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Coccolithophore fluxes in the open tropical North Atlantic: influence of thermocline depth, Amazon water, and Saharan dust

2017-10Journal article Open access
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dc.contributor.authorGuerreiro, Catarina V.
dc.contributor.authorBaumann, Karl-Heinz
dc.contributor.authorBrummer, Geert-Jan A.
dc.contributor.authorFischer, Gerhard
dc.contributor.authorKorte, Laura F.
dc.contributor.authorMerkel, Ute
dc.contributor.authorSa, Carolina
dc.contributor.authorde Stigter, Henko
dc.contributor.authorStuut, Jan-Berend W.
dc.date.accessioned2018-12-07T14:58:07Z
dc.date.available2018-12-07T14:58:07Z
dc.date.issued2017-10
dc.description.abstractCoccolithophores are calcifying phytoplankton and major contributors to both the organic and inorganic oceanic carbon pumps. Their export fluxes, species composition, and seasonal patterns were determined in two sediment trap moorings (M4 at 12 degrees N, 49 degrees W and M2 at 14 degrees N, 37 degrees W) collecting settling particles synchronously from October 2012 to November 2013 at 1200 m of water depth in the open equatorial North Atlantic. The two trap locations showed a similar seasonal pattern in total coccolith export fluxes and a predominantly tropical coccolithophore settling assemblage. Species fluxes were dominated throughout the year by lower photic zone (LPZ) taxa (Florisphaera profunda, Gladiolithus flabellatus) but also included upper photic zone (UPZ) taxa (Umbellosphaera spp., Rhabdosphaera spp., Umbilicosphaera spp., Helicosphaera spp.). The LPZ flora was most abundant during fall 2012, whereas the UPZ flora was more important during summer. In spite of these similarities, the western part of the study area produced persistently higher fluxes, averaging 241 x 10(7) +/- 76 x 10(7) coccoliths m(-2) d(-1) at station M4 compared to only 66 x 10(7) +/- 31 x 10(7) coccoliths m(-2) d(-1) at station M2. Higher fluxes at M4 were mainly produced by the LPZ species, favoured by the westward deepening of the thermocline and nutricline. Still, most UPZ species also contributed to higher fluxes, reflecting enhanced productivity in the western equatorial North Atlantic. Such was the case of two marked flux peaks of the more opportunistic species Gephyrocapsa muellerae and Emiliania huxleyi in January and April 2013 at M4, indicating a fast response to the nutrient enrichment of the UPZ, probably by wind-forced mixing. Later, increased fluxes of G. oceanica and E. huxleyi in October-November 2013 coincided with the occurrence of Amazon-River-affected surface waters. Since the spring and fall events of 2013 were also accompanied by two dust flux peaks, we propose a scenario in which atmospheric dust also provided fertilizing nutrients to this area. Enhanced surface buoyancy associated with the river plume indicates that the Amazon acted not only as a nutrient source, but also as a surface density retainer for nutrients supplied from the atmosphere. Nevertheless, lower total coccolith fluxes during these events compared to the maxima recorded in November 2012 and July 2013 indicate that transient productivity by opportunistic species was less important than "background" tropical productivity in the equatorial North Atlantic. This study illustrates how two apparently similar sites in the tropical open ocean actually differ greatly in ecological and oceanographic terms. The results presented here provide valuable insights into the processes governing the ecological dynamics and the downward export of coccolithophores in the tropical North Atlantic.
dc.description.sponsorshipNetherlands Organization for Scientific Research (NWO) [822.01.008]; European Research Council (ERC) [311152]; University of Bremen; European Union [600411]
dc.description.versioninfo:eu-repo/semantics/publishedVersion
dc.identifier.doi10.5194/bg-14-4577-2017
dc.identifier.issn1726-4170
dc.identifier.issn1726-4189
dc.identifier.urihttp://hdl.handle.net/10400.1/11871
dc.language.isoeng
dc.peerreviewedyes
dc.publisherCopernicus Gesellschaft Mbh
dc.relationTransatlantic fluxes of Saharan dust: changing climate through fertilising the ocean?
dc.relationCOFUND Fellowships for Transnational Academic Careers
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/
dc.subjectOcean primary production
dc.subjectUpper-layer circulation
dc.subjectOrganic-carbon fluxes
dc.subjectDeep-Ocean
dc.subjectBrazil current
dc.subjectAnnual cycle
dc.subjectEquatorial atlantic
dc.subjectExport production
dc.subjectBenguela system
dc.subjectRiver discharge
dc.titleCoccolithophore fluxes in the open tropical North Atlantic: influence of thermocline depth, Amazon water, and Saharan dust
dc.typejournal article
dspace.entity.typePublication
oaire.awardTitleTransatlantic fluxes of Saharan dust: changing climate through fertilising the ocean?
oaire.awardTitleCOFUND Fellowships for Transnational Academic Careers
oaire.awardURIinfo:eu-repo/grantAgreement/EC/FP7/311152/EU
oaire.awardURIinfo:eu-repo/grantAgreement/EC/FP7/600411/EU
oaire.citation.endPage4599
oaire.citation.issue20
oaire.citation.startPage4577
oaire.citation.titleBiogeosciences
oaire.citation.volume14
oaire.fundingStreamFP7
oaire.fundingStreamFP7
person.familyNameGuerreiro
person.familyNameSá
person.givenNameCatarina
person.givenNameCarolina
person.identifier.ciencia-idF514-4DBA-D0E0
person.identifier.orcid0000-0001-8524-540X
person.identifier.orcid0000-0001-8252-4593
person.identifier.ridM-7745-2013
person.identifier.ridC-2268-2012
person.identifier.scopus-author-id26422511200
project.funder.identifierhttp://doi.org/10.13039/501100008530
project.funder.identifierhttp://doi.org/10.13039/501100008530
project.funder.nameEuropean Commission
project.funder.nameEuropean Commission
rcaap.rightsopenAccess
rcaap.typearticle
relation.isAuthorOfPublication5133f866-f051-4442-a35e-751c4358984f
relation.isAuthorOfPublicationd644ae17-1d70-4875-a901-d6664061b8b3
relation.isAuthorOfPublication.latestForDiscovery5133f866-f051-4442-a35e-751c4358984f
relation.isProjectOfPublication6588059b-f6e5-4f29-8f48-a75eba8290e9
relation.isProjectOfPublication53f55ddc-4245-44f4-9c33-bd78f08f199d
relation.isProjectOfPublication.latestForDiscovery6588059b-f6e5-4f29-8f48-a75eba8290e9

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