Sunflower sea stars put to the test in California kelp restoration trials
The story at a glance
Researchers and partners ran field trials in Monterey Bay in 2026 to test whether captive-reared sunflower sea stars could help restore kelp ecosystems by preying on sea urchins. The work included a month-long caged experiment with 16 stars and brief, supervised releases outside cages.12
The laboratory reports that 99% of adult urchins near the trial cages moved away, with the behavioural effect lasting for weeks after the stars were removed. The experiments do not show that releases can restore kelp across open habitats.2
The story in brief
What you need to know
- The trial tests a proposed restoration mechanism: sunflower sea stars eat sea urchins, which graze on kelp. The loss of the stars has been associated with increased urchin pressure and deterioration of some kelp ecosystems.134
- The reported urchin response is an experimental result, not a measure of kelp recovery. The project team’s account describes effects near the cages and over a limited period; it does not establish what would happen after permanent releases at larger scales.2
- A peer-reviewed study found that nearly 95% of historic bull-kelp canopy was lost in the Sonoma–Mendocino study region of Northern California. That figure applies to this region and habitat, not to all kelp forests along the Pacific coast.3
- NOAA identifies sea-star wasting syndrome as the primary threat to sunflower sea stars, and says the outbreak contributed to steep declines from 2013 to 2017. NOAA also says there is no single systematic dataset establishing population size and long-term trend across the species’ range.4
- In June 2026, NOAA reported sunflower sea star detections at six California sites using environmental DNA, including south of San Francisco for the first time in a decade. These are local monitoring detections, not evidence of broad population recovery.5
Conservation context
Why this matters
The trials examine whether restoring a predator affected by disease could help address urchin pressure on kelp. They offer evidence about a possible tool, but the sources do not establish that it can reverse kelp decline in the wild.234
The developing story
What happens next
The reporting does not set out a timetable for permanent releases. Further work would need to establish whether captive-reared stars survive and reproduce after release, and whether any effects on urchins lead to sustained kelp recovery in open habitats.12
Established evidence
What we know
- The Monterey Bay work combined a month-long caged experiment involving 16 captive-reared stars with brief, supervised uncaged releases.2
- The laboratory reports that 99% of adult urchins near the cages moved away, and that the behavioural effect persisted for weeks after the stars were removed.2
- The Northern California bull-kelp canopy loss estimate comes from the Sonoma–Mendocino study region; it is not a coast-wide estimate.3
- NOAA’s 2026 environmental-DNA survey detected sunflower sea stars at six California sites, including a site south of San Francisco.5
Open questions
What we don't know
- It is not known whether captive-reared stars would survive and reproduce after permanent release, or which sites and release sizes would be suitable.2
- The available trials do not establish whether the observed changes in urchin behaviour and feeding would persist in open habitats or produce measurable kelp recovery.2
- The sources identify disease risk, ocean conditions and other urchin predators as factors whose effects on future releases remain unresolved.2
- The California detections do not show how representative local observations are of sunflower sea star recovery across the species’ full range. NOAA says there is no single systematic dataset establishing population size and long-term trend across that range.45
Source coverage
