Taking a stand at sea
SEA cucumbers sit limp on the bottom of the ocean most of their lives, but when it’s time for mating, these marine creatures really stand to attention.
A marine scientist has captured remarkable photographs of mass spawning of snakefish sea cucumbers (Holothuria coluber) at Lizard Island, on the Great Barrier Reef.
James Cook University researcher Victor Huertas, from the ARC Centre of Excellence for Coral Reef Studies, encountered the display while conducting field work in the shallows of Blue Lagoon at the island in mid-December last year.
A scientific paper detailing the observation was recently published in the SPC Bechede-mer Information Bulletin.
Mr Huertas said while spawning behaviour of some sea cucumber species was well-studied and highly predictable, the phenomenon was less known in snakefish sea cucumbers – so called for their serpentine body shapes.
Several individuals were observed lifting the ends of their bodies above the reef’s substrate, high in the water column.
They then appeared to actively adjust their orientation to remain erect.
“It is quite a sensational display,” Mr Huertas said.
“When they reproduce, sea cucumbers typically raise their front end and keep adjusting their position to remain straight up, despite the current.
“Imagine seeing a group of cobras rising in synchrony, swaying back and forth.
“Then, they release their eggs and sperm into the water, where the eggs will be fertilised and disseminated.”
Lizard Island has been one of the worst affected parts of Great Barrier Reef’s two consecutive mass bleaching events during the past three years.
Mr Huertas said the island’s fringing reefs appeared to still be in dire condition.
“The loss of live corals is very harmful to coral reefs because they provide the structural foundation that supports the high diversity of marine life that we see in coral reefs,” he said.
“This includes reef fishes, shellfish and lobsters.
“However, the good news is that if we reduce carbon emissions, we can make a positive impact to prevent future coral bleaching and ensure healthy and diverse coral reefs on our Great Barrier Reef.”