北極擁有地球史上最慘重生物大滅絕的相關線索

原始網址：www.sciencedaily.com/releases/2016/08/160824111100.htm

Arctic gives clues on worst mass extinction of life

北極擁有地球史上最慘重生物大滅絕的相關線索

Extreme global warming 252 million years ago caused a severe mass extinction of life on Earth. It took life up to 9 million years to recover. New study finds clues in the Arctic as to why this recovery took so long.

2.52億年前極端的全球暖化在地球上造成相當慘種的生物滅絕事件。生命花了長達9百萬年的時間才從這齣慘劇中回復過來。新的研究從北極找到線索透露出為何生命要經過那麼久的時間才能重新復甦。

96 percent of marine species, and 70 percent of terrestrial life died off in the Permian-Triassic extinction event, as geologists know it. It is also known as The Great Dying Event for obvious reasons.

就地質學家所知，在這起二疊紀—三疊紀滅絕事件(Permian-Triassic extinction event)中，當時96%的海洋生物和70%的陸地生物就此滅亡。因此這起事件又被稱作「大死亡」(The Great Dying Event )的原因可說是顯而易見。

"The mass extinction was likely triggered by a explosive event of volcanic eruptions in what is now Siberia. These eruptions lasted for a million years and emitted enormous amounts of volatiles, such as carbon dioxide and methane, which made our planet unbearably hot." says Jochen Knies, researcher at Centre for Arctic Gas Hydrate, Environment and Climate at UiT The Arctic University of Tromsø.

「這件大滅絕事件可能是由現今西伯利亞地區發生的劇烈火山爆發所導致。這些火山持續噴發了數百萬年並釋放出大量像是二氧化碳和甲烷的揮發物質，使我們星球的溫度升高至令人無法承受的境界。」 Jochen Knies說。他在挪威特羅姆瑟北極圈大學(The Arctic University of Tromsø)的北極圈天然氣水合物、環境與氣候中心擔任研究人員。

Life took an extraordinary amount of time to recover from this extinction, from 5 to 9 million years. Why recovery was so delayed, has remained a mystery.

生命耗費了超乎尋常的歲月，可能有5至9百萬年才從這起滅絕事件造成的打擊中重新回復過來。為什麼復原所需的時間會延長至這麼久？至今仍是一道未解之謎。

Clues are in the Arctic

線索就隱藏在北極圈

Knies is the co-author of a study in Geology that took to the Arctic to look for clues as to what limited return of life to world´s oceans. The results of the study illustrate potential long-term impacts on marine ecosystems in response to global warming.

在Knies為共同作者，發表在《地質》(Geology)期刊上的這篇研究中，研究人員前往北極去尋找阻撓生命回歸海洋的線索。研究結果顯示可能是全球暖化對海洋生態系造成了長期影響。

"What used to be the northwestern continental margin of the supercontinent Pangaea is now Canadian High Arctic. There we found evidence in geological records for a significant nutrient gap during this period. This means that global oceans were severely poor in nutrients such as nitrogen," says Knies.

「過去曾是盤古超大陸西北大陸邊緣的海域現在位於加拿大的極地地區。我們在這邊的地質紀錄中找到了證據顯示出當時海洋養分不足的情形十分嚴重。意味著全球海洋相當缺乏像是氮元素這類的重要養分。」 Knies表示。

This nutrient gap is most likely the result of extremely high ocean surface temperatures in the aftermath of the extinction.

養分缺乏最有可能是因為大滅絕過後海洋表面溫度飆升所造成。

Be cool -- stay alive

溫度下降，才能存活

Our oceans are not a single body of water. They are comprised of layers and boundaries based on temperature (thermocline) and nutrients (nutricline) among others.

我們的海洋並不只是由單一水體組成。海水根據彼此之間的溫度和養分差異作為邊界(斜溫層和營養躍層)而可以劃分成許多水層。

"The high temperatures caused deepening of the thermocline and nutricline in the ocean so that upwelling of nutrients from the bottom to the surface of ocean ceased. With that the marine algae productivity was stalled," according to Knies.

根據Knies的說法，「高溫導致海洋中的斜溫層和營養躍層的深度變深，造成深海的養分停止往海水表層上湧。因為這種現象使得海洋藻類的生產活動停滯下來。」

And without algae, which are the base of the food chain, the life in the ocean did not thrive.

而藻類作為食物鏈的基礎，沒有了它們，海洋中的其他生命自然也無法倖免於難。

Once oceans finally started cooling 6-7 million years after the extinction, nutrient rich waters returned.

海洋終於在滅絕事件發生的6至7百萬年後開始逐漸冷卻下來，富含養分的海水也重新回歸。

"The boundaries that kept the nutrients from reaching the surface were weakened and the ocean waters were mixed. This caused the upwelling of nutrients, resuscitating the oceans, and leading to an explosion of life. The ecosystem voids created by the worst mass extinction in Earth history were finally filled." states Jochen Knies.

「之前阻擋富含養分的海水到達表層的界面終於減弱，使得海水得以重新混和。這造成養分重新上湧而為整座海洋帶來生機，促成生命大量繁衍。地球史上最慘重的大滅絕事件在生態系挖出的大量空缺終於再次被一一填補起來。」 Jochen Knies如此敘述。

In many ways the Permian-Triassic mass extinction reset the evolution of life, and paved the way for evolution of dinosaurs. They, in turn, died off in another mass extinction 66 million years ago. Today some scientists argue that we are facing a new mass extinction period, mostly caused by human activities.

二疊紀—三疊紀大滅絕事件重新設定了生命在各種層面的演化方向，也為恐龍的出現鋪下了康莊大道。而牠們接著又在6600萬年前發生的另一次大滅絕事件中殞落。今日有些科學家主張我們正步入新的大滅絕時代，其起因則大半要歸咎於人類自身的活動。

引用自：University of Tromso (Universitetet i Tromsø - UiT). "Arctic gives clues on worst mass extinction of life." ScienceDaily. ScienceDaily, 24 August 2016. 

論文來源：Stephen E. Grasby, Benoit Beauchamp, Jochen Knies. Early Triassic productivity crises delayed recovery from world’s worst mass extinction. Geology, 2016; 44 (9): 779