Just one month after a diver alerted Vancouver Aquarium staff to dozens of dead sea stars in the waters near Whytecliff Park, British Columbia, the invertebrates appear to have completely disappeared. Several videos have been posted showing sea stars in Howe Sound and Vancouver Harbour disintegrating into white goo.
Sea stars, commonly referred to as starfish, are invertebrate echinoderms that exist in oceans throughout the world. While the five-arm variety is the most common, there are nearly 2,000 different species of varying sizes with some having as many as 40 arms. Their vital organs are located in their arms, making sea stars capable of regenerating not only other limbs but in some cases the entire body. Multiple species appear to be affected in this most recent die-off in the Pacific Northwest, including sunflower sea stars (Pycnopodia helianthoides) and morning sun stars (Solaster dawsoni).
Canadian Broadcasting Corporation’s CBC News reports that some, like diver and marine scientist Jonathan Martin, suspect that the recent population boom may be part of the explanation for the die-off – being referred to as Sea Star Wasting Syndrome, or Starfish Wasting Disease. As a population increases in size, food and nutrients may become scarce, stressing individuals and making them more susceptible to disease. Environmental factors such as weather may also offer an explanation. Others suggest that recent heavy rains may have changed the water’s salinity, adversely affecting sea stars. Other possible causes such as warming ocean waters due to climate change, bacterial disease, and parasites are being investigated. As invertebrates living in tidal areas, sea stars are particularly sensitive and die-offs may indicate environmental change.
Similar die-offs are also being studied along the East coast of the United States where sea stars have been found dying in large numbers. It is unclear if the die-offs are related. It is also unknown how far the die-off in British Columbia may spread and whether the species affected will recover. The Vancouver Aquarium has asked divers and members of the public to help monitor spread of the disease by reporting sea star deaths to them via email (firstname.lastname@example.org).