In the (very warm, tropical) waters between Australia and Southeast Asia lies an important piece of Earth’s history. A new study by Edith Cowan University (ECU) shows that 20 to 10 million years ago, this region was the site of a massive coral reef expansion over 100 million years, which helped create many of today’s exceptional marine biodiversity.
Dr Alexandre Siqueira, Vice Chancellor’s Research Fellow at ECU, explains: “Coral reefs are among the most biodiverse ecosystems on Earth, supporting around a quarter of all marine species while covering less than one per cent of the oceans. Yet how this diversity formed has remained unclear. This study uncovers a turning point deep in Earth’s history, a time when reefs didn’t just grow, but magnified on a scale far beyond anything we see today.”
The research team combined geological records, fossils, and genetic data to show how tectonic movements and environmental changes opened vast shallow seas, which served as perfect nurseries for coral. These reefs grew, creating new ecological niches that encouraged the evolution of major groups, such as parrotfish.
The discoveries pinpoint northwestern Australia as an unforeseen hotspot for this primitive reef expansion. Ashmore Reef, Scott Reef, and the Rowley Shoals may be remnants of the Great Indo-Australian Miocene Reef System, as researchers call it.
“Previous geological work has shown that this ancient west Australian barrier reef rivaled the extent of the present-day Great Barrier Reef. The new findings go further, suggesting individual reefs within this system may have been far larger than any modern reef. In fact, the roots of modern marine fish and coral biodiversity may lie in this unexpected place off Australia’s west coast,” he said.
This study adds an important piece to the puzzle in understanding reef evolution.
“There is a lot of research that has been done to show this specific point in time was special for some reason. Some hypothesize that this was the time when the tectonic plate from Australia was moving northwards, and that when it reached Southeast Asia, it created a lot of shallow waters that are ideal for the development of coral reefs. But what we are adding to the story is that coral reefs were significantly larger then, and that part of history continues to shape life in our oceans today,” Dr. Siqueira explained.
From these hidden giants offshore Australia to the colors of the Indo-Pacific coral reefs teeming with biodiversity, is how that story is being rewritten, and, in some cases, completely reshaped, by ancient ecosystems still here and defining our oceans today.
Journal Reference:
- Alexander C. Siqueira, Wolfgang Kiessling, Nussaibah Raja and David Bellwood. The rise and fall of the world’s greatest marine biodiversity hotspot. Science Advances. DOI: 10.1126/sciadv.aec7264