若干重大地質(zhì)環(huán)境突變的地球生物學(xué)過程

謝樹成　王風(fēng)平　顏佳新　儲(chǔ)雪蕾　史曉穎

摘 要：MCG古菌代表了一類自然界較古老的古菌，提議將MCG古菌歸類于一個(gè)全新的門類——深古菌門（Bathyarchaeota）。高濃度CO2造成的海水酸化對(duì)西太平洋海區(qū)浮游細(xì)菌的豐度、高DNA含量細(xì)菌、生產(chǎn)力等有促進(jìn)作用，但對(duì)細(xì)菌的多樣性有一定程度的抑制作用。火山灰造成海洋異養(yǎng)細(xì)菌和真核自養(yǎng)生物的豐度均顯著升高，降低浮游病毒的豐度，導(dǎo)致微生物群落多樣性降低，使整個(gè)群落朝著不同方向演替。發(fā)現(xiàn)AOM細(xì)胞團(tuán)在其表面形成粘土礦物，而在周圍環(huán)境中形成碳酸鹽，這可能與AOM反應(yīng)產(chǎn)生的HS-增加環(huán)境堿度有關(guān)。西南印度洋深海微生物群落結(jié)構(gòu)與鈣、磷、硫等元素具有相關(guān)性。提出了兩類示蹤古水文條件的微生物脂類指標(biāo)、三類靈敏響應(yīng)古溫度的微生物脂類指標(biāo)。有機(jī)質(zhì)-粘土礦物復(fù)合體能有效保護(hù)有機(jī)質(zhì)遭受微生物的作用，對(duì)碳循環(huán)產(chǎn)生重要影響。不同微生物功能群的共存能促進(jìn)粘土礦物結(jié)構(gòu)鐵的還原，微生物成因的白云石主要與細(xì)胞表面的羧基官能團(tuán)有關(guān)。發(fā)現(xiàn)古、中生代之交海洋環(huán)境具有高溫、缺氧、低硫酸鹽濃度、氮素匱乏的特征，生態(tài)系統(tǒng)不同營養(yǎng)層次的生物對(duì)海洋環(huán)境具有不同的響應(yīng)能力，微生物對(duì)海洋水化學(xué)和全球變暖起重要作用。提出了兩幕生物危機(jī)與兩幕環(huán)境變化，溫度變化和缺氧環(huán)境可能導(dǎo)致了二疊紀(jì)-三疊紀(jì)之交的幕式生物危機(jī)。大滅絕后，在Griesbachian早期、Dienerian-Smithian之交、Smithian-Spathian之交出現(xiàn)嚴(yán)重的海洋缺氧、硫化事件，出現(xiàn)了微生物巖、鮞?；?guī)r等異常沉積。 在雪球地球之前的拉伸紀(jì)古氣候已經(jīng)開始不穩(wěn)定。埃迪卡拉紀(jì)海洋的化學(xué)分層造成不同的生境及其不同的地球微生物學(xué)過程，造成DOC碳庫與DIC碳庫的分離，也造成不同于顯生宙的海洋碳循環(huán)。陡山沱組II和IV段在缺氧或硫化的水體中存在一個(gè)大DOC碳庫；陡山沱早期（II段）以光合自養(yǎng)微生物體系為主，到晚期（IV段）隨著透光帶硫化水體的發(fā)育，有大量化能異養(yǎng)微生物加入。晚埃迪卡拉紀(jì)-早寒武世海洋仍具有缺氧分層的高梯度狀態(tài)。早寒武世早期可能缺乏固氮作用相關(guān)，隨后趨于正常，氧化明顯并伴生多細(xì)胞生物發(fā)育。 華北中元古界發(fā)現(xiàn)大量微生物成因的凝塊石，在燕山盆地中元古代發(fā)現(xiàn)了兩個(gè)重要的生物群更替事件，分別與海洋化學(xué)變化以及火山活動(dòng)導(dǎo)致的營養(yǎng)鹽輸入相關(guān)。發(fā)現(xiàn)了多種真核生物化石，表明這個(gè)時(shí)期真核生物已經(jīng)出現(xiàn)明顯的多樣性分化。中元古代海洋DIC庫經(jīng)歷了逐漸減小的演變，海洋硫酸鹽濃度較低，氧化還原界面較淺。在淺水環(huán)境自養(yǎng)微生物控制了碳的代謝過程，而深水環(huán)境厭氧微生物代謝對(duì)海水化學(xué)組成有很大影響。

關(guān)鍵詞：地質(zhì)微生物功能群 全球變化 海洋水化學(xué) 極端環(huán)境 重大地質(zhì)環(huán)境突變

Abstract： MCG is one of the earlier archaeal branches and taxonomically assigned to a new branch， Bathyarchaeota. CO2-induced oceanic acidification promotes the abundance of planktonic bacteria and the primary production but decreases bacterial diversity. Addition of volcanic ash induces the elevated abundance of heterotrophic bacteria and eukaryotic autotrophs， but decreases the abundance of planktonic viruses and microbial diversity. Microbial cells related to AOM lead to the precipitation of clay mineral on the cell surface but the carbonate in surrounding environments. Microbial lipid proxies were proposed to show sensitive responses to temperature and hydrological conditions. Organic-clay association could prevent organics from microbial degradation， which in turn impacts carbon cycle. Co-occurrence of microbial functional groups accelerates the reduction of iron within clay minerals. It is found that the ocean across the Permian-Triassic boundary is featured by hot， anoxic conditions with low concentration of sulfate and nitrate. Organisms of different trophic levels show varied responses to the deteriorative environmental conditions. Microbes play important roles in changing the oceanic chemistry and global warming at that time. Two episodes of faunal mass extinction and environmental crisis were proposed. Enhanced anoxia and euxinia were present in association with microbialites and giant oolites in early Griesbachian， Dienerian-Smithian transition and Smithian-Spathian. Oceanic stratification in Neoproterozoic results in the differentiation of bio-habitat and thus the different geomicrobiological processes， which in turn causes the separation of DOC pool and DIC pool and thus a carbon cycle different from that in Phanerozoic. Large DOC pool is present in association with anoxic or euxinic conditions during Doushantuo deposition. Photosynthetic autotrophs are dominant in Early Doushantuo but later replaced by chemoheterotrophs due to the expansion of euxinic zones. Thrombolites were demonstrated to be of microbial origin in Mesoproterozoic in North China craton. Two important replacements of microbes were found to relate to the change in oceanic chemistry and the enhanced input of nutrients resulted from volcanism， respectively. Eukaryote was documented to diversify at that period. Mesoproterozoic oceans are characterized by the decrease in DIC pool， the shallow chemocline and low concentration of sulfate.

Key Words： Geomicrobial functional group； Global change； Oceanic chemistry； Extreme environments

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