Eastern Tropical North Pacific (ETNP) yog qhov loj, tsis tu ncua, thiab ua kom cov pa oxygen tsawg kawg nkaus (OMZ) uas suav txog yuav luag ib nrab ntawm tag nrho thaj tsam ntawm OMZs thoob ntiaj teb. Tsis pub dhau OMZ core (∼350-700 m qhov tob), cov pa oxygen yaj feem ntau nyob ze lossis qis dua qhov ntsuas ntsuas ntsuas ntawm cov ntsuas niaj hnub (∼10 nM). Cov pa oxygen gradients saum toj thiab hauv qab ntawm OMZ cov tub ntxhais ua rau txoj hauv kev ntsug ntawm cov zej zog microbial uas kuj sib txawv ntawm cov khoom sib txuas (PA) thiab cov nyob dawb (FL) qhov loj me. Ntawm no, peb siv 16S amplicon sequencing (iTags) los tshuaj xyuas qhov sib txawv thiab kev faib tawm ntawm cov neeg prokaryotic ntawm FL thiab PA qhov loj me feem thiab ntawm qhov ntau ntawm ambient redox tej yam kev mob. Cov dej num ntawm peb cheeb tsam kawm tau txawv ntawm cov uas tau tshaj tawm yav dhau los hauv ETNP thiab lwm yam OMZs, xws li ETSP. Cov pa oxygen concentrations (∼0.35 μM) muaj nyob thoob plaws hauv OMZ core ntawm peb qhov chaw kuaj. Yog li ntawd, nitrite accumulations feem ntau qhia rau OMZ cores tsis tuaj raws li yog ib theem zuj zus rau cov kab mob anammox (Brocadiales genusCov neeg sib twScalindua), uas feem ntau pom thoob plaws oxic-anoxic ciam teb hauv lwm lub tshuab. Txawm li cas los xij, cov kab mob ammonia-oxidizing (AOB) thiab archaea (AOA) faib thiab qhov siab tshaj plaws autotrophic carbon assimilation tus nqi (1.4 μM C d.-1) coincided nrog ib tug pronounced ammonium concentration siab tshaj nyob rau hauv lub sab saum toj ntawm lub OMZ core. Tsis tas li ntawd, cov tswv cuab ntawm genusNitrospina, ib qho tseem ceeb nitrite-oxidizing kab mob (NOB) clade tau tam sim no qhia tias ob qho tib si ammonia thiab nitrite oxidation tshwm sim ntawm cov pa oxygen concentration. Kev soj ntsuam ntawm qhov kev xeem zoo sib xws (ANOSIM) thiab Tsis-metric Dimensional Scaling (nMDS) tau qhia tias cov kab mob thiab cov kab mob archaeal phylogenetic muaj qhov sib txawv ntawm qhov loj me. Raws li ANOSIM thiab iTag cov ntaub ntawv, qhov sib xyaw ntawm PA cov khoom sib dhos tsis tshua muaj cuam tshuam los ntawm qhov tob-dependent biogeochemical tsoom fwv tshaj li FL feem. Raws li lub xub ntiag ntawm AOA, NOB thiab taug qab cov pa oxygen hauv OMZ core peb xav tias nitrification yog cov txheej txheem nquag hauv lub voj voog nitrogen ntawm cheeb tsam no ntawm ETNP OMZ.
Taw qhia
Hauv kev teb rau kev hloov pauv huab cua tsis tu ncua thiab kev ua haujlwm hauv tib neeg hauv cheeb tsam, qhov ntau ntawm cov pa oxygen yaj tau poob qis hauv dej hiav txwv qhib thiab hauv ntug hiav txwv dej hiav txwv (Breitburg thiab al., 2018). Kwv yees cov pa oxygen los ntawm cov dej hiav txwv qhib hauv 60 xyoo dhau los tshaj li 2% (Schmidtko thiab al., 2017), tsim kev txhawj xeeb txog qhov tshwm sim ntawm oxygen-depleted zone expansion (Paulmier thiab Ruiz-Pino, 2009). Qhib dej hiav txwv OMZs daim ntawv thaum qhov chaw siab tshaj qhov tseem ceeb ntawm cov khoom siv roj ntsha lom neeg xav tau hauv cov dej hauv qab dej uas ntau tshaj qhov ua pa ntawm lub cev qhov tob. Cov pa oxygen ntau hauv OMZ cov kab dej tuaj yeem muaj cov gradients ntxhab (oxycline) saum toj thiab hauv qab cov pa oxygen-depleted core tsim hypoxic (feem ntau ntawm 2 thiab ∼90 μM), suboxic (<2 μM) thiab anoxic (hauv qab kev txwv (∼10 nM) txheej ntawm qhov sib txawv (Bertagnolli thiab Stewart, 2018). Oxygen gradients ua rau cov txheej txheem ntsug ntawm metazoan thiab microbial cov zej zog thiab cov txheej txheem biogeochemical raws cov oxyclines uas nws kim heev (Belmar et al., 2011).
Qee qhov siab tshaj plaws ntawm nitrogen poob tau raug sau tseg hauv OMZs ntawm Eastern Tropical North Pacific (ETNP) thiab South Pacific (ETSP) (Callbeck thiab al., 2017;Penn thiab al., 2019), lub stratified mus tas li Cariaco Basin (Montes et al., 2013), lub hiav txwv Arabian (Ward et al., 2009), thiab OMZ ntawm Benguela upwelling system (Kuypers et al., 2005). Hauv cov kab ke no, cov txheej txheem microbial ntawm canonical denitrification (heterotrophic txo cov nitrate rau nitrogen intermediates thiab feem ntau rau dinitrogen gas) thiab anammox (anaerobic ammonium oxidation) ua rau nitrogen poob uas muaj peev xwm txwv cov thawj tsim (Ward et al., 2007). Ntxiv mus, dej hiav txwv nitrous oxide emissions (ib lub tsev cog khoom muaj zog) los ntawm microbial denitrification tshwm sim nyob rau hauv OMZs yog kwv yees li ib feem peb ntawm lub ntiaj teb no natural nitrous oxide emissions (Naqvi et al., 2010).
