Eastern Tropical North Pacific (ETNP) ndi malo akuluakulu, okhazikika, komanso owonjezera mpweya (OMZ) omwe amawerengera pafupifupi theka la malo onse a OMZ padziko lonse lapansi. Mkati mwa OMZ core (∼350–700 m kuya), mpweya wosungunuka nthawi zambiri umakhala pafupi kapena pansi pa malire ozindikira a masensa amakono (∼10 nM). Kuchuluka kwa mpweya woipa pamwamba ndi pansi pa OMZ core kumabweretsa kapangidwe kowongoka ka magulu a tizilombo toyambitsa matenda omwe amasiyananso pakati pa tinthu tating'onoting'ono tomwe timagwirizana (PA) ndi tinthu tating'onoting'ono (FL). Pano, timagwiritsa ntchito 16S amplicon sequencing (iTags) kuti tifufuze kusiyanasiyana ndi kufalikira kwa anthu a prokaryotic pakati pa FL ndi PA size fractions komanso pakati pa mikhalidwe ya redox yozungulira. Mikhalidwe ya hydrographic m'dera lathu lophunzirira inali yosiyana ndi yomwe idanenedwa kale mu ETNP ndi ma OMZ ena, monga ETSP. Kuchuluka kwa mpweya wochepa (∼0.35 μM) kunalipo m'kati mwa OMZ pamalo athu oyesera. Chifukwa chake, kuchulukana kwa nitrite komwe kumanenedwa kuti ndi kwa OMZ cores sikunalipo monga momwe zinalili ndi mabakiteriya a anammox (mtundu wa Brocadiales).CandidatusScalindua), zomwe zimapezeka kwambiri m'malire a okosijeni m'machitidwe ena. Komabe, mabakiteriya ochulukitsa okosijeni a ammonia (AOB) ndi archaea (AOA) ndi kuchuluka kwakukulu kwa okosijeni a autotrophic (1.4 μM C d–1) zinagwirizana ndi kuchuluka kwakukulu kwa ammonium pafupi ndi pamwamba pa OMZ core. Kuphatikiza apo, mamembala a mtunduwoNitrospina, panali gulu la mabakiteriya otchedwa nitrite-oxidizing bacterial (NOB) lomwe limasonyeza kuti ammonia ndi nitrite oxidation zimachitika pa kuchuluka kwa mpweya wochepa. Kusanthula kwa mayeso ofanana (ANOSIM) ndi Non-metric Dimensional Scaling (nMDS) kunawonetsa kuti ma bacterial ndi archaeal phylogenetic representation anali osiyana kwambiri pakati pa ma fractions a kukula. Kutengera ma profiles a ANOSIM ndi iTag, kapangidwe ka PA assemblages sikunakhudzidwe kwambiri ndi njira ya biogeochemical yomwe imadalira kuzama kuposa FL fraction. Kutengera kukhalapo kwa AOA, NOB ndi trace oxygen mu OMZ core, tikuwonetsa kuti nitrification ndi njira yogwira ntchito mu nayitrogeni cycle ya dera lino la ETNP OMZ.
Chiyambi
Poyankha kusintha kwa nyengo komwe kukuchitika komanso zochita za anthu m'deralo, kuchuluka kwa mpweya wosungunuka kwakhala kukuchepa m'nyanja yotseguka komanso m'madzi am'mphepete mwa nyanja (Breitburg ndi ena, 2018Kutayika kwa okosijeni kuchokera ku nyanja yotseguka m'zaka 60 zapitazi kwapitirira 2% (Schmidtko ndi ena, 2017), zomwe zimapangitsa kuti pakhale nkhawa zokhudza zotsatira za kufalikira kwa malo okhudzidwa ndi mpweya (Paulmier ndi Ruiz-Pino, 2009). Ma OMZ otseguka m'nyanja amapangika pamene kupanga kwakukulu kwa pamwamba kumalimbikitsa kufunikira kwa okosijeni m'madzi apansi panthaka komwe kumaposa kuchuluka kwa mpweya wokwanira m'madzi akuya. Kuchuluka kwa okosijeni m'mizere yamadzi ya OMZ kumatha kukhala ndi ma gradients otsetsereka (oxycline) pamwamba ndi pansi pa pakati pomwe mpweya watha, zomwe zimapangitsa kuti pakhale mpweya wochepa (nthawi zambiri pakati pa 2 ndi ∼90 μM), suboxic (<2 μM) ndi anoxic (pansi pa malire ozindikira (∼10 nM) zigawo zosiyanasiyana (Bertagnolli ndi Stewart, 2018Kuchuluka kwa okosijeni kumabweretsa kapangidwe kowongoka ka magulu a metazoan ndi tizilombo toyambitsa matenda komanso njira za biogeochemical m'ma oxyclines awa (Belmar ndi ena, 2011).
Zina mwa ziwerengero zazikulu kwambiri za kutayika kwa nayitrogeni zalembedwa mu OMZs za Eastern Tropical North Pacific (ETNP) ndi South Pacific (ETSP) (Callbeck ndi ena, 2017;Penn ndi ena, 2019), Cariaco Basin yokhala ndi magawo osatha (Montes ndi ena, 2013), Nyanja ya Arabia (Ward ndi ena, 2009), ndi OMZ ya dongosolo la Benguela upwelling (Kuypers ndi ena, 2005). Mu machitidwe awa, njira za microbial za canonical denitrification (kuchepetsa heterotrophic nitrate kukhala nitrogen intermediates ndipo nthawi zambiri kukhala dinitrogen gas) ndi anammox (anaerobic ammonium oxidation) zimapangitsa kuti nayitrogeni itayike zomwe zingathe kuchepetsa kupanga koyamba (Ward ndi ena, 2007). Kuphatikiza apo, mpweya wa nitrous oxide wochokera m'nyanja (mpweya wamphamvu wowonjezera kutentha) wochokera ku kuchotsedwa kwa ma microbial omwe amapezeka mu OMZs akuti amachititsa pafupifupi gawo limodzi mwa magawo atatu a mpweya wachilengedwe wa nitrous oxide padziko lonse lapansi (Naqvi ndi ena, 2010).
