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There's a Huge Geological Structure Hiding Behind the Great Barrier Reef

Reefs on reefs on reefs.

by Daniel Oberhaus
Aug 27 2016, 6:08pm

Great Barrier Reef, Australia. Image: Flickr

A team of Aussie researchers has discovered an enormous reef behind the Great Barrier Reef which had been "hiding in plain sight" for decades.

As the researchers detailed in a paper published this week in Coral Reefs, high-resolution seafloor maps created by Navy aircraft revealed a massive field of donut-shaped mounds. Each were between 600 to 1000 feet across, and some were 30 meters deep, according to data provided by the Royal Australian Navy.

"We've known about these geological structures in the northern Great Barrier Reef since the 1970s and 80s, but never before has the true nature of their shape, size and vast scale been revealed," said Robin Beaman, a marine geologist at Australia's James Cook University. "The deeper seafloor behind the familiar coral reefs amazed us."

These mounds were discovered using aircraft outfitted with LiDAR, a type of radar imaging which uses lasers instead of radio waves. They are made of Halimeda, a common type of green algae which turns into limestone flakes upon death. Over time these limestone flakes accumulate into reef-like mounds which are known as bioherms.

According to the researchers, over 6000 square kilometers of seafloor around the Great Barrier Reef have been mapped, revealing the extent of this field of Halimeda bioherms.

"That's three times the previously estimated size, spanning from the Torres Strait to just north of Port Douglas," said Mardi McNeil, the lead author of the paper and a researcher at the Queensland University of Technology. "They clearly form a significant inter-reef habitat which covers an area greater than the adjacent coral reefs."

The presence of this massive reef poses a lot of questions about the past and future of Earth's oceans. Halimeda are calcifying organisms, which means they are sensitive to the acidification and warming of the ocean—but how this shift in oceanic conditions has affected their development remains to be seen.

These bioherms can also tell researchers a lot about how the environmental conditions in this region of the ocean have changed during the last 10,000 years, and can provide insight into fine-scale patterns of marine life currently existing in the area.

In order to better understand these processes, the researchers hope to carry out sediment coring and subsurface exploration of the area with autonomous underwater vehicles in the future.

In the meantime, try to keep this awesome discovery on the DL because the Australian government has a history of ruining nice things.

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marine science
Halimeda
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geological structure
seafloor maps