By Roberta Attanasio
Up and down the U.S. and Canada Pacific coastlines, starfish are disappearing, dying by the millions of a mysterious disease that makes them “turn into goo.”
The disease — starfish wasting syndrome — initially causes white lesions that lead to death of body tissue. Eventually, the arms twist and tear off — and they do not regenerate (healthy starfish may shed their arms, but then new ones are formed in a relatively short time). At the end, the entire body of the wasting starfish disintegrates. The wasting syndrome affects about a dozen starfish species, but has been noticed mostly in sunflower starfish (Pycnopodia helianthoides) and ochre stars (Pisaster ochraceus).
Starfish die-offs have been observed along the California coast in 1983 and 1997 — however, this year, the die-off is occurring at an unprecedented rate. No cause has been identified, but speculations abound.
Claims that Fukushima radiation could be implicated in the die-off have been disproved by Chris Mah (a researcher at the Smithsonian National Museum of Natural History and one of the world’s leading experts on starfish), on the basis of three major considerations — the syndrome pre-dates Fukushima by 3 to 15 years, it occurs on both East and West coasts, and it does not seem to affect any other marine life in these regions.
Gary Wessel, a professor at Brown University, told NBC News that a combination of stressors, both pathogenic (a new bacterium or virus) and environmental (a change in ocean temperature) may be responsible for the syndrome. He also thinks that the disease is unlikely to affect humans or other larger marine life.
An accepted explanation is that an infectious microbe (a virus, bacterium, fungus or other) could impair the starfish immune system, making them susceptible to secondary bacterial infections that ultimately cause wasting.
Back in November, Pete Raimondi, a professor at the University of California, Santa Cruz, told the Los Angeles Times “Imagine a wound on your finger that you never treated. The bacteria would continue to build up and just eat away the flesh until it fell off. That’s how this disease goes.”
Global warming is an important factor in the occurrence of disease outbreaks of infectious microbes that affect marine life. Increasing temperatures favor the growth of these microbes and allow their spread across an extended geographical range. In addition, increasing temperatures induce heat stress, which adversely affects the defense/immune mechanisms. Indeed, the spread and progression of the wasting syndrome — in starfish and other species — are temperature-sensitive and increase at warmer temperatures.
The starfish is a voracious predator and a keystone species — a species that plays a critical role in maintaining the structure of an ecological community. Starfish eat snails, sea urchins, mussels and clams, and are essential to maintain kelp forests, one of the most productive ecosystems on our planet. Southern sea otters, also a keystone species in the kelp forest ecosystem, have been decimated by an ongoing epidemic of toxoplasmosis. Thus, the loss of starfish could have far-reaching consequences for the marine communities of North America.