Gabashin Tropical North Pacific (ETNP) babba ne, mai tsayin daka, kuma yana ƙara ƙaramar yankin iskar oxygen (OMZ) wanda ya kai kusan rabin jimlar OMZs na duniya. A cikin ainihin OMZ (zurfin ~ 350-700 m), narkar da iskar oxygen yawanci yana kusa ko ƙasa da iyakar gano na'urori na zamani (~ 10 nM). Tsuntsayen iskar oxygen sama da ƙasa da ainihin OMZ suna kaiwa zuwa ga tsarin tsaye na al'ummomin ƙananan ƙwayoyin cuta waɗanda suma sun bambanta tsakanin ɓangarori masu alaƙa (PA) da girman rayayye (FL). Anan, muna amfani da 16S amplicon sequencing (iTags) don nazarin bambance-bambancen da rarraba yawan prokaryotic tsakanin FL da PA masu girman juzu'i da kuma tsakanin kewayon yanayin redox na yanayi. Yanayin yanayin ruwa a yankin bincikenmu ya bambanta da waɗanda aka ruwaito a baya a cikin ETNP da sauran OMZs, kamar ETSP. Bincika adadin iskar oxygen (~ 0.35 μM) sun kasance a ko'ina cikin ainihin OMZ a wurin samfurin mu. Sakamakon haka, tarin nitrite da aka ba da rahoton yawanci don muryoyin OMZ ba su nan kamar yadda jerin kwayoyin cutar anammox suke (Brocadiales genus).CandidatusScalindua), waɗanda galibi ana samun su a cikin iyakokin oxic-anoxic a cikin wasu tsarin. Duk da haka, kwayoyin ammonia-oxidizing (AOB) da archaea (AOA) rarrabawa da maximal autotrophic carbon assimilation rates (1.4 μM C d–1) ya zo daidai da iyakar adadin ammonium mai faɗi kusa da saman ainihin OMZ. Bugu da kari, membobin jinsinNitrospina, Mahimmancin nitrite-oxidizing kwayoyin cuta (NOB) clade sun kasance suna nuna cewa duka ammoniya da nitrite oxidation suna faruwa a gano adadin iskar oxygen. Binciken Gwaji (Anosim) da kuma rashin daidaituwa na awo (nmds) wanda ba a bayyana cewa ƙwarewar ƙwayar cuta da wakilcin Phylogetic na Archaeal sun kasance bambance-bambance tsakanin yanki ba. Dangane da bayanan bayanan ANOSIM da iTag, haɗin ginin tarukan PA bai yi tasiri sosai ta tsarin tsarin ilimin halittu mai zurfi mai dogaro fiye da juzu'in FL. Dangane da kasancewar AOA, NOB da gano iskar oxygen a cikin OMZ core muna ba da shawarar cewa nitrification wani aiki ne mai aiki a cikin yanayin nitrogen na wannan yanki na ETNP OMZ.
Gabatarwa
Dangane da canjin yanayi mai gudana da ayyukan ɗan adam na gida, adadin iskar oxygen da aka narkar da shi yana raguwa a cikin buɗaɗɗen teku da kuma tsarin magudanar ruwa na bakin teku.Breitburg et al., 2018). Kiyasin asarar iskar oxygen daga buɗaɗɗen teku a cikin shekaru 60 da suka gabata ya wuce 2% (Schmidtko et al., 2017), haifar da damuwa game da sakamakon daɗaɗɗen yanki na oxygen-depleted (Paulmier da Ruiz-Pino, 2009). Bude tekun OMZs yana samuwa lokacin da manyan abubuwan samarwa na farko ke haifar da buƙatun iskar oxygen a cikin ruwan da ke ƙarƙashin ƙasa wanda ya wuce ƙimar iskar jiki a zurfin. Matsakaicin iskar oxygen a cikin ginshiƙan ruwa na OMZ na iya samun m gradients (oxycline) sama da ƙasa da iskar oxygen-depleted core halitta hypoxic (yawanci tsakanin 2 da ~ 90 μM), suboxic (<2 μM) da anoxic (ƙasa da ganewa iyaka (~ 10 nM) yadudduka na sãɓãwar launukansa girma dabam (~ 10 nM).Bertagnolli da Stewart, 2018). Oxygen gradients suna kaiwa zuwa ga tsarin tsaye na metazoan da al'ummomin microbial da tsarin biogeochemical tare da waɗannan fa'idodin oxyclines (Belmar et al., 2011).
Wasu daga cikin mafi girman adadin asarar nitrogen an yi rikodin su a cikin OMZs na Gabashin Tropical North Pacific (ETNP) da Kudancin Pacific (ETSP) (Callbeck et al., 2017;Penn et al., 2019), Basin Cariaco Basin na dindindin (Montes et al., 2013), Tekun Arabiya (Ward et al., 2009), da kuma OMZ na Benguela upwelling tsarin (Kuypers et al., 2005). A cikin waɗannan tsarin, tsarin microbial na denitrification na canonical (raguwar heterotrophic na nitrate zuwa tsaka-tsakin nitrogen kuma sau da yawa zuwa iskar dinitrogen) da anammox (anaerobic ammonium oxidation) yana haifar da asarar nitrogen wanda zai iya yuwuwar iyakance samar da farko.Ward et al., 2007). Haka kuma, iskar nitrous oxide na teku (wani mai ƙarfi mai ƙarfi) daga ƙarancin ƙwayoyin cuta da ke faruwa a cikin OMZs an ƙiyasta aƙalla kashi ɗaya bisa uku na iskar nitrous oxide na duniya.Naqvi et al., 2010).
