Abstract

The HumboldtCurrentSystem(HCS)isahighlydynamicupwellingsystem implying astronglyvariableenvironmentforzooplanktoninhabitingthecoastal zone.Thisvariabilityhasmajorconsequencesforpopulationdynamics, community composition,andultimatelydiversitypatternsofplanktonic copepods whichdominatethebulkofzooplanktonbiomass.Inthiswork,we tested thehypothesisthatenvironmental stabilityisthekeymodulating mechanismofcopepoddiversitypatternsintheHCS.Weuseda17-years (1995-2011)databaseonspeciesoccurrenceofcopepodsalongwith environmental datafortheupper500moftheocean(dividedinto five vertical strata) fortheupwellingzoneoffChile,distinguishingtworegions(northernand southern)havingdifferentseasonalregimesofwind-drivenupwelling.We estimated indicesforcopepoddiversityandtheirdistribution,segregatedby regions anddepthstrata.Theindiceswerethenassociatedwithoceanographic variables forcedbyupwellingintensity,alongwithanestimateofeddykinetic energy (EKE),asaproxyofenvironmentalstability.Fromtheentirecommunity, we found18dominantspecieswidelydistributedinthestudyarea.Somewere exclusive speciesfortheupperdepthstratumwithdifferencesinthenumberof exclusive speciesperregionanddepth.FromLinearMixedModelswefoundthat the diversityindicessignificantly differedbetweenregionsandstrata,andtheir variance wasmainlyexplainedbytemperature,salinity,oxygenconcentration, temperature stability,andeddykineticenergy(EKE).Bothtemperaturestability and EKEwerethebestpredictorsofcopepodsdiversity,suggestingthatclimate- oceanographicstability,forcedbyupwellingintensity,isthekeydriverfor promoting andmaintainingcopepoddiversityintheHCS.