You wouldn't expect to find a colony of tropical marine reptiles swimming next to a power plant in a concrete channel. It sounds like a glitch in the matrix. Yet, if you stand on the bike path in Long Beach or Seal Beach, looking down into the greenish murk of the water, you'll see them. Huge, dark shapes. Ancient-looking heads poking up for air. These are the San Gabriel River sea turtles, a population of East Pacific Green sea turtles (Chelonia mydas) that has basically decided that a Southern California drainage pipe is the perfect place to call home.
It’s weird. Honestly, it shouldn't work. Most green sea turtles are migratory nomads that travel thousands of miles between nesting beaches in Mexico and feeding grounds elsewhere. But this specific group? They’re residents. They’ve ditched the commute. Scientists have found that some of these turtles stay in this tiny, highly urbanized stretch of river for years—even decades.
The Weird Science of the "Hot Tub" Effect
So, why here? Why would a creature that belongs in a coral reef choose to hang out in a river squeezed between the 405 freeway and a massive industrial complex?
The answer is actually pretty simple: it’s the heat.
The San Gabriel River isn't naturally warm. However, the Haynes Generating Station and the AES Alamitos power plants use river water to cool their machinery. When they discharge that water back into the river, it’s significantly warmer than the surrounding Pacific Ocean. For a cold-blooded reptile, this is basically a 24/7 heated pool. While the rest of the ocean gets chilly in the winter, the San Gabriel River stays a balmy 70 to 80 degrees Fahrenheit in certain pockets.
It’s a thermal refuge.
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Because they don't have to use energy to stay warm or migrate south to avoid the cold, these turtles grow fast. Like, surprisingly fast. Research led by NOAA Fisheries and Dr. Dan Lawson has shown that these turtles are often larger and reach maturity quicker than their counterparts in more "natural" settings. It’s a bit of an ecological irony. An industrial byproduct created a thriving habitat for an endangered species.
What Most People Get Wrong About the River
People see the concrete and the trash and assume the river is "dead" or "toxic." While urban runoff is a massive problem—don't go swimming in there after a rainstorm—the ecosystem is surprisingly robust.
The turtles aren't just there for the heat. They’re there for the buffet.
Green sea turtles are primarily herbivores once they hit adulthood. They graze on algae and seagrass. The lower San Gabriel River and the adjacent Alamitos Bay provide a massive amount of eelgrass and various types of macroalgae. They spend their days munching on the greenery growing on the rocks and the riverbed.
- They aren't "lost."
- They aren't "trapped" by the dams.
- They are choosing to be there.
Interestingly, these turtles are actually part of the Mexican nesting population. Every few years, the mature adults will make the long trek down to Michoacán, Mexico, to lay eggs before returning straight back to the 7th Street bridge in Long Beach. It’s their home base.
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The Risks of Living in a City
It’s not all lounging in warm water and eating salad. Living in a river that cuts through one of the most densely populated regions on earth has some major downsides.
Poaching isn't really the issue here. The real killers are boats and plastic. Because the river is a narrow channel, turtles surfacing for air are at a high risk of being struck by boat propellers. You’ll often see turtles in the area with "skeg" marks—deep scars on their shells from close calls with outboard motors.
Then there’s the pollution. Urban runoff brings everything from heavy metals to lawn fertilizers into the water. However, the most visible threat is "entanglement." Fishing line is a nightmare for these guys. A turtle gets a flipper caught in a discarded monofilament line, the circulation cuts off, and they lose the limb or drown.
There's also the weird reality of the power plants. As California moves toward renewable energy, these gas-fired plants are being decommissioned or "repowered" with systems that don't discharge warm water. This has biologists worried. What happens to a population that has relied on an artificial heat source for 60 years when the "heater" gets turned off?
Will they leave? Will they freeze? It’s an ongoing study, but the "cold-stunning" of these turtles is a legitimate fear for the future.
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How to Actually See Them
If you want to spot the San Gabriel River sea turtles, you don't need a boat. You just need patience and a pair of polarized sunglasses.
The best spot is usually the bike path along the river in Seal Beach, specifically between the PCH bridge and the 7th Street bridge. Go during an incoming tide. The turtles tend to be more active when the water is moving, popping their heads up every few minutes.
Don't feed them. Seriously. It messes with their natural diet and makes them associate humans (and boats) with food, which leads to those propeller strikes I mentioned.
The Bigger Picture of Urban Wildlife
The San Gabriel River population is a reminder that nature is incredibly adaptable. We tend to think of endangered species as these fragile things that can only exist in pristine wilderness. But these turtles are tough. They’ve navigated the noise of the freeways and the chemical soup of the city and found a way to thrive.
They are a flagship species for the river. Because people care about the "cool turtles," there is more pressure to clean up the trash and manage the water quality of the San Gabriel. They are accidentally saving their own habitat by being charismatic.
Actionable Steps for River Stewards
If you live in the area or just care about marine life, there are real things you can do that actually matter. This isn't just "awareness"—it's boots-on-the-ground stuff.
- Report Sightings: If you see a turtle that looks sick, injured, or entangled, don't try to be a hero. Call the West Coast Marine Mammal Stranding Network or the NOAA Fisheries tip line. They have the gear to safely handle a 300-pound reptile.
- Pick Up Fishing Line: If you're fishing in the area, use the monofilament recycling bins. If you see line tangled on the rocks, pull it out. That's one less turtle losing a flipper.
- Watch Your Wake: If you’re boating in Alamitos Bay or the river mouth, slow down. These turtles are "log-like" when they surface. At high speeds, you won't see them until it's too late.
- Manage Runoff: It sounds boring, but what you put on your lawn in Whittier or West Covina eventually ends up in the turtle's mouth. Use organic fertilizers and keep trash out of the storm drains.
The San Gabriel River sea turtles are a living anomaly. They shouldn't be here, but they are. They are a piece of the wild inside the machine, and as long as the water stays warm and the eelgrass grows, they’ll likely keep calling Long Beach home. Keep your eyes on the water next time you're on the bike path. You might see a prehistoric survivor staring back at you.