Wednesday April 9, 2025
PhysOrg —
New research has uncovered a crucial clue to understanding the spread of “barrens” in the Great Southern Reef, which are threatening the reef ecosystem.
“Barrens” are areas of low, or no, seaweed cover in the reef. Barren habitat has lower productivity and absorbs less carbon dioxide than the seaweed forest it replaces. In New South Wales, barrens can form in areas where there is an overrepresentation of long-spined sea urchins.
It’s assumed that large fish—believed to be a key predator of urchins—play a significant role in controlling long-spined urchin populations and in turn, barrens. However, this study found almost no evidence of large fish preying on these urchins in the Great Southern Reef.
The unexpected findings are critical to inform future reef management strategies, particularly now that barrens are emerging further south in Tasmania, decreasing productivity for local marine environments.
The research, led by University of Newcastle Ph.D. candidate Jeremy Day, found that key predatory fish—blue groper and pink snapper—consume very few long-spined sea urchins, despite being thought to play a major role in controlling their numbers. The paper is published in the journal Estuaries and Coasts.