ETNP OMZ ndi malo ocheperako okosijeni, okhazikika, komanso owonjezera mphamvu omwe amawerengera pafupifupi theka la malo onse a OMZ padziko lonse lapansi, omwe ali pakati pa 0–25°N latitude ndi 75 ndi 180°W longitude (Paulmier ndi Ruiz-Pino, 2009;Schmidtko ndi ena, 2017Chifukwa cha kufunika kwawo kwa chilengedwe, biogeochemistry ndi kusiyanasiyana kwa tizilombo toyambitsa matenda m'madera osiyanasiyana a ETNP OMZ zaphunziridwa mozama (monga,Beman ndi Carolan, 2013;Duret ndi ena, 2015;Ganesh ndi ena, 2015;Chronopoulou ndi ena, 2017;Pack ndi ena, 2015;Peng ndi ena, 2015Kafukufuku wakale adanenanso kuti mpweya wosungunuka m'kati mwa OMZ iyi (kuya kwa ~ 250-750 m) nthawi zambiri umakhala pafupi kapena pansi pa malire ozindikira (~ 10 nM) (Tiano ndi ena, 2014;Garcia-Robledo ndi ena, 2017Komabe, m'mphepete mwa kumpoto kwa OMZ ya ETNP (malo ophunzirira ∼22°N) kuchuluka kwa mpweya wa okosijeni pa 500 m kumatha kufika pa avareji ya pachaka pakati pa 10 ndi 20 μM (Paulmier ndi Ruiz-Pino, 2009Deta kuchokera ku World Ocean Atlas 2013)1Pa nthawi ya kampeni yomwe yanenedwa pano, tinayesa mpweya m'kati mwa OMZ pamlingo wokwanira (0.35 μM) kuti tithandizire njira za tizilombo toyambitsa matenda, monga ammonium ndi nitrite oxidation, ndikuletsa pang'ono njira zofunika za tizilombo toyambitsa matenda. Njira za tizilombo toyambitsa matenda za aerobic zapezeka kale m'magawo omwe amawoneka ngati suboxic kapena anoxic a ETNP OMZ (Peng ndi ena, 2015;Garcia-Robledo ndi ena, 2017;Penn ndi ena, 2019Komabe, zinthu zomwe zimalamulira kufalikira ndi ntchito za magulu enaake ogwira ntchito a tizilombo toyambitsa matenda mu OMZs sizikumveka bwino.
Kupezeka kwa ma nitrifiers komwe mpweya sungathe kuoneka mu OMZ kungafotokozedwe ndi kusintha kwaposachedwa kwa malo oyima a oxycline chifukwa cha mpweya wozungulira wa oxygen, zomwe zingayambitse kuchuluka kwa mpweya wochepa mkati mwa OMZ cores (Muller-Karger ndi ena, 2001;Ulloa ndi ena, 2012;Garcia-Robledo ndi ena, 2017). Zinthu zosakhalitsa zotere zitha kugwiritsidwa ntchito ndi magulu a aerobic kapena microaerophilic, kuphatikizapo nitrifiers. Kuphatikiza apo, tinthu tomwe timamira kuchokera ku epipelagic (maselo ogwirizana, ndowe, ndi zinthu zovuta zachilengedwe) zitha kukhala ndi mpweya wochepa (Ganesh ndi ena, 2014). Motero, mpweya ndi tizilombo toyambitsa matenda a aerobic zimatha kunyamulidwa kupita kumadzi omwe alibe poizoni, zomwe zimapangitsa kuti kagayidwe ka aerobic kachitike kwakanthawi mogwirizana ndi tinthu tating'onoting'ono. Tinthu tating'onoting'ono timadziwika kuti ndi malo omwe tizilombo toyambitsa matenda timayendera (Simon ndi ena, 2002;Ganesh ndi ena, 2014) ndipo imatha kuthandizira njira zosiyanasiyana za tizilombo toyambitsa matenda zomwe sizimawonedwa mu mkhalidwe wa free-living (Alldredge ndi Cohen, 1987;Wright ndi ena, 2012;Suter ndi ena, 2018).
Mu kafukufukuyu, tikufufuza madera a prokaryotic omwe ali kumpoto kwa OMZ ya ETNP ndi zinthu zachilengedwe zomwe mwina zimakhudza kugawa kwawo kolunjika pogwiritsa ntchito 16S amplicon sequencing (iTags) pamodzi ndi ziwerengero za multivariate. Tafufuza magawo awiri a kukula; gawo la free-living (0.2–2.7 μm), ndi gawo logwirizana ndi tinthu tating'onoting'ono (>2.7 μm, lomwe limagwira tinthu tating'onoting'ono komanso maselo a protistan) pamlingo wosiyanasiyana motsatira oxycline womwe umagwirizana ndi mikhalidwe yosiyana ya redox.
Tikhoza kupereka masensa osungunuka a okosijeni okhala ndi magawo osiyanasiyana, kuti kuchuluka kwa mamolekyulu kuzitha kuyang'aniridwa nthawi yeniyeni. Takulandirani kuti mukambirane nafe.
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Nthawi yotumizira: Julayi-05-2024