Sea Star Wasting Disease and San Diego Tide Pools: What Athletes Should Know

If you’ve explored San Diego’s tide pools lately—whether at Cabrillo Point, Point Loma, or the rocky reefs near Torrey Pines—you’ve likely noticed something unsettling: far fewer sea stars than you remember. The culprit is sea star wasting disease (SSWD), a condition that has ravaged starfish populations across the Pacific Coast since 2013. Understanding what’s happening in our local tide pools isn’t just ecological curiosity—it affects how we interact with these fragile ecosystems as athletes and outdoor enthusiasts.

What Is Sea Star Wasting Disease?

Sea star wasting disease is caused by a densovirus that attacks sea stars’ immune systems, causing tissue degeneration, arm loss, and eventually death. The disease progresses rapidly: an infected star can deteriorate within days, literally falling apart. Multiple species are vulnerable—purple sea stars, red sea stars, and sunflower stars have been hit hardest along the California coast.

The virus spreads through seawater, making dense populations particularly susceptible. San Diego’s rocky intertidal zones, especially at low tide when animals are concentrated, create ideal conditions for transmission. The disease isn’t selective: it affects stars of all sizes and ages, though juvenile stars tend to show faster mortality rates.

The San Diego Impact

San Diego’s tide pools experienced the worst outbreak between 2013 and 2016. During those years, some sites lost up to 95% of their sea star populations. While populations have shown some recovery, the die-offs fundamentally altered our local intertidal communities. Sites like Cabrillo Point and the reefs near Bird Rock saw dramatic changes in predator-prey dynamics. With fewer stars grazing on sea urchins, urchin populations exploded in some areas, leading to kelp forest collapse nearby.

By 2024, local populations remain fragile. You’ll still find sea stars in San Diego’s tide pools, but abundance varies significantly by location and season. Winter months (December–February) tend to show slightly healthier populations, though the disease persists year-round.

Where to See the Effects

The most visible impacts are at our most-visited tide pool sites:

Cabrillo Point remains accessible during extreme low tides and shows mixed recovery. Purple sea stars here are less abundant than historical records suggest, though a few specimens typically appear during spring and summer.

Point Loma’s rocky reefs near Sunset Cliffs still host sea stars, but you’ll need to look carefully and access during minus tides (typically April–June and October–November for San Diego’s best extreme lows).

Torrey Pines State Natural Reserve’s tide pools have rebounded slightly better than southern locations, possibly due to lower human traffic and cooler water temperatures that may suppress viral transmission.

Mission Bay’s rocky outcrops show less severe impacts, likely because lower salinity and warmer, shallower waters create less-ideal conditions for SSWD transmission.

What This Means for Tide Pool Visitors

If you’re planning a tide pool session, recognize that what you’re observing is an ecosystem in recovery. The absence of sea stars isn’t just a curiosity—it cascades through the food web. Fewer predators mean more sea urchins, which overgraze kelp. Fewer stars also mean less competition for filter-feeding mussels and anemones, which can lead to dense mussel beds that crowd out other species.

Practical considerations for athletes:

• Timing matters: Explore during extreme low tides (minus 1.5 feet or lower). San Diego’s best tide pools are accessible March–May and September–November. Check the Element app for precise tide forecasts.
• Minimize disturbance: If you find a sea star, observe without handling. Stressed animals shed arms more readily, and any remaining populations need all the help they can get.
• Report observations: The Birch Aquarium and UC San Diego’s Coastal and Marine Laboratory still track SSWD. Documenting healthy stars helps scientists understand recovery patterns.
• Respect closures: Some tide pool areas periodically close for ecosystem recovery. Honor these restrictions—they exist because the system is vulnerable.

The Bigger Picture

Sea star wasting disease reminds us that San Diego’s marine environment, while resilient, isn’t invulnerable. Climate change, warming ocean temperatures, and pollution can all amplify viral transmission. The disease persists because conditions haven’t fundamentally changed since 2013.

Recovery is happening, but slowly. Some researchers predict full population restoration could take decades. Until then, tide pool exploration remains rewarding—just with a different cast of characters and a responsibility to observe carefully.

Use the Element app to track tide times and plan low-tide sessions when you’ll see the most life. Better conditions mean better observations, and better awareness means better stewardship of our local coast.