Role of microbial and phytoplanktonic communities in the control of seawater viscosity off West Antarctica (30-80°W).

• Published in: Deep Sea Research Part II: Topical Studies in Oceanography
• Main Authors: Seuront, Laurent, Leterme, Sc, Seymour, Js, Mitchell, Jg., Ashcroft, D., Noble, W., Thompson, Pg, Davidson, At, van den Enden, R., Scott, Fj, Wright, Sw, Chapperon, C., Cribb, N.
• Other Authors: Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD France-Nord )
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2010
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; West Antarctica; Antarc*; Antarctica
• Online Access: https://hal.archives-ouvertes.fr/hal-00767876; https://doi.org/10.1016/j.dsr2.2008.09.018

International audience Despitethelong-standingbeliefthatseawaterviscosityisdrivenbytemperatureandsalinity, biologicallyincreasedseawaterviscosityhasrepeatedlybeenreportedinrelationtophytoplankton exudatesinshallow,productivecoastalwaters.Here,seawaterviscositywasinvestigatedinrelationto microbialandphytoplanktoniccommunitiesoffthecoastofEastAntarcticaalonglatitudinaltransects located between301E and801E insub-surfacewatersandatthedeepchlorophyllmaximum(DCM).The physicalcomponentofseawaterviscosityobservedalongeachtransectsrangedfrom1.80to1.95cP, while theactualseawaterviscosityrangedfrom1.85to3.69cP.Thisresultedinbiologicallyincreased seawaterviscosityreachingupto84.9%insub-surfacewatersand77.6%attheDCM.Significantpositive correlationswerefoundbetweenelevatedseawaterviscosityand(i)bacterialabundanceinsub-surface watersand(ii)chlorophyll a concentrationandtheabundanceofflowcytometrically-definedauto-and heterotrophicprotistsattheDCM.Amongthe12groupsand108speciesofprotistsidentifiedunder light microscopy,dinoflagellatesandmorespecifically Alexandriumtamarense and Prorocentrum sp. were themaincontributorstothepatternsobservedforelevatedseawaterviscosity.Ourobservations, which generalisedthelinkpreviouslyidentifiedbetweenseawaterviscosityandphytoplankton compositionandstandingstocktotheSouthernOcean,arethefirstdemonstrationofincreasesin seawaterviscositylinkedtomarinebacterialcommunities,andsuggestthatthemicrobially-increased viscositymightquantitativelybeatleastasimportantastheonerelatedtophytoplanktonsecretion. & 2009 ElsevierLtd.Allrightsreserved