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12 pages, 8 figures, 1 table.-- Data availability: Data will be made available on request, Subpolar coastal waters are key hotspots in the global carbon cycle. However, the small-scale distribution of partial pressure of carbon dioxide (pCO2) in these environments and the physical and biological controls underlying this variability are still poorly understood. Here, we examine simultaneous high-resolution spatial measurements of wind speed and pCO2, temperature, salinity, and in-vivo chlorophyll-a fluorescence (chl-a fluo, a proxy of phytoplankton biomass) in surface waters that were obtained during an oceanographic survey in the Argentinian Beagle Channel (subantarctic Atlantic Patagonian) in early fall 2017. The 240 km study transect (centered at 55°S - 67°W) was divided into two zones: (A1) The Beagle Channel innermost portion, semi-enclosed and subject to strong continental influence and (A2) its eastern outlet towards the open Southwest Atlantic. Discrete seawater samples were also collected for apparent oxygen utilization (AOU), nutrients and pH measurements. High-resolution spatial measurements revealed the persistence of pCO2 below atmospheric equilibrium, increasing in median (interquartile range 25–75%) from 314 μatm in the inner Beagle Channel (A1) to 348 μatm towards the adjacent open sea (A2). A decrease in atmospheric CO2 sequestration was associated with an increase in water temperature from 9.5 °C to 10.7 °C, salinity from 30.8 to 32.5, and chl-a fluo from 2.24 to 2.91 mg m−3 along the coastal-offshore gradient. Low AOU and nutrient levels were found in regions inside the channel. Indeed, the relationships between CO2 and temperature or salinity were significantly different from those expected from the theoretical solubility effect, indicating a dominance of metabolic over physicochemical controls on this gas. Moreover, physical factors such as vertical stratification contributed to the variable surface pCO2 values. These findings reveal the existence of short-scale spatial variability of CO2 in the Beagle Channel, improving our understanding of the multiple controls on atmospheric carbon sequestration in extensive subpolar continental shelves, We acknowledge support from the Spanish Government through grants CTM2014-56987-P (VA-DE-RETRO Project) and RTI2018-100844-B-C33 (SAGA project) and also recognize the institutional support of the Spanish Government through the Severo Ochoa Centre of Excellence accreditation (CEX2019-000928-S). This study was funded by grants from the Council for Research and Scientific Development of Brazil (CNPq, 203366/2019-0, 314995/2020-0) and the Research Support Foundation of the State of Rio de Janeiro (E-26/211.329/2021 and E-26/201.118/2022). H.M. and L.C.C. were awarded by CNPq Research Productivity and FAPERJ Scientist of Our State fellowships. L.C.C. was awarded by UERJ/PROCIENCIA fellowship

11 pages, 5 figures, 1 table, supporting information https://doi.org//10.1371/journal.pone.0104536, The offshore displacement of commercial bottom trawling has raised concerns about the impact of this destructive fishing practice on the deep seafloor, which is in general characterized by lower resilience than shallow water regions. This study focuses on the flanks of La Fonera (or Palamós) submarine canyon in the Northwestern Mediterranean, where an intensive bottom trawl fishery has been active during several decades in the 400-800 m depth range. To explore the degree of alteration of surface sediments (0-50 cm depth) caused by this industrial activity, fishing grounds and control (untrawled) sites were sampled along the canyon flanks with an interface multicorer. Sediment cores were analyzed to obtain vertical profiles of sediment grain-size, dry bulk density, organic carbon content and concentration of the radionuclide 210Pb. At control sites, surface sediments presented sedimentological characteristics typical of slope depositional systems, including a topmost unit of unconsolidated and bioturbated material overlying sediments progressively compacted with depth, with consistently high 210Pb inventories and exponential decaying profiles of 210Pb concentrations. Sediment accumulation rates at these untrawled sites ranged from 0.3 to 1.0 cm y -1. Sediment properties at most trawled sites departed from control sites and the sampled cores were characterized by denser sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sediments caused by trawling gears. Other alterations of the physical sediment properties, including thorough mixing or grain-size sorting, as well as organic carbon impoverishment, were also visible at trawled sites. This work contributes to the growing realization of the capacity of bottom trawling to alter the physical properties of surface sediments and affect the seafloor integrity over large spatial scales of the deep-sea. © 2014 Martín et al., This work was funded by the HERMIONE project (http://www.eu-hermione.net) under the European Commission's Seventh Framework Programme (Grant agreement no: 226354) and by the Spanish national Research Plan (Ref. CTM2010-11084-E). J. Martín was funded through a JAEDOC contract within the Program «Junta para la Ampliación de Estudios», granted by Consejo Superior de Investigaciones Científicas (wwww.csic.es) and co-financed by the European Social Fund. P. Masqué received financial support through the ICREA (www.icrea.cat) Academia award

11 pages, 7 figures, 3 tables, This dataset, gathered during the RETRO-BMC cruise, reports multiple-scale measurements at the Confluence of the Brazil and Malvinas Currents. The cruise was carried out between 8 and 28 April 2017 onboard R/V Hespérides, departing from Ushuaia and arriving to Santos. Along its track, the vessel recorded near-surface temperature and salinity, as well as the horizontal flow from 20 m down to about 800 m. A total of 33 hydrographic stations were completed in a region off the Patagonian Shelf, within 41.2°S–35.9°S and out to 53.0°W. At each station, a multiparametric probe and velocity sensors were deployed inside the frame of a rosette used to collect water samples at selected depths; these samples were later used for several water analyses, including inorganic nutrient concentrations. Microstructure measurements were carried out in 11 of these hydrographic stations. In addition, two high-resolution three-dimensional surveys were conducted with an instrumented undulating vehicle between 40.6°S–39.0°S and 55.6°W–53.8°W. Lastly, eight high-frequency vertical profilers were deployed in the region and five position-transmitting drifters were launched. These data allow the description of the Confluence from the regional scale to the microscale, and provide a view of the variability of the frontal region on time scales from days to weeks, This research has been supported by the Spanish government (Ministerio de Economía and Competitividad through project VA-DE-RETRO, CTM2014-56987-P, and Ministerio de Ciencia, Innovación y Universidades through project SAGA, RTI2018‐100844‐BC33). Dorleta Orúe-Echevarría (FPU2013-02884) and Ignasi Vallés-Casanova (BES‐2015‐071314) have also been funded with PhD scholarships by the Spanish government (Ministerio de Ciencia, Innovación y Universidades). Paola Castellanos has been partly supported by the Portuguese government (Fundação para a Ciência e a Tecnologia through project COASTNET, PINFRA/22128/2016), With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

This study examines the distribution and seasonal evolution of hydrographic, hydrodynamic, and nepheloid layers in Ushuaia Bay and the submerged glacial valley that connects it to the Beagle Channel. The hydrographic structure is highly seasonal, with a total mixing of the water column in winter and the appearance of a pycnocline between 50 and 70 m deep from spring to late autumn, mainly due to desalination. A counter-clockwise current sweeps the entire bay regardless of the season or phase of the tide. This current is at its maximum in the surface layer, allowing the rapid renewal of the bay&rsquo, s waters, while deep currents are weak and imply a slow renewal of the valley&rsquo, s waters. Turbid and oxygen-depleted structures are observed in summer in the valley. The combination of seasonal stratification, high organic matter inputs from planktonic production, oxygen consumption for remineralization, and sluggish circulation results in a decrease in near-bottom oxygen concentration in the glacial valley at the end of the stratified season, before mixing and re-oxygenation of the water column during the southern winter. The possible impact of dissolved oxygen depletion in the bottom waters of the valley on benthic organisms, like crustaceans, is discussed.

Continental dust can be suspended and transported by the wind, reaching seawater masses far away from its source. The deposition of the aerosols on the ocean surface can alter the abundance of chemical species in the water column and contribute to element inventories in seafloor sediments. A major Saharan dust intrusion into the Western Mediterranean Sea was recorded at the DYFAMED site (Ligurian Sea) in 20th February 2004. We determined the influence of this dust event on the concentration of 30 minor and trace level elements (TE) in sinking particles collected by sediment traps deployed at 200 m and 1000 m depth, and how a dust flux event like this contributed to the exchange of TE, including Fe, with the water column during major dust events. With coupled sediment traps and aerosol samples, we assessed the short-term implications of dust events in the water column. The event produced a flux of fast (>111 m d−1) and slow (60% for Cr and Cu, >70% for Al, >80% for Ni and Zn, >90% for V and Mn, >100% for Fe and Pb). The corresponding Enrichment Factors (EF) for the minor and TE analyzed in the sediment traps during the dust event were calculated. EF was used to determine how minor and trace element concentrations in sinking particles vary. The values ranged between 0.35 and 421 in both 200 m and 1000 m sediment traps. For most of the analyzed elements, the obtained EF values were higher than 1. On the contrary, V, Y, Zr, Nb, and Ce showed EF ~ 1 while Cr, Ni, Cu, Zn, Sn, and Pb showed EF < 1. Despite the variability in the EF values, vertical fluxes integrated during the dust deposition event increased from 200 m to 1000 m, except for I, which decreased. This contrasts strongly with the element fluxes integrated for the complete sampling period, which decrease or increase from 200 m to 1000 m, depending on the element. This suggests that sinking dust particles were acting generally as sinks of the TE. We conclude that, apart from I, a substantial portion of the elements from atmospheric dust input from a single deposition event can reach the mesopelagic layer of the Western Mediterranean basin without increasing the budget of those elements in the water column., The IAEA is grateful for the support provided to its Environment Laboratories by the Government of the Principality of Monaco.

