Iron-limitation and high light stress on phytoplankton popul

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TitleIron-limitation and high light stress on phytoplankton populations from the Australian Sub-Antarctic Zone (SAZ)AbstractThe high nutrient low chlorophyll (HNLC) surface waters of the Southern Ocean are characterised by high concentrations of nitrate and phosphate, low concentrations of dissolved iron and deep vertical mixing. Future climate scenarios predict increased surface temperatures and ocean stratification in the region. These changes to vertical mixing will result in a slowdown of nutrient supply to surface waters and an increase in the integrated irradiance in the upper mixed layer. To investigate the influence of iron-limitation and high irradiance on phytoplankton growth and physiology, a 6-day shipboard incubation experiment was conducted during the Sub-Antarctic Zone Sensitivity to Environmental Change (SAZ Sense) voyage using phytoplankton populations from the upper mixed layer in the north-eastern SAZ region. Iron-limitation was induced with an organic siderophore and was compared with a 1nM iron-enriched incubation and an unamended treatment (under silicate replete conditions). As expected, iron enrichment led to dominance by large diatoms and enhanced photosynthetic performance, while the iron-limited community showed a decline in total chl a and photochemical efficiency. Under the added stress of high light, the iron-limited community was able to cope with the shift from in situ (<150Î¼molphotonsm-2s-1) to incubation (mean=765Î¼molphotonsm-2s-1) irradiance by increasing the proportion of photoprotective pigments and diverting excess light energy via energy-dependent quenching (qE). The responses to iron-limitation under high light showed that the phytoplankton community was able to acclimate to these conditions, but exhibited an overall decline in photosynthetic activity. Data presented here suggest the community shifts, in particular the decrease in diatoms, and the decline in photosynthetic performance of phytoplankton under low iron-high irradiance conditions has the potential to impact future ocean productivity and biogeochemical cycling. Â© 2011 Elsevier Ltd.Funding DetailsUTS, University of Technology Sydney; 2/07-287, ARC, Division of Arctic Sciences; SD/CA/03A, BELSPO, Federaal Wetenschapsbeleid; CSIRO, Commonwealth Scientific and Industrial Research Organisation; AAD, Australian Antarctic Division; 511106-2; 2752

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1st AuthorPetrou, K. AuthorPetrou, K.Hassler, C.Doblin, M.Shelly, K.Schoemann, V.van den Enden, R.Wright, S.Ralph, P.Year2011JournalDeep-Sea Research Part II: Topical Studies in OceanographyVolume58Number21-22Pages2200-2211DOI10.1016/j.dsr2.2011.05.020URLhttps://www.scopus.com/inward/recor.....00698ab7707322c54dd66bc4fKeywordsBiogeochemical cyclingDissolved ironEnergy dependentEnvironmental changeFuture climateHigh concentrationHigh nutrient low chlorophyllsIn-situIron enrichmentIron-limitationLight energyLight stressLow concentrationsMixed layerNutrient supplyOcean stratificationPhotochemical efficiencyPhotosynthetic activityPhytoplankton communityPhytoplankton growthSiderophoresSouthern OceanSurface temperaturesVertical mixingXanthophyll cycling, Algae controlChlorophyllNutrientsOceanographyPhytoplanktonPopulation statisticsSilicatesSurface waters, Iron, biogeochemical cyclechlorophylldiatomenvironmental changegrowth rateironirradiancemixed layernitratenutrient cyclingnutrient limitationphytoplanktonpigmentsiderophorestratificationsubantarctic regionsurface temperaturesurface watervertical mixing, Southern Ocean, BacillariophytaAuthor KeywordsIronLight stressPhytoplanktonSouthern OceanXanthophyll cycling

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CitationPetrou, K., Hassler, C., Doblin, M., Shelly, K., Schoemann, V., van den Enden, R., Wright, S. and Ralph, P. (2011). Iron-limitation and high light stress on phytoplankton populations from the Australian Sub-Antarctic Zone (SAZ). Deep-Sea Research Part II: Topical Studies in Oceanography, 58(21-22):2200-2211