Aspects of krill growth and condition during late winter-early spring off East Antarctica (110-130°E)

• Published in: Deep Sea Research Part II: Topical Studies in Oceanography
• Main Authors: O'Brien, CJ, Virtue, P, Kawaguchi, S, Nichols, PD
• Format: Article in Journal/Newspaper
• Language: English
• Published: Pergamon-Elsevier Science Ltd 2011
• Subjects: Biological Sciences; Ecology; Marine and Estuarine Ecology (incl. Marine Ichthyology); East Antarctica; Antarc*; Antarctica
• Online Access: https://doi.org/10.1016/j.dsr2.2010.11.001; http://ecite.utas.edu.au/76369

Antarctickrill, Euphausiasuperba, isakeystonespeciesintheSouthernOcean.However,informationongrowth,dietandconditionduringwinterandearlyspringislimited,hamperingourunderstandingofthese fundamentalbiologicalparametersatthisimportantperiodintheirlifecycle.Ourstudyassesseddiet andconditionoflarvalandpostlarvalkrillcollectedfromopenwaterandbelowtheiceoffEastAntarctica(110130% oE) inSeptember/October2007.Conditionwasassessedusinglipidcontent,growthratesanddigestiveglandsize;feedinghistorywasassessedusingfattyacidprofilesandstomachcontentanalysis;anda207-daystarvationstudyinvestigatedtheresponseofkrilltolong-termfooddeprivation.Potentialfooditems(Calanuspropinquus and sea-icebiota)wereanalysedforlipidandfattyacidcompositiontocomparewithkrillsamples.Krillwerefoundtobeingoodcondition,withmeangrowthrate of0.95%permoultforpostlarvaeand14.79%forlarvae,andmeanlipidcontentof24.1%forpostlarvaeand 6.6%forlarvae.Fattyacidprofilesandstomachcontentanalysisrevealedtwomainfeedingstrategies- krillbelowtheicewerefeedingmostlyonsea-icediatoms,whilethoseinopenwaterwereingestingcopepodsanddetritus.Krillbelowtheicehadlargerdigestiveglandsthanthoseinopenwater.Furciliaefatty acidprofilesindicatedadietofheterotrophicflagellatesand/ordetritus.Postlarvalkrillsurvived207days offooddeprivationbyusingbodyproteinandlipidreservesforenergy.Incontrast,krillfurciliaewere severelydepletedafterjust5daysoffooddeprivation,indicatingthattheymustfeedcontinuallyatthis timeofyear.Krill,copepodsandsea-icebiotawerealllowinpolyunsaturatedfattyacids,indicatingthat krillmustrelyonlaterspringphytoplanktonbloomstoobtaintheseessentialnutrientsrequiredforreproduction.