There has already been much reporting on the gruesome epidemic spreading like wildfire through several species of sea star in the NE Pacific Ocean.
“Sea star wasting syndrome” is incredibly virulent and is causing the mass mortality of some sea star species in British Columbia and beyond. “Sea stars go from “appearing normal” to becoming a pile of white bacteria and scattered skeletal bits is only a matter of a couple of weeks, possibly less than that” (Source #1).
What I have strived to do below is bundle the state of knowledge so far, relying heavily on the expertise of two extraordinary divers and marine naturalists: (1) Neil McDaniel, marine zoologist and underwater photographer / videographer who maintains a website on local sea stars and has put together A Field Guide to Sea Stars of the Pacific Northwest, and (2) Andy Lamb, whose books include Marine Life of the Pacific Northwest.
I am hoping that kayakers, beach-walkers and fellow divers will help monitor and report on the spread of the disease via this link on the Vancouver Aquarium webpage but I am also hoping that all of us may learn from this tragedy that has impacted “one of the most iconic animals on the coast of British Columbia . . . more abundant and diverse in our waters than anywhere else in the world” (Source #3).
Sea star wasting syndrome reminds us of the fragility of ocean ecosystems; how very quickly disease can spread in the ocean; and how we are all empowered to reduce stressors that increase the likelihood of pathogens (viruses and bacteria) manifesting as disease e.g. increased temperatures, highlighting the importance of reducing our carbon footprints.
I will provide updates as the state of knowledge expands.
Species impacted? (Update November 30th - Source #14)
High mortalities (note that the first 4 are members of the same family – the Asteriidae):
- Sunflower star (Pycnopodia helianthoides) hardest hit in British Columbia. From communication with Neil McDaniel ” . . .so far I estimate it has killed tens, possibly hundreds of thousands of Pycnopodia in British Columbia waters.”
- Mottled star (Evasterias troschelii)
- Giant pink star (Pisaster brevispinus)
- Ochre star aka purple star (Pisaster ochraceus) reported to be the primary species affected in California
- Morning sun star (Solaster dawsoni)
More limited mortalities:
- Vermillion star (Mediaster aequalis)
- Rainbow star (Orthasterias koehleri)
- Leather star (Dermasterias imbricata)
- Striped sun star (Solaster stimpsoni)
- Six-rayed stars (Leptasterias sp.)
Update November 20th: The Vancouver Aquarium reports on which sea stars are and are not affected: “The majority of those species affected by the sunflower star epidemic are members of the same sea star family” and that the closely related morning sun star and giant pink star appear to get infected after feeding these “meals”. (Source #10, includes video).
Symptoms and progression of the syndrome:
Neil McDaniel shared the following 7 images for the progression of the disease in sunflower stars [Source #2 and #14]. See the end of this blog item for images showing symptoms in other sea star species as well as a 1 minute time-lapse clip showing the progression of the syndrome in a sunflower star over 7 hours.
1. In this image most of the sunflower stars appear healthy “other than one just right of center frame is exhibiting the syndrome, looking “thinned-out” and emaciated.”
2. This images “shows this thinning in close-up. Note how distinct the edges of the rays look and how flat the star is.”
3. This image “shows how the body wall begins to rupture, allowing the gonads and pyloric caeca to spill out.”
As the animals become more stressed, they often drop several rays (which wander off on their own for a while). At this point the body wall becomes compromised and the pyloric caeca and/or gonads may protrude through lesions. As things progress, the animals lose the ability to crawl and may even tumble down steep slopes and end up in pile at the bottom. Soon after they die and begin to rot
4. This image “shows the gonads breaking through holes in the body wall. At this point rays often break off and crawl away briefly.”
5. As things progress, the animals lose the ability to crawl [and hold grip surfaces] and may even tumble down steep slopes and end up in pile at the bottom. Soon after they die and begin to rot.
6. The bacteria Beggiatoa then takes over and consumes all of the organic matter, leaving a scattering of skeletal plates on the bottom. The syndrome develops quickly and in only one to two weeks animals can go from appearing healthy to a white mat of bacteria and skeletal plates
7. This image “shows an individual star that is being consumed by mat bacteria.”
The pathogen(s) have not yet been identified. But, as with any pathogen (like the flu virus), the expression of the pathogen as disease is influenced by number and proximity of individuals and stressors such as increased temperature.
- ”In previous outbreaks the “proximal cause” was found to a vibrio bacterium but “a recent wasting event on the east coast of the United States has been attributed to a virus . . . such events are often associated with warmer than typical water temperatures . . . Please note that we do not know what is causing Sea Star Wasting Syndrome, and the cause may be different in different regions . . . the period prior to Wasting was characterized by warm water temperatures” (University of California, Source #4).
- Update November 30th: Bates et al reported on an outbreak of wasting syndrome in ochre stars in Barkley sound in 2008. This included conducting lab experiments finding that the “prevalence and infection intensity were always higher in warm temperature treatments” and that “small increases in temperature could drive mass mortalities of Pisaster [ochre stars] due to wasting disease.” [Source #13 and #14].
- “Overpopulation” of sunflower stars appears to be a factor with outbreaks occurring where there is a high abundance of sea stars. “Often when you have a population explosion of any species you end up with a disease outbreak” (Source #5).
