normalized biomass size spectrum. Different spatial patterns of zooplankton size spectra were highlighted for spring 2000 and 2001. The highest slopes were found for the coastal zone, showing a large ratio of small organisms, although this was less marked in the springtime 2000. Stations characterized by high proportions of large organisms were located in majority in the north of the bay and at the shelf break. A second analysis using the size probability distributions of organisms revealed a nearly permanent nonlinearity of probability distributions. This implied the community structure was not in an equilibrium state during spring and this nonlinearity could be locally related to dominant species dynamics.
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Trophic ecology of commercial-size meagre, Argyrosomus regius, in the Bay of Biscay (NE Atlantic)★

Trophic ecology of commercial-size meagre, Argyrosomus regius, in the Bay of Biscay (NE Atlantic)★

Observatoire PELAGIS, UMS 3462 CNRS-Université La Rochelle, 5 allée de l'océan, 17000 La Rochelle, France Received 5 September 2016 / Accepted 27 January 2017 Abstract – In the north-eastern Atlantic, meagre (Argyrosomus regius) is one of the largest fish living on the shelf and this species has important commercial interest. Over the past two decades, large variations in meagre abundance have been observed with pluri-annual cycles but the factors involved in such variations are still unclear. Trophic interactions between meagre and other species (both prey and competitors) might be one explanatory variable of the observed variations in meagre recruitment and abundance. In the present study, we described the diet of commercial-size meagre in the Bay of Biscay from stomach content and stable isotope analyses, and explored its dietary ontogeny. We found that commercial-size meagres were mostly piscivorous with a diet dominated by clupeiform fish (mainly anchovy and sardine) completed by demersal fish (mainly pout and whiting). Cannibalism also accounted for a non-negligible part of the diet. Interestingly, stable isotope and stomach content analyses showed only a very slight increase in prey length and trophic level during the ontogeny of large meagre after 50 cm of total length and despite a 3 fold-change of the individual length in our sampling. Our results suggested that speci fic trophic interactions (i.e. bottom- up control by clupeiform fish on meagre population, competitive effects on piscivorous populations or top- down control by meagre on clupeiform fish populations) may occur in the Bay of Biscay and can impact meagre abundance dynamics. Our study underlined the interest to enhance ecological knowledge of prey- predator relationships in the development of ecosystem-based approach to understand trophic controls impacting aquatic living resources and fishery economy.
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Community structure and grazing of the nano-microzooplankton on the continental shelf of the Bay of Biscay

Community structure and grazing of the nano-microzooplankton on the continental shelf of the Bay of Biscay

a b s t r a c t In order to investigate the parameters controlling the heterotrophic protists (nano-microzooplankton) on the continental shelf of the southern Bay of Biscay, plankton communities and their physico-chemical environment were studied 4 times in February, April, June and SeptembereOctober 2004 at three stations in the euphotic zone in the Bay of Biscay. The abundance and carbon biomass of heterotrophic protists (ciliates, heterotrophic dinoflagellates and nanoflagellates) as well as all the others groups of plankton (picoplankton, nanophytoplankton, diatoms, autotrophic dinoflagellates, metazoan micro- zooplankton and mesozooplankton), the environmental parameters and the primary and bacteria production were evaluated at each sampling period. Microzooplankton grazing experiments were undertaken at the same time. Ciliates and heterotrophic dinoflagellates accounted for the main major component of nano- and microzooplankton communities in term of biomass. The total carbon biomass of heterotrophic protists was highest in spring and lowest at the end of summer. The development of heterotrophic protists started after a winter microphytoplankton bloom (principally large diatoms), the biomass was lower in June and was low in September (through inappropriate prey). The carbon requirement of microzooplankton ranged from 50 to more than 100% of daily primary, bacterial and nanoflagellate production. The heterotrophic protist community was predominantly constrained by bottom-up control in spring and at the end of summer via food availability and quality.
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Lower trophic levels and detrital biomass control the Bay of Biscay continental shelf food web: Implications for ecosystem management

Lower trophic levels and detrital biomass control the Bay of Biscay continental shelf food web: Implications for ecosystem management

Marquis, E., Niquil, N., Dupuy, C., in press. Does the study of microzooplankton community size structure effectively define their dynamics? Investigation in the Bay of Biscay (France). Journal of Plankton Research. Meynier, L., Pusineri, C., Spitz, J., Santos, M.B., Pierce, G.J., Ridoux, V., 2008. Intraspecific dietary variation in the short-beaked common dolphin (Delphinus delphis) in the Bay of Biscay: importance of fat fish. Marine Ecology Progress Series 354, 277-287.

