A silent death, which began in 2013 along the Pacific coast, from Mexico to Alaska. In a few years, billions of starfish have disappeared, literally “dissolved” within a few days. Now, after more than a decade of research, an international scientist team has finally identified the cause of the “Wasting Disease”: it is a bacterium strain called FHCF-3, belonging to the family of Pectenicide vibrio.
The study, published in the magazine Nature Ecology & Evolutionbears the signature of researchers from the University of British Columbia (UBC), the Hakai Institute and the University of Washington.
The bacterium responsible for the epidemic is not new in the marine world: the bacteria of the genre Vibrium They are already known to hit corals, molluscs and, in some forms, also the human being. The element that complicated everything, according to researchers, is the water temperature: these microorganisms reproduce much more easily in hot environments.
Dr. Melanie Preetice, the first author of the study and researcher at the UBC and the Hakai Institute, explained:
We observe that the disease manifests itself before and more aggressively when the waters are warmer. Stars are already undergoing the stress of climate change. If we add a bacterium to this that develops in the same conditions, for some species it can be a fatal blow.
The course of the disease is rapid and dramatic: it begins with lesions on the skin, and then progress until the tissues of the animals literally dissolves. Within about two weeks, the stars affected lose their arms, deform and die.
Identifying the disease was not easy, because the symptoms overlap with those caused by other factors, such as temperature changes or pollution. For this reason it took four years of targeted investigations and comparisons between healthy and infected individuals.
The FHCF-3 strain kills in a few days
The definitive test came thanks to targeted tests on sunflower starfish (Pycnopody Helianthoides), a species that has already lost over 90% of the population. Scientists exposed healthy specimens to three sources of contagion: contaminated water, infected fabric and celomatic fluid (a sort of “blood” of starfish). In all cases, the infection has been transmitted, with a mortality greater than 90% within a few days.
But the turning point came to the laboratory. Dr. Amy M. Chan, co-author of the study, managed to isolate the FHCF-3 strain from the fluids of the sick specimens.
When I cultivated the samples, I saw a single type of bacterium grow. I thought: it must be him.
And so it was. Injected in healthy starfish, the FHCF-3 strain caused the death of all infected specimens. Dr. Alyssa Gehman, a marine biologist of the Hakai Institute, explained:
In the comparison between healthy and sick individuals, there was only one difference: the presence of Vibrium. At that moment we understood: it was him. We had finally found the head of the Wasting Disease.
Marine ecosystems in crisis: the disappearance of starfish has detonated the sea urchins, which are destroying Kelp’s forests
The consequences of this epidemic do not stop at the disappearance of a species. Sunflower starfish are in fact natural predators of sea curls. Without their control, the curls are multiplying in an uncontrolled way and are literally devouring the forests of Kelp, giant algae that form fundamental habitats for thousands of marine species.
These forests are not just a refuge for biodiversity. They absorb carbon dioxide, protect the coasts from erosion, support local fishing and have a profound cultural value for the indigenous communities of the peaceful coast.
In a nutshell, the loss of starfish has triggered an ecological domino effect whose damage are becoming increasingly evident.
Now we work on reconstruction
Identified the bacterium, concrete roads finally open to save the starfish and restore the balance of coastal ecosystems. According to Jono Wilson, scientific director of The Nature Conservancy in California, the goal is now:
This discovery allows many other researchers to join efforts to find solutions. We want to understand what the best places and methods are to bring marine star to their natural habitats.
It will not be a simple path, but it is a first, important step towards the reconstruction of a balance that was believed to be lost.
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