Ochre Sea Stars Show Signs of Recovery Along Oregon Coast

CORVALLIS, Ore. – A significant recovery of ochre sea star populations is underway along the Oregon Coast, following a substantial decline a decade ago. Research conducted by scientists from Oregon State University and Cal Poly San Luis Obispo has identified a remarkable resurgence among these sea stars, often referred to as a “baby boom.” The findings were published in the journal Ecosphere.

The study, which spans 23 years and includes data from eight locations along the coast, does not confirm whether this increase is a direct response to the wasting disease epidemic that nearly led to the species’ extinction in Oregon. Nonetheless, the evidence points to a significant rebound. “Wasting disease remains in circulation and populations continue to fluctuate, but there’s also much evidence that ochre sea stars are bouncing back,” stated Sarah Gravem, the study’s lead author and an assistant professor at Cal Poly.

The research team, which also included Bruce Menge, a distinguished professor of integrative biology at OSU, observed that many of the younger sea stars have matured into adults, with current population counts reaching or surpassing their pre-wasting disease levels. Gravem noted that after experiencing declines of up to 84% in sea star numbers in 2014, the population saw an astonishing 8,000% increase in young sea stars appearing on shore.

Ecological Impact of Recovery

The resurgence of ochre sea stars is crucial for the intertidal ecosystem. These sea stars serve as keystone predators, and their return is helping to restore balance in their environment. At approximately three-quarters of the study sites, predation on California mussels has improved, allowing other marine species to thrive. “We showed that sea stars have now grown abundant and large enough that they are eating mussels at similar rates to before the epidemic at most sites in Oregon,” added Menge, who has dedicated decades to studying the intertidal zone.

Despite these positive developments, challenges remain. The average body size of the sea stars is still 25% to 65% smaller than historical averages at almost all locations, indicating that the population has not fully stabilized. The researchers attribute this variability to ongoing pulses of young sea stars and sporadic outbreaks of the wasting disease, which continues to pose a threat.

Gravem remarked, “The connection between the sudden decline of ochre sea stars and the baby boom remains elusive. It’s certainly possible they are linked, which would mean these sea stars may be resilient to mass mortality events.” Alternatively, the recovery could be coincidental, driven by favorable conditions that allowed for rapid population growth.

Wasting disease manifests in sea stars through lesions and twisted arms, leading to a condition that appears as if they are melting away. The causative agent, a strain of the bacterium Vibrio pectenicida, was recently identified through collaborative research involving institutions such as the University of British Columbia and the U.S. Geological Survey. The findings of this collaboration were published in the journal Nature Ecology & Evolution.

The study underscores the resilience of ochre sea stars and their vital role in marine ecosystems, highlighting the importance of continued monitoring and research to ensure their ongoing recovery along the Oregon Coast.