Thaj Chaw Eastern Tropical North Pacific (ETNP) yog ib thaj chaw loj, nyob mus ib txhis, thiab muaj zog ntxiv rau cov pa oxygen tsawg kawg nkaus (OMZ) uas suav txog yuav luag ib nrab ntawm tag nrho thaj chaw ntawm OMZs thoob ntiaj teb. Hauv OMZ core (~350–700 m tob), cov pa oxygen uas yaj feem ntau nyob ze lossis qis dua qhov kev ntsuas ntawm cov sensors niaj hnub (~10 nM). Cov pa oxygen gradients siab dua thiab hauv qab OMZ core ua rau muaj kev teeb tsa ntsug ntawm cov zej zog microbial uas kuj sib txawv ntawm cov feem me me (PA) thiab cov feem me me uas nyob dawb (FL). Ntawm no, peb siv 16S amplicon sequencing (iTags) los tshuaj xyuas qhov sib txawv thiab kev faib tawm ntawm cov pej xeem prokaryotic ntawm FL thiab PA qhov loj me thiab ntawm ntau yam ntawm cov xwm txheej redox ambient. Cov xwm txheej hydrographic ntawm peb thaj chaw kawm txawv ntawm cov uas tau tshaj tawm yav dhau los hauv ETNP thiab lwm yam OMZs, xws li ETSP. Cov pa oxygen concentration (~0.35 μM) tau muaj nyob thoob plaws OMZ core ntawm peb qhov chaw kuaj. Yog li ntawd, cov nitrite accumulations feem ntau tshaj tawm rau OMZ cores tsis muaj ib yam li cov kab mob anammox (Brocadiales genus)Cov neeg raug xaiv tsaScalindua), uas feem ntau pom muaj nyob thoob plaws cov ciam teb oxic-anoxic hauv lwm lub cev. Txawm li cas los xij, cov kab mob ammonia-oxidizing (AOB) thiab archaea (AOA) kev faib tawm thiab cov nqi siab tshaj plaws ntawm cov pa roj carbon autotrophic (1.4 μM C d–1) sib xws nrog qhov siab tshaj plaws ntawm ammonium concentration ze rau sab saum toj ntawm OMZ core. Tsis tas li ntawd, cov tswv cuab ntawm genusNitrospina, ib qho tseem ceeb ntawm cov kab mob nitrite-oxidizing (NOB) clade tau muaj nyob qhia tias ob qho tib si ammonia thiab nitrite oxidation tshwm sim ntawm cov pa oxygen concentration. Kev tshuaj xyuas ntawm kev sim zoo sib xws (ANOSIM) thiab Non-metric Dimensional Scaling (nMDS) tau qhia tias cov kab mob thiab archaeal phylogenetic sawv cev tau sib txawv ntawm cov feem loj. Raws li ANOSIM thiab iTag profiles, cov khoom sib xyaw ntawm PA assemblages tau cuam tshuam tsawg dua los ntawm qhov tob-nyob ntawm biogeochemical regime dua li FL feem. Raws li qhov muaj AOA, NOB thiab cov pa oxygen hauv OMZ core peb xav tias nitrification yog ib qho txheej txheem nquag hauv lub voj voog nitrogen ntawm thaj chaw no ntawm ETNP OMZ.