ETNP OMZ yog ib qho loj, tsis tu ncua, thiab ua kom cov pa oxygen tsawg kawg nkaus uas suav nrog yuav luag ib nrab ntawm tag nrho cov cheeb tsam ntawm lub ntiaj teb OMZs, nyob nruab nrab ntawm 0-25 ° N latitude thiab 75 thiab 180 ° W longitude (Paulmier thiab Ruiz-Pino, 2009;Schmidtko thiab al., 2017). Vim lawv cov ecological tseem ceeb, biogeochemistry thiab microbial ntau haiv neeg ntawm txawv ETNP OMZ cheeb tsam tau kawm intensively (xws li,Beman thiab Carolan, 2013;Duret thiab al., 2015;Ganesh li al., 2015;Chronopoulo et al., 2017;Pack et al., 2015;Peng et al., 2015). Cov kev tshawb fawb yav dhau los tshaj tawm tias cov pa oxygen yaj hauv OMZ core (∼ 250-750 m qhov tob) feem ntau nyob ze lossis qis dua qhov ntsuas ntsuas ntsuas (∼10 nM) (Tiano et al., 2014;Garcia-Robledo li al., 2017). Txawm li cas los xij, nyob rau sab qaum teb ntawm ETNP's OMZ (qhov chaw kawm qhov chaw ∼22 ° N) oxygen concentrations ntawm 500 m tuaj yeem ncav cuag qhov nruab nrab txhua xyoo ntawm 10 thiab 20 μM (Paulmier thiab Ruiz-Pino, 2009; Cov ntaub ntawv los ntawm World Ocean Atlas 2013)1. Thaum lub sijhawm kev tshaj tawm hauv cheeb tsam no, peb tau ntsuas cov pa oxygen hauv OMZ core ntawm qhov muaj peev xwm txaus (0.35 μM) los txhawb cov txheej txheem aerobic microbial, xws li ammonium thiab nitrite oxidation, thiab ib nrab inhibits cov txheej txheem tseem ceeb anaerobic microbial. Cov txheej txheem aerobic microbial tau kuaj pom yav dhau los hauv seemingly suboxic lossis anoxic txheej ntawm ETNP OMZ (Peng et al., 2015;Garcia-Robledo li al., 2017;Penn thiab al., 2019). Txawm li cas los xij, yam tseem ceeb tswj kev faib khoom thiab kev ua ub no ntawm cov pab pawg ua haujlwm tshwj xeeb ntawm cov kab mob hauv OMZs tseem tsis tau nkag siab tag nrho.
Lub xub ntiag ntawm nitrifiers nyob qhov twg oxygen yog undetectable nyob rau hauv ib tug OMZ yuav piav qhia los ntawm tsis ntev los no hloov nyob rau hauv txoj hauj lwm ntsug ntawm oxycline vim yog episodic ntsug pa pa cua, uas yuav ua tau rau ephemeral kab nyob rau hauv oxygen nyob rau hauv OMZ cores (Muller-Kager et al., 2001;Ulloa et al., 2012;Garcia-Robledo li al., 2017). Cov xwm txheej zoo li no tuaj yeem siv los ntawm cov neeg aerobic lossis microaerophilic, suav nrog nitrifiers. Ntxiv mus, sinking hais los ntawm lub epipelagic (sib sau ua hlwb, fecal pellets, thiab complex organic cov ntaub ntawv) muaj peev xwm muaj ib tug kab ntawm oxygen (Ganesh li al., 2014). Yog li, cov pa oxygen thiab aerobic microbes tuaj yeem thauj mus rau lwm qhov dej anoxic, ib ntus tso cai rau cov metabolism hauv aerobic tshwm sim hauv kev koom nrog cov khoom. Cov khoom tau paub tias yog hotspots ntawm microbial biogeochemical cycling (Simon et al., 2002;Ganesh li al., 2014) thiab tuaj yeem txhawb qhov sib txawv anaerobic lossis aerobic microbial txheej txheem uas tsis tau pom nyob rau hauv lub xeev dawb-nyob (Alldredge thiab Cohen, 1987;Wright thiab al., 2012;Suter et al., 2018).
Hauv txoj kev tshawb fawb tam sim no, peb tshawb xyuas cov zej zog prokaryotic uas nyob rau sab qaum teb ntawm ETNP's OMZ thiab ib puag ncig yam uas yuav cuam tshuam rau lawv cov kev faib tawm ntsug siv 16S amplicon sequencing (iTags) ua ke nrog ntau yam kev txheeb cais. Peb tshuaj xyuas ob qhov loj me; cov dawb-nyob (0.2–2.7 μm) feem, thiab cov particle-sociated feem (> 2.7 μm, capturing particles as well as protistan cells) ntawm ntau qhov tob ntawm cov oxycline uas sib haum rau cov xwm txheej redox.
Peb tuaj yeem muab cov pa oxygen sensors nrog cov ntsuas sib txawv, kom cov molecular concentration tuaj yeem saib xyuas lub sijhawm. Txais tos kom sab laj
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Post lub sij hawm: Jul-05-2024