Opportunistic omnivory impairs the use of the Atlantic blue crab Callinectes sapidus as a trace metal biomonitor in invaded Mediterranean coastal waters

Thecontributionofnon-indigenousspeciestothetransferofcontaminantsininvadedfoodwebsrepresentsan activeresearcharea.HerewemeasuredtracemetalsandCNstableisotopesinfivepopulationsoftheinvasive AtlanticbluecrabCallinectessapidusandinbaselinebivalvespeciesfromSpain,ItalyandGreece.Theywereused toestimatetrophictransfereffectsandthetrophicpositionandisotopicnicheofC. sapidus.Maximumtrophic transfer effects occurredwhere the crab showed the largest isotopicniches andhighest trophic positions; furthermore, theconsistencyof tracemetalprofilesbetweenbivalvesandcrabsco-variedwiththetrophicpositionofthelatters.Omnivorymayinfluencethesuccessofaninvasivespecies,butalsolimititseffectivenessfor biomonitoring.However, our results indicatedthat stable isotopesanalysisprovidesaclarifyingbackground wheretocastpatternsofcontaminationofthebluecrabaswellasofotheromnivorousbiomonitorspecies.