In changing oceans, starfish can ‘drown’

For more than seven years, a mysterious debilitating disease has almost killed populations of starfish across the world. Some of these species are on the verge of extinction.

Research from New Cornell University suggests that starfish, victims of starfish wasting disease (SSWD), may in fact be in respiratory distress – literally “drowned” in their own environment – because the activity High microbial derived from nearby organic matter and warm ocean temperatures rob creatures of their ability to breathe.

“As humans, we breathe, we ventilate, we bring air into our lungs and we exhale,” said Ian Hewson, professor of microbiology at Cornell University. “Starfish diffuse oxygen on their outer surface through small structures called papules, or skin gills. If there is not enough oxygen around the papules, starfish cannot breathe. . “

The research, “Evidence that microorganisms at the animal-water interface cause debilitating starfish disease”, was published in Frontiers in microbiology.

According to Hewson, ocean conditions lead to the production of unusual amounts of organic matter, which he says prompts bacteria to thrive. As bacteria consume organic matter, they deplete oxygen from the water, creating a low oxygen microenvironment that surrounds starfish and results in deflation, discoloration, puffiness and twists or waves of the limbs.

“It’s a cascade of problems that begins with changes in the environment,” Hewson said, explaining that most of the organic matter comes from microscopic algae exudation (a release), excretion and the digestion of zooplankton, and rotting animal carcasses. This stimulates a group of bacteria called copiotrophs, which survive on carbon and quickly consume organic matter, he said.

Copiotrophs breathe, he says, so while absorbing organic matter, they deplete oxygen in the starfish’s aquatic space.

“These are the concentrations of organic matter in the water,” he said. “If you have a dead, rotten sea star next to a sea star that is healthy, all that dead organic matter is drifting around and feeding the bacteria, creating a hypoxic environment. It looks like the disease is spread.”

Hewson said that while more scientific work needs to be done, “It reframes the discussion on the ecology of marine diseases, which has focused on pathogenic diseases,” he said. “We should now include microorganisms that do not directly cause the pathology, as they may hold a key to affecting the health of starfish.”