Tiny Algae May Have Prompted a Mass Extinction
https://eos.org/articles/tiny-algae-may-have-prompted-a-mass-extinction
Source: By Katherine Kornei, Eos/AGU.
Excerpt: More than three quarters of all marine life died about half a billion years ago. ...Below a certain depth in the stratigraphic record, trilobites, corals, and brachiopods thrived in the ocean. Above it, many types of these organisms are missing. What could have caused 85% of marine species—at a time when life largely existed only in the oceans—to just up and perish? New research offers an unlikely linchpin in this vast die-off: tiny algae. Around the time of this extinction event, algae populations were rising ocean-wide. When these abundant organisms lived, they soaked up atmospheric carbon and stored it in their tissues. But when they died, they may have sunk quickly through the water column, scientists have proposed, rapidly sequestering carbon in the depths of the ocean.... The new study “reveals how algal evolution could have been vital in regulating the Earth’s carbon cycle.” The planet then cooled as a result of having less carbon dioxide in the atmosphere, plausibly triggering the widespread glaciation that’s believed to have prompted one of the Earth’s largest mass extinction events, the new work suggests. ...The new study “reveals how algal evolution could have been vital in regulating the Earth’s carbon cycle,” .... ...The key to this hypothesis lies in ancient ocean sediments unearthed from Nevada dating to the very end of the Ordovician period, roughly 444 million years ago. Jiaheng Shen, lead author of the paper and a geochemist at Harvard University, and her colleagues collected samples of these sediments—mostly shale and limestone—and found that they contained compounds derived from chlorophyll...created by ancient algae, which died and sank to the seafloor to create the sediments. ...samples from younger rocks...appeared to contain more and more material from algae. Over a period of just a few million years, the amount of the telltale compounds increased by approximately fivefold, the team estimated....
Source: By Katherine Kornei, Eos/AGU.
Excerpt: More than three quarters of all marine life died about half a billion years ago. ...Below a certain depth in the stratigraphic record, trilobites, corals, and brachiopods thrived in the ocean. Above it, many types of these organisms are missing. What could have caused 85% of marine species—at a time when life largely existed only in the oceans—to just up and perish? New research offers an unlikely linchpin in this vast die-off: tiny algae. Around the time of this extinction event, algae populations were rising ocean-wide. When these abundant organisms lived, they soaked up atmospheric carbon and stored it in their tissues. But when they died, they may have sunk quickly through the water column, scientists have proposed, rapidly sequestering carbon in the depths of the ocean.... The new study “reveals how algal evolution could have been vital in regulating the Earth’s carbon cycle.” The planet then cooled as a result of having less carbon dioxide in the atmosphere, plausibly triggering the widespread glaciation that’s believed to have prompted one of the Earth’s largest mass extinction events, the new work suggests. ...The new study “reveals how algal evolution could have been vital in regulating the Earth’s carbon cycle,” .... ...The key to this hypothesis lies in ancient ocean sediments unearthed from Nevada dating to the very end of the Ordovician period, roughly 444 million years ago. Jiaheng Shen, lead author of the paper and a geochemist at Harvard University, and her colleagues collected samples of these sediments—mostly shale and limestone—and found that they contained compounds derived from chlorophyll...created by ancient algae, which died and sank to the seafloor to create the sediments. ...samples from younger rocks...appeared to contain more and more material from algae. Over a period of just a few million years, the amount of the telltale compounds increased by approximately fivefold, the team estimated....