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Counting The Sea Turtles of Long Beach

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Green sea turtle in the San Gabriel River | Photo: Eric Austin Yee

Another story in our series on citizen science in California, as part of Redefine's celebration of Citizen Science Day on April 16.

It's a warm Saturday in Long Beach and a group of folks have gathered on a small spit of land between the San Gabriel River and a narrow channel that diverts water from the coast into a power plant. Their mission? To count sea turtles.

Despite a fair amount of news coverage in recent years, many folks are still surprised to find out that green sea turtles, Chelonia mydas, also confusingly known as black sea turtles, range as far north as Los Angeles. They're usually thought of as a more tropical species; you can snorkel with them in Hawaii, and they lay their eggs on sandy Mexican beaches.

But there's a group of sea turtles that can be found all year long right here in the brackish waters at the bottom of the San Gabriel River. And the Long Beach Aquarium of the Pacific has assembled a dedicated group of volunteer citizen scientists to study them.

Once a vast coastal wetland where the fresh water flowing from the Los Angeles and San Gabriel rivers met the ocean, much of the landscape has given way to manicured lawns, parking lots, and concrete. Despite the ecological turnover, the rivers still wind their way through the southland and dump into the Pacific, and many of the wild animals that live alongside continue to persist.

Some think that the sea turtles have made a home here for a very peculiar reason. On each side of the river sits a power plant. To keep their equipment cool, the plants suck up cold salty seawater and, after they're done with it, they flush it back into the river. This creates a sort of artificially warm habitat, perfect for marine reptiles like the turtles.

But NOAA Fisheries biologist Dan Lawson, who helps oversee the sea turtle monitoring effort here, isn't so sure. It's possible, he says, that sea turtles have always come up to Los Angeles. Sea turtles are common in the Bolsa Chica wetlands just to the south, after all, and some suspect that Native Americans like the Tongva and Chumash were aware of local sea turtles before European people arrived in Southern California.

Whether or not sea turtles were present in Long Beach before the power plants heated things up, they're certainly here now. Citizen scientist Celeste Hassler recalls counting 42 turtle heads one day, and even if that included some repeats, it's an indication that it's not just a few wayward individuals. Over the last few years, Lawson has caught and assessed about fifty turtles, with only a handful of recaptures.

And they're all turtle teenagers. With the smallest river-dwelling turtles being at least as large as a dinner plate, they're not newly hatched infants, but they're also not adults of breeding age. They may be using the river as a fairly safe space to avoid becoming lunch for a hungry sea lion while they wait to mature. Since all the animals are of the same age class, that means there are constantly newcomers entering the river and long-term residents who pack up and move. Nobody knows quite how many are here at one time. Radio trackers revealed that some turtles spend all of their time in the river, but a few venture out to sea during the day and return at night, to rest.

Until a few years ago, the presence of turtles in the four or five miles of river that retains its natural, soft bottom was a fairly well kept secret, the stuff of rumors. But once a bike path was laid out alongside the river, more folks had more opportunities to spot a turtle coming to the surface of the murky water to fill its lungs with air.

Indeed, as I stand near the bike path with Lawson and Cassandra Davis, the aquarium's volunteer coordinator, scanning the greenish-brown water for signs of (non-avian) life, cyclist after cyclist shouts "seen any turtles yet?" or "how many turtles so far?" as they whiz on by. Thanks also to the rise of social media, the turtles have attained pseudo-celebrity status, at least in the neighborhood. They're not quite as internationally newsworthy as P-22, but they're far more exciting to many than the more humdrum, introduced red-eared sliders that can be found just about anywhere.

To wit: "when it was first reported it was thought that they were red-eared sliders," says Davis. But once folks from the aquarium verified that they were indeed sea turtles, two projects started up almost immediately, independently of each other. In one, researchers from CSU-Long Beach placed radio transmitters on turtles in an effort to chart their daily movements. The second was the aquarium's citizen science-based monitoring effort. "The two in tandem helped us to figure out more about the population than we would have with either study on its own," she says.

One Saturday each month, volunteers meet up and then disperse across ten different observation points along a two-mile span of the river. It's the sort of herculean effort that would be nearly impossible to achieve without relying upon volunteers like Hassler, a music teacher. She's been volunteering on the project for nearly three years. Sea turtle monitoring, she decided, was a perfect activity for her and her then eleven-year-old twin sons, both of whom were already interested in animals. "Both now want to go into some form of oceanography as a career," she says, something for which she at least partially credits the hours scanning for sea turtles as an inspiration. As for her, she's thrilled to participate in an activity that actively contributes to scientific knowledge building. "One of the beauties of this program is that people who have an interest but no training can actually become part of the [scientific] process," she says.

Training sea turtle observers on the San Gabriel River | Photo: Long Beach Aquarium of the Pacific

It's this continuous observation by citizen scientists that allows Lawson and his colleagues from NOAA and elsewhere to more comprehensively understand this community of enigmatic reptiles. If he was out monitoring them alone, he might spot one sea turtle at one spot, and then half an hour later, he might spot a second one at a different spot. So did he see one turtle, or two? Only by conducting simultaneous observations along the river can researchers even begin to guess how many turtles there are, and how they use the habitat.

By combining the citizen science data with genetic information acquired during the radio telemetry study, researchers have learned that these turtles are part of the same population that nests on Mexico's Pacific coast, members of the Eastern Pacