By 2013 and into 2014 several diseases were suspected and most die-offs seem to have been linked to a virus that causes Sea Star Wasting Disease (SSWD). This is terrific because there were not enough acronyms already; so good to have another.
The acronym notwithstanding, this disease is aptly named. Sea stars so afflicted appear to waste away, losing body fluid and parts as they morph into an amorphous mass. First to appear are sours in the skin. Then these start to ooze eventually causes whole arms start falling off. The animal ends up as nearly a liquid. The liquid ooze that was once an animal washes easily away on the incoming tide. Though one can easily see the destructive nature of this disease when encountering an afflicted animal, the evidence left after a die-off is simply the lack of sea stars.
Along the east coast the die-off has so devastated the animals that sea stars, a once common tide pool sight, are rare. The surviving populations of animals have yet to rebound. It is possible that the die-offs continue, and it is further possible that they will never recover.
By the way, yes, you guessed it, the ultimate nemesis is, at least partially, the warming planet. The warming seas, brought on primarily by increased carbon dioxide levels (global climate change), adds to the devastation brought on by the disease. That’s is, warmer areas have more pronounced die-offs. There is some evidence that the virus that appears to be the major cause, Sea Star Associated Densovirus (SSaDV), is more active in warming waters. Another acronym, yeah! Or that the sea stars are more susceptible to the virus under these situations.
It also turns out that, this is in the ‘more bad news department’, sea star immune systems are hampered when the water becomes more acidic. This is occurring all over the planet right now. The increasing level of carbon dioxide in the air, cause more to dissolved into the water. As larger amounts of carbon dioxide dissolve, the carbon shifts into other molecules. One of the molecules is carbonic acid…well fuck…..or it shifts further releasing free hydrogen ions, which is basically what we measure when we measure pH (causes water to be more acidic). On a related note (yes, this is again in the ‘more bad news department’), as the water becomes more acidic, and the carbon shifts into other molecules, it leaves less in the form carbonate, which means less is available for organisms to build their shells, and exoskeletons.
Will sea stars recover? will we?
Similar die-offs of echinoderms have been documented in the past. Along the California coast past die-offs of sea stars are well documented. In the related sea urchins, a well-known die-off event killed massive numbers of the Long-spined Black Sea Urchin, Diadema antillarumwithin the Caribbean in 1983. I saw evidence of this particular devastation along the Jamaican coast in 1988. The region has not yet recovered from this event. Let me restate that, this region has not yet recovered from this event (that was more than 35 years ago). The last assessment done found the population of these urchins to still be a small fraction of their former numbers (maybe 12%). Die-offs have devastating consequences, echinoderms influenced these systems and their deaths lead to altered ecosystem states (called hysteresis in the ecology world). On Jamaican reefs this state is more algae, less coral. In coral reef systems, it’s the coral that sustain the biodiversity.
Devastating events, die-offs, and species extinctions are happening faster and with more regularity due to humans changing the planet. Speaking of extinctions and sea stars, in Australia, the Derwent River Seastar has recently been declared extinct. One more down.
I need to change the title; this is not “…another Canary in the coal mine”. The canary died long ago, so did Billy’s parakeet, we used that after all the canaries died. We are to the point where we are going to use Billy’s dog, and closing in on the point where the next “Canary” is us. Hold on tight.
References
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DelSesto, Caitlin Jessica. 2015.Assessing the Pathogenic Cause of Sea Star Wasting Disease in Asterias forbesiAlong the East Coast of the United States. Open Access Master's Theses. Paper 793.http://digitalcommons.uri.edu/theses/793
Fahsbender E, Hewson I, Rosario K, Tuttle AD, Varsani A, Breitbart M. Discovery of a novel circular DNA virus in the Forbes sea star, Asterias forbesi. Arch Virol. 2015; 160: 2349–2351.
Hernroth, B, Baden S, Thorndyke M, Dupont S. 2011. Immune suppression of the echinoderm Ateria rubens (L.) following long-term ocean acidification. Aquatic Toxicology 103: 222-224.
Hewson I, Button JB, Gudenkauf BM, Miner BG, Newton AL, Gaydos JK, et al. 2014. Densovirus associated with sea-star wasting disease and mass mortality. Proceedings of the National Academy of Sciences 111: 17278–17283.
Kohl WT, McClure TI, Miner BG. 2016. Decreased Temperature Facilitates Short-Term Sea Star Wasting Disease Survival in the Keystone Intertidal Sea Star Pisaster ochraceus. PLoS ONE 11 (4): e0153670.
Lessios, HA. 2016. The Great Diadema antillarumDie-Off: 30 Years Later. Annual Review Marine Science. 8:1.1–1.17
Lloyd MM, Pespeni MH. 2018. Microbiome shift with onset and progression of Sea Star Wasting Disease revealed through time course sampling. Scientific Reports 8: 16476.
Miner CM, Burnaford JL, Ambrose RF, Antrim L, Bohlmann H, Blanchette CA, et al. 2018. Large-scale impacts of sea star wasting disease (SSWD) on intertidal sea stars and implications for recovery. PLoS ONE 13(3): e0192870.
Schrope, M. 2014. Sea star wasting. Proceedings of the National Academy of Sciences. 1111: 6855.