- “Some initial samples sent to DFO [Department of Fisheries and Oceans] and UBC [University of British Columbia] have not isolated a specific causative agent for this sea star die off. More samples are being collected and additional tests will be conducted” (Source #2 and #7). Viruses are notoriously difficult to detect. Cornell University (New York) has begun viral and bacterial culturing (Source #8). Updates will be provided here as they become available. See Source #14 for the results of pathology reports from October 4, November 12 and November 13.
- Update November 25th: Quote from Drew Harvell, a Cornell University professor of ecology and evolutionary biology who studies marine diseases: “these kinds of events are sentinels of change. When you get an event like this, I think everybody will say it’s an extreme event and it’s pretty important to figure out what’s going on . . . Not knowing is scary . . . If a similar thing were happening to humans, the Centers for Disease Control and Prevention would commit an army of doctors and scientists to unraveling the mystery.” (Source #12)
- On social media, many have speculated that radiation from Fukushima is a contributing factor. There is no data to date to support this and, while of course radiation benefits nothing, I worry that pointing the finger away from ourselves takes away from the opportunity to recognize and act on how we all contribute to ocean conditions such as increasing temperature.
Range and timeline?
- Late August 2013 – first reported from Howe Sound (Whytecliff and Kelvin Grove) by recreational diver Jonathan Martin (his photos here; video here). Howe Sound appears to have been grown zero (Source #14).
- Mass mortality noted in Indian Arm in early October. “By late October the syndrome had been reported from the Gulf Islands, around Nanaimo and into Puget Sound and the San Juan Islands. It appears to be spreading throughout the entire Strait of Georgia and Puget Sound.” [Source #14].
- First detected in Washington State as of late October (Source #11). See a video here of a site in West Seattle before and after the outbreak.
- No outbreaks from Campbell River north through Johnstone Strait. [Source #14]. I have seen no sea stars with wasting syndrome to date anywhere around NE Vancouver Island.
- No outbreaks on the west coast of Vancouver Island [Source #14].
- The University of California reports documenting the syndrome in ochre stars in some locations from Alaska from California - see map (Source 4).
- “A smaller and isolated Atlantic outbreak, at points off Rhode Island and Maine, has also been noted.” (Source #12).
- With regard to finding sunflower stars with the syndrome in Sechelt Inlet “This sighting is both disturbing and perplexing for a couple of reasons. First, Sechelt Inlet is hydrographically quite isolated from the rest of the Strait of Georgia, being a nearly land-locked fjord with minimal water exchange through Sechelt Rapids. Secondly [in Sechelt Inlet] Pycnopodia is a common sea star, but by no means abundant and certainly not found in anything near the incredible densities (up to 11/square metre) that we have encountered at the Defence Islands in Howe Sound” (Source #1). Jeff Marliave (VP of Marine Sciences at the Vancouver Aquarium) relates that the epicentre of the outbreak in Sechelt Inlet appears to be Egmont and that this correlates with a high abundance of sunflower stars there (Source #8).
- You can aid understanding of the range and spread by inputting your data at this link on the Vancouver Aquarium webpage.
Has this happened before?
Never to this large a scale.
- “Southern California in 1983-1984 and again (on a lesser scale) in 1997-98″ (Source #4 and #13)
- Florida (Source #5).
- Update November 30: Sunflower die offs [on much smaller scale] have been noted in the past in Barkley Sound. In 2008 ochre star die offs were documented in Barkley Sound. In 2009 Bates et. al. reported on this and observed that the prevalence of disease “was highly temperature sensitive and that populations in sheltered bays appeared to sustain chronic, low levels of infection.” (Source #14 and #15).
- “Similar events have occurred elsewhere over the last 30 years. Sea stars have perished in alarming numbers in Mexico, California and other localities” (Source #2).
- “In July, researchers at the University of Rhode Island reported that sea stars were dying in a similar way from New Jersey to Maine . . a graduate student collected starfish for a research project and then watched as they “appeared to melt” in her tank” (Source #5).
The impacted sea star species are carnivores, feeding high up in the food chain. This massive die off may lead to shifts / changes in marine ecosystems since there will be less predation by the affected sea star species (Source #9 and #12). Their prey includes: bivalves like mussels, marine snails, urchins and sea cucumbers.
- “Once that disease is in the environment, it can be difficult to get the population [of the affected sea stars] back” (Source #5).
- Update November 25th: ”Scientists disagree slightly on the potential ecological impacts of the current die-off. Sea stars control mussel populations by relentlessly eating them. In their absence, mussels may proliferate and ruin portions of undersea kelp forests that hide small fish from predators and help protect coastal areas from sea surge and storm flooding” (Source #12).
- Email communication with Neil McDaniel.
- Email communication with Andy Lamb.
- Shellfish Health Report from the Pacific Biological Station (DFO) conducted on 1 morning sun star and 7 sunflower stars collected on October 9, 2013 at Croker Island, Indian Arm; case number 8361.
- Email communication with Jeff Marliave.
- Sea star wasting syndrome, Nov 30-13; http://jackiehildering.files.wordpress.com/2013/11/sea-star-wasting-syndrome-nov-30-13.pdf
- Bates AE, Hilton BJ, Harley, CDG 2009. Effects of temperature, season and locality on wasting disease in the keystone predatory sea star Pisaster ochraceus. Diseases of Aquatic Organisms Vol. 86:245-251 http://www.ncbi.nlm.nih.gov/pubmed/20066959
- Video showing impacts in Elliott Bay, Seattle http://earthfix.info/flora-and-fauna/article/sea-stars-dying-off-west-seattle/
Images showing symptoms in other sea star species: