Yankin da ya mutu (ecology)

Yankunan da suka mutu sune yankunan Hypoxic (low-oxygen) a cikin Tekuna na duniya da manyan tabkuna. Hypoxia yana faruwa ne lokacin da aka narkar da iskar oxygen (DO) ya fadi zuwa ko ƙasa da 2 ml na O2/lita. Lokacin da jiki na ruwa ke fuskantar yanayin hypoxic, tsire-tsire na ruwa da fauna suna fara canza halayyar don isa sassan ruwa tare da matakan iskar oxygen mafi girma. Da zarar DO ya ragu ƙasa da 0.5 ml O2/lita a cikin ruwa, yawan mace-mace yana faruwa. Tare da irin wannan ƙarancin DO, waɗannan jikin ruwa sun kasa tallafawa Rayuwar ruwa da ke zaune a can. A tarihi, yawancin waɗannan shafuka suna faruwa ne ta halitta. Koyaya, a cikin shekarun 1970s, masu nazarin teku sun fara lura da karuwar lokuta da faɗin wuraren da suka mutu. Wadannan suna faruwa a kusa da bakin teku da aka zauna, inda rayuwar ruwa ta fi mayar da hankali. 

Yankunan bakin teku, kamar Tekun Baltic, arewacin Tekun Mexico, da Chesapeake Bay, da kuma manyan ruwa masu rufewa kamar Tafkin Erie, sun shafar deoxygenation saboda eutrophication. Ana shigar da kayan abinci masu gina jiki a cikin waɗannan tsarin ta koguna, daga ƙarshe daga rugujewar birane da aikin gona kuma an kara da shi ta hanyar sare daji. Wadannan abubuwan gina jiki suna haifar da babban aiki wanda ke samar da kayan halitta wanda ke nutsewa zuwa kasa kuma yana numfashi. Rashin numfashi na wannan kayan kwayoyin yana amfani da iskar oxygen kuma yana haifar da hypoxia ko anoxia.

Shirin Muhalli na Majalisar Dinkin Duniya ya ba da rahoton yankuna 146 da suka mutu a cikin 2 a cikin tekun duniya inda ba za a iya tallafawa Rayuwar ruwa ba saboda matakan iskar oxygen. Wasu daga cikin wadannan sun kasance ƙananan kamar murabba'in kilomita (0.4 mi2), amma mafi girman yankin da ya mutu ya rufe murabba'i kilomita 70,000 (27,000 mi2). Wani binciken da aka yi a shekara ta 2008 ya ƙidaya yankuna 405 a duk duniya.Diaz, R. J.; Rosenberg, R. (August 15, 2008). "Spreading Dead Zones and Consequences for Marine Ecosystems". Science. 321 (5891): 926–929. Bibcode:2008Sci...321..926D. doi:10.1126/science.1156401. ISSN 0036-8075. PMID 18703733. S2CID 32818786.  

 Dalilan da suka haifar 
Yankunan ruwa da na ruwa na iya haifar da karuwar abubuwan gina jiki (musamman nitrogen da phosphorus) a cikin ruwa, wanda aka sani da eutrophication. Wadannan abubuwan gina jiki sune mahimman abubuwan gini na kwayoyin halitta guda ɗaya, masu kama da shuke-shuke waɗanda ke rayuwa a cikin ginshiƙi na ruwa, kuma ci gaban su yana iyakance a wani ɓangare ta hanyar wadatar waɗannan kayan. Tare da ƙarin abubuwan gina jiki, kwayoyin ruwa guda ɗaya (kamar algae da cyanobacteria) suna da albarkatun da ake buƙata don wuce iyakar ci gaban da suka gabata kuma su fara ninkawa a cikin ƙimar da ta fi yawa. Girman da ke haifar da karuwa mai sauri a cikin yawan wasu nau'ikan waɗannan phytoplankton, wani abu da aka sani da furewar algal.

Limnologist David Schindler, wanda bincikensa a yankin Experimental Lakes ya haifar da haramtacciyar phosphate mai cutarwa a cikin kayan wanki, ya yi gargadi game da fure da wuraren da suka mutu."Fure-fure-fuse da ke kashe kifi da suka lalata Great Lakes a cikin shekarun 1960 da 1970 ba su tafi ba; sun koma yamma zuwa cikin duniyar da ba ta da ruwa inda mutane, masana'antu, da aikin gona ke ƙara haraji akan ingancin abin da ƙananan ruwan sha za a samu a nan....Wannan ba matsala ce kawai. Yaduwar duniya na wuraren da suka mutu da algaloms suka haifar yana ƙaruwa da sauri. "

 Tasirin 
Mafi sanannun tasirin eutrophication shine furanni na kayan lambu, wani lokacin mai guba, asarar halittu da anoxia, wanda zai iya haifar da mutuwar kwayoyin ruwa.

Saboda yanayin hypoxic da ke cikin yankunan da suka mutu, rayuwar ruwa a cikin waɗannan yankuna ba ta da yawa. Yawancin kifaye da kwayoyin motsi suna ƙaura daga yankin yayin da yawan iskar oxygen ke fadowa, kuma yawan mutanen benthic na iya fuskantar asarar mai tsanani lokacin da yawan isƙar oxygen ke ƙasa da 0.5 MG l-1 O2. A cikin mawuyacin yanayi, rayuwar microbial na iya fuskantar canje-canje masu ban mamaki a cikin asalin al'umma, wanda ke haifar da karuwar yawan kwayoyin anaerobic kamar yadda kwayoyin aerobic ke raguwa a cikin adadi da sauya tushen makamashi don oxidation kamar nitrate, sulfate, ko rage ƙarfe. Rage sulfur wani damuwa ne na musamman kamar yadda Hydrogen sulfide yana da guba kuma yana jaddada yawancin kwayoyin a cikin yankin, yana kara haɗarin mutuwa. 

Ƙananan matakan iskar oxygen na iya samun mummunar tasiri a kan rayuwar kwayoyin a cikin yankin yayin da suke sama da yanayin anoxic. Nazarin da aka gudanar a bakin Tekun Gulf na Arewacin Amurka sun nuna yanayin hypoxic yana haifar da raguwar yawan haihuwa da ƙimar girma a cikin kwayoyin halitta iri-iri ciki har da kifi da invertebrates na benthic. Kwayoyin da ke iya barin yankin yawanci suna yin hakan lokacin da yawan iskar oxygen ya ragu zuwa ƙasa da 2 MG l-1.Rabalais, Nancy N.; Turner, R. Eugene; Wiseman, William J. (2002). "Gulf of Mexico Hypoxia, A.K.A. "The Dead Zone"". Annual Review of Ecology and Systematics. 33 (1): 235–263. Bibcode:2002AnRES..33..235R. doi:10.1146/annurev.ecolsys.33.010802.150513. ISSN 0066-4162. A waɗannan maida hankali ga iskar oxygen da ƙasa, kwayoyin da ke rayuwa a cikin yanayin da ba su da iskar oxygen kuma ba za su iya tserewa daga yankin ba sau da yawa za su nuna halin damuwa da ke ci gaba da tabarbarewa kuma su mutu. Kwayoyin da ke rayuwa da ke jure wa yanayin hypoxic sau da yawa suna nuna sauye-sauyen ilimin lissafi wanda ya dace da ci gaba a cikin yanayin hypoxic. Misalan irin wannan daidaitawa sun haɗa da haɓaka ingancin iskar oxygen da amfani, rage adadin iskar oxygen ta hanyar rage yawan girma ko barci, da haɓaka amfani da hanyoyin anaerobic metabolic.

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