Ochre Sea Stars Show Recovery Signs Along Oregon Coast

Research from Oregon State University and Cal Poly San Luis Obispo reveals that the ochre sea star population on the Oregon Coast is rebounding following a significant decline caused by a devastating wasting disease epidemic nearly a decade ago. This resurgence, highlighted in a study published in the journal Ecosphere, points to a promising future for the species, although questions remain regarding the factors behind this recovery.

Encouraging Signs of Recovery

The study, led by Sarah Gravem, an assistant professor at Cal Poly and former postdoctoral researcher at OSU, and Bruce Menge, a distinguished professor of integrative biology at OSU, examined ochre sea star populations across eight sites over a span of 23 years. The findings indicate that many young sea stars, referred to as “baby boomers,” have matured into adults, leading to population numbers that now meet or exceed levels seen before the epidemic.

“After declines in sea star numbers of up to 84% in 2014, we quickly observed an 8,000% increase in young sea stars landing on shore,” Gravem noted. The research demonstrates that populations have grown sufficiently to resume their critical role as predators in the intertidal ecosystem. Notably, at three-quarters of the study sites, predation on California mussels has returned to levels similar to those before the disease outbreak.

This predation is vital, as it prevents mussels from forming expansive beds that can inhibit the growth of other marine species, including various invertebrates and seaweeds. The presence of healthy sea star populations allows for a more diverse intertidal environment, promoting ecological stability.

Continuing Challenges and Uncertainties

Despite these positive trends, challenges persist. The average size of the sea stars remains about 25% to 65% smaller than pre-epidemic averages at most locations. Additionally, the sea star populations are less stable than they were prior to the epidemic, indicating fluctuations in numbers year to year. This instability is likely due to ongoing recruitment of young sea stars and sporadic resurgences of the wasting disease.

“The connection between the sudden decline of ochre sea stars and the subsequent baby boom remains unclear,” Gravem explained. “It is possible they are linked, suggesting that these sea stars may possess resilience against mass mortality events. Alternatively, the boom might be a result of coincidental luck, enabling a rapid recovery.”

The sea star wasting disease is characterized by symptoms such as lesions and twisted arms, which give the appearance of melting away. Researchers recently identified the cause of this disease as a strain of the bacterium Vibrio pectenicida, with findings published by a collaboration of scientists from the University of British Columbia, University of Washington, U.S. Geological Survey, and the Hakai Institute in Nature Ecology & Evolution.

The recovery of the ochre sea star is not only significant for the species itself but also for the broader marine ecosystem along the Oregon Coast. As these sea stars regain their role as keystone predators, the health and diversity of intertidal habitats stand to benefit, underscoring the intricate connections within marine environments.