19 pages, 18 figures, 1 table, supplementary data https://doi.org/10.1016/j.margeo.2017.02.015, Bottom trawling leads to recurrent sediment resuspension events over fishing grounds. Recent studies have shown how bottom trawling can drive seascape reshaping at large spatial scales and enhance sediment transport in submarine canyons, which subsequently impacts deep-sea ecosystems. Present knowledge on the transfer and accumulation of sediment flows triggered by bottom trawling is based on localized and infrequent measurements whilst a more complete picture of the process is needed. The present work focuses on the modeling of sediment transport and accumulation resulting from trawling activities in La Fonera submarine canyon, northwestern Mediterranean Sea, thus contributing to an improved assessment of trawling impacts. Based on mooring data within a canyon gully, we use an inverse model to retrieve the unknown time series of resuspension due to trawling over the fishing grounds. This resuspension is later used as forcing for the direct problem: we simulate trawling-induced flows through the canyon and provide a 3D visualization of potential trawling impacts on sediment dynamics, including the identification of the propagation patterns of sediments resuspended by trawling. Flows coming from shallower fishing grounds are funneled through canyon flank gullies towards the canyon axis, with part of the resuspended sediment reaching the continental rise out of the canyon across the open continental slope. Trawling-induced sediment flows promote sediment accumulation beyond the canyon mouth. Given the wide geographical distribution of bottom trawling, our results have far-reaching implications that go much beyond La Fonera submarine canyon. Our study represents a starting point for the assessment of the sedimentary impact of bottom trawling in deep continental margins, This work was supported by various research projects: HERMIONE (226354 and CTM2010-11084-E), DOS MARES (CTM2010-21810-C03), OASIS DEL MAR—Obra Social “la Caixa”, GRACCIE-CONSOLIDER (CSD2007-00067), REDECO (CTM2008-04973-E) and ABIDES (CTM2015-65142-R). We also received support from Catalan Government Grups de Recerca Consolidats grants (2009 SGR 899 and 1305). VMS data and support were provided by the Spanish General Secretariat of Maritime Fishing (SEGEMAR). [...] MPP's work was supported by the “Laboratoire d'Excellence” LabexMER and co-funded by a state grant from the French government through Agence Nationale de la Recherche (ANR) under the «Investissements d'Avenir» Programme, reference ANR-10-LABX-19-01, and by a grant from the Regional Council of Brittany. Additional support was also provided by Actions-Marges Program (Mediterranée Occidentale).

In February 2004, anthropogenic radionuclides (137Cs, 236U, 239Pu and 240Pu), transported from the Sahara Desert, were observed in the Monaco air, and later in water and sediment samples collected at the DYFAMED site in the northwest (NW) Mediterranean Sea. While 236U and 137Cs in Saharan dust particles showed a high solubility in seawater, Pu isotopes were particle reactive in the water column and in the sediment. The impact of the Saharan deposition was found at 0–1.0 cm of the sediment core for 236U and 137Cs, and between 1.0 and 1.5 cm for Pu isotopes. The excess of 236U was observed more in the water column than in the sediment, whereas the 239+240Pu total inventories were comparable in the water column and the sediment. This single-day particle event represented 72% of annual atmospheric deposition in Monaco. At the DYFAMED site, it accounted for 10% (137Cs) and 15% (239+240Pu) activities of sinking particles during the period of the highest mass flux collected at the 200 and 1000 m water depths, and for a significant proportion of the total annual atmospheric input to the NW Mediterranean Sea (28–37% for 137Cs and 34–45% for 239+240Pu). Contributions to the total 137Cs and 239+240Pu sediment inventories were estimated to be 14% and 8%, respectively. The Saharan dust deposition phenomenon (atmospheric input, water column and sediment) offered a unique case to study origin and accumulation rates of radionuclides in the NW Mediterranean Sea., The IAEA is grateful to the Government of the Principality of Monaco for the support provided to its Environment Laboratories.

The sub-Antarctic Namuncura Marine Protected Area at Burdwood Bank (NMPA/BB) is an area of favorable conditions for the development of planktonic organisms and the sustenance of numerous species of ecological importance. The current study aimed to evaluate the spatial distribution of the abundance, biomass, community structure, and functional diversity of the mesozooplankton from the NMPA/BB during spring 2014. We also assessed the potential of zooplankton as prey for upper trophic levels, in particular the larvae of the Fuegian sprat (Sprattus fuegensis), a key species in the food web of the NMPA/BB. A total of 26 zooplankton taxa were identified. Nauplii and copepods evidenced the highest abundances, with the latter representing the dominant group in terms of biomass. Copepods showed a strong eastward gradient in their abundance, biomass, and diversity. This spatial structure in the community composition seems to be modulated by a west-to-east decreasing trend in the size of available preys, with nano- and picoplankton playing a major role in the eastern part of the NMPA/BB. Such pattern would be, in turn, a consequence of productivity gradients along hydrographic features. The high abundance of nauplii and copepods suggests that spring is an appropriate time for their reproduction and, given their size structure, they represent an adequate food source for Fuegian sprat larvae. This would be enhanced by anticyclonic cells present in the NMPA/BB, which can gather and retain sprat larvae along with their zooplanktonic preys. The results of our study, which is the first comprehensive approach addressing the zooplanktonic indicators of the NMPA/BB, serve as a baseline for future ecosystem-based policies aiming to manage and protect the natural marine resources sheltered here.

In the sub-Antarctic waters of southern South America, two species that form conspicuous pelagic aggregations are considered both potential fishery resources and ecologically important: the Fuegian sprat Sprattus fuegensis and the squat lobster Munida gregaria. Here, we estimate spatio-temporal patterns of the relative abundance, distribution and potential areas of overlapping of M. gregaria and S. fuegensis in the Beagle Channel. Acoustic data were collected from 18 surveys conducted between 2009 and 2016 in the Beagle Channel. Our observations on the pelagic aggregations revealed that M. gregaria swarms and S. fuegensis schools occurred along the channel throughout the year. However, the occurrence of S. fuegensis was more evident in the inner part of the channel during the winter. There was a negative relationship between the relative abundance of squat lobsters and Fuegian sprats throughout the year. This interaction may result from spatial competition associated with resources, particularly in summer. The vertical distribution and morphology of aggregations of both species showed seasonal differences. Specifically, schools of Fuegian sprats were typically pelagic in summer, whereas in winter they were bigger and associated with the bottom layer. This change could be associated with a seasonal change in the oceanographic regime of the Beagle Channel. The information presented here is necessary to understand processes in a context of possible opening of fisheries targeting these two species that have key ecological roles in this sub-Antarctic ecosystem. Fil: Diez, Mariano Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Cabreira, Ariel G.. Instituto Nacional de Investigaciones y Desarrollo Pesquero; Argentina Fil: Madirolas, Adrian Osvaldo Madirolas. Instituto Nacional de Investigaciones y Desarrollo Pesquero; Argentina Fil: Martín de Nascimento, Jacobo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Scioscia, Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Schiavini, Adrian Carlos Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Lovrich, Gustavo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina

As part of the international, multidisciplinary project Malina, downward particle fluxes were investigated by means of a drifting multi-sediment trap mooring deployed at three sites in the Canadian Beaufort Sea in late summer 2009. Mooring deployments lasted between 28 and 50 h and targeted the shelf-break and the slope along the Beaufort-Mackenzie continental margin, as well as the edge between the Mackenzie Shelf and the Amundsen Gulf. Besides analyses of C and N, the collected material was investigated for pigments, phyto- and microzooplankton, faecal pellets and swimmers. The measured fluxes were relatively low, in the range of 11–54 mg m−2 d−1 for the total mass, 1–15 mg C m−2 d−1 for organic carbon and 0.2–2.5 mg N m−2 d−1 for nitrogen. Comparison with a long-term trap data set from the same sampling area showed that the short-term measurements were at the lower end of the high variability characterizing a rather high flux regime during the study period. The sinking material consisted of aggregates and particles that were characterized by the presence of hetero- and autotrophic microzooplankters and diatoms and by the corresponding pigment signatures. Faecal pellets contribution to sinking carbon flux was important, especially at depths below 100 m, where they represented up to 25 % of the total carbon flux. The vertical distribution of different morphotypes of pellets showed a marked pattern with cylindrical faeces (produced by calanoid copepods) present mainly within the euphotic zone, whereas elliptical pellets (produced mainly by smaller copepods) were more abundant at mesopelagic depths. These features, together with the density of matter within the pellets, highlighted the role of the zooplankton community in the transformation of carbon issued from the primary production and the transition of that carbon from the productive surface zone to the Arctic Ocean's interior. Our data indicate that sinking carbon flux in this late summer period is primarily the result of a heterotrophic-driven ecosystem. Fil: Miquel, J. C.. International Atomic Energy Agency. Environment Laboratories; Mónaco Fil: Gasser, B.. International Atomic Energy Agency. Environment Laboratories; Mónaco Fil: Martín de Nascimento, Jacobo. International Atomic Energy Agency. Environment Laboratories; Mónaco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Marec, M.. Laval University; Canadá Fil: Babin, M.. Laval University; Canadá Fil: Fortier, L.. Laval University; Canadá Fil: Forest, A.. Laval University; Canadá

Scientific Reports 7: Article number: 43332; published online: 24 February 2017; updated: 20 October 2017. This Article contains an error in Figure 3, where the sedimentation rate from Besòs-3 ‘0.078 cm/y’ is incorrectly given as ‘0.39 cm/y’. The correct Figure 3 appears below as Figure 1.

