29 April, 2024, Sydney: In an Australian first, a recent scientific diving expedition reached new depths of 152 metres while researching mesophotic coral ecosystems (MCE) in the Coral Sea and Great Barrier Reef, Australia. The expedition was led by Australian Museum Curator of Fishes, Dr Yi-Kai Tea, and California Academy of Sciences, USA, Curator of Fishes, Dr Luiz Rocha.
Significantly different from shallow water coral reefs, MCEs are home to unique fauna found nowhere else in the world. The international dive team logged a total of seven dives across nine days in the Coral Sea, during March with the deepest dive record logged at 152 metres in Flora Reef, Coral Sea.
Dr Tea said MCEs remain a critically understudied component of coral reefs, particularly in Australia.
"This is the first mesophotic deep diving expedition below 100 metres conducted in Australia. The reefs of the Coral Sea are some of the most breathtaking I've seen, with low nutrient 'gin-clear' water. In some of our sites, you could see up to 40 meters below, straight from the surface. We were able to document a plethora of species, including many that are new for the Coral Sea, and several that are potentially new to science. Work is already underway to name some of these new species," Dr Tea said.
"You cannot save a species from extinction if we do not know it exists or fully understand its taxonomic relationship to other species. Mesophotic coral ecosystems hold remarkable amounts of unique biodiversity with many new species in critical need of scrutiny and research."
The diving expedition conducted aboard the research vessel, Norkat II, was co-led by Dr Rocha, California Academy of Sciences who said the team used cutting-edge techniques to explore, collect and preserve the specimens, setting new standards for underwater research.
"Tissue samples for all specimens were flash frozen in liquid nitrogen direct from the field and will be used for high-quality genome sequencing," Dr Rocha said. During the dive, Dr Rocha noted the warm temperature of the water and the widespread extent of coral bleaching throughout the Coral Sea.
"The water was the warmest I've ever experienced – even at depth, temperatures were 21-22 deg C. Sadly, these very warm waters are causing corals of all sizes and across a wide depth range to bleach in the Coral Sea, meaning there will be very few adult corals reproducing next year," Dr Rocha said.
Australian Museum Chief Scientist and Director of the Australian Museum Research Institute, (AMRI) Professor Kris Helgen said the work by Dr Yi-Kai Tea and Dr Luiz Rocha will enhance understanding of deep coral reef environments and further research.
"We know that mesophotic reefs serve as important habitat for fish to spawn, breed and feed, yet up until now, research has been sporadic and scarce. Like our rainforests which are rich in life on land, so are coral reefs in the ocean. They are not only complex environments but also very productive landscapes which underpin our cultural, social and economic way of life. There is a symbiosis between the reefs and us, and we need to work harder to save them," Professor Helgen said.
"The AM thanks the Minderoo Foundation and the California Academy of Sciences for supporting international cooperation and pioneering research into one of the most important ecosystems in Australia. Only through research are we able to look after our ecosystems and inform and adapt to more sustainable ways of life," he said.
This highly-collaborative, international team was generously supported by the Minderoo Foundation (Western Australia) and Under the Pole – part of the Rolex Perpetual Planet Initiative.
Minderoo Foundation, research manager, OceanOmics, Dr Shannon Corrigan said collaborating with collections scientists from the Australian Museum and California Academy of Sciences presented an incredible opportunity to enhance our collective understanding of the unique diversity of mesophotic fauna and the natural ecosystems in which they live.
"Documenting species and genomic diversity provide vital resources for tracking ecosystem change and informing conservation efforts in the face of challenges like climate change," Dr Corrigan said.
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