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Dissolved Inorganic Carbon dynamics in the northern Bay of Biscay during a Coccolithophore bloom

Dissolved Inorganic Carbon dynamics in the northern Bay of Biscay during a Coccolithophore bloom

The western continental shelf and edge of the Bay of Biscay undergo strong hydrodynamic conditions that sustain high rates of productivity (Fig. 2-right). Among the 11 stations sampled for biogeochemical processes, 4 are presented here for various parameters (Fig. 3); their geographic locations are shown on figures 5 and 6 along the 200m isobath.

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Biogeochemistry of a late coccolithophorid bloom at the continental margin of the Bay of Biscay

Biogeochemistry of a late coccolithophorid bloom at the continental margin of the Bay of Biscay

Coccolithophores, among which Emiliania huxleyi is a major species, are minute phytoplantonic organisms capable of producing large amounts of calcium carbonate as well as particulate organic carbon (POC). The presence of abundant suspended minute calcite plates in the water column results in a change in seawater optical properties leading to a high reflectance (HR), which can be observed from space by remote sensing. Their contribution to carbon cycling in the ocean is not only linked to primary production and calcification. Coccolithophores also produce large amounts of transparent exopolymer particles (TEP) that may lead to the formation of marine snow by aggregation of suspended material in the water column. The formation of macro-aggregates, combined with the ballast effect of calcite, makes them good candidates for the export and sequestration of carbon in the ocean. Massive coccolithophorid blooms occur each year at the continental margin of the Bay of Biscay between April and July. Our study reports the relative importance of processes, such as primary production, calcification, respiration rates and air-sea CO 2 fluxes, measured during a campaign in early June 2006 . We compare the patterns of various parameters, including TEP and the bacterial community
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Optimal selectivity and effort cost: A simple bioeconomic model with an application to the Bay of Biscay Nephrops fishery

Optimal selectivity and effort cost: A simple bioeconomic model with an application to the Bay of Biscay Nephrops fishery

Applied Model Compared to the theoretical model presented in the irst part of this article, the applied model we use to analyse the case study provides a more realistic description of the ish- ery. An extended bio-economic model of the Bay of Biscay Nephrops ishery is described in (Macher et al. 2008). Several groups of vessels are considered to differentiate between two ishing strategies (a Northern leet, targeting Nephrops most of the year, and a South- ern leet, targeting Nephrops occasionally) and various cost structures linked to vessel length categories. The age-structured biological component describes the dynamics of the nine Nephrops age group. Discards are taken into account. For the sake of the pres- ent application, a simpliied version of this model is considered. The main simpliications are that the Nephrops leet is described as a whole and that age-groups are aggregated into two main categories—“small Nephrops,” which correspond to age groups 1 to 4 and “large Nephrops,” which correspond to age groups 5 to 9—to be better linked to the model described in the former part of the article. The model is comprised of three compo- nents: biological, technical, and economic. Inputs are detailed in table 1.
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Contribution of a bioenergetics model to investigate the growth and survival of European seabass in the Bay of Biscay - English Channel area

Contribution of a bioenergetics model to investigate the growth and survival of European seabass in the Bay of Biscay - English Channel area

Early-life stages A B S T R A C T The European seabass (Dicentrarchus labrax) is a species of particular ecological and economic importance. Stock assessments have recently revealed the worrying state of the “Northern stock”, probably due to overfishing and a series of poor recruitments. The extent to which these poor recruitments are due to environmental variability is difficult to assess, as the processes driving the seabass life cycle are poorly known. Here we investigate how food availability and temperature may affect the growth and survival of wild seabass at the individual scale. To this end, we developed a bioenergetics model based on the Dynamic Energy Budget (DEB) theory. We applied it to seabass population of the Northeast Atlantic region (Bay of Biscay – English Channel area) throughout their entire life cycle. We calibrated the model using a combination of age-related length and weight datasets: two were from aquaculture experiments (larvae and juveniles raised at 15 and 20°C) and one from a wild population (juveniles and adults collected during surveys or fish market sampling). By calibrating the scaled functional response that rules the ingestion of food and using average temperature conditions experienced by wild seabass (obtained from tagged individuals), the model was able to reproduce the duration of the different stages, the growth of the individuals, the number of batches and their survival to starvation. We also captured one of the major differences encountered in the life traits of the species: farmed fish mature earlier than wild fish (3 to 4 years old vs. 6 years old on average for females, respectively) probably due to better feeding conditions and higher temperature. We explored the growth and survival of larvae and juveniles by exposing the individuals to varying temperatures and food levels (including total starvation). We show that early life stages of seabass have a strong capacity to deal with food deprivation: the model estimated that first feeding larvae could survive 17 days at 15°C. We also tested individual variability by adjusting the specific maximum assimilation rate and found that larvae and juveniles with higher assimilation capacity better survived low food levels at a higher temperature. We discuss our results in the context of the recent years of poor recruitment faced by European seabass.
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Abundance and size distribution of transparent exopolymer particles (TEP) in a coccolithophorid bloom in the northern Bay of Biscay

Abundance and size distribution of transparent exopolymer particles (TEP) in a coccolithophorid bloom in the northern Bay of Biscay

The present study shows agreement between the vertical distribution of TEP determined with the micro- scopic (this study) and the colorimetric ( Engel, 2004 ; Harlay et al., in prep.) approaches. The estimates of TEP-C obtained with the microscopic approach are comparable to those previously obtained with the colorimetric one in the Bay of Biscay (coccolithophorid bloom in June 2004, Harlay et al., in prep.) and during an offshore transect at the same latitude in the NE Atlantic Ocean ( Engel, 2004 ). High absorbance of particles issued from the area where coccolithophores occurred, or had occurred in the past history of the water mass, has been pointed out. We suggest that during coccolithophorid blooms, the produc- tion of TEP is also occurring, as already determined for other phytoplankton groups ( Passow, 2002 ) as a possible consequence of carbon over-consumption by this taxon. The implication of those particles for the seasonal cycling of carbon is enhanced by the physical properties of the water column. The formation of aggregates potentially contributes, through the ballast of aggregates with biogenic calcite, to efficient and rapid export of carbon out of the photic layer and important deposition over the seafloor. Carbon over-consumption by phytoplankton and the subsequent transformation of the cellular releases into TEP ( Schartau et al., 2007 ) account for an additional sink for carbon sequestration in coccolithophorid blooms, where the efficiency of the carbon pump may not be limited to the production of biomass, as computed from variations in Chl-a concentration (e.g. Iglesias-Rodriguez et al., 2002 ). However, such a mechanism has been neglected in carbon inventories because of the complexity of the study of gel phases in marine environments. The significance of gel particles in the global carbon cycle may have been under-estimated, so far, and improvement in the description of these processes is required to better constrain this flux as well as the development of techniques to estimate the coupling between the surface and the seafloor.
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Biogeochemistry and carbon budget during a coccolithophorid bloom in the northern Bay of Biscay (June 2006)

Biogeochemistry and carbon budget during a coccolithophorid bloom in the northern Bay of Biscay (June 2006)

Biogeochemistry and carbon budget during a coccolithophorid bloom in the northern Bay of Biscay (June 2006) INTRODUCTION During coccolithophorid blooms, carbon (C) cycling in the photic zone is driven by the production and the degradation of organic matter (primary production and community respiration), as well as the production and the dissolution of biogenic calcium carbonate (CaCO 3 ). Organic and inorganic metabolisms lead to a transfer of carbon to depth and both impact the flows of carbon dioxide (CO 2 ) in the water column and the CO 2 flux across the air-sea interface. Furthermore, due to complex dynamics of coccolithophores, the impact of metabolic C fluxes on CO 2 fluxes is variable in time, depending on the stage of the bloom development, and mainly on the ratio of calcification to primary production (CAL:GPP). Understanding and quantifying C cycling of coccolithophorid blooms in natural conditions is a prerequisite to correctly validate biogeochemical models aiming at predicting feedbacks related to ocean acidification, which incorporate knowledge obtained from perturbation laboratory experiments.
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Biogeochemistry and carbon mass balance of a coccolithophore bloom in the northern Bay of Biscay (June 2006)

Biogeochemistry and carbon mass balance of a coccolithophore bloom in the northern Bay of Biscay (June 2006)

