High lipid composition of particulate organic matter in the northern Chukchi Sea, 2011

Abstract

Weinvestigatedthebiochemicalcompositions(lipids,proteins,andcarbohydrates)ofparticulate organic matter(POM)asapotentialfoodsourceinthenorthernChukchiSea.Weaimedtounderstand physiologicalstatusofphytoplankton,determineimportantcontrollingfactors,andestimate the energeticcontentsofPOM.Themajorinorganicnutrientsweregenerallydepletedatupper mixed-layerdepth(420 m).Theaveragechlorophylla(chl-a) concentrationwas31.9mgm 2 (S.D.¼731.3mgm 2) inthisstudy,significantly higherthanthatreportedpreviouslyinthenorthern Chukchi Sea.Smallphytoplankton(0.7？5 mm) accountedfor65.9%oftotalchl-a concentration. The overallaveragecompositionsoflipids,carbohydrates,andproteinswere50%(S.D.¼710.7%),35% (S.D.¼711.0%),and15%(S.D.¼711.2%)forPOM,respectively.Alongwithotherevidence(e.g.,lowN:P and protein？carbohydrateratios),thehighlipidandlowproteincompositionsofPOMinthisstudy suggests thatphytoplanktonmighthavehadanitrogenlimitationand/orstationarygrowthphaseinthe northern ChukchiSeaduringthecruiseperiod,2011.Theoverallaveragecalorific contentoffood material (FM)was149.2 μg L 1 (S.D.¼736.5 μg L 1) or1.0Kcalm 3 (S.D.¼70.2 Kcalm 3). The relativelyhighercalorific contentsinthenorthernChukchiSeawereduetohighlipidcontributions and theconsiderablyhighcalorific contentofFMperPOC.