Bleaching survey finds few healthy sites on northern sections of Reef

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By Cosmos

From James Cook University

With a mass coral bleaching event unfolding across the Great Barrier Reef, scientists from James Cook University have documented coral bleaching around six islands in the far north of the Great Barrier Reef Marine Park.

The latest in-water surveys follow the team’s reports in early February at the Keppel Islands at the southern end of the Great Barrier Reef, more than 1,100km away, where severe coral bleaching was observed.

The monitoring is part of a 25-year program focusing on 42 high-value islands within the Great Barrier Reef Marine Park. It provides managers with critical information on disturbance and recovery patterns of island coral reefs, including events like coral bleaching, floods and cyclones.

The University’s Centre for Tropical Water and Aquatic Ecosystem Research (TropWATER) inshore island monitoring team, led by Dr Maya Srinivasan, surveyed 15 sites around six islands in the Turtle Group National Park in the far northern Great Barrier Reef.

Bleached acros blue staghorn
Bleached Acros blue staghorn (Image: James Cook University TropWATER)

“We saw a few relatively healthy areas of reef, mostly in deeper waters. All shallow areas were starting to bleach, and there were spots on the reef flats where the corals were totally white,” Srinivasan says.

“We also saw a few corals that had died recently, with filamentous turf algae starting to grow over them.

“Our in-water surveys have now documented coral bleaching in both the far north and the southern Great Barrier Reef islands, and the Great Barrier Reef Marine Park Authority has confirmed a mass coral bleaching event is unfolding.”

Coral bleaching is a stress response to elevated water temperatures, causing corals to expel the symbiotic algae living within their tissues. A bleached coral is still alive, and it can recover by regaining the algae if temperatures cool. But if water temperatures remain high for too long, the coral will die.

The inshore island monitoring program includes 21 islands that have been monitored every one to two years for over 25 years, and 21 new islands have been added to the monitoring program in the last two years.

Bleached staghorn corymbose acros
Bleached staghorn & corymbose Acros (Image James Cook University TropWATER)

Srinivasan says while the six islands in the Turtle Group were new additions to the monitoring program, the team could now track how the reefs recover in the years that follow.

“Maintaining consistent, long-term monitoring at the same sites is really important,” she says.

“We are now in a position where we can track the recovery, or further decline, of the fish and benthic communities of these island reefs.”

More on bleaching: Potential Reef “saviours.”

The program allows scientists to observe changes in fish and benthic (coral, algae, sponges and more) communities over time. It assesses impacts of disturbances such as cyclones, floods, and coral bleaching, and helps track the patterns of recovery following these events. The monitoring also looks at fish abundances in relation to marine park zoning, with the ability to provide critical advice to managers.

The team will be surveying islands offshore from Mackay and Townsville in the coming weeks.

The program is funded by the partnership between the Australian Government’s #ReefTrust and the Great Barrier Reef Foundation. This project is part of a joint program managed by the Australian Institute of Marine Science, in partnership with JCU TropWATER, University of the Sunshine Coast, Great Barrier Reef Marine Park Authority and Queensland Agriculture.

Original article published with permission James Cook University

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