Dark community respiration CO2 fluxes a b s t r a c t Primary production (PP), calcification (CAL), bacterial production (BP) and dark community respiration (DCR) were measured along with a set of various biogeochemical variables, in early June 2006, at several stations at the shelf break of the northern Bay of Biscay. The cruise was carried out after the main spring diatom bloom that, based on the analysis of a time-series of remotely sensed chlorophyll-a (Chl-a), peaked in mid-April. Remotely sensed sea surface temperature (SST) indicated the occurrence of enhanced vertical mixing (due to internal tides) at the continental slope, while adjacent waters on the continental shelf were stratified, as confirmed by vertical profiles of temperature acquired during the cruise. The surface layer of the stratified water masses (on the continental shelf) was depleted of inorganic nutrients. Dissolved silicate (DSi) levels probably did not allow significant diatom development. We hypothesize that mixing at the continental slope allowed the injection of inorganic nutrients that triggered the blooming of mixed phytoplanktonic communities dominated by coccolithophores (Emiliania huxleyi) that were favoured with regards to diatoms due to the low DSi levels. Based on this conceptual frame, we used an indicator of vertical stratification to classify the different sampled stations, and to reconstruct the possible evolution of the bloom from the onset at the continental slope (triggered by vertical mixing) through its development as the water mass was advected on-shelf and stratified. We also established a carbon mass balance at each station by integrating in the photic layer PP, CAL and DCR. This allowed computation at each station of the contribution of PP, CAL and DCR to CO 2 fluxes in the photic layer, and
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Biogeochemistry and carbon mass balance of a coccolithophore bloom in the northern Bay of Biscay (June 2006)

Biogeochemistry and carbon mass balance of a coccolithophore bloom in the northern Bay of Biscay (June 2006)

Primary production (PP), calcification (CAL), bacterial production (BP) and dark community respiration (DCR) were measured along with a set of various biogeochemical variables, in early June 2006, at several stations at the shelf break of the northern Bay of Biscay. The cruise was carried out after the main spring diatom bloom that, based on the analysis of a time-series of remotely sensed chlorophyll-a (Chl-a), peaked in mid-April. Remotely sensed sea surface temperature (SST) indicated the occurrence of enhanced vertical mixing (due to internal tides) at the continental slope, while adjacent waters on the continental shelf were stratified, as confirmed by vertical profiles of temperature acquired during the cruise. The surface layer of the stratified water masses (on the continental shelf) was depleted of inorganic nutrients. Dissolved silicate (DSi) levels probably did not allow significant diatom development. We hypothesize that mixing at the continental slope allowed the injection of inorganic nutrients that triggered the blooming of mixed phytoplanktonic communities dominated by coccolithophores (Emiliania huxleyi) that were favoured with regards to diatoms due to the low DSi levels. Based on this conceptual frame, we used an indicator of vertical stratification to classify the different sampled stations, and to reconstruct the possible evolution of the bloom from the onset at the continental slope (triggered by vertical mixing) through its development as the water mass was advected on-shelf and stratified. We also established a carbon mass balance at each station by integrating in the photic layer PP, CAL and DCR. This allowed computation at each station of the contribution of PP, CAL and DCR to CO 2 fluxes in the photic layer, and how they changed from one station to another along
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Biogeochemical Investigations of Coccolithophore Blooms along the Continental Margin of the Northern Bay of Biscay: Highlights of the PEACE Project

Biogeochemical Investigations of Coccolithophore Blooms along the Continental Margin of the Northern Bay of Biscay: Highlights of the PEACE Project

Surface-water carbon dioxide dynamics Carbon dioxide (CO 2 ) data were obtained in the nothern Bay of Biscay in June 2006 and May 2007 during coccolithophore blooms. Total alkalinity (TA) showed non conservative behaviour with respect to salinity, highlighting strong TA drawdown related to calcification (Figure 5). The TA anomalies were negatively correlated to pCO 2 due to the production of CO 2 during calcification (Ca 2+ + 2HCO 3 - → CaCO 3 + H 2 O + CO 2 ). The slope of the correlation was different during both years since the cruises were carried out at different stages of the phytoplankton bloom, highlighting the contribution of primary production to CO 2 dynamics during coccolithophore blooms.
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Biogeochemical study of a coccolithophore bloom in the northern Bay of Biscay (NE Atlantic Ocean) in June 2004

Biogeochemical study of a coccolithophore bloom in the northern Bay of Biscay (NE Atlantic Ocean) in June 2004