26 pages, 7 figures, 2 tables, supplementary material https://www.frontiersin.org/article/10.3389/fmars.2017.00005/full#supplementary-material, Submarine canyons are major geomorphic features of continental margins around the world. Several recent multidisciplinary projects focused on the study of canyons have considerably increased our understanding of their ecological role, the goods, and services they provide to human populations, and the impacts that human activities have on their overall ecological condition. Pressures from human activities include fishing, dumping of land-based mine tailings, and oil and gas extraction. Moreover, hydrodynamic processes of canyons enhance the down-canyon transport of litter. The effects of climate change may modify the intensity of currents. This potential hydrographic change is predicted to impact the structure and functioning of canyon communities as well as affect nutrient supply to the deep-ocean ecosystem. This review not only identifies the ecological status of canyons, and current and future issues for canyon conservation, but also highlights the need for a better understanding of anthropogenic impacts on canyon ecosystems and proposes other research required to inform management measures to protect canyon ecosystems, UF was funded by the Balearic Government post-doctoral grant 2016, co-financed by European Social Plan; VH was supported by the CODEMAP project (ERC Starting Grant no 258482) and the NERC MAREMAP programme; PP has been funded by the ABIDES project (CTM2015-65142-R); AR was supported by NIWA research project “Impact of resource use on vulnerable deep-sea communities” (MBIE contract CO1X0906). IV was funded by Ifremer and Région Bretagne. ALA is supported by Science Foundation Ireland / Marine Institute IvP award 15/IA/3100

6 pages, 4 figures, Bottom trawling has many impacts on marine ecosystems, including seafood stock impoverishment, benthos mortality, and sediment resuspension. Historical records of this fishing practice date back to the mid-1300s. Trawling became a widespread practice in the late 19th century, and it is now progressively expanding to greater depths, with the concerns about its sustainability that emerged during the first half of the 20th century now increasing. We show here that compared with untrawled areas, chronically trawled sediments along the continental slope of the north-western Mediterranean Sea are characterized by significant decreases in organic matter content (up to 52%), slower organic carbon turnover (ca. 37%), and reduced meiofauna abundance (80%), biodiversity (50%), and nematode species richness (25%). We estimate that the organic carbon removed daily by trawling in the region under scrutiny represents as much as 60-100% of the input flux. We anticipate that such an impact is causing the degradation of deep-sea sedimentary habitats and an infaunal depauperation. With deep-sea trawling currently conducted along most continental margins, we conclude that trawling represents a major threat to the deep seafloor ecosystem at the global scale, This study was conducted within the framework of the Hotspot Ecosystem Research and Man’s Impact On European Seas European Union Collaborative Project (EC Contract 226354). The oceanographic cruise was funded by the Spanish Research Plan (Project CTM2010-11084-E). This study was supported by the Project Ricerca Italiana per il Mare. J.M. received funding from a Junta para la Ampliación de Estudios contract granted by Consejo Superior de Investigaciones Científicas and cofinanced by the European Social Fund. P.M. acknowledges funding from the Government of Catalonia through the Institució Catalana de Recerca i Estudis Avançats Academia prize

The winter of 2012 experienced peculiar atmospheric conditions that triggered a massive formation of dense water on the continental shelf and in the deep basin of the Gulf of Lions. Multiplatforms observations enabled a synoptic view of dense water formation and spreading at basin scale. Five months after its formation, the dense water of coastal origin created a distinct bottom layer up to a few hundreds of meters thick over the central part of the NW Mediterranean basin, which was overlaid by a layer of newly formed deep water produced by open-sea convection. These new observations highlight the role of intense episodes of both dense shelf water cascading and open-sea convection to the progressive modification of the NW Mediterranean deep waters.

The process of resuspension by bottom trawling leads to recurrent transfer of sediment from shallower to deeper areas, and occurs practically worldwide. Recent studies have shown the importance of trawling as a driver of sediment transfer in canyons. Our aim is to assess trawling impact on sediment dynamics in La Fonera submarine canyon (NW Mediterranean). Our methodology combines inverse modelling and the implementation of a numerical process-based model, and allows us to simulate trawling-induced flows in the canyon on the basis of trawling fleet activity (derived from Vessel Monitoring System data). The model simulates turbidity current hydrodynamics and deposition for events whose magnitude and initial volume concentration is defined from the inverse analysis. Mooring data in the axis of a tributary valley is used to validate the model hypothesis. Based on the good agreement found between modelled transport and measurements at the mooring site, we have quantified fishing activity over the fishing grounds and obtained the propagation patterns of the resuspended sediment towards the canyon axis and beyond. Trawling-induced sediment flows lead to the development of new trawl-driven depocentres.

5 pages, 4 figures, Bottom trawling is a non-selective commercial fishing technique whereby heavy nets and gear are pulled along the sea floor. The direct impact of this technique on fish populations1, 2 and benthic communities3, 4 has received much attention, but trawling can also modify the physical properties of seafloor sediments, water–sediment chemical exchanges and sediment fluxes5, 6. Most of the studies addressing the physical disturbances of trawl gear on the seabed have been undertaken in coastal and shelf environments7, 8, however, where the capacity of trawling to modify the seafloor morphology coexists with high-energy natural processes driving sediment erosion, transport and deposition9. Here we show that on upper continental slopes, the reworking of the deep sea floor by trawling gradually modifies the shape of the submarine landscape over large spatial scales. We found that trawling-induced sediment displacement and removal from fishing grounds causes the morphology of the deep sea floor to become smoother over time, reducing its original complexity as shown by high-resolution seafloor relief maps. Our results suggest that in recent decades, following the industrialization of fishing fleets, bottom trawling has become an important driver of deep seascape evolution. Given the global dimension of this type of fishery, we anticipate that the morphology of the upper continental slope in many parts of the world’s oceans could be altered by intensive bottom trawling, producing comparable effects on the deep sea floor to those generated by agricultural ploughing on land, This work was supported by various research projects: HERMIONE (226354 and CTM2010-11084-E), DOS MARES (CTM2010-21810-C03),OASIS DEL MAR—Obra Social ‘‘la Caixa’’, GRACCIE-CONSOLIDER (CSD2007-00067) and REDECO (CTM2008-04973-E). We also received support from Catalan Government Grups de Recerca Consolidats grants (2009 SGR 899 and 1305). VMS data and support were provided by the Spanish General Secretariat of Maritime Fishing (SEGEMAR). Assistance at sea by the crews of RV Hespérides, RV Sarmiento de Gamboa and RV García del Cid is also acknowledged. J.M. was funded through a JAE-DOC contract granted by Consejo Superior de Investigaciones Científicas and co-financed by the European Social Fund. F. Sarda and T. Milligan provided comments on the manuscript. The final document benefited from a review by P. Talling

21 pages, 13 figures, 4 tables, The DYFAMED time-series station, located in the open Ligurian Sea, is one of the few pluriannual flux programs in the world and the longest in the Mediterranean Sea. The trap data series is one of only three multi-decadal data sets in existence, and it provides flux information for an environment that is distinct from the other long-term data sets. At DYFAMED, downward fluxes of particles, carbon and other major elements have been regularly measured with sediment traps since 1986 at fixed depths of 200 and 1000 m. An overview is presented of the main trends of particle and carbon fluxes observed during the period 1988–2005, period when the mooring was located on the northern side of the Ligurian Sea. In spite of considerable interannual variability, fluxes displayed a marked seasonal pattern with the highest fluxes occurring during winter and spring and lowest fluxes throughout the stratified season (summer–autumn). Organic carbon fluxes measured at both depths were highly variable over time, ranging from 0.3 to 59.9 (mean 6.8) mg C m−2 d−1 at 200 m, and from 0.2 to 37.1 (mean 4.3) mg C m−2 d−1 at 1000 m. Mass fluxes were maximal in winter, whereas carbon fluxes were maximal in late spring. Reasonably good agreement existed between particle fluxes at both depths over the years, indicating a relatively efficient and rapid transport of particles from the upper ocean to the deep sea. However, during certain periods mass flux increased with depth suggesting lateral inputs of particles that by-pass the upper trap. Since 1999, the system has apparently shifted towards an increasing occurrence of extreme flux events in response to more vigorous mixing of the water column during the winter months. Although annual mass fluxes have increased in the last years, mean POC fluxes have not substantially changed over time, due mainly to lower carbon contents of the sinking particles during maxima of mass flux, J. Martín was partially funded by ‘‘Secretaría de Estado de Universidades e Investigación del Ministerio de Educación y Ciencia’’ (Spanish Ministry of Science) and by ‘‘Fundación Española para la Ciencia y la Tecnología’’ (FECYT). The International atomic Energy Agency is grateful to the Government of the Principality of Monaco for the support provided to its Environment Laboratories

