A recent theory sheds light on how young crown-of-thorns sea stars, often referred to as starfish, are capable of destabilizing coral reefs. The concept of a ‘degraded reef framework’ reveals that the decline of live coral, which crown-of-thorns starfish consume, ironically favors their juvenile counterparts. As live coral decreases, these starfish congregate in rubble areas that act as nurseries for young starfish.
New research into one of the most enduring coral predators in the Great Barrier Reef has uncovered a concerning paradox within reef ecosystems: the crown-of-thorns starfish (COTS) seems to flourish in the very environments of coral decline it contributes to.
This study, led by Professor Maria Byrne from the University of Sydney along with marine science researcher Dr. Kennedy Wolfe, clarifies the relationship between coral health and COTS population trends, providing essential insights for conservation initiatives.
Professor Byrne, affiliated with the School of Life and Environmental Sciences at the University of Sydney, stated: “This research reinforces our understanding that species capable of resilience often excel in adapting to changed environments. Tragically, in the situation of the Great Barrier Reef, one of those resilient species — the crown-of-thorns starfish — is among its most relentless coral predators.”
Coral reefs, often called the “rainforests of the sea,” are crucial ecosystems that host a wide variety of marine life. Sadly, these ecosystems are currently facing severe threats from various factors such as climate change, pollution, and overfishing. One of the most pressing issues is the outbreaks of COTS, which can severely diminish coral populations and contribute to extensive reef damage.
This research, published in the Marine Environmental Research journal, introduces a “degraded reef hypothesis” aimed at understanding why COTS remain so prevalent, despite numerous management efforts.
The degraded reef framework suggests that the decline of live coral, which crown-of-thorns starfish rely on for food, unexpectedly aids juvenile COTS. With less live coral available, these starfish gather in rubble habitats that offer nurseries for their young.
This buildup of juvenile starfish can lead to a sudden surge in COTS populations as they mature into coral-eating adults just when corals begin to heal. This situation exacerbates the ongoing cycle of coral decline and reef damage.
“Our previous studies have indicated that juvenile COTS can wait for the perfect opportunity to emerge in significant numbers; this can last for up to six years,” noted Professor Byrne.
The research by Professor Byrne and Dr. Wolfe highlights that the very conditions causing coral decline — such as heatwaves, cyclones, and pollution — create inviting habitats for COTS to thrive. This resilience presents a critical challenge for reef management and conservation efforts, as initiatives aimed at restoring coral health might inadvertently favor the growth of these harmful starfish.
“Our findings reveal an important feedback loop within reef ecosystems,” explained Dr. Wolfe, who began his research journey as a PhD student at the University of Sydney.
“COTS populations may prosper as coral reefs degrade, leading to even more coral loss. This cycle poses a threat not only to corals but also to the numerous species that rely on healthy reefs for their survival,” he added.
Professor Byrne emphasized: “This feedback loop clarifies the reason behind recurrent outbreaks on the Great Barrier Reef, even with rigorous management through manual removal.”
The results highlight the necessity for a comprehensive strategy for coral reef conservation that tackles the fundamental issues of degradation while considering the wider ecological interactions at play.
Professor Byrne concluded: “Effective management approaches need to acknowledge the resilience of crown-of-thorns starfish and their ability to take advantage of damaged habitats. These coral predators are an indication of ongoing environmental issues.”
By comprehending the connection between coral vitality and COTS populations, conservationists can create specific strategies that lessen the effects of these starfish. This could involve habitat restoration strategies that enhance coral resilience, as well as measures to manage nutrient runoff and sediment buildup.
This latest research adds to the significant contributions made by Professor Byrne and her team, enhancing our understanding of how the crown-of-thorns starfish continues to persist as a problematic species on the Great Barrier Reef.
