Green Urchins grazing on Split Kelp. ©2016 Jackie Hildering.
Last update: December 2017
Sea Star Wasting Disease summary:
- Has been raging since June 2013.
- Unprecedented in both range, duration and number of species impacted – 20 species of sea star species since 2013 from Alaska to Mexico (local variation in intensity of the disease and which species are impacted the worst). It is one of the largest wildlife die-off events in recorded history.
- A virus has been found in the sick sea stars but this virus has been around for at least 72 years (was isolated in preserved sea stars). A stressor (or stressors) must be reducing the resistance of the sea stars to the virus.Virus is “Sea Star associated Densovirus” (SSaDV) (Hewson, et al www.pnas.org/content/early/2014/11/12/1416625111.abstract ).
- A correlation was found between increased temperature and death in sea stars but that other factors are likely play a role as well (Eisenlord, et al www.ncbi.nlm.nih.gov/pmc/articles/PMC4760142).
- Another study found that the disease also progressed when temperatures have decreased. (Menge, et al https://doi.org/10.1371/journal.pone.0157302)
- Current situation: Varies by location and species of sea star. While there have been some “waves” of baby and juvenile sea stars, numbers of all species remain low and signs of wasting continue.
- From my own observations on NE Vancouver Island: Here, Sunflower Stars are impacted the worst (the largest sea star in the NE Pacific Ocean with 20+ legs). Leather Stars may be more impacted than in other areas. Ochre Stars appear less impacted than in other areas. I have seen waves of Sunflower Star babies and juveniles. What I find most plausible is that the babies are the result of adults spawning at depth, where it is colder (reduced stressor). A stressor or stressors then reduces the resistance of the babies and juveniles in shallower water whereby they may succumb to SSWD.
- It terms of ecosystem impacts, consider the important role of many sea stars as predators. I put forward that this can be likened to the death of many Sea Otters. With less sea stars there an be more of their prey like mussels and clams. But, with less sea stars, there are definitely more urchins which graze away more kelp. Thereby, there is less habitat for many species and a loss of biodiversity.
- Why share this information? It is often marine species that testify to environmental problems first; that serve as indicators for the resources upon which we too depend. The hypothesis is that the sea stars have succumbed to the pathogen in an unprecedented way because of changed ocean conditions (stressors). For me, this is an additional motivator to do what I can to reduce impacts through impacts of carbon and harmful chemicals.
- My album of photos of sea stars with symptoms can be found at this Facebook link.
Where to relay sea star data (of great value in understanding the range, extent and potentially, contributing factors):
Update December 2017: Recent rash of astoundingly erroneous news articles suggesting that sea stars are all one “species” and that they are rebounding e.g.Starfish making comeback after syndrome killed millions
Update May 2016: New paper – Menge BA, Cerny-Chipman EB, Johnson A, Sullivan J, Gravem S, et al. (2016) Correction: Sea Star Wasting Disease in the Keystone Predator Pisaster ochraceus in Oregon: Insights into Differential Population Impacts, Recovery, Predation Rate, and Temperature Effects from Long-Term Research. PLOS ONE 11(6): e0157302. https://doi.org/10.1371/journal.pone.0157302
Update February 2016: New paper – Eisenlord, et al : ” . . . reported that temperature plays a role in the prevalence of Sea Star Wasting Syndrome (SSWS). Analyses showed that risk of disease-associated death was correlated with sea star size as well as water temperature. In adults, time between emergence of disease symptoms and death was influenced by temperature. Experiments also showed that adult mortality was higher in the warmer water treatments. Although adults showed disease symptoms more quickly than juveniles, diseased juveniles perished more quickly. This study was conducted in Washington State, where high mortality rates were experienced during 2014 in many areas, which coincided with warm temperature anomalies. While this study explained some factors that lead to SSWS, their models indicate that other unknown factors are likely playing a role as well.” Source: SSWS updates University of California at Santa Cruz
Update October 2016: New paper – Montecino-Latorre D, Eisenlord ME, Turner M, Yoshioka R, Harvell CD, Pattengill-Semmens CV, et al. (2016) Devastating Transboundary Impacts of Sea Star Wasting Disease on Subtidal Asteroids. PLoS ONE 11(10): e0163190. doi:10.1371/journal.pone.0163190
Update April 2016: Concern about decrease in sea stars leading to more urchins and, thereby, less kelp. CBC News; April 25, 2016 Scientists study ecological fallout of sea star die-off – Marine scientists are studying kelp to see how starfish wasting disease is changing the ecosystem. Study upon which this article is based: (2016) Evidence for a trophic cascade on rocky reefs following sea star mass mortality in British Columbia. PeerJ 4:e1980; https://doi.org/10.7717/peerj.1980
Update February 2016: Cornell University study showing link between temperature and incidence of the Syndrome: Ochre star mortality during the 2014 wasting disease epizootic: role of population size structure and temperature, Reporting on the study includes this item on the front page of the Seattle times on February 21st: “Scientists now link massive starfish die-off, warming ocean.”
