Physical and biogeochemical processes controlling particle fluxes variability and carbon export in the Southern Adriatic

In theframeworkoftheVectorProjectdownwardparticlefluxeshavebeenmeasuredinastation located inthecentreoftheSouthAdriaticPitfromNovember2006toAugust2008. Sedimenttrapsampleswerecollectedattwodifferentdepths,belowthephoticlayer(168m)and near thebottom(1174m),andanalysedfortotalmassflux,fortotalandorganiccarbon,totalnitrogen, carbonate,stableisotopeoforganiccarbon(d13Corg) andbiogenicsilicacontents.Theresultshavebeen integratedandcomparedwithdataobtainedfrompreviousresearchprojects,carriedoutinthe SouthernAdriaticareain1994-1995and1997-1998. Fluxes ofparticulatemattershowedhighseasonalandinterannualvariability,withmaximum values inlatewinter-springseason.Theorganiccarbonflux,followedthesameseasonaltrend,with higher valuesbelowthephoticzone,andpeaksinspring,relatedtobloomsofsilicaand/orcarbonates phytoplanktonorganisms(e.g.,diatoms,coccolithophorids).Theorganiccarbonexportfromthephotic layer wasof5.2and2.1gCm2 y1 reachedthebottom. Climatologicalcyclesand,inparticular,themaximumdepthoftheconvectiveverticalmixing determinedthehighfluxesmeasuredin1998andin2008springs. Total massfluxesmeasuredatthebottomtrapweretwofoldthosemeasuredbelowthephoticlayer, and showedahighlithogenicfraction,highlightingthepresenceofadvectiveprocessesthatappear particularlyactiveinthearea.Theseprocessescanbecorrelatedwiththespreadingofdensewaters coming fromthenorthandcentralAdriatic,generallyobservedinspring.Theelementalandisotopic compositionofbottomtrapsamples,resultedsimilartothatofsamplescollectedinthesouth-western Adriatic slope,corroboratingtheassumptionthatlateraladvectionotherthanverticalinputwere contributingtobottomparticlefluxes.