Coral Sea Marine Park Environmental Assessment of Islands, Islets and Cays of the Central Reef System 2024

In July 2024, Parks Australia undertook a nine-day voyage in the Coral Sea Marine Park (CSMP), to assess the health of islands, islets and cays in the central region of the CSMP.

The islands visited and assessed:

• Mid Islet (Willis Islets)
• South Islet (Willis Islets)
• North West Islet (Magdelaine Cays)
• South East Cay (Magdelaine Cays)
• Georgina Cay (Lihou Reef)
• East Diamond Islet (Diamond Islets)
• Central Diamond Islet (Diamond Islets)
• West Diamond Islet (Diamond Islets)South West Islet (Coringa Islets)
• Chilcott Islet (Coringa Islets)
• North East Cay (Herald Cays)
• South West Cay (Herald Cays).

The CSMP Island Health Project is undertaken through a collaboration of agencies and experts, bringing a suite of specialist skills to provide assessments on ecosystem health and identify change and emerging pressures across several indicator areas including:

• description and mapping of vegetation communities
• establishing permanent vegetation BioCondition monitoring sites to compare structure, floristc composition and ecosystem function over time and to provide benchmarks for Coral Sea terrestrial vegetation
• compiling comprehensive plant species lists
• collecting data on bird breeding, population demographics and species diversitysurveying for introduced and invasive species
• monitoring for threats and pressures to natural values, such as human activity
• removing marine debris and recording type and weight
• installing and maintaining Parks Australia information signs on vegetated islands
• high resolution spatial drone imagery and
• describing and checking for change of island geomorphology.

Assessments on the 2024 voyage are a continuation of Coral Sea Island Health voyages to the 60+ islands undertaken in November/December 2019 (Hemson et al. 2020), July 2021 (Chapman et al. 2022), May/June 2022 (McDougall and Brushe 2023) and July 2023 (Director of National Parks 2024), and represent a critical ongoing assessment and evaluation process that informs management of these ecosystems.

Key findings from the 2024 voyage:

• Pisonia grandis communities on North East Herald Cay were in good condition with no evidence of scale insect outbreaks or associated ant population increases. Some leaves on the Pisonia grandis communities on Magdelaine Cay South exhibited damage from insect attack.
• Cordia subcordata (sea trumpet) communities continue to exhibit varying degrees of dieback and recovery, indicating stress related to insect attack and climatic pressures.
• The nine introduced weed species (weeds) recorded during the 2023 vegetation survey of South Islet were all present in July 2024. The dominant weeds were Cenchrus echinatus (Mossman river grass) and Euphorbia cyathophora (dwarf poinsettia). The extent and density of C. echinatus in July 2024 was similar to the status in June 2023. Extent of E. cyathophora was similar to 2023 but the density was significantly less. Three weed species, previously recorded only in the Operational Area were found to have spread to natural areas outside the Operational Area in 2024.
• Parks Australia and the Bureau of Meterology staff undertook a scoping assessment to better understand the extent and distrbtuion of weeds on South Islet. Requirements of, and issues associated with development of an ecological restoration project that includes weed management were documented.
• Most of the E. cyathophora on South Islet and all weeds on the two access tracks were removed by hand pulling. Targeted weeds in the mown area were spot sprayed with glyphosate. Methodologies were established for weed management in selected manageable areas over the next 12 months by the on-island Bureau staff including photo monitoring and monthly reporting.
• Two new permanent BioCondition monitoring sites were established and surveyed during the 2024 voyage. There are now 29 Permanent BioCondition monitoring sites established on 15 islands across the CSMP.
• Sixteen plant specimens were collected for incorporation into Queensland Herbarium in Brisbane, the Australian National Herbarium in Canberra, and the Australian Tropical Herbarium in Cairns including specimens of five species that have not previously been collected on the island on which they were collected. Two of these are the first records for the island for these species. The other eleven species were from South West Herald Cay to complement collections made during the 2019 voyage.
• A total of 26 bird species were recorded during this voyage 15 seabird species (of which 13 were breeding), 5 migratory shorebird species and 6 land and wetland species, including the resident Coral Sea subspecies of the buff-banded rail (Gallirallus philippensis tounelieri). A new breeding site for New Caledonian fairy tern was discovered at North West Islet (Magdelaine Cays).
• New Caledonian fairy terns were observed nesting on Georgina Cay (Lihou Reef), two Herald petrels were observed prospecting for nest sites at Central Diamond Islet (Tregrosse Reefs), and more than 600 breeding pairs of red-tailed tropicbirds were counted on the Herald Cays.
• A total of 3,130 individual marine debris items (approximately 5.5 cubic metres weighing almost 1.3 tonnes) were removed from 11 islands. These items were weighed, identified and databased using Tangaroa Blue Foundation methodology.
• This voyage is the first time avian influenza surveillance was undertaken on these voyages.The detection of the H9N2 LPAI was quite distinct from other H9 influenza viruses detected in Australia in the recent past.