Kev Taw Qhia
Vim yog kev hloov pauv ntawm huab cua thiab tib neeg tej haujlwm hauv zos, cov pa oxygen uas yaj hauv dej hiav txwv tau poob qis hauv dej hiav txwv qhib thiab hauv cov dej hiav txwv ntug dej hiav txwv (Breitburg thiab lwm tus, 2018). Kwv yees li ntawm 2% ntawm cov pa oxygen uas poob los ntawm dej hiav txwv qhib thaum 60 xyoo dhau los (Schmidtko thiab lwm tus, 2017), tsim kev txhawj xeeb txog qhov tshwm sim ntawm kev nthuav dav ntawm thaj chaw uas tsis muaj oxygen (Paulmier thiab Ruiz-Pino, 2009). Cov dej hiav txwv qhib OMZs tsim thaum muaj kev tsim khoom loj heev ua rau muaj kev xav tau cov pa oxygen hauv cov dej hauv qab uas ntau dua li qhov ceev ntawm kev ua pa ntawm qhov tob. Cov pa oxygen hauv cov kem dej OMZ tuaj yeem muaj qhov sib txawv (oxycline) saum toj no thiab hauv qab lub plawv uas tsis muaj pa oxygen ua rau hypoxic (feem ntau ntawm 2 thiab ~ 90 μM), suboxic (<2 μM) thiab anoxic (qis dua qhov txwv kev kuaj pom (~ 10 nM) txheej ntawm ntau qhov loj me (Bertagnolli thiab Stewart, 2018). Cov pa oxygen gradients ua rau muaj kev teeb tsa ntsug ntawm cov metazoan thiab cov zej zog microbial thiab cov txheej txheem biogeochemical raws cov oxyclines dav dav no (Belmar thiab lwm tus, 2011).
Qee qhov kev poob nitrogen siab tshaj plaws tau raug kaw tseg hauv OMZs ntawm Eastern Tropical North Pacific (ETNP) thiab South Pacific (ETSP) (Callbeck thiab lwm tus, 2017;Penn thiab lwm tus, 2019), lub Cariaco Basin uas tau muab faib ua ntu zus tas mus li (Montes thiab lwm tus, 2013), Hiav Txwv Arabian (Ward thiab lwm tus, 2009), thiab OMZ ntawm Benguela upwelling system (Kuypers thiab lwm tus, 2005). Hauv cov kab ke no, cov txheej txheem microbial ntawm canonical denitrification (heterotrophic txo ntawm nitrate rau nitrogen intermediates thiab feem ntau rau dinitrogen roj) thiab anammox (anaerobic ammonium oxidation) ua rau nitrogen poob uas tuaj yeem txwv tsis pub thawj zaug tsim khoom (Ward thiab lwm tus, 2007). Ntxiv mus, cov pa roj nitrous oxide hauv dej hiav txwv (cov pa roj av uas muaj zog heev) los ntawm kev ua kom cov kab mob tsis muaj zog tshwm sim hauv OMZs kwv yees tias yuav suav nrog tsawg kawg yog ib feem peb ntawm cov pa roj nitrous oxide thoob ntiaj teb (Naqvi thiab lwm tus, 2010).
Lub ETNP OMZ yog ib cheeb tsam loj, ruaj khov, thiab muaj zog ntau ntxiv uas suav txog yuav luag ib nrab ntawm tag nrho thaj tsam ntawm OMZs thoob ntiaj teb, nyob nruab nrab ntawm 0–25°N latitude thiab 75 thiab 180°W longitude (Paulmier thiab Ruiz-Pino, 2009;Schmidtko thiab lwm tus, 2017). Vim lawv qhov tseem ceeb ntawm kev sib raug zoo, cov biogeochemistry thiab microbial diversity ntawm ntau thaj chaw ETNP OMZ tau raug kawm ntau yam (piv txwv li,Beman thiab Carolan, 2013;Duret thiab lwm tus, 2015;Ganesh thiab lwm tus, 2015;Chronopoulou thiab lwm tus, 2017;Pack thiab lwm tus, 2015;Peng thiab lwm tus, 2015). Cov kev tshawb fawb yav dhau los qhia tias cov pa oxygen uas yaj hauv lub OMZ core no (~250–750 m tob) feem ntau nyob ze lossis qis dua qhov kev ntsuas analytical (~10 nM) (Tiano thiab lwm tus, 2014;Garcia-Robledo thiab lwm tus, 2017). Txawm li cas los xij, raws ntug qaum teb ntawm ETNP's OMZ (qhov chaw kawm ~22°N) cov pa oxygen concentration ntawm 500 m tuaj yeem ncav cuag qhov nruab nrab txhua xyoo ntawm 10 thiab 20 μM (Paulmier thiab Ruiz-Pino, 2009Cov ntaub ntawv los ntawm World Ocean Atlas 2013)1. Thaum lub sijhawm tshaj tawm hauv daim teb no, peb ntsuas cov pa oxygen hauv OMZ core ntawm qhov concentration txaus (0.35 μM) los txhawb cov txheej txheem aerobic microbial, xws li ammonium thiab nitrite oxidation, thiab ib feem tiv thaiv cov txheej txheem anaerobic microbial tseem ceeb. Cov txheej txheem aerobic microbial tau pom ua ntej hauv cov txheej suboxic lossis anoxic ntawm ETNP OMZ (Peng thiab lwm tus, 2015;Garcia-Robledo thiab lwm tus, 2017;Penn thiab lwm tus, 2019). Txawm li cas los xij, cov yam ntxwv tswj kev faib tawm thiab kev ua ub no ntawm cov pab pawg ua haujlwm tshwj xeeb ntawm cov kab mob me me hauv OMZs tseem tsis tau nkag siab tag nrho.
Qhov muaj cov nitrifiers qhov twg oxygen tsis pom hauv OMZ tuaj yeem piav qhia los ntawm kev hloov pauv tsis ntev los no hauv qhov chaw ntsug ntawm oxycline vim yog qhov cua oxygen ntsug episodic, uas tuaj yeem ua rau cov pa oxygen ephemeral hauv OMZ cores (Muller-Karger thiab lwm tus, 2001;Ulloa thiab lwm tus, 2012;Garcia-Robledo thiab lwm tus, 2017). Cov xwm txheej ib ntus no tuaj yeem siv los ntawm cov pej xeem aerobic lossis microaerophilic, suav nrog nitrifiers. Ntxiv mus, cov khoom me me los ntawm epipelagic (cov hlwb sib sau ua ke, cov quav pellets, thiab cov khoom siv organic nyuaj) tuaj yeem muaj cov pa oxygen me me (Ganesh thiab lwm tus, 2014). Yog li, cov pa oxygen thiab cov kab mob aerobic tuaj yeem raug thauj mus rau lwm cov dej uas tsis muaj pa oxygen, ib ntus cia cov metabolisms aerobic tshwm sim nrog cov khoom me me. Cov khoom me me paub tias yog cov chaw kub ntawm kev voj voog biogeochemical ntawm cov kab mob microbial (Simon thiab lwm tus, 2002;Ganesh thiab lwm tus, 2014) thiab tuaj yeem txhawb nqa cov txheej txheem anaerobic lossis aerobic microbial sib txawv uas tsis pom nyob rau hauv lub xeev nyob dawb (Alldredge thiab Cohen, 1987;Wright thiab lwm tus, 2012;Suter thiab lwm tus, 2018).
Hauv kev tshawb fawb tam sim no, peb tshawb nrhiav cov zej zog prokaryotic nyob rau sab qaum teb ntawm ETNP's OMZ thiab cov yam ntxwv ib puag ncig uas yuav cuam tshuam rau lawv cov kev faib tawm ntsug siv 16S amplicon sequencing (iTags) ua ke nrog ntau yam kev suav txheeb. Peb tau tshuaj xyuas ob qhov loj me; qhov dawb-nyob (0.2–2.7 μm) feem, thiab qhov feem cuam tshuam nrog cov khoom me me (> 2.7 μm, ntes cov khoom me me nrog rau cov hlwb protistan) ntawm ntau qhov tob raws li oxycline uas sib raug rau cov xwm txheej redox sib txawv.
Peb tuaj yeem muab cov ntsuas pa oxygen uas yaj nrog cov kev ntsuas sib txawv, yog li ntawd qhov concentration ntawm cov molecular tuaj yeem saib xyuas tau tiag tiag. Txais tos rau kev sab laj
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Lub sijhawm tshaj tawm: Lub Xya Hli-05-2024