4.1. Environmental settings during the coccolithophore bloom The northern Bay of Biscay continental margin is characterized by complex hydrodynamics due to the steep bathymetric change at continental slope separating the deep abyssal plain (>3000 m) from the shallow continental shelf (<200 m). In the study area, internal wave breaking is at the origin of seasonal changes in the direction and the intensity of surface residual currents and cause at the shelf break enhanced vertical mixing of deep waters with surface waters ( Huthnance et al., 2001 ). The vertical mixing at the shelf break leads to discontinuous inputs of nutrients to surface waters that sustain high primary production ( Joint et al., 2001 ). Along the shelf break primary production is higher in the southern area (La Chapelle Bank) than further north (Goban Spur) due to a steeper continental slope that leads to stronger vertical mixing by internal tides ( Wollast and Chou, 2001a,b ). In June 2004, cooling of surface waters was observed at the continental shelf break on the composite image of remotely sensed SST ( Fig. 1 b). The vertical profiles of temperatures over the continental shelf (stations 10, 8, 5, 2 and 12) showed stronger thermal stratification with vertical gradients of 3–4 °C across the thermocline and higher SST values (ranging between 14.0 °C and 15.0 °C) than over the continental slope ( Fig. 2 ). The coldest station was station 7, where SST (12.7 °C) was close to the value recorded at 100 m depth. Such a distribution of SST and vertical temperature gradients is related to enhanced vertical mixing over the continental slope. No haline stratification was observed, except at station 1 due to the inputs from the Loire and Gironde rivers (e.g. Kelly-Gerreyn et al., 2006 ). The cold water patches were constrained on a narrow band along the shelf break and were associated with higher remotely sensed Chl-a concentrations ( Fig. 1 c). The patch of higher Chl-a ex- tended over the continental shelf and values declined in the direc- tion of station 1. The in situ Chl-a measurements agreed with the patterns of the remotely sensed data, with higher concentrations in surface waters at station 2 and lower concentrations at adjacent stations, but in situ concentrations rarely exceeded 1.0 l g L 1 ( Fig. 4 ). The vertical distribution of Chl-a showed a consistent pat- tern at all stations with maxima at the surface (3 m) or sub-surface (20 m), and very low values below 60 m depth.
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Towards a comprehensive C-budgeting approach of a coccolithophorid bloom in the Northern Bay of Biscay (June 2006)

Towards a comprehensive C-budgeting approach of a coccolithophorid bloom in the Northern Bay of Biscay (June 2006)

Fig. 3: a- Depth averaged HPLC relative percentage of Prymnesiophytes (filled circles) and other phytoplankton groups (open circles) in the 30 m top layer, b- calcification to gross particulate primary production (CAL:GPP p ) ratio and c- GPP p to pelagic respiration (GPP p :PCR) ratio versus the degree stratification computed as the difference of density at 3 m depth and at 100 m depth. The linear regression and the 95% confidence interval (dashed curves) are represented together with the determination coefficient (r²). d- GPP:PCR ratio versus GPP in June 2006 in the Bay of Biscay (filled circles) and in June 1999 (open circles) for the North Sea (Robinson et al. , 2002).
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Sources and transport of dissolved iron and manganese along the continental margin of the Bay of Biscay

Sources and transport of dissolved iron and manganese along the continental margin of the Bay of Biscay

Abstract. Dissolved iron (DFe; <0.2 µm) and dissolved manganese (DMn; <0.2 µm) concentrations were deter- mined in the water column of the Bay of Biscay (eastern North Atlantic Ocean) in March 2002. The samples were collected along a transect traversing from the European con- tinental shelf over the continental slope. The highest DFe and DMn concentrations (2.39 nM and 6.10 nM, respectively) were observed in the bottom waters on the shelf at stations closest to the coast. The release of trace metal from resus- pended particles and the diffusion from pore waters were probably at the origin of elevated DFe and DMn concen- trations in the Bottom Boundary Layer (BBL). In the slope region, the highest total dissolvable iron (TDFe), DFe and DMn values (24.6 nM, 1.58 nM and 2.12 nM, respectively) were observed close to the bottom at depth of ca. 600–700 m. Internal wave activity and slope circulation are thought to be at the origin of this phenomenon. These processes were also very likely the cause of elevated concentrations (DFe: 1.27 nM, DMn: 2.34 nM) measured in surface waters of sta- tions located in the same area. At stations off the continental slope, the vertical distribution of both metals were typical of open ocean conditions, indicating that inputs from the con- tinental margin did not impact the metal distributions in the offshore waters.
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