A sick ochre star surrounded by apparently healthy ones from Olympic National Park. Photo: Steve Fradkin
By Drew Harvell and Laura James
In World War Z, a super- transmissible virus that turns humans into twisted, rabid zombies spreads freakishly fast across the globe.
In terms of real human diseases, the Spanish Flu of 1918 was the most devastating in a global spread, killing 10% of the world’s population.
Sea stars along both coasts of the US have been struck by a massive, extremely virulent mass mortality.
It is currently sweeping along the west coast and affecting both our most abundant species like the sunflower star and ochre star and a series of 10 other species as reported in Seastarwasting.org by the monitoring group MARINEe (based at UC Santa Cruz).
Although our sick stars are not rabid and biting each other, the syndrome is called sea star wasting because they become deflated, lose skeletal ossicles and develop lesions in the body wall.
Then their arms become twisted and drop off. Like the zombie virus, when it hits some areas, the sea stars drop dead very quickly, (as we’ll describe from Alki Beach, Seattle).
In the movie version of the human zombie virus, a person was bitten and showed “zombie symptoms” 10 seconds later. The disease transmission picture is not so clear for sea stars.
In the sea star event we still lack clear evidence for a route of transmission, even though it seems so likely to have an infectious cause.
Scientists think this is caused by an infectious agent because:
1) new cases appear at different times and locations along the coast, starting last June in Olympic National Park.
2) In the Seattle Aquarium, stars in UV filtered water, which would kill viruses or bacteria, survived and others died.
3) At some locations, the spread to new unaffected stars takes a few days and appears to move as a wave.
4) Molecular typing shows bacteria and viruses in the sick animals that are not present in healthy.
Work is underway at Cornell to confirm and test the sequence of bacteria and viruses present in the sick that are not present in most healthy stars.
Scientists are also perplexed by the timing of the sea star event this fall. It did not correspond with unusually warm or unusually cold conditions, or cold upwelling or low oxygen conditions.
In some places like the Northwest, there were big mortality events near urban places like Vancouver and Seattle. But more pristine locations like on the outer coast of Vancouver Island, in Olympic National Park and in central California also experienced big mortality events.
There are hints at some sites that low salinity might be associated with sickness. This makes sense because sea stars are unusual in having no kidneys and have no ability to regulate their inner salinity levels.
We speculate freshwater inputs could either facilitate disease through stress or even convey infectious agents in freshwater run-off.
A Horrifying Personal Look at Sea Star Collapse
This is by far the largest Pacific coast-wide sea star disease event that scientists have recorded. We’d like to recount the story from a single site: Alki Beach, Seattle.
Laura James tells me one of the best dives around Puget Sound is right across from downtown Seattle. It’s a place filled with cool stuff like giant pacific octopus, small red east pacific octopus, seals and, once upon a time, 8 species of sea star.
When she dove there last summer, Cove 1 was a teeming star-filled galaxy: sunflower stars of all sizes scavenging, morning sun stars chasing the occasional rose star, mottled stars, brittle stars, vermillion stars, blood stars, striped sun stars. And more.
On November 12, Laura dove there and witnessed a scene from a horror film and you can see this on her accompanying video.
Sea stars of three species are sick, hanging from a few tube feet attached to pilings or fallen dead underneath. Some stars so far gone that only an arm or two was left hanging.
Underneath, the pilings were surrounded by hundreds of decomposing stars. On the December 14 evening low tide, just after leaving the Conservancy’s All Science meeting, I joined Laura and we were surprised to find 130 live ochre stars hidden away high in the intertidal above the continuing devastation in the subtidal.
About half of these had signs of illness such as contorted arms, lesions all the way through their body, and slack non-gripping tube feet. These tube feet were once powerful enough to open a mussel by brute force.
This week, Laura dove once again in Cove 1 to collect stars for our experiments to decipher the causative microorganism. On this night, there was only a single star here and there.
Pilings that held hundreds of stars before the outbreak were now almost completely barren, adding up to a body count of several thousand at just this one site. The remaining few were in various states of disease.
It was a terribly poignant last film that Laura shot of this site, joined in silent witness by a curious seal, along to help.
I am at once extremely interested and driven to unravel the mystery of this die-off, because it is iconic of the knowledge gap we have about how disease propagates in the ocean.
At the same time, I am personally devastated by the loss of so many sea stars, from so many different species.
I am hoping that the locations of the mortality events are patchy enough, with healthy stars left in places, that we do not yet have to fear extinction.
But these are top keystone, ecologically important species and their loss will have an impact. And I still feel like my own highly treasured biodiversity of our most iconic invertebrate species is being robbed, and each continuing mortality event in this continuing epidemic worries me.
If this were a real zombie virus affecting humans, we would have massive resources at our disposal to figure out the pressing questions.
And yet many people act as if this huge epidemic affecting a keystone species in the ocean is simply a curiosity and a normal event in the oceans.
They assume scientists will figure it out. Scientists will not figure it out unless they have the funding and investment in infrastructure that is needed.
Our country is quite good at surveillance of disease in hospitals, the CDC is adept at identifying and typing new human disease and the USDA is good at monitoring terrestrial food safety. But who is providing enough funding to adequately monitor health and disease in the ocean?
This is just the latest in a series of new disease outbreaks in the ocean and we are terribly under-prepared. Just this year, we have had catastrophic losses of dolphins to disease and this major outbreak of sea star deaths on both coasts.
These outbreaks can be thought of as sentinels of changes we don’t understand in our oceans.
Opinions expressed on Cool Green Science and in any corresponding comments are the personal opinions of the original authors and do not necessarily reflect the views of The Nature Conservancy.