Voyage finds healthy islands in the Coral Sea Marine Park

Monday 7 September 2026

A recent expedition to the central Coral Sea Marine Park has found healthy island ecosystems and thriving seabird populations, with varied results from coral reefs still recovering from heat stress.

The 1250km voyage in waters off Queensland visited 11 remote cay and islets and 6 reef systems, including Moore, Lihou and Mellish Reefs.

The expedition team included marine park managers from Parks Australia, reef health specialists from James Cook University (JCU), a bird specialist from Queensland Parks and Wildlife, botanists, and an insect expert.

Over 14 days, they collected data for the Coral Sea Marine Park Island and Reef Health projects, which are vital to the ongoing management and protection of the complex habitats and stunning native species in the marine park.

The work on the islands included identifying and counting birds and testing for H5 avian influenza (bird flu), monitoring for invasive species such as weeds, rats and insects, assessing cyclone damage, removing marine debris, and interestingly, counting hermit crabs, which are an important indicator of the health of island ecosystems.

At the same time, a second team of Parks Australia staff, Indigenous rangers from Mandubarra Indigenous Land and Sea Inc., and ecological consultants spent 15 days on South Islet (known as Willis Island), working to reduce invasive weeds that are threatening seabird nesting sites.

Parks Australia acting Director, East Marine Region, Martin Russell led the main expedition and said both voyages were highly successful.

"These islands are wild, remote and important nesting and roosting sites for seabirds," he said. "It was encouraging to see healthy populations of sooty terns, boobies and frigatebirds.

"With the recent detections of H5 bird flu in Australia, it is more important than ever to ensure our seabird populations are as resilient as possible.

"Projects like restoring nesting habitat, and monitoring for invasive species that place pressures seabird populations, help ensure native species are in the best condition to withstand and recover from the potential impacts of H5 bird flu.

"Importantly, there is currently no evidence of H5 bird flu in the Coral Sea Marine Park, and all the testing carried out during the expedition was negative."

Part of a pisonia forest, featuring trees with wisted branches, vivid green leaves and sandy, muddy soil.. — A pisonia forest in North East Cay

In another key project, an expert entomologist surveyed for invasive scale insects in the Pisonia grandis forests on North East Cay in the Herald Cays, and Magdelaine Cay South.

These 2 islands are home to the Coral Sea Marine Park's last remaining stands of the flowering tree. Both were closed at the beginning of 2026 to prevent introduction of pest species and reduce the impact of potentially problematic species like scale insect and the hawkmoth caterpillar, which have devastated Pisonia on other islands.

"The forests on both islands are in generally good condition, but on North East Cay, we did see a few patches of defoliation due to hawkmoth caterpillars, and several areas with high numbers of scale insects and ants," Mr Russell said.

"All together, the data we collected on this expedition indicates the islands in the central Coral Sea Marine Park are healthy and largely free of the impacts of invasive species, the way they should be."

The results for reef health were more varied, with some reefs still recovering from previous years' heat stress events.

To collect reef information, the researchers from James Cook University spent 120 hours in the water, surveying 20 sites across reef systems including Lihou, Diamond Islets, Mellish and Moore, gathering data on coral, fish and invertebrates.

Mellish and Moore Reefs are standout ‘bright spot' reefs in this part of the marine park, showing good coral cover and healthy fish populations.

Lihou Reef and Diamond Islets showed less recovery from recent heat stress, with reduced coral cover, and some loss of grazing fish that eat algae growing on the coral.

Another voyage in the Coral Sea Marine Park is planned in September with a team venturing into the southern part of the marine park to continue island and reef monitoring work.

The Coral Sea Marine Park is the largest in Australian waters, covering nearly one million square kilometres, and protecting huge reef systems and more than 60 islets and coral cays.

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