Evidence of localised upwelling in Pemba Channel (Tanzania) during the southeast monsoon

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dc.contributor.authorPainter, Stuart C.
dc.contributor.authorSekadende, Baraka
dc.contributor.authorMichael, Angelina
dc.contributor.authorNoyon, Margaux
dc.contributor.authorShayo, Salome
dc.contributor.authorGodfrey, Brian
dc.contributor.authorMwadini, Mtumwa
dc.contributor.authorKyewalyanga, Margareth
dc.date.accessioned2022-03-23T08:58:23Z
dc.date.available2022-03-23T08:58:23Z
dc.date.issued2021
dc.descriptionFull text article. Also available at https://doi.org/10.1016/j.ocecoaman.2020.105462en_US
dc.description.abstractOceanographic and biogeochemical observations collected in Pemba Channel, a deep-water (800 m) channel separating Pemba Island from mainland Tanzania, during the South East monsoon indicate the presence of active upwelling along the western edge of Pemba Island. Surface salinity values, nutrient concentrations and the presence of coccolithophore species previously reported from the mid to lower euphotic zone all suggest upwelling from at least 80–100 m depth. The surface waters of the channel were characterised with low NO3−:PO43− (0.68:1) and NO3−:Si (0.04:1) ratios far below the Brzezinski-Redfield ratio indicating the presence of N-limitation and the possibility that these waters may be susceptible to anthropogenic N inputs. Surface NO3− concentrations averaged 0.09 ± 0.10 μmol L−1 but increased to 0.5 μmol L−1 in the centre of upwelling where coincidentally both integrated nutrient concentrations and surface POC/PON pools were approximately 2-fold higher than the channel average. Despite its significance for local productivity upwelling is tentatively estimated, via stoichiometric assumptions, to enhance local productivity by only 20%. The modest productivity response to upwelling may be explained by picoplankton (0.2–2 μm) dominance of the phytoplankton community with this size-class representing ~80% of total chlorophyll-a. Nevertheless, important spatial variability was identified in larger size fractions and supported by taxonomic analyses with indications that the distribution of Chaetoceros spp. alone may be particularly relevant for understanding the variability in larger (>20 μm) chlorophyll-a size fractions. The location of upwelling has previously been shown to host large concentrations of small pelagic fish thus management of this regionally important resource would benefit from additional investigation of the underlying physical mechanism driving upwelling and subsequently how trophic interactions and ecosystem productivity are influenced.en_US
dc.identifier.citationPainter, S. C., Sekadende, B., Michael, A., Noyon, M., Shayo, S., Godfrey, B., ... & Kyewalyanga, M. (2021). Evidence of localised upwelling in Pemba Channel (Tanzania) during the southeast monsoon. Ocean & Coastal Management, 200, 105462.en_US
dc.identifier.otherDOI: 10.1016/j.ocecoaman.2020.105462
dc.identifier.urihttp://hdl.handle.net/20.500.12661/3514
dc.language.isoenen_US
dc.publisherElsevier Ltden_US
dc.subjectPemba channelen_US
dc.subjectWestern indian oceanen_US
dc.subjectBiogeochemistryen_US
dc.subjectPhytoplanktonen_US
dc.subjectCoccolithophoresen_US
dc.subjectGephyrocapsaen_US
dc.subjectTanzaniaen_US
dc.titleEvidence of localised upwelling in Pemba Channel (Tanzania) during the southeast monsoonen_US
dc.typeArticleen_US
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