Update January 21, 2016: Province: “Sea star wasting disease among worst wildlife die-offs say scientists“. Includes: “”This is, if not the, certainly one of the biggest wildlife die-offs that have ever been recorded, and we’re not just talking marine die-offs.”
Update May 3 , 2015: Seattle Times; “Starfish babies offer glimmer of hope amid mass die-off”. Includes: ” . . . a few baby starfish offered a glimmer of hope for the creature’s recovery . . . .“the question is when these babies get big, will you expect them to die like the adults? . . . . Not all the sites have seen juveniles and it hasn’t been broad . . .One theory for why there are so many juveniles [at this site in Washington] is that when adult starfish were stressed from the wasting disease, they released millions of eggs and sperm, increasing the chances for fertilization. Ideal conditions in recent months have helped push those larvae to the shore, where they’re able to cling to hard surfaces such as rocks and pilings to grow . . . And the worst of the wasting disease might still be ahead in some places, including along Washington’s Olympic Coast, where it was first reported in June 2013.”
Update April 9, 2015: California – wasting symptoms being seen in urchins. http://news.nationalgeographic.com/2015/03/150401-urchins-sea-stars-monterey-bay-california-animals/
Update March 1, 2015: While symptoms of Sea Star Wasting Syndrome are still being seen in BC and I have seen no adult Sunflower Stars in the sites I have been monitoring on NE Vancouver Island, in several areas in BC, we are beginning to see juvenile Sunflower Stars. Sunflower Stars are the species that appeared to be most impacted in many areas of BC. Where are the young Sunflower Stars coming from? It may be, and this is my speculation, that there are Sunflower Stars at depth that survived the Syndrome possibly because they were not exposed to the same stressors e.g. the water at depth may be colder.
Update November 18, 2014: Study published today – cause of Sea Star Wasting Syndrome a densovirus that has been present for at least 72 years? Why has it led to mass mortality now? What makes sense is that, like any virus, the incidents of “pathogenicity” depends on stressors (e.g. temperature change) and proximity of individuals. The virus has also been found in other echinoderms like urchins and sand dollars and it persists in sediment = can be transmitted by those vectors and there is the potential that the other echinoderms are/will be affected. See the study by Cornell University at the link below (lead author Ian Hewson). Includes “If SSaDV is the cause of the current SSWD event, it is unclear why the virus did not elicit wide disease outbreaks in the past during periods in which it was detected; however, there are several possible reasons why the current SSWD event is broader and more intense than previous occurrences. SSaDV may have been present at lower prevalence for decades and only became an epidemic recently due to unmeasured environmental factors not present in previous years that affect animal susceptibility or enhance transmission.”
Update December 2014: Seeing juvenile Sunflower Stars around Northern Vancouver Island. The hope is that there might be a deep, cold water reservoir of animals. I suggest that this offers further support that increased temperature may be the stressor that has increased the pathogenicity of the virus.
Good coverage in a 7-minute radio interview
Science Friday; December 5, 2014: “What’s Killing West Coast Starfish?” http://www.sciencefriday.com/segment/12/05/2014/what-s-killing-west-coast-starfish.html#path/segment/12/05/2014/what-s-killing-west-coast-starfish.html ]
Original blog November 10, 2013:
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 could spread in the ocean; and how we are all empowered to reduce stressors that increase the likelihood of pathogens manifesting as disease or even that pathogens enter the environment (e.g. sewage).
Update January 18, 2014 – Video by Neil McDaniel showing the extent of the mortality in some parts of southern British Columbia. Click here.
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 southern 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)
- Morning sun star (Solaster dawsoni)
More limited mortalities:
- Vermillion star (Mediaster aequalis); video of an afflicted star here.
- Rainbow star (Orthasterias koehleri)
- Leather star (Dermasterias imbricata)
- Striped sun star (Solaster stimpsoni)
- Six-rayed stars (Leptasterias sp.)
Update January 21st, 2014: Possibly: Rose star (Crossaster papposus) – I have noted symptoms in this species on NE Vancouver Island as has Neil McDaniel in S. British Columbia).
Update November 20th: The Vancouver Aquarium reports on which sea stars are and are not affected in S. British Columbia: “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. [Note that the progression of the Syndrome on NE Vancouver Island appears that it may be different from what has been observed further to the south.]
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 1-minute time-lapse video below shows the progression of the Syndrome in a sunflower star over 7 hours.
To date (January 2014), the cause (s) have not yet been identified. Scientific opinion appears to be that most likely the cause is one or more viruses or bacteria that have not yet been identified (more advanced investigations like DNA sequencing and metagenomics are now underway at Cornell University – Source #18 and #19) but toxins and environmental factors have not been ruled out as the primary cause or confounding causes (Source #18). As with any pathogen (like the flu virus), the expression of a pathogen as disease is influenced by number and proximity of individuals and could be exacerbated by environmental stressors. It is NOT radiation [Source #18, #19 and others].
