Nearly a year after scientists began recording a massive die-off of sea stars in Northern California waters and farther up the coast, the unnamed malady that dissolves their limbs and bodies has spread to San Diego and all points in between.
The epidemic was first noticed in Vancouver, Canada, and Washington State last June and dumbfounded scientists who had seen similar, smaller outbreaks in much warmer waters, usually spurred by an approaching El Niño. There were also some sightings as far south as Orange County toward the end of the year, but whatever is killing the starfish is now firmly entrenched off the San Diego coast.
The starfish develop white lesions, which sometimes become ulcerous, before the disintegration begins. Limbs start falling off within days or weeks. “The sick ones tend to just fall apart in front of your eyes,” Vancouver Aquarium biologist Jeff Marliave said. “An arm will actually break off and crawl away. They turn into goo.”
Sea stars are considered a Keystone species because of the crucial role they play in the ecosystem. They contribute mightily to biological diversity by eating animals like mussels that tend to crowd out other aquatic creatures.
The rapidity with which the starfish decline can disguise the die-off because they are washed out to sea before casual observers notice. But scientists say millions have perished since April and have been sighted in Agua Hedionda Lagoon, La Jolla, Mission Bay and Point Loma.
Scientists don’t know if they are dealing with the same pathogen that has caused problems in past years, but this year seems far worse. Scientists at Cornell University told KTCS9 in Seattle that they are sequencing the DNA from diseased starfish but have not yet reached any conclusions.
Theories abound about the mechanism of death. The shellfish could be getting the disease from mussels and clams they eat, physical contact with other diseased starfish or from the water they swim in. The observed link to warmer waters is of particular concern to the 99.9% of scientists and 25% of Republicans who consider global warming a major threat.
Carol Blanchette, a research biologist at University of California, Santa Barbara, is monitoring 30 sites in Southern California and told KCTS9 that the disease progressed more rapidly at spots where waters were warmer than usual. Cornell marine epidemiologist Drew Harvell echoed that observation and warned of the consequences:
“A warmer world would be a sicker world. Under warming conditions a lot of microorganisms do better. They grow faster. They replicate faster. Many of our hosts can actually be stressed by warm conditions. And so it kind of creates a perfect storm of sickness.”