ETNP OMZ babban yanki ne, mai tsayi, kuma yana haɓaka mafi ƙarancin oxygen wanda ke lissafin kusan rabin jimlar OMZs na duniya, yana tsakanin latitude 0-25°N da 75 da 180°W longitude (Paulmier da Ruiz-Pino, 2009;Schmidtko et al., 2017). Saboda mahimmancin muhallin su, an yi nazari mai zurfi kan ilimin kimiyyar halittu da bambance-bambancen microbial na yankuna ETNP OMZ daban-daban (misali,Beman da Carolan, 2013;Duret et al., 2015;Ganesh et al., 2015;Chronopoulou et al., 2017;Pack et al., 2015;Peng et al., 2015). Nazarin da suka gabata sun ba da rahoton cewa narkar da iskar oxygen a cikin wannan ainihin OMZ (~ 250-750 m zurfin) yawanci yana kusa ko ƙasa da iyakokin ganowa (~ 10 nM) (Tiano et al., 2014;Garcia-Robledo et al., 2017). Koyaya, tare da gefen arewa na ETNP's OMZ (wurin wurin binciken ~ 22°N) yawan iskar oxygen a 500 m na iya kaiwa matsakaicin shekara tsakanin 10 da 20 μM (Paulmier da Ruiz-Pino, 2009; Bayanai daga Atlas Tekun Duniya 2013)1. Yayin yakin neman zabe da aka ruwaito a nan, mun auna iskar oxygen a cikin OMZ core a isassun yawa (0.35 μM) don tallafawa tsarin ƙwayoyin cuta na aerobic, irin su ammonium da nitrite oxidation, kuma wani ɓangare na hana mahimman hanyoyin ƙwayoyin cuta na anaerobic. An gano matakan ƙwayoyin cuta na Aerobic a baya a cikin alamun suboxic ko nau'ikan anoxic na ETNP OMZ (Peng et al., 2015;Garcia-Robledo et al., 2017;Penn et al., 2019). Koyaya, abubuwan da ke sarrafa rarrabawa da ayyukan takamaiman ƙungiyoyin ƙwayoyin cuta a cikin OMZs har yanzu ba a fahimci su sosai ba.
Kasancewar nitrifiers inda iskar oxygen ba ta iya ganowa a cikin OMZ ana iya bayyana shi ta sauye-sauye na baya-bayan nan a cikin matsayi na tsaye na oxycline saboda iskar oxygen a tsaye na episodic, wanda zai iya haifar da gano matakan iskar oxygen a cikin cores OMZ.Muller-Karger et al., 2001;Ulloa et al., 2012;Garcia-Robledo et al., 2017). Irin waɗannan yanayi na wucin gadi za a iya amfani da su ta hanyar aerobic ko microaerophilic yawan jama'a, gami da nitrifiers. Haka kuma, ɓangarorin da ke nutsewa daga epipelagic (haɗaɗɗen sel, fecal pellets, da hadaddun kayan halitta) na iya ƙunsar matakan iskar oxygen.Ganesh et al., 2014). Don haka, ana iya jigilar iskar oxygen da microbes na aerobic zuwa ruwan anoxic, na ɗan lokaci yana ƙyale ƙwayoyin cuta na aerobic su faru a cikin haɗin gwiwa tare da barbashi. An san barbashi a matsayin wuraren hawan keken ƙwayoyin cuta na ƙwayoyin cuta (biogeochemical).Simon et al., 2002;Ganesh et al., 2014) kuma zai iya tallafawa bambance-bambancen anaerobic ko tsarin ƙwayoyin cuta na aerobic waɗanda ba a lura da su ba a cikin yanayin rayuwa mai 'yanci (Alldredge da Cohen, 1987;Wright et al., 2012;Suter et al., 2018).
A cikin binciken na yanzu, mun bincika al'ummomin prokaryotic waɗanda ke mamaye arewacin OMZ na ETNP da abubuwan muhalli waɗanda ke da yuwuwar tasiri rarrabawar su ta tsaye ta amfani da jerin amplicon 16S (iTags) haɗe tare da ƙididdiga masu yawa. Mun yi nazarin girman juzu'i biyu; ɓangarorin rayayye na kyauta (0.2-2.7 μm), da ɓangarorin da ke da alaƙa (> 2.7 μm, ɗaukar ƙwayoyin cuta da ƙwayoyin protistan) a zurfin zurfi tare da oxycline wanda ya dace da yanayin redox daban-daban.
Za mu iya samar da narkar da na'urori masu auna iskar oxygen tare da sigogi daban-daban, ta yadda za'a iya lura da ƙwayar kwayoyin halitta a ainihin lokaci. Barka da zuwa tuntuba
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Lokacin aikawa: Jul-05-2024