Museum biological collections are the records of life on Earth and as such, they are frequently used to investigate serious environmental issues. When public health officials were concerned about the levels of mercury in fish and birds, for example, scientists studied museum specimens to assess historical changes in mercury contamination. Eggs in museum collections were analyzed to establish the connection between DDT, thinning eggshells, and the decline in bird populations. And now, specimens from the Natural History Museum of Los Angeles County (NHM) have helped explain the mysteriously sudden appearance of a disease that has decimated sea stars on the North American Pacific Coast. In a paper published Monday, November 17, 2014 in the journal Proceedings of the National Academy of Sciences, Cornell University microbiologist Ian Hewson and colleagues identify the Sea Star Associated Densovirus (SSaDV) virus as the microbe responsible for Sea Star Wasting Disease (SSWD). NHM Curator of Echinoderms Gordon Hendler and Collections Manager Cathy Groves, along with scientists from universities and aquariums along the coast (including NHM neighbor, the California Science Center), collaborated in the study.

Since June 2013, the largest die-off of sea stars ever recorded has swept the Pacific Coast. At least 20 different species of sea stars have been affected -- including iconic species like the "ochre star" and the multi-armed "sunflower star" -- and many populations of sea stars from Southern Alaska to Baja California have already disappeared.

Their large-scale disappearance is anticipated to have a serious and long-lasting ecological impact on coastal habitats, because sea stars are voracious predators, with a key role in regulating the ecology of the ocean floor.

Museum samples prove that the virus has existed at a low level for at least the past 72 years -- it was detected in preserved sea stars collected in 1942, 1980, 1987, and 1991. The study suggests the disease may have recently risen to epidemic levels because of sea star overpopulation, environmental changes, or mutation of the virus.