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Sporadic Events: Monterey Bay

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Sea Stars Impacted by Wasting Disease (2013)

October, 2013

Pisaster giganteus deteriorating. Photo credit: Dr. Steve Lonhart, NOAA MBNMS.

‘Sea star wasting disease’ is a term used to refer to a set of symptoms found in sea stars.  Typically, lesions appear in the ectoderm followed by decay of tissue surrounding the lesions, which leads to eventual fragmentation of the body and death.  It appears that the star is ‘dissolving’ and individuals may have a deflated appearance prior to other morphological signs of the disease.  All of these symptoms are also associated with ordinary attributes of unhealthy stars and can arise when an individual is stranded too high in the intertidal zone (for example) and simply desiccates.  “True” wasting disease will be present in individuals that are found in suitable habitat, often in the midst of other individuals that might also be affected.

The progression of wasting disease can be rapid, leading to death within a few days, and its impacts can be devastating on seastar populations. The proximal cause of the disease, when pathological studies have been done, is typically a bacterium (vibrio), although a recent wasting event on the east coast of the United States has been attributed to a virus.  The ultimate cause is not clear although such events are often associated with warmer than typical water temperatures as was the case for the major die off in southern California in 1983-1984 and again (on a lesser scale) in 1997-98. Following the 1983-1984 event, the ochre star, Pisaster ochraceus, was virtually absent along southern California shorelines for years.

In Summer 2013 there is evidence that we are at the onset of another disease event and one that is particularly troubling because of its spatial extent. MARINe and the Pacific Rocky Intertidal Monitoring groups have documented wasting in Pisaster ochraceus from Alaska through California.  Two common attributes for many of the sites are: (1) the period prior to wasting was characterized by warm water temperatures, and (2) the effects are dramatic.

To learn more about this, visit the the Pacific Rocky Intertidal Monitoring web site.  This site includes an interactive map indicating current locations and how to report sightings.