Algae Bleaching Key to Past Global Warming Event

American Geophysical Union, Fall Meeting 2007

What triggered the extreme global warming event during the Paleocene-Eocene Thermal Maximum (PETM) 55 million years ago? Multiple theories have emerged on the cause, including asteroids, massive volcanic eruptions and even suggestions of a giant methane belch. Richard Norris, professor of paleobiology at Scripps Institution of Oceanography at UC San Diego provides new evidence that environmental stress existed prior to the extreme warming event; therefore, a one-time catastrophic event is not likely to have occurred.

A scanned electron micrograph image of the planktonic foraminifera, Acarinina soldadoensis, a species known to bleach during past extreme warming periods.

Norris will discuss details of his research, titled "Bleaching of Symbiotic Foraminifera During Extreme Global Warming at the Paleocene-Eocene Boundary," during the 2007 American Geophysical Union Fall Meeting.

Norris' study is the first to document bleaching of foraminifera, single-celled organisms in the kingdom Protista that paleontologists study to reconstruct Earth's climate history.

Like reef corals, many types of foraminifera play host to symbiotic algae, but this symbiosis broke down during the extreme warmth of the PETM.

By measuring the isotopic carbon soaked up by the symbiotic algae contained within the foraminifera, Norris demonstrates that the symbiotic algae disappeared for a period of time during the warming event, resulting in a large-scale bleaching event.

"Clearly things were going wrong prior to the event," said Norris.

Geochemical studies on fossilized foraminifera can help scientists to better understand what was happening on Earth during the extreme global warming event 55 million years ago that produced tropical temperatures 4-5 degrees warmer than today.

Reconstruction of past global warming events has enormous implications for life now and what will happen on Earth in the future. This research can provide insight into what is happening on earth now from a climatic and geochemical perspective, notes Norris.

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