Simultaneous measurements of atmospheric deposition and of sinking particles at 200 and 1000 m depth, were performed in the Ligurian Sea (North-Western Mediterranean) between 2003 and 2007, along with phytoplanktonic activity derived from satellite images. Atmospheric deposition of Saharan dust particles was very irregular and confirmed the importance of sporadic high magnitude events over the annual average (11.4 g m−2 yr−1 for the 4 years). The average marine total mass flux was 31 g m−2 yr−1, the larger fraction being the lithogenic one (~37%). The marine total mass flux displayed a seasonal pattern with a maximum in winter, occurring before the onset of the spring bloom. The highest POC fluxes did not occur during the spring bloom nor could they be directly related to any noticeable increase in the surface phytoplanktonic biomass. Over the 4 years of the study, the strongest POC fluxes were concomitant with large increases of the lithogenic marine flux, which had originated from either recent Saharan fallout events (February 2004 and August 2005), from "old" Saharan dust "stored" in the upper water column layer (March 2003 and February 2005), or alternatively from lithogenic material originating from Ligurian riverine flooding (December 2003, Arno, Roya and Var rivers). Those associated export fluxes defined as "lithogenic events", are believed to result from a combination of forcing (winter mixing or Saharan events, in particular extreme ones), biological (zooplankton) activity, and also organic-mineral aggregation inducing a ballast effect. By fertilising the surface layer, mixed Saharan dust events were shown to be able to induce "lithogenic events" during the stratification period. These events would be more efficient in transferring POC to the deeper layers than the spring bloom itself. The extreme Saharan event of February 2004 exported ~45% of the total annual POC, compared to an average of ~25% for the bloom period. This emphasises the role played by these "lithogenic events", and in particular those that are induced by the more extreme Saharan events, in the carbon export efficiency in the North-western Mediterranean Sea.

Characterization of atmospheric aerosols collected in Monaco (2004–2008) and in sediment traps at 200 m and 1000 m water depths at the DYFAMED (Dynamics of Atmospheric Fluxes in the Mediterranean Sea) station (2004) was carried out to improve our understanding of the impact of Saharan dust on ground-level air and on the water column. Activity concentrations of natural (Pb, Po, uranium and radium isotopes) and anthropogenic (Cs, Pu, Pu, and Pu) radionuclides and their isotopic ratios confirmed a Saharan impact on the investigated samples. In association with a large particulate matter deposition event in Monaco on 20 February 2004, the Cs (∼40 Bq kg) and Pu (∼1 Bq kg) activities were almost a factor of two higher than other Saharan deposition dust events. This single-day particle flux represented 72% of the annual atmospheric deposition in Monaco. The annual deposition of Saharan dust on the sea was 232–407 mBq m for Cs and 6.8–9.8 mBq m for Pu and contributed significantly (28–37% for Cs and 34–45% for Pu) to the total annual atmospheric input to the northwest Mediterranean Sea. The Cs/Pu activity ratios in dust samples collected during different Saharan dust events confirmed their global fallout origin or mixing with local re-suspended soil particles. In the sediment trap samples the Cs activity varied by a factor of two, while the Pu activity was constant, confirming the different behaviors of Cs (dissolved) and Pu (particle reactive) in the water column. The Cs and Pu activities of sinking particles during the period of the highest mass flux collected in 20 February 2004 at the 200 m and 1000 m water depths represented about 10% and 15%, respectively, of annual deposition from Saharan dust events., PPP acknowledges a support provided by the EU Research and Development Operational Program funded by the ERDF (project No. 26240220004). The IAEA is grateful to the Government of the Principality of Monaco for the support provided to its Environment Laboratories.

15 pages, 15 figures, Transfers of particulate matter on continental margins primarily occur during energetic events. As part of the CASCADE (CAscading, Storm, Convection, Advection and Downwelling Events) experiment, a glider equipped with optical sensors was deployed in the coastal area of the Gulf of Lions, NW Mediterranean in March 2011 to assess the spatio-temporal variability of hydrology, suspended particles properties and fluxes during energetic conditions. This deployment complemented a larger observational effort, a part of the MOOSE (Mediterranean Ocean Observing System of the Environment) network, composed of a coastal benthic station, a surface buoy and moorings on the continental slope. This set of observations permitted to measure the impact of three consecutive storms and a flood event across the entire continental shelf. Glider data showed that the sediment resuspension and transport observed at the coastal station during the largest storm (Hs>4m) was effective down to a water depth of 80m. The mid-shelf mud belt, located between 40 and 90m depth, appears as the zone where the along-shelf flux of suspended sediment is maximum. Besides, the across-shelf flux of suspended sediment converges towards the outer limit of the mid-shelf mud belt, where deposition of suspended particles probably occurs and contributes to the nourishment of this area. Hydrological structures, suspended particles transport and properties changed drastically during stormy periods and the following flood event. Prior to the storms, the shelf waters were weakly stratified due in particular to the presence of cold dense water on the inner- and mid-shelf. The storms rapidly swept away this dense water, as well as the resuspended sediments, along the shelf and towards a downstream submarine canyon. The buoyant river plumes that spread along the shelf after the flooding period provoked a restratification of the water column on the inner- and mid-shelf. The analysis of glider's optical data at different wavelengths suggests that the coastal area and the bottom nepheloid layer during the largest storm are primarily composed of coarse particles, probably macroflocs, and that the size of particles decreases further offshore. A similar trend, albeit less contrasted, is observed after the flooding. This work provided a unique synoptic view across the entire shelf of the impact of a typical Mediterranean storm on bottom sediment erosion and particulate fluxes. Repeated glider transects across the south-western part of the Gulf of Lions shelf permitted for the first time to measure continuously the thermo-haline structures, the suspended particles concentrations and size, the current speed, and to estimate the particulate transport before, during and after typical Mediterranean storm events. Glider data complement and compare well with concomitant high frequency time series at fixed stations along the coast and in a downstream submarine canyon. © 2015 Elsevier Ltd., This work was funded by the HERMIONE Project (FP7-ENV-2008-1-226354) under the European Commission's Seventh Framework Program, the MERMEX project under the MISTRALS Programme, and the TUCPA project under the CNRS EC2CO DRILL Programme

8 pages, 4 figures, Previous studies conducted in La Fonera (Palamós) submarine canyon (NW Mediterranean) found that trawling activities along the canyon flanks cause resuspension and transport of sediments toward the canyon axis. 210Pb chronology supported by 137Cs dating applied to a sediment core collected at 1750 m in 2002 suggested a doubling of the sediment accumulation rate since the 1970s, coincident with the rapid industrialization of the local trawling fleet. The same canyon area has been revisited a decade later, and new data are consistent with a sedimentary regime shift during the 1970s and also suggest that the accumulation rate during the last decade could be greater than expected, approaching ~2.4 cm yr−1 (compared to ~0.25 cm yr−1 pre-1970s). These results support the hypothesis that commercial bottom trawling can substantially affect sediment dynamics and budgets on continental margins, eventually initiating the formation of anthropogenic depocenters in submarine canyon environments, This work was funded by the HERMIONE and PERSEUS projects (7FP grant agreements: 226354 and 287600) and by the Generalitat de Catalunya supporting grants 2014 SGR-1642 and 2014 SGR-1356. P. Masqué acknowledges the financial support through the ICREA Academia award and by a Gledden Visiting Fellowship awarded by the Institute of Advanced Studies at the University of Western Australia

Currents, particle fluxes and ecology were studied in the Palamós submarine canyon (also known as the Fonera canyon), located in the northwestern Mediterranean. Seven mooring arrays equipped with current meters and sediment traps were deployed along the main canyon axis, on the canyon walls and on the adjacent slope. Additionally, local and regional hydrographic cruises were carried out. Current data showed that mean near surface and mid-depth currents were oriented along the mean flow direction (NE-SW), although at 400 and 1200 m depth within the canyon current reversals were significant, indicating a more closed circulation inside the canyon. Mean near-bottom currents were constrained by the local bathymetry, especially at the canyon head. The most significant frequency at all levels was the inertial frequency. A second frequency of about three days, attributed to a topographic wave, was observed at all depths, suggesting that this wave was probably not trapped near the bottom. The current field observed during the most complete survey revealed a meandering pattern with cyclonic vorticity just upstream from and within the canyon. The associated vertical velocity ranged between 10 and 20 m/day and was constrained to the upper 300 m. This latter feature, together with other computations, suggests that during this survey the meander was not induced by the canyon but by some kind of instability of the mean flow. In the canyon, suspended sediment concentration, downward particle fluxes, chlorophyll and particulate C and N were significantly higher up-canyon from about 1200 m depth than offshore, defining, along with the different hydrodynamics, two canyon domains: one from the canyon head to about 1200 m depth more affected by the canyon confinement and the other deeper than 1200 m depth more controlled by the mean flow and the shelf-slope front. The higher near-bottom downward total mass fluxes were recorded in the canyon axis at 1200 m depth along with sharp turbidity increases and are related to sediment gravity flows. During the deployment period, the increase in downward particle fluxes occurred by mid-November, when a severe storm took place. On the canyon walls at 1200 m depth, suspended sediment concentrations, downward particle fluxes, chlorophyll and particulate C and N were higher on the southern wall than on the northern wall inversely to the current's energy. This could be caused by an upward water supply on the southern canyon wall and/or the mean flow interacting with the canyon bathymetry. In the swimmers collected by the sediment traps, the dominant species was an elasipod holothurian, which has not been recorded in other canyons or elsewhere in the Mediterranean, indicating particular speciation. © 2005 Elsevier Ltd. All rights reserved.

