Genetic detection tools identify rare sunflower sea stars along California coast

A handful of DNA copies per liter of seawater has provided the first evidence of sunflower sea stars south of San Francisco in more than a decade. The discovery, facilitated by a refined environmental DNA (eDNA) detection method developed at NOAA’s Pacific Marine Environmental Laboratory, marks a technical shift in how marine ecologists monitor the recovery of the species following its near-extirpation during the 2013–2016 Pacific marine heatwave.

The sunflower sea star serves as a biological regulator of kelp forest health. Its absence since the marine heatwave—and the subsequent outbreak of wasting disease—allowed sea urchin populations to proliferate unchecked. These grazers have converted vast tracts of productive kelp nurseries into barren seafloor. By detecting genetic material shed into the water column, scientists can now confirm the presence of these predators at depths and in conditions that prohibit traditional dive surveys.

The efficacy of the tool was verified against manual counts in Mendocino and Sonoma counties, where higher eDNA concentrations correlated consistently with visual sightings of juvenile stars. For conservation planners, the speed of the assay—returning results within forty-eight hours—provides a mechanism to direct dive teams toward specific sites for physical confirmation. This targeted approach is currently being integrated into the monitoring protocols of the Olympic Coast National Marine Sanctuary to track whether the species is reclaiming its historic range.