Research press release


Nature Communications

Earth sciences: A harbinger of mass extinction



今回、Thijs Vandenbrouckeたちは、シルル紀後期の絶滅事象の開始時に起こったプランクトンの奇形の発生過程が、高濃度の金属毒素に対する現代の生物の応答に非常によく似ていることを明らかにした。Vandenbrouckeたちは、奇形のあるプランクトンの発生とその化石が保存された岩石の金属含有量の急増が同時に起こっていたことから、金属中毒も古代のプランクトンの奇形の原因だった可能性があると考えている。金属含有量が高いということは、海洋の化学組成が変化し、酸素欠乏の拡大が生物の死滅をもたらすメカニズムとなって、この初期絶滅事象に寄与したことを示唆している。


Evidence that malformed plankton may indicate alternative drivers of mass extinction has been presented this week in Nature Communications. Although glacial episodes have previously been linked to the oldest major mass extinctions, the authors suggest that the cause is more likely to be spreading oxygen depletion and harmful metals in the oceans.

Ordovician-Silurian extinction events are thought to have occurred in pulses more than 420 million years ago, when the vast majority of life was flourishing in the sea and very little survived on land. Previous studies have suggested that these events were the result of cooling climate and reductions in habitat, but those models do not account for all palaeontological and geochemical observations.

Thijs Vandenbroucke and colleagues show that malformations in plankton during the initiation of a Late Silurian extinction event occurred in a very similar manner to the response seen in modern organisms to high levels of metallic toxins today. The authors suggest that metal poisoning may also have caused the ancient malformations, as the misshapen plankton coincide with dramatic increases in the metal content of the rocks they are preserved in. The high levels of metals suggest changes in the ocean chemistry at that time and that spreading anoxia may have been a contributing kill-mechanism during these early extinction events.

More recent work implicates anoxia in the oceans as a driving force behind mass extinctions, and the current study supports this and suggests that malformed fossil plankton may be a new forensic tool to identify the onset of these periods of low oxygen.

doi: 10.1038/ncomms8966

「Nature 関連誌注目のハイライト」は、ネイチャー広報部門が報道関係者向けに作成したリリースを翻訳したものです。より正確かつ詳細な情報が必要な場合には、必ず原著論文をご覧ください。

メールマガジンリストの「Nature 関連誌今週のハイライト」にチェックをいれていただきますと、毎週最新のNature 関連誌のハイライトを皆様にお届けいたします。