Contribution of small phytoplankton to total primary production in the Chukchi Sea

Abstract

GivenaprojectionofthrivingsmallphytoplanktonintheArcticOceanunderclimate-induced environmentalchanges,itisimportanttoestimatethecontributionofsmallphytoplankton(0.7？ 5 μm) to thetotalprimaryproductionintheChukchiSea,whichisanimportantconduitoforganicmatterfrom the NorthPacific totheArcticOcean.Basedona 13C？ 15N dualisotopetracertechnique,small phytoplanktonproductivitymeasurementsweretakenduringtwoconsecutivecruisesintheChukchi Sea in2004.Thetotalphytoplanktoncarbonuptakeratesrangedfrom0to25.38mgCm 3 h 1, whereas the uptakeratesofsmallphytoplanktonrangedfrom0to2.87mgCm 3 h 1. Incomparisonwiththe carbon uptakerates,totalphytoplanktonnitrateuptakeratesrangedfrom0to4.40mgNm 3 h 1 while small phytoplanktonnitrateuptakeratesrangedfrom0to0.39mgNm 3 h 1. Ammoniumuptakerates rangedfrom0to8.34mgNm 3 h 1 and from0.01to2.18mgNm 3 h 1, fortotalandsmall phytoplankton,respectively.Smallphytoplanktoncontributed24.80%(S.D.¼723.0%) tothetotal chlorophyll-a concentration, and59.41%(S.D.¼752.12%)tothetotalcarbonbiomassduetoitshigher particulate organiccarbonperchlorophyll-a unit duringthetwocruisesin2004.IntheChukchiSea,the averagecontributionsofsmallphytoplanktontocarbonandtotalnitrogen(nitrateþammonium) uptake rateswere31.72%(S.D.¼723.59%) and37.31%(S.D.¼726.06%),respectively.antconduitoforganicmatterfrom the NorthPacific totheArcticOcean.Basedona 13C？ 15N dualisotopetracertechnique,small phytoplanktonproductivitymeasurementsweretakenduringtwoconsecutivecruisesintheChukchi Sea in2004.Thetotalphytoplanktoncarbonuptakeratesrangedfrom0to25.38mgCm 3 h 1, whereas the uptakeratesofsmallphytoplanktonrangedfrom0to2.87mgCm 3 h 1. Incomparisonwiththe carbon uptakerates,totalphytoplanktonnitrateuptakeratesrangedfrom0to4.40mgNm 3 h 1 while small phytoplanktonnitrateuptakeratesrangedfrom0to0.39mgNm 3 h 1. Ammoniumuptakerates rangedfrom0to8.34mgNm 3 h 1 and from0.01to2.18mgNm 3 h 1, fortotalandsmall phytoplankton,respectively.Smallphytoplanktoncontributed24.80%(S.D.¼723.0%) tothetotal chlorophyll-a concentration, and59.41%(S.D.¼752.12%)tothetotalcarbonbiomassduetoitshigher particulate organiccarbonperchlorophyll-a unit duringthetwocruisesin2004.IntheChukchiSea,the averagecontributionsofsmallphytoplanktontocarbonandtotalnitrogen(nitrateþammonium) uptake rateswere31.72%(S.D.¼723.59%) and37.31%(S.D.¼726.06%),respectively.