Temporal and spatial distribution of floating objects in coastal waters of central-southern Chile and Patagonian fjords

Floating objectsaresuggestedtobetheprincipalvectorforthetransportanddispersalofmarine invertebrateswithdirectdevelopmentaswellascatalystsforcarbonandnutrientrecyclingin accumulationareas.Thefirststepinidentifyingtheecologicalrelevanceoffloatingobjectsinaspecific area istoidentifytheirspatio-temporaldistribution.Weevaluatedthecomposition,abundance, distribution,andtemporalvariabilityoffloatingobjectsalongthecontinentalcoastofcentral–southern Chile (33–421S) andthePatagonianfjords(42–501S) usingshipsurveysconductedinaustralwinter (July/August)andspring(November)oftheyears2002–2005and2008.Potentialsourcesoffloating items wereidentifiedwiththeaidofpubliclyavailabledatabasesandscientificreports.Wefoundthree main typesoffloatingobjects,namelyfloatingmarinedebris(mainlyplasticobjectsandStyrofoam), wood (trunksandbranches),andfloatingkelps(Macrocystispyrifera and Durvillaea antarctica).Floating marinedebriswereabundantalongmostoftheexaminedtransects,withmarkedlylowerabundances towardthesouthernfjordareas.Floatingmarinedebrisabundancesgenerallycorrespondedtothe distributionofhumanactivities,andwerehighestintheInteriorSeaofChiloe´ , whereaquaculture activitiesareintense.Floatingwoodappearedsporadicallyinthestudyarea,oftenclosetothemain rivers. Inaccordancewithseasonalriverrun-off,woodwasmoreabundantalongthecontinentalcoast in winter(rainyseason)andinthePatagonianfjordsduringthespringsurveys(snowmelt).Densitiesof the twofloatingkelpspeciesweresimilaralongthecontinentalcoast,withoutaclearseasonalpattern. M. pyrifera densitiesincreasedtowardsthesouth,peakinginthePatagonianfjords,whereitwas dominantover D. antarctica. Densitiesof M. pyrifera in thePatagonianfjordswerehighestinspring. Correlationanalysesbetweentheabundancesoffloatingobjectsandthedistancetothenearestsources were generallynon-significant,suggestingthatpost-supplyprocessesaffectthedistributionofthe floating objectsinthestudyregion.Theidentificationofseveralmajorretentionzonessupportsthis idea.Accumulationareasoffloatingobjectsappeartobemorecommoninthefjordzones.Ingeneral, the resultsunderscoretheabundanceoffloatingobjectsthroughoutthestudyregionandthefactthat floating marinedebrissourcesaremostlylocal,whereasfloatingalgaemaybedispersedovergreater distances.Futurestudiesshouldfocusontheecologicalroleoffloatingobjectsinbiotadispersaland nutrientcycling.