Nearly 1,700 sea dragons reported dead during SA's algal bloom - ABC News & Headlines – Australian Broadcasting Corporation

The leafy sea dragon is also the official marine emblem of South Australia.  (Supplied: Steve Jones)

Dragon Search SA analysed 1,540 citizen science reports.

It documented 1,524 dead weedy sea dragons and about 159 leafy sea dragons.

Researchers are looking into ways to boost the species' breeding rate.

Nearly 1,700 sea dragons are documented to have died during South Australia's harmful algal bloom (HAB), a new report has found, amid hopes of a strong breeding season next month.

The Dragon Search SA report, led by local marine ecologist Janine Baker, analysed 1,540 reports uploaded by 253 people to citizen science platform, iNaturalist, about sea dragons, pipefish and seahorses from January 1, 2025, to May 31, 2026.

About 1,524 weedy sea dragons were recorded dead in South Australia, while 159 leafy sea dragons were also reported dead.

"The weedy and the leafy in particular occur in South Australia as a world hotspot," said sea dragon researcher David Booth from the University of Technology Sydney.

The HAB first emerged in South Australian waters in early 2025.

Encounter Bay, St Vincent and Spencer gulfs, Investigator Strait and waters off Kangaroo Island were particularly affected by an extended outbreak that killed countless marine animals and affected human health.

Sea dragons are a part of the Syngnathidae family, which have small gill pores that can be easily clogged by microalgae, and cannot swim away rapidly from patches of water where the bloom is dense.

There were more than 700 observations of weedy sea dragons reported. (Supplied: Nerida Wilson)

Deaths caused by HAB spanned 13 species in the family, which also included pipefish and seahorses.

At least 787 seagrass-dwelling brushtail pipefish mortalities were recorded, along with 574 spotted pipefish and 42 long-snout pipefish, while thousands more dead pipefish were observed in metropolitan seagrass wash-ups but not counted.

More than 160 short-head seahorse were recorded, while the south-eastern Australian big-belly seahorse washed up in small numbers.

The report found that pipefish and seahorses mainly washed up over winter and spring in 2025, but dead sea dragons continued to be observed from summer 2025 to autumn 2026.

Professor Booth told 891 ABC Adelaide that sea dragons were entering their October breeding season in SA. 

He said researchers were also looking at ways to boost sea dragon numbers, including bringing pregnant males into the laboratory to hatch the eggs and rear their fry before releasing them.

"But that's only of use if we can fix the habitat. There's been so much habitat destruction — huge losses of sponges, kelp, seagrasses — all those sorts of things that these animals need, and their food in little shrimps.

"We really need to be working on that and we are. There's habitat restoration going on but it is a big job."

This includes shellfish reef restoration projects across multiple locations, and research to restore approximately 6,000 hectares of seagrass meadows — natural filters of microalgae — that have been lost from Adelaide's coastline since the 1950s.

The report stated that the HAB's impact on the full population of Syngnathidae remained unknown because there had not been an official systematic survey undertaken in the past or present.

Dragon Search SA said previous data came from divers, snorkellers, beachgoers, independent research surveys, museums, fishers and trawler bycatch, with much of it dating from the 1980s to 2000s.

"There is no doubt that leafy sea dragon numbers are lower than pre-bloom in those inshore habitats, but offshore numbers away from dived locations remain undocumented," Janine Baker said.

The old Rapid Bay jetty has been a drawcard for divers but an exclusion zone remains. (ABC South East SA: Caroline Horn)

Since spring 2025, citizen science divers in seven areas of SA had been documenting live sea dragon records in near-shore areas monitored by Dragon Search SA.

This included small aggregations of juvenile weedy sea dragons.

Professor Booth said there had been reports of sea dragons in Second Valley but at Rapid Bay, one of the state's renowned dive sites, the ongoing closure of the old jetty and its 20-metre exclusion zone for diving was hindering any surveying of the species.

He is a sea dragon specialist on the International Union for Conservation of Nature, which lists weedy sea dragons as "vulnerable" on its red list for species at a higher risk of extinction.

It also includes the leafy sea dragon, currently listed in the "least concern" category.

"Locally, of course, your wonderful citizens, scientists and government people are very, very worried about your state [marine] emblem the leafy, and the weedy as well, which we have in our lab in boxes and boxes of carcasses.