4億1500萬年前的畸形浮游生物化石顯示了過去某些大滅絕事件的元凶，可能是重金屬污染

原文網址：www.sciencedaily.com/releases/2015/08/150825115031.htm

415-million-year-old malformed fossil plankton reveal that heavy metal pollution might have contributed to some of the world's largest extinction events

4億1500萬年前的畸形浮游生物化石顯示了過去某些大滅絕事件的元凶，可能是重金屬污染

Several Palaeozoic mass extinction events during the Ordovician and Silurian periods (ca. 485 to 420 to million years ago) shaped the evolution of life on our planet. Although some of these short-lived, periodic events were responsible for eradication of up to 85% of marine species, the exact kill-mechanism responsible for these crises remains poorly understood.

發生在奧陶紀以及志留紀之際的數次古生代大滅絕事件，塑造了地球生命的演化方向。這些短暫而週期性發生的事件，消滅了85%的海洋生命，然而我們仍然不甚了解它們危害生物的確切機制。

An international team led by Thijs Vandenbroucke (researcher at the French CNRS and invited professor at UGent) and Poul Emsbo (US Geological Survey) initiated a study to investigate a little known association between 'teratological' or 'malformed' fossil plankton assemblages coincident with the initial stages of these extinction events.

由Thijs Vandenbroucke(法國國家科學研究中心的研究員以及根特大學的訪問教授)和Poul Emsbo(美國地質調查所)領導的國際團隊進行的研究中，調查了畸形浮游生物化石群的組成，跟大滅絕事件的起始階段之間鮮為人知的關聯。

In a paper just published in Nature Communications, they present evidence that malformed fossil remains of marine plankton from the late Silurian (415 million years ago) contain highly elevated concentrations of heavy metals, such as iron, lead, and arsenic. These are well-known toxins that cause morphologic abnormalities in modern aquatic organisms; which led the authors to conclude that metal poisoning caused the malformation observed in these ancient organisms and may have contributed to their extinction and that of many other species.

在新發表於《自然通訊》(Nature Communications)的論文中，他們呈現的證據表達出晚志留纪的畸形海洋浮游生物化石，含有濃度相當高的重金屬，像是鐵、鉛、砷。這些惡名昭彰的毒素會讓現代的水生生物發育不正常，因此作者認為重金屬中毒扭曲了這些古海洋生物的外貌，甚至將牠們以及許多其他生物消滅殆盡。

Documented chemical behavior of these metals, which correlates with previously observed disturbances in oceanic carbon, oxygen and sulphur signatures, strongly suggests that these metal increases resulted from reductions of ocean oxygenation.

記錄到代表這些金屬元素的化學訊號的時間，與先前觀察中海洋碳、氧、硫突然變化的時間相當一致，強烈顯示這些金屬元素增加的原因是海洋從氧化狀態變成還原態。

Thus, metal toxicity, and its expressions in fossilized malformations, could provide the 'missing link' that relates organism extinctions to widespread ocean anoxia. As part of a series of complex systemic interactions accompanying oceanic geochemical variation, the mobilisation of metals in spreading anoxic waters may identify the early phase of the kill-mechanism that culminated in these catastrophic events.

因此，重金屬中毒還有它造成的畸形化石，可能就是生物滅絕與海洋大規模缺氧現象二者間的「失落環節」。隨著海洋的地球化學性質發生變化，不同系統之間會產生一連串複雜的連動，後果之一即為金屬元素到處充斥在缺氧的海水中。或許這就是滅絕事件在巔峰期剛開始時殺害大量生物的機制。

The recurring correlation between fossil malformations and Ordovician-Silurian extinction events raises the provocative prospect that toxic metal contamination may be a previously unrecognized contributing agent to many, if not all, extinction events in the ancient oceans.

奧陶紀-志留紀大滅絕事件與畸形化石之間反覆出現的關聯，讓這些科學家提出了較激進的想法：就算不是全部，但在許多古代海洋大滅絕事件中，毒性金屬污染也許是之前未被重視的重要因子。

引用自：Ghent University. "415-million-year-old malformed fossil plankton reveal that heavy metal pollution might have contributed to some of the world's largest extinction events." ScienceDaily. ScienceDaily, 25 August 2015.