Sea stars play a vital ecological role as top level predators shaping nearshore ecosystems. The absence of sea stars can enable other organisms that sea stars eat, like mussels, to multiply and drive out other nearshore inhabitants. An epidemic wasting disease, caused by a virus (Hewson et al. 2014) began in 2013, affecting sea stars from Alaska to Baja California, Mexico. A recent paper suggests that warmer water temperatures in the Pacific Ocean could have increased the spread of the disease and the high rates of sea star death in Washington State (Eisenlord et al. 2016).
The epidemic affects at least 20 sea star species, and sea star populations along the west coast of the U.S. have experienced very high levels of death. As the disease progresses, sea stars often lose arms and can have a jelly-like appearance. Death can occur within a few days of the initial signs of infection. This disease has been observed in several locations in southeast Alaska, and more recently in Western Prince William Sound and Kachemak Bay.
The National Park Service, in partnership with the U.S. Geological Survey, the University of Alaska, Fairbanks (UAF), the National Oceanic Atmospheric Administration (NOAA), and GulfWatch Alaska began a concerted effort to look for the disease in southcentral Alaska starting in 2014. Researchers from various institutions searched for the disease at long-term GulfWatch Alaska monitoring sites in Prince William Sound (1), Kenai Fjords National Park (1), Katmai National Park and Preserve (1), and in Kachemak Bay (2). GulfWatch Alaska collaborators from UAF also investigated sites in the Western Aleutian Islands (3), outside the scope of this long-term monitoring program.
Sea star data from Kenai Fjords National Park, Katmai National Park and Preserve, Prince William Sound, and Kachemak Bay were examined to determine spatial and temporal trends in sea star abundance and diversity and to determine if effects of sea star wasting could be detected. Our analyses demonstrated high spatial and temporal variability in sea star densities in all surveyed regions. In addition to high temporal variability in abundance, the diversity and dominance of individual species varied greatly among regions (Figure 1).
A dramatic decline in sea star numbers, most likely attributable to sea star wasting, has been seen across all regions in recent years (Figure 2). Gulf Watch Alaska will continue monitoring these important species in the future. Continued monitoring will also provide insights into the impacts that sea star wasting is having on intertidal communities over time.
How you can help
Many sea stars can exhibit bodily damage, due to impact injuries from boulders moved by large waves, exposure to freshwater, and predators. These injuries can be confused with wasting disease, but you can visit seastarwasting.org for comprehensive identification guides. We encourage the use of citizen science in collecting data on diseased sea stars. If you observe a sea star that exhibits signs of this disease, please take a photograph, note the location and date, and send to: firstname.lastname@example.org, email@example.com, or firstname.lastname@example.org.