15 pages, 6 figures, Fishing gear and techniques have evolved through the centuries, and particularly after the Second World War, towards a mass production industry in such a scale that it has placed many commercial stocks in a delicate or depleted status. Furthermore, certain fishing methods have other undesirable side effects on ecosystems and habitats. In this work, the known impacts of bottom-dragged gear on the seafloor are reviewed. Some of the least known issues are emphasized, namely, impacts on the physical properties of deep-sea sediments, resuspension, erosion, near-bottom turbidity and seabed morphology. Due to its recurrence, mobility and wide geographical extent, bottom trawling has become an effective driver on shaping the physical basis of benthic habitats: its composition, texture and morphology at scales from micro to the entire continental margin. It is concluded that trawling is comparable in its transforming power over seascapes to the effects of agriculture or deforestation on land. © 2015 2015 Elsevier B.V. All rights reserved

Special issue Submarine Canyons: Complex Deep-Sea Environments Unravelled by Multidisciplinary Research.-- 11 pages, 5 figures, 2 tables, The Cap-Ferret Canyon (CFC), a major morphologic feature of the eastern margin of the Bay of Biscay, occupies a deep structural depression that opens about 60km southwest of the Gironde Estuary. Detailed depth profiles of the particle-reactive radionuclides 234Th and 210Pb in interface sediments were used to characterise the present sedimentation (bioturbation, sediment mass accumulation, and focusing) in the CFC region. Two bathymetric transects were sampled along the CFC axis and the southern adjacent margin. Particle fluxes were recorded from the nearby Landes Plateau by means of sediment traps in 2006 and 2007. This dataset provides a new and comprehensive view of particulate matter transfer in the Cap-Ferret Canyon region, through a direct comparison of the canyon with the adjacent southern margin. Radionuclide profiles (234Th and 210Pb) and mass fluxes demonstrate that significant particle dynamics occur on the SE Aquitanian margin in comparison with nearby margins. The results also suggest show three distinct areas in terms of sedimentary activity. In the upper canyon (2000m) can be considered inactive at annual or decadal scales. In contrast with the slow and continuous accumulation of relatively fresh material that characterises the middle canyon, the lower canyon receives pulses of sediment via gravity flows on longer time scales. At decadal scale, the CFC can be considered as a relatively quiescent canyon. The disconnection of the CFC from major sources of sediment delivery seems to limit its efficiency in particle transfer from coastal areas to the adjacent ocean basin. © 2013 Elsevier Ltd., Cruises were supported respectively by the ANR FORCLIM and EC2CO BIOMIN programs.The acquisition of the low-background gamma detector was funded in part by the CNRS (LEBE-CYBER), the Aquitain Research council and the University of Bordeaux. A3-year doctoral fellowship was provided to P.Duros by the Regional Council of Pays de la Loire

28 pages, 5 figures, Submarine canyons are morphological incisions into continental margins that act as major conduits of sediment from shallow- to deep-sea regions. However, the exact mechanisms involved in sediment transfer within submarine canyons are still a subject of investigation. Several studies have provided direct information about contemporary sedimentary processes in submarine canyons that suggests different modes of transport and various triggering mechanisms. Storm-induced turbidity currents and enhanced off-shelf advection, hyperpycnal flows and failures of recently deposited fluvial sediments, dense shelf-water cascading, canyon-flank failures, and trawling-induced resuspension largely dominate present-day sediment transfer through canyons. Additionally, internal waves periodically resuspend ephemeral deposits within canyons and contribute to dispersing particles or retaining and accumulating them in specific regions. These transport processes commonly deposit sediments in the upper- and middle-canyon reaches for decades or centuries before being completely or partially flushed farther down-canyon by large sediment failures. Copyright © 2014 by Annual Reviews

16 pages, 14 figures, 1 table, A monitoring effort to address the physical effects of bottom trawling was conducted on the Ebro prodeltaic mud belt during the RESPONSE project. The monitoring was carried out for 14 months covering periods of different trawling intensities and a close season for the trawling fleet. The seabed morphology was studied by side-scan sonar and sediment texture and organic carbon content were analysed. Suspended sediment vertical distribution was recorded by CTD+turbidity hydrographic profiles and sediment transport was computed using time series from moored turbidimeters and current meters. The results show that the seabed of the fishing ground is strongly affected by scraping and ploughing induced by bottom trawling. Part of the finer fraction of the prodeltaic mud resuspended by trawling is winnowed, increasing the silt content of the settling sediment and also near-bottom turbidity. Sediment resuspended by trawling is incorporated in the bottom nepheloid layer and transported across- and along-shelf, increasing sediment fluxes. Trawling also induces an increase in the organic carbon content in the bottom sediment. All these effects induced by trawling have occurred during the last few decades, changing natural conditions in the fishing ground. © 2013 Elsevier Ltd., Data used in this work was collected in the framework of the EU Research Project RESPONSE (Q5RS-2002-00787) and the Research Project COSTEM (CTM2009-07806) funded by the Ministerio de Ciencia e Innovación. [...] A.P., P.P.J.G. and J.M.belong to CRG on Littoral and Oceanic Processes, supported by Grant 2009 SGR 899 of the Generalitat de Catalunya. J. Martín is funded through a JAE-DOC contract within the program “Junta para la Ampliaciónd e Estudios”, granted by the Consejo Superior de Investigaciones Científicas (Spanish National Research Council) and co-financed by the European Social Fund

10 pages, 8 figures, Commercial bottom trawling is one of the anthropogenic activities causing the biggest impact on the seafloor due to its recurrence and global distribution. In particular, trawling has been proposed as a major driver of sediment dynamics at depths below the reach of storm waves, but the issue is at present poorly documented with direct observations. This paper analyses changes in water turbidity in a tributary valley of the La Fonera (=Palamós) submarine canyon, whose flanks are routinely exploited by a local trawling fleet down to depths of 800 m. A string of turbidimeters was deployed at 980 m water depth inside the tributary for two consecutive years, 2010–2011. The second year, an ADCP profiled the currents 80 m above the seafloor. The results illustrate that near-bottom water turbidity at the study site is heavily dominated, both in its magnitude and temporal patterns, by trawling-induced sediment resuspension at the fishing ground. Resuspended sediments are channelised along the tributary in the form of sediment gravity flows, being recorded only during working days and working hours of the trawling fleet. These sediment gravity flows generate turbid plumes that extend to at least 100 m above the bottom, reaching suspended sediment concentrations up to 236 mg l−1 close to the seafloor (5 m above bottom). A few hours after the end of daily trawling activities, water turbidity progressively decreases but resuspended particles remain in suspension for several hours, developing bottom and intermediate nepheloid layers that reach background levels ∼2 mg l−1 before trawling activities resume. The presence of these nepheloid layers was recorded in a CTD+turbidimeter transect conducted across the fishing ground a few hours after the end of a working day. These results highlight that deep bottom trawling can effectively replace natural processes as the main driving force of sediment resuspension on continental slope regions and generate increased near-bottom water turbidity that propagates from fishing grounds to wider and deeper areas via sediment gravity flows and nepheloid layer development, We are grateful to the crew and officers of B/O García del Cid (CSIC) and “Lluerna” (Generalitat de Catalunya) and to the participants in the HERMIONE-I & II surveys for their help at sea. This work is funded by the HERMIONE project (Grant agreement 226354) under the European Commission's 7th framework Programme. J. Martín was funded through a JAE DOC contract within the Program «Junta para la Ampliación de Estudios», granted by Consejo Superior de Investigaciones Científicas and co-financed by the European Social Fund. We thank the two anonymous reviewers who helped to improve the submitted manuscript through their constructive comments

27 pages, 12 figures, 13 tables, Molecular lipid biomarkers (hydrocarbons, alcohols, sterols and fatty acids) and compound-specific isotope analysis of suspended particulate organic matter (SPM) and surface sediments of the Mackenzie Shelf and slope (southeast Beaufort Sea, Arctic Ocean) were studied in summer 2009. The concentrations of the molecular lipid markers, characteristic of known organic matter sources, were grouped and used as proxies to evaluate the relative importance of fresh algal, detrital algal, fossil, C3 terrestrial plants, bacterial and zooplankton material in the organic matter (OM) of this area. Fossil and detrital algal contributions were the major fractions of the freshwater SPM from the Mackenzie River with ~34% each of the total molecular biomarkers. Fresh algal, C3 terrestrial, bacterial and zooplanktonic components represented much lower percentages, 17, 10, 4 and 80%), with a minor contribution of fossil and C3 terrestrial biomarkers. Characterization of the sediments revealed a major sink of refractory algal material mixed with some fresh algal material, fossil hydrocarbons and a small input of C3 terrestrial sources. In particular, the sediments from the shelf and at the mouth of the Amundsen Gulf presented the highest contribution of detrital algal material (60–75%), whereas those from the slope contained the highest proportion of fossil (40%) and C3 terrestrial plant material (10%). Overall, considering that the detrital algal material is marine derived, autochthonous sources contributed more than allochthonous sources to the OM lipid pool. Using the ratio of an allochthonous biomarker (normalized to total organic carbon, TOC) found in the sediments to those measured at the river mouth water, we estimated that the fraction of terrestrial material preserved in the sediments accounted for 30–40% of the total carbon in the inner shelf sediments, 17% in the outer shelf and Amundsen Gulf and up to 25% in the slope sediments. These estimates are low compared to other studies conducted 5–20 yr earlier, and they support the increase in primary production during the last decade mainly because of the increase in the number of ice-free days and due to the strength and persistence of winds favouring upwelling, The IAEA is grateful for the support provided to the Environment Laboratories by the Government of the Principality of Monaco. This study was conducted as part of the Malina Scientific Program funded by ANR (Agence nationale de la recherche), INSU-CNRS (Institut national des sciences de l’univers – Centre national de la recherche scientifique), CNES (Centre national d’etudes spatiales) and ESA (European Space Agency). The authors would like to thank M. Babin, chief scientist of the cruise and coordinator of the Malina program, A. Forest, H. Link and G. Chaillou and three anonymous reviewers for their constructive comments

Forest, A. ...et al. -- 34 pages, 19 figures, 5 tables, A better understanding of how environmental changes affect organic matter fluxes in Arctic marine ecosystems is sorely needed. Here we combine mooring times series, ship-based measurements and remote sensing to assess the variability and forcing factors of vertical fluxes of particulate organic carbon (POC) across the Mackenzie Shelf in 2009. We developed a geospatial model of these fluxes to proceed to an integrative analysis of their determinants in summer. Flux data were obtained with sediment traps moored around 125 m and via a regional empirical algorithm applied to particle size distributions (17 classes from 0.08–4.2 mm) measured by an Underwater Vision Profiler 5. The low fractal dimension (i.e., porous, fluffy particles) derived from the algorithm (1.26 ± 0.34) and the dominance (~ 77%) of rapidly sinking small aggregates (< 0.5 mm) in total fluxes suggested that settling material was the product of recent aggregation processes between marine detritus, gel-like substances, and ballast minerals. Modeled settling velocity of small and large aggregates was, respectively, higher and lower than in previous studies within which a high fractal dimension (i.e., more compact particles) was consequential of deep-trap collection (~400–1300 m). Redundancy analyses and forward selection of abiotic/biotic parameters, linear trends, and spatial structures (i.e., principal coordinates of neighbor matrices, PCNM) were conducted to partition the variation of the 17 POC flux size classes. Flux variability was explained at 69.5% by the addition of a temporal trend, 7 significant PCNM, and 9 biophysical variables. The first PCNM canonical axis (44.5% of spatial variance) reflected the total magnitude of POC fluxes through a shelf-basin gradient controlled by bottom depth and sea ice concentration (p < 0.01). The second most important spatial structure (5.0%) corresponded to areas where shelf break upwelling is known to occur under easterlies and where phytoplankton was dominated by diatoms. Among biophysical parameters, bacterial production and northeasterly wind (upwelling-favorable) were the two strongest corollaries of POC fluxes (r2 cum. = 0.37). Bacteria were correlated with small aggregates, while northeasterly wind was associated with large size classes (> 1 mm ESD), but these two factors were weakly related with each other. Copepod biomass was overall negatively correlated (p < 0.05) with vertical POC fluxes, implying that metazoans acted as regulators of export fluxes, even if their role was minor given that our study spanned the onset of diapause. Our results demonstrate that on interior Arctic shelves where productivity is low in mid-summer, localized upwelling zones (nutrient enrichment) may result in the formation of large filamentous phytoaggregates that are not substantially retained by copepod and bacterial communities, This work would not have been possible without the professional and enthusiastic assistance of the officers and crew members of the CCGS Amundsen. We express gratitude to L. Prieur and C. Marec for their help in the deployment of the CTD rosette and for the onboard processing of UVP5 data. We thank J. Martin, J. Gagnon, A. Mignot, and M. Gosselin for sharing the chlorophyll data in order to post-calibrate the fluorometer. We thank P. Guillot for the validation of physical data. We thank M. Fortier, K. L´evesque, and J. Ehn for the organization of the fieldwork and workshops and for support at sea. We are grateful to three anonymous reviewers for insightful comments that improved the initial manuscript. This study was conducted as part of the Malina Scientific Program funded by ANR (Agence nationale de la recherche), INSU-CNRS (Institut national des sciences de l’univers – Centre national de la recherche scientifique), CNES (Centre national d’´etudes spatiales) and ESA (European Space Agency). Additional support from ArcticNet (a Network of Centres of Excellence of Canada) and from the ArcticNet-Imperial Oil Research Collaboration was welcomed and appreciated. The IAEA is grateful to the Government of the Principality of Monaco for the support provided to its Environment Laboratories. This work is a joint contribution to the Malina Project and to the research programs of Qu´ebec-Oc´ean, ArcticNet, the Takuvik Joint Universit´e Laval/CNRS Laboratory, the Arctic in Rapid Transition (ART) Initiative, to the Canada Research Chair on the Response of Marine Arctic Ecosystems to Climate Warming, and to the Canada Excellence Research Chair (CERC) in Remote Sensing of Canada’s New Arctic Frontier

Martín, Jacobo ...et al. -- 19 pages, 12 figures, Cap de Creus Canyon (CCC) is known as a preferential conduit for particulate matter leaving the Gulf of Lion continental shelf towards the slope and the basin, particularly in winter when storms and dense shelf water cascading coalesce to enhance the seaward export of shelf waters. During the CASCADE (CAscading, Storm, Convection, Advection and Downwelling Events) cruise in March 2011, deployments of recording instruments within the canyon and vertical profiling of the water column properties were conducted to study with high spatial-temporal resolution the impact of such processes on particulate matter fluxes. In the context of the mild and wet 2010–2011 winter, no remarkable dense shelf water formation was observed. On the other hand, the experimental setup allowed for the study of the impact of E-SE storms on the hydrographical structure and the particulate matter fluxes in the CCC. The most remarkable feature in terms of sediment transport was a period of dominant E-SE winds from 12 to 16 March, including two moderate storms (maximum significant wave heights = 4.1–4.6 m). During this period, a plume of freshened, relatively cold and turbid water flowed at high speeds along the southern flank of the CCC in an approximate depth range of 150–350 m. The density of this water mass was lighter than the ambient water in the canyon, indicating that it did not cascade off-shelf and that it merely downwelled into the canyon forced by the strong cyclonic circulation induced over the shelf during the storms and by the subsequent accumulation of seawater along the coast. Suspended sediment load in this turbid intrusion recorded along the southern canyon flank oscillated between 10 and 50 mg L−1, and maximum currents speeds reached values up to 90 cm s−1. A rough estimation of 105 tons of sediment was transported through the canyon along its southern wall during a 3-day-long period of storm-induced downwelling. Following the veering of the wind direction (from SE to NW) on 16 March, downwelling ceased, currents inside the canyon reversed from down- to up-canyon, and the turbid shelf plume was evacuated from the canyon, most probably flowing along the southern canyon flank and being entrained by the general SW circulation after leaving the canyon confinement. This study highlights that remarkable sediment transport occurs in the CCC, and particularly along its southern flank, even during mild and wet winters, in absence of cascading and under limited external forcing. The sediment transport associated with eastern storms like the ones described in this paper tends to enter the canyon by its downstream flank, partially affecting the canyon head region. Sediment transport during these events is not constrained near the seafloor but distributed in a depth range of 200–300 m above the bottom. Our paper broadens the understanding of the complex set of atmosphere-driven sediment transport processes acting in this highly dynamic area of the northwestern Mediterranean Sea, We are grateful to the crew and officials of R/V l’Atalante and to all the scientific and technical staff involved in the CASCADE cruise. This work was funded by the HERMIONE Project (FP7-ENV-2008-1-226354) under the European Commission’s Seventh Framework Programme, the French programme MERMEX under the MISTRALS framework, the GRACCIE-CONSOLIDER project (CSD2007-00067) and the Spanish project DOS MARES (CTM2010-21810-C03-01). University of Barcelona researchers benefitted from grant 2009 SGR 1305 by Generalitat de Catalunya to excellence research groups. L. Houpert acknowledges the support of the Direction Générale de l’Armement (supervisor: Elisabeth Gibert-Brunet). J. Martín was funded through a JAE-DOC contract within the programme “Junta para la Ampliación de Estudios”, granted by Consejo Superior de Investigaciones Científicas (Spain) and co-financed by the European Social Fund. We thank the constructive comments of two reviewers who helped to improve the manuscript