Using cutting-edge DNA sequencing and metagenomics, Hewson is analyzing the samples for viruses as well as bacteria and other protozoa in order to pinpoint the infectious agent among countless possibilities.
“It’s like the matrix,” Hewson said. “We have to be very careful that we’re not identifying something that’s associated with the disease but not the cause.”
- ”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 Santa Cruz, Source #4).
- 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]
- “Do not believe this is related to a warming trend” (Source #18).
- “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). “This could be perfectly normal as a way to control overpopulation” (Source #18).
- “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.
- 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)
- 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 stressors such as increasing temperature. From Source #19 – “scientists see Fukushima as an unlikely culprit because the die-offs are patchy, popping up in certain places like Seattle and Santa Barbara and not in others, such as coastal Oregon, where wasting has only been reported at one location.”
- Ballast water? “From Source #19- “Others have wondered if a pathogen from the other side of the world may have hitched a ride in the ballast water of ocean-going ships. Scientists say this fits with the fact that many of the hot spots have appeared along major shipping routes. However, the starfish in quiet Monterey Bay, Calif. have been hit hard, whereas San Francisco’s starfish are holding strong.”
Range and timeline?
- [Update December 21, 2013 – The Syndrome has been documented in sites from Alaska to the Mexican border – with gaps in knowledge especially off central and northern BC. See data acquired through the University of California, Santa Cruz on this map (Source #4) and the data acquired through the Vancouver Aquarium on this map (Source #3).]
- June 2013 – First noted in the intertidal zone in ochre stars along the Washington Coast. “As of December, signs of wasting had been observed at 45 of 84 MARINe sites [USA – Multi-Agency Rocky Intertidal Network] sampled since summer 2013, spanning the entire coast from Alaska to San Diego but varying in intensity from low levels of infection to mass mortality” [and with large gaps in data especially in northern British Columbia]. (Source #17). See map (Source #4) documenting the Syndrome in ochre stars in some locations from Alaska to the Mexican Border.
- Late August 2013 – first reported in the sub-tidal in Howe Sound (Whytecliff and Kelvin Grove) by recreational diver Jonathan Martin (his photos here; video here). Sunflower stars were the main species impacted.
- 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 the sub-tidal in sunflower stars in Washington State as of late October (Source #11 and #17). See a video here of a site in West Seattle before and after the outbreak. Update December 22nd: First reported off Whidbey Island, Washington.
- Update December 21st: I am very sad to report that I have now found afflicted animals on NE Vancouver Island (Bear Cove, Port Hardy). Please see my blog at this link for photos, details and updates on the progression of the Syndrome on NE Vancouver Island].
- Update January 19th, 2014: Morning sunstar with symptoms found in Campbell River [Reported by Dylan Smith].
- No outbreaks on the west coast of Vancouver Island [Source #14].
- “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).
- Baby sea stars now seem to be coming back to areas where adult sunflower stars have been wiped out (Source #18).
- 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. “Although similar sea star wasting events have occurred previously, a mortality event of this magnitude, with such broad geographic reach has never before been documented.” (Source #17).
- “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).
- Ecologists consider sunflower and ochre stars to be keystone speices because they have a disproportionately large influence on the distribution and abundance of many other species. Scientists anticipate that such a large mortality event in keystone species could change the intertidal and sub tidal seascapes . . . Previous examples of large-scale, mass mortality of individual marine species have resulted in dramatic ecosystem-wide changes” (Source #17).
- “Sea stars are voracious predators, like lions on the seafloor. They gobble up mussels, clams, sea cucumbers, crab and even other starfish. That’s why they’re called a keystone species, meaning they have a disproportionate impact on an ecosystem, shaping the biodiversity of the seascape. “These are ecologically important species,” . . . “To remove them changes the entire dynamics of the marine ecosystem. When you lose this many sea stars it will certainly change the seascape underneath our waters.” (Source #19)
- Seeing baby sunflower stars back where adults have been wiped out in Howe Sound. Getting species like agarum kelp back (good habitat that was suppressed due to previous abundance of sea stars) but also seeing green urchins come back (will graze on kelp like sea stars do). (Source #18).
Video (7 min) on the state of knowledge on the Syndrome (January 2014) and showing the progression of the Syndrome in sunflower stars around Washington / Southern BC.
- 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; https://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/
- University of California, Santa Cruz Press Release; December 22, 2013; Unprecedented Sea Star Mass Mortality Along the West Coast of North America due to Wasting Syndrome
- Vancouver Aquarium; January 21, 2014; Presentation – Mass Dying of Seastars in Howe Sound and Vancouver Harbour (Dr. Jeff Marliave and Dr. Marty Haulena).
- Earth Fix; January 30, 2014; Northwests starfish experiment gives scientists clues to mysterious mass die-offs
Images showing symptoms in other sea star species: