The effects of a strong winter storm on physical and biological variables at a shelf site in the Mediterranean Effets d'une forte tempête hivernale sur les variables physiques et biologiques à une station côtière méditerranéenne

AbstractAsurveyinvolvingbothpermanentmooringandhighfrequencysamplingwascarriedintheBayofBanyuls-sur-Merduringthefallof1999toassesstheeffectofstrongandunpredictablemeteorologicaleventsonthefunctioningofacoastalMediterraneanecosystem.Aseverewinterstorm took place on 12 November, which generated waves with a significant height of 7 m and a sea surface rise of about 0.5 m. Thenear-bottom current speed at 24 m reached 30 cm s –1 .This storm induced a significant increase in total suspended matter through resuspensionand then a subsequent increase in gross sedimentation rates. It also resulted in an increase of the proportion of refractory particulate organicmatter in the water column. It also tended to increase nutrient availability in the water column through resuspension and desorption processes.Thekineticofthisincreasedifferedamongnutrients.Bacterialbiomassandproductionweresignificantlyenhancedbythestorm.Theseeffectswere transitory and probably not due to resuspension alone. The distribution of plant pigments was modified at the immediate vicinity of thewater-sediment interface due to differential resuspension and sedimentation but the storm had no effect on integrated phytoplanktonicbiomass. Such a lack of response may be linked to low precipitations and/or light limitation. The storm resulted in a transitory increase of theabundance of fine particles at the water-sediment interface. These particles were coated with refractory organic matter. The storm induced asignificant decrease of meiofauna abundance. The duration of the relaxation periods varied among parameters. It lasted 2 weeks for totalsuspended matter, surface sediment granulometry and carbohydrate contents.© 2003 Editions scientifiques et medicales Elsevier SAS and Ifremer/CNRS/IRD. All rights reserved.ResumeUne etude faisant intervenir des mouillages permanents et un echantillonnage haute frequence a ete conduite en baie de Banyuls-sur-Merpendant l’automne 1999 afin de determiner les effets d’evenements meteorologiques forts et imprevisibles sur le fonctionnement d’un