61 pages, 12 figures, 13 tables, Molecular lipid biomarkers (hydrocarbons, alcohols, sterols and fatty acids) and compound specific isotope analysis of suspended particulate organic matter (SPM) and surface sediments of the Mackenzie Shelf and slope (Southeast Beaufort Sea, Arctic Ocean), were studied in summer 2009. The concentrations of the molecular lipid markers, characteristic of known organic matter sources, were grouped and used as proxies to evaluate the relative importance of fresh algal, detrital algal, fossil, C3 terrestrial plants, bacterial and zooplankton material in the sedimentary organic matter (OM). Fossil and detrital algal contributions were the major fractions of the freshwater SPM from the Mackenzie River with ~34% each of the total molecular biomarkers. Fresh algal, C3 terrestrial, bacterial and zooplanktonic components represented much lower percentages, 17, 10, 4 and < 1%, respectively. In marine SPM from the Mackenzie slope, the major contributions were fresh and detrital algal components (> 80%) with a minor contribution of fossil and C3 terrestrial biomarkers. Characterization of the sediments revealed a major sink of refractory algal material mixed with some fresh algal material, fossil hydrocarbons and a small input of C3 terrestrial sources. In particular, the sediments from the shelf and at the mouth of the Amundsen Gulf presented the highest contribution of detrital algal material (60–75%) whereas those from the slope contained the highest proportion of fossil (40%) and C3 terrestrial plant material (10%). Overall, considering that the detrital algal material is marine derived, autochthonous sources contributed more than allochthonous sources to the OM lipid pool. Using the ratio of an allochthonous biomarker (normalized to total organic carbon, TOC) found in the sediments to those measured at the river mouth water, we estimated that the fraction of terrestrial material preserved in the sediments accounted for 30–40% of the total carbon in the inner shelf sediments, 17% in the outer shelf and Amundsen Gulf and up to 25% in the slope sediments, The IAEA is grateful for the support provided to the Environment Laboratories by the Government of the Principality of Monaco. This study was conducted as part of the Malina Scientific Program funded by ANR (Agence nationale de la recherche), INSU-CNRS (Institut national des sciences de l’univers – Centre national de la recherche scientifique), CNES (Centre national d’ etudes spatiales) and ESA (European Space Agency)

15 pages, 14 figures, An array of mooring lines deployed between 300 and 1900 m depth along the Lacaze-Duthiers and Cap de Creus canyons and in the adjacent southern open slope was used to study the water and sediment transport on the western Gulf of Lions margin during the 2006 intense cascading period. Deep-reaching cascading pulses occurred in early January, in late January and from early March to mid-April. Dense water and sediment transport to the deep environments occurred not only through submarine canyons, but also along the southern open slope. During the deep cascading pulses, temporary upper and mid-canyon and open slope deposits were an important source of sediment to the deep margin. Significant sediment transport events at the canyon head only occurred in early January because of higher sediment availability on the shelf after the stratified and calm season, and in late February because of the interaction of dense shelf water cascading with a strong E–SE storm. During the January deep cascading pulses, increases in suspended sediment concentration within the canyon were greater and earlier at 1000 m depth than at 300 m depth, whereas during the March–April deep cascading pulses sediment concentration only increased below 300 m depth, indicating resuspension and redistribution of sediments previously deposited at upper and mid-canyon depths. Deeper than 1000 m depth, net fluxes show that most of the suspended sediment left the canyon and flowed along the southern open slope towards the Catalan margin, whereas a small part flowed down-canyon and was exported basinward. Additionally, on the mid- and lower-continental slope there was an increase in the near-bottom currents induced by deep open-sea convection processes and the propagation of eddies. This, combined with the arrival of deep cascading pulses, also generated moderate suspended sediment transport events in the deeper slope regions, We thank all participants, UTM technicians and crews of R/V Garcia del Cid and R/V Universitatis, for their help and dedication during the cruises. The research projects HERMES (GOCE-CT-2005-511234-1), HERMIONE (FP7-ENV-2008-1-226354), DOS MARES (CTM2007-66316-C02-01/MAR) and GRACCIE-CONSOLIDER (CSD2007-00067) supported this research. A.S.V., C.P., A.C. and M.C. belong to CRG on Marine Geosciences, supported by Grant 2009 SGR 1305 of the Generalitat de Catalunya. A.P., P.P. and J.M. belong to CRG on Littoral and Oceanic Processes, supported by Grant 2009 SGR 899 of the Generalitat de Catalunya. J.M was partially funded through a JAE-Doc contract granted by CSIC and co-financed by CEE

14 pages, 9 figures, 1 table, Two mooring lines equipped with near-bottom sediment traps were deployed in the axis of the Nazaré submarine canyon at ∼1600 and ∼3300 m depth, respectively. We studied time-series of particle flux, composition (biogenic silica, carbonates, organic matter and lithogenic fractions), granulometry, mineralogy and 210Pb concentration of particulate matter over five sediment trap deployments between October 2002 and December 2004. Current meters equipped with turbidimeters were also deployed at trap depths to monitor the water flow, temperature, salinity and suspended particle concentration. The composition of the collected particles was fairly constant year-round, dominated by the lithogenic fraction and with OC/N ratios in the range 11–21, suggesting an important terrigenous influence inside the canyon. The results show contrasting dynamic environments in the upper (1600 m depth) and middle (3300 m depth) canyon. High current speeds (spring tides up to 80 cm s−1) and high apparent mass fluxes of particulate matter (mean 65 g m−2 d−1; maximum 265 g m−2 d−1) are permanent at the shallowest station. At the deepest site, fluxes were below 10 g m−2 d−1 most of the time and the annual flux was governed by events of sharp flux increase. Storms affecting the continental shelf during autumn and winter are a major driver of down-canyon dispersal of sediments to the middle canyon and beyond. Important nepheloid activity developed inside the canyon in response to storms with significant wave heights between 4 and 6 m, as testified by turbidimeters deployed in midwater and near the seabed at 1600 m water depth. On three occasions during the study period, significant wave heights of incident storms surpassed 7 m, leading to notable episodes of down-canyon transport that were clearly observed in the middle canyon. During one of these stormy periods (January 2003) a sediment gravity flow transporting unusual quantities of sand and coastal plant debris was observed at 3200 m. However, a storm with significant wave heights as low as 5 m was apparently able to trigger a sediment gravity flow reaching beyond the middle canyon. The role of storms in the offshore dispersal of sediments is clearly relevant but seems to be modulated by synergic factors such as river flooding, J. Martín was funded during this study through an FPI scholarship granted by Ministerio de Ciencia y Tecnología (Spanish Ministry of Science and Technology), and by the EUROSTRATAFORM project (EKV3-CT-2002-00079)

8 pages, 4 figures, Shelf-to-basin sediment transport during storms was studied at the southwestern end of the Gulf of Lions from November 2003 to March 2004. Waves, near-bottom currents, temperature and sediment fluxes were measured on the inner shelf at 28-m depth, in the Cap de Creus submarine canyon head at 300-m depth and in the northwestern Mediterranean basin at 2350-m depth. This paper is a synthesis of results published separately in different papers; it includes some new data and focusses on the subject of storms. It is the first paper in which simultaneous data about the effect of storms on the shelf, the slope and in the basin are shown together. During the winter studied, there were two severe E-SE storms with significant wave heights ≥ 7 m: one in December 2003 and one in February 2004. During these storms, coastal water was exported off-shelf producing strong near-bottom currents (up to 82 cm s−1) at the canyon head that resuspended sediment and increased the downcanyon sediment fluxes by several orders of magnitude. The suspended sediment flux increase in the canyon head was much larger during the February storm than during the December storm. At the deep basin site, particle fluxes also increased drastically (1–2 orders of magnitude) immediately after the February storm but not after the December storm. The reason was that the February storm was reinforced by dense shelf water cascading and was long enough (43 h) to transfer large amounts of resuspended sediment from shallow shelf areas to the canyon head and from there to the northwestern Mediterranean basin. Thus, in the western Gulf of Lions, severe winter E-SE storms occurring during the dense shelf water cascading period can significantly increase the transfer to deep-sea (> 2000 m) environments of shelf and slope resuspended material, including anthropogenic contaminants and organic matter, This study was supported by the European research projects EUROSTRATAFORM (EVK3-CT-2002-00079), and HERMIONE (ref. 544 226354). We thank the officers and crew of the R/V Thetis II and the Nereis for their help and dedication during the cruises

[1] The northwestern Mediterranean is known to be a privileged area of deep water formation via dense shelf water cascading and offshore convection. The impact of the former in the sedimentary dynamics of the deep basin has been highlighted in recent years, while open sea convection has been solely studied from a hydrological perspective. Particle fluxes and hydrodynamics were monitored at the DYFAMED site (Ligurian Sea, western Mediterranean) at 200, 1000 m and near the seafloor (2350 m depth) during winter 2005–2006. From February to April 2006, and in coincidence with an unusual episode of deep water formation, a notable intensification of currents was observed in the entire water column and near-bottom particle flux increased up to two orders of magnitude. These observations suggest that offshore convection must be taken into account together with cascading as a major driving force for sedimentary dynamics in the deep western Mediterranean.

