Origin and variability of downward biogeochemical fluxes on the Rhone continental margin (NW mediterranean) |
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| Institution: | 1. Wildlife Ecology, Forest Research Institute of Baden-Wuerttemberg FVA, Wonnhaldestr. 4, 79100 Freiburg, Germany;2. Conservation Biology, Institute of Ecology and Evolution, Univ. of Bern, Hochschulstr. 6, 3012 Bern, Switzerland;1. Soil Science, Institute for Geography, University of Jena, Löbdergraben 32, 07743 Jena, Germany;2. Department of Soil Ecology, Helmholtz-Centre for Environmental Research – UFZ, Theodor-Lieser-Straße 4, 06120 Halle (Saale), Germany;1. Departamento de Ciências Farmacêuticas, Centro de Ciências da Saúde, Universidade Federal de Pernambuco, 50740-520 Recife, PE, Brazil;2. Laboratório de Bioquímica Experimental e Computacional de Fármacos, Instituto Oswaldo Cruz, FIOCRUZ, 21040-900 Rio de Janeiro, RJ, Brazil;3. Molecular Discovery Research, Tres Cantos Medicines Development Campus, GlaxoSmithKline, Tres Cantos, Spain;4. Departamento de Microbiologia, Centro de Pesquisas Aggeu Magalhães, 50670-420 Recife, PE, Brazil;1. School of Environment, University of Auckland, Private Bag 92019, Auckland, 1142, Auckland, New Zealand;2. Soil Science, Institute of Geography, Friedrich Schiller University Jena, Löbdergraben 32, 07743, Jena, Germany;1. Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling FK9 4LA, UK;2. Centre for Ecology and Hydrology Edinburgh, Bush Estate, Penicuik, Midlothian EH26 0QB, UK;3. CREAF (Centre de Recerca Ecológica i Aplicacions Forestals), Campus UAB, Edifici C. E-08193, Belaterra (Barcelona), Spain;4. Institute of Dendrology, Polish Academy of Sciences, Parkowa 5, 62-035 Kórnik, Poland;5. Yugra State University, Centre for Environmental Dynamics and Climate Change, Khanty-Mansiysk 628012, Russia;1. The Institute for Sub-arctic Landscape Research, Silvermuseet, Torget, SE-938 31 Arjeplog, Sweden;2. Department of Forest Ecology and Management, SLU, SE-901 83 Umeå, Sweden;3. W.A. Franke College of Forestry & Conservation, University of Montana, 32 Campus Drive, Missoula, MT 59812, USA;4. Department of Ecosystem and Conservation Sciences, University of Montana, Missoula, MT 59812, USA |
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| Abstract: | A one year study of downward particle fluxes conducted in the northwestern Mediterranean Sea is presented. Two mooring lines equipped with sediment traps and current meters were deployed at around 1000 m depth on the northeastern continental slope of the Gulf of Lions, one inside the Grand-Rhône canyon and the other outside on the adjacent open slope. Mean total mass fluxes increased slightly with trap depth inside the canyon, a feature quite typical of fluxes in continental margin environments. The near-bottom trap inside the canyon collected more material than its counterpart deployed at equivalent depth on the open slope, indicating a preferential transport of material within the canyon. Major biogeochemical constituents (organic and inorganic carbon, opal, and siliciclastic residue) revealed a marked difference in particle composition between the sub-surface (80 m) and deeper traps, suggesting the existence of at least two sources of material. The two shallower traps showed a clear biological signal: flux peaks were related to periods of surface biological production, especially perceptible in summer and autumn. The particulate matter trapped at deeper levels in the canyon and on the open slope was characterized by a more stable composition with a major lithogenic contribution, originating from sedimentary material most probably resuspended on the upper- or mid-slope. The seasonal variability was dominated by the summer/winter alternation; the latter period was characterized by a weak stratification of the water column and an enhanced current variability favoring vertical exchanges. The present results are compared with those obtained previously in the Lacaze-Duthiers canyon on the southwestern side of the Gulf of Lions. The comparison shows strong differences between the NE entrance and the SW exit of the gulf, with respect to the general along-slope circulation of water masses, both in terms of intensity of particulate fluxes and transport processes. |
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