A group of NSW high school students were snorkelling as part of a marine science class when they spotted something that sparked their curiosity.
It was a large and striking starfish they hadn't seen before in Mid North Coast waters.
With the help of their science teacher Simon Patterson they took photos and reported the finding to the Australian Museum.
"A regular part of our course in Year 9 and Year 10 is we do a lot of snorkelling," Mr Patterson said.
"There were quite a few of them. They were very dominant in the area [and] we tried to identify them in class and couldn't."
Discovery of starfish moving south
The students from the Great Lakes College Tuncurry campus were taking part in a Marine and Aquaculture Technology class and made the discovery in late 2020.
Mr Patterson said the Australian Museum's marine invertebrate collection manager Stephen Keable examined the student's photos and then worked with them to do further research.
"Dr Keable asked our class for help in collecting and preserving specimens the next time we went snorkelling," he said.
Dr Keable later went on to identify the sea stars as Pentaceraster regulus during a visit to Wallis Lake with the students.
The species is typically found along the Queensland coast and also offshore near Lord Howe Island, and Ningaloo reef in Western Australia.
Prior to the students' discovery, the furthest south the species had been observed was at North Stradbroke Island, 800 kilometres north of Wallis Lake.
The museum had two examples collected from Wallis Lake in 2008, but it was thought they weren't then native to the area, but had been brought in by vessels entering the marina.
"The specimens found by the students and additional observations led us to conclude that the sea star, Pentaceraster regulus, normally occurring in tropical waters further north, has now established itself in Wallis Lake," Dr Keable said.
Work noted in scientific journal
The work of the students in logging the movement of the sea star southwards has now been recorded in the academic journal, AM's Technical Reports.
Dr Keable co-authored the paper appearing in the journal with Dr Christopher Mah from the Smithsonian Institute in Washington DC, an international authority on the biology and evolution of sea stars.
Mr Patterson said the discovery highlighted the importance of citizen science.
"To have our name acknowledged in that paper is excellent, it's really exciting," he said.
"It's students like ours who are regularly in these waters who are able to identify that 'hey, that's unusual'.
Year 11 student Baden Bell said it had been a great experience.
"I have always been in the water, surfing, snorkelling and to find this discovery was just incredible," he said.
"Growing up I have always wanted to be a marine biologist and this discovery has just furthered my passion."
Climate change concerns
Baden said the discovery did raise concerns about climate change.
"It's a big warning sign because we don't know if they are moving south because of the warming of the climate and they are moving to colder waters, or other reasons," he said.
Mr Patterson said it was also too soon to tell the impact the tropical sea star species would have.
Mr Patterson said he hoped the students' experience would help motivate their future work.
"We've already had the Australian Museum contact us and ask if any of our students would be willing to go down there for work experience," he said.
"If we can help them build connections that lead to a career, it's awesome. We do everything we can to get them outside and into the real world."