The DYFAMED sediment trap station in the Ligurian Sea (NW Mediterranean) has been active since 1986 and today comprises the longest time-series of downward particle flux in the Mediterranean Sea. As such, it provides valuable information on the interannual variability of the particle flux, and also documents possible recent changes in the NW Mediterranean pelagic ecosystems. We report an unprecedented episode of downward flux of mucilaginous material at the DYFAMED station during summer 2002 in association with singular hydrometeorological conditions. The rain of mucilaginous aggregates clogged a PPS5 sediment trap at 260 m depth and was also clearly detected at 1080 m depth. The possible factors governing the development and sinking of the mucilaginous material are discussed. A very sharp increase of sea surface temperature during June and the presence of freshened waters in the surface the following month resulted in a stronger than usual stratification of the upper water column throughout the summer season. We suggest that the steepness of the vertical density gradient was responsible for the unusual accumulation of mucous aggregates. Additionally, a diatom bloom took place during the nutrient-depleted conditions typical of summer, a factor which may have contributed to feed the pycnocline with transparent exopolymer substances. A storm occurring in the beginning of August relaxed the stratification and promoted the deposition of the mucilaginous aggregates accumulated in the upper water column during the preceding months. Important similarities of ambient conditions preceding the apparition of mucilaginous material in our open-sea site and those reported in the Adriatic Sea during major mucilage events, suggest that general climatic conditions, rather than local factors, drive the occurrence of major accumulations of mucilaginous material in the water column at both sub-basins of the Mediterranean Sea. In this regard, the strength of the air temperature increase during the onset of the stratified season is proposed as a major controlling factor.

6 pages, 5 figures, In order to study sediment accumulation rates in the Palamós submarine canyon (Northwestern Mediterranean) during the last century, three sediment cores were extracted from the canyon axis at depths of 450, 1200 and 1750 m respectively, where instrumented moorings were previously located. Estimated sedimentation rates based on 210Pb and 137Cs profiles suggest that the contemporary trends of sediment transfer and accumulation in the canyon may be different from secular trends. During the seventies, a two-fold increase of the sediment accumulation rate took place at the 1750 m depth site. This change has been associated to trawling activities and is attributed to the rapid technical development that the local trawling fleet underwent during the seventies. The surroundings and rims of submarine canyons are frequently targeted by commercial trawling fisheries, an activity that may enhance the input of resuspended particles into canyons, and eventually trigger sediment gravity flows. Our results suggest that the effects of trawling over the dynamics of the seafloor may extend further and deeper from the fishing grounds, eventually extending to bathyal depths. Hence the anthropogenic influence on the sedimentary budget of some deep submarine environments may be more important than previously thought, This study was conducted within the CANYONS project, funded by “Dirección General de Enseñanza Superior e Investigación Científica” (MAR99-1060-CO3-01, 02 and 03). J. Martín was funded by the Spanish Ministry of Education and Science (MEC) through a FPI scholarship and later by the HERMES Project (Contract no.: 511234-2, EU Sixth Framework Programme: Global Change and Ecosystems). 210Pb analysis of sediment samples was conducted at the School of Oceanography (University of Washington) by kind invitation of C.A. Nittrouer. C. Bas, J.B. Company and F. Maynou from ICM-CSIC provided important clues in the quest for fisheries data

11 pages, 5 figures, 2 tables, One hundred and fifty specimens of the elasipod holothurian Penilpidia ludwigi (von Marenzeller, 1893) were collected in sediment traps moored near the seabed in the La Fonera Canyon (Catalan Sea, north-western Mediterranean) and on the adjacent continental slope. These provide the third record of this apparently endemic Mediterranean species and the first record from the western Mediterranean. This was the only holothurian species trapped and the most abundant macroscopic organism found in the traps between 1200 and 1700 m depth over the whole sampling period (March–November 2001). It was particularly abundant in spring during the main flux of organic particles in the canyon. This coupling suggests that Penilpidia may aggregate at the seafloor during these events, making food availability a plausible explanation of the seasonal occurrence. Lateral transport of material re-suspended locally or up-canyon by near bottom currents appear to be the mechanism behind this uncommon occurrence, although in situ observations have recently been made on the swimming capability of this holothurian. The occurrence of benthic organisms in sediment traps set close to the seabed can provide information on bathyal benthic and benthopelagic populations, This study has been supported by the HERMES project, funded by the European Commission's Six Framework Programme, under the priority Sustainable Development, Global Change and Ecosystems (Contract no. GOCE-CT-2005-511234-1)

26 pages, 14 figures, From March to November 2001, six current meters equipped with turbidimeters were moored 12 meters above the bottom inside the Palamós submarine canyon and on the adjacent slope. Horizontal particle fluxes were calculated from current and suspended sediment concentration data. This work aims to evaluate the advective sediment fluxes taking place in the Palamós canyon region, and to discern the nature and time-scales of the processes involved in the across-margin transfer of particles over the study period. Near-bottom currents inside the canyon were constrained by the local topography and displayed a high spatio-temporal variability. The net near-bottom transport of suspended matter in the canyon was largely driven by sharp increases of sediment load and current speed, most of them attributed to sediment gravity flows. These energetic events dominated over the current-driven sediment transport, which was relatively weak due to periodical up-canyon/downcanyon inversions along the canyon axis, and to complex current patterns and the presence of low sediment loads for most of the time at the other sites. During this 8-month experiment, the mid-canyon (>1200 m depth) acted as a by-pass zone, while at the canyon head, net sediment transport was directed persistently up-canyon. These patterns were further heightened during a major storm in November 2001. However, in this particular submarine canyon, substantial sedimentary activity and offshore export of particulate matter also occur in the absence of significant external forcings (storms, river floods). Human activities (deep trawling) induced sediment gravity flows during the dry and calm season (spring-summer) and enhanced the offshore transfer of particles during this time period, This work was carried out in the framework of the CANYONS project funded by the Spanish National R+D Plan. The first author was funded during this study by an FPI fellowship from the Spanish Ministry of Science and Technology (MCYT)

23 pages, 5 tables, 11 figures, To study the temporal and spatial variability of downward particle fluxes in the Palamós submarine canyon, seven sediment traps were moored inside and in the vicinity of the canyon from March to November 2001. Total mass fluxes, major constituent (organic carbon, opal, calcium carbonate and lithogenics) contents and fluxes, and 210Pb activity of particulate matter were obtained from two consecutive deployments at intervals of 10 and 12 days, respectively. Downward particle fluxes measured at the Palamós canyon head were 2 to 9 times higher than those measured in other northwestern Mediterranean canyons, and this relation increased drastically at 1200 m depth, where observed particle fluxes were 1 to 2 orders of magnitude higher than those reported in other surrounding canyons at similar depths. The highest near-bottom downward particle fluxes were not recorded in the canyon head but in the mid-canyon axis during late spring/summer, as a result of sediment gravity flows triggered by trawling activities at the canyon rims. In comparison to the adjacent open slope, Palamós Canyon is a prime site for the focusing and across-margin transference of total and organic matter. Off-shelf sediment transport was enhanced during a severe storm in November 2001, when a sharp increase in downward particulate fluxes was observed in the whole canyon both near the bottom and at intermediate waters. Despite the dominance of lithogenic particles all year round, a siliceous bloom affected the whole study area in March–April. An asymmetrical pattern was observed between the north and south canyon walls, with higher mean downward fluxes in the latter case, a fact related to the flow regime inside the canyon. The spatial–temporal distribution of total mass fluxes and major constituents defined two domains in the Palamós Canyon: an “inner” domain (up to 1200 m depth) constricted by the canyon topography and mainly influenced by a lateral transport of particles resuspended from the adjoining shelf and upper slope, and an “outer” domain, where slope dynamics and seasonal trends are more important in determining the composition and amount of downward particulate fluxes, This work was carried out in the framework of the CANYONS project, funded by the “Dirección General de Enseñanza Superior e Investigación Científica” (MAR99-1060-CO3-01, 02 and 03). 210Pb analysis of sediment trap samples was conducted in the laboratories at the School of Oceanography (University of Washington) by courtesy of Dr. C.A. Nittrouer. We thank to the officers and crew of R/V Garcia del Cid, for their help during the deployment operations