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Boyd, Philip W; Abraham, Edward R (2001): Phytoplankton photosynthetic competence, underway data of SOIREE cruise track 1999-02-08 to 1999-02-24. PANGAEA,, Supplement to: Boyd, PW; Abraham, ER (2001): Iron-mediated changes in phytoplankton photosynthetic competence during SOIREE. Deep Sea Research Part II: Topical Studies in Oceanography, 48(11-12), 2529-2550,

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Active fluorescence (fast repetition rate fluorometry, FRRF) was used to follow the photosynthetic response of the phytoplankton community during the 13-day Southern Ocean Iron RElease Experiment (SOIREE). This in situ iron enrichment was conducted in the polar waters of the Australasian-Pacific sector of the Southern Ocean in February 1999. Iron fertilisation of these high nitrate low chlorophyll (HNLC) waters resulted in an increase in the photosynthetic competence (Fv/Fm) of the resident cells from around 0.20 to greater than 0.60 (i.e. close to the theoretical maximum) by 10/11 days after the first enrichment. Although a significant iron-mediated response in Fv/Fm was detected as early as 24 h after the initial fertilisation, the increase in Fv/Fm to double ambient levels took 6 days. This response was five-fold slower than observed in iron enrichments (in situ and in vitro) in the HNLC waters of the subarctic and equatorial Pacific. Although little is known about the relationship between water temperature and Fv/Fm, it is likely that low water temperatures - and possibly the deep mixed layer - were responsible for this slow response time. During SOIREE, the photosynthetic competence of the resident phytoplankton in iron-enriched waters increased at dissolved iron levels above 0.2 nM, suggesting that iron limitation was alleviated at this concentration. Increases in Fv/Fm of cells within four algal size classes suggested that all taxa displayed a photosynthetic response to iron enrichment. Other physiological proxies of algal iron stress (such as flavodoxin levels in diatoms) exhibited different temporal trends to iron-enrichment than Fv/Fm during the time-course of SOIREE. The relationship between Fv/Fm, algal growth rate and such proxies in Southern Ocean waters is discussed.
Related to:
Boyd, Philip W; Law, Cliff S (2001): The Southern Ocean Iron RElease Experiment (SOIREE)-introduction and summary. Deep Sea Research Part II: Topical Studies in Oceanography, 48(11-12), 2425-2438,
Median Latitude: -51.297965 * Median Longitude: 155.227990 * South-bound Latitude: -61.000700 * West-bound Longitude: 138.998200 * North-bound Latitude: -41.595230 * East-bound Longitude: 171.457780
Date/Time Start: 1999-02-08T00:01:00 * Date/Time End: 1999-02-24T22:59:00
Minimum DEPTH, water: m * Maximum DEPTH, water: m
SOIREE-track * Latitude Start: -61.000700 * Longitude Start: 138.998200 * Latitude End: -41.595230 * Longitude End: 171.457780 * Date/Time Start: 1999-02-08T23:07:00 * Date/Time End: 1999-02-28T01:39:00 * Location: Southern Ocean - Australasian-Pacific Sector * Campaign: SOIREE * Basis: Tangaroa * Method/Device: Underway cruise track measurements (CT)
Uncalibrated fluorescence data from ships data-acquisition system (DAS). Position not given.
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
2DEPTH, waterDepth watermGeocode
3Fluorescence, chlorophyllFluoresµg/lAbraham, Edward RFluorometer, Chelsea Instruments
4Photosynthetic competenceFv/FmAbraham, Edward RFast repetition rate fluorometry (FRRF) (Kolber & Falkowski, 1993)
5Radiation, photosynthetically activePARµmol/m2/sAbraham, Edward RQuantum Irradiance Meter, LI-COR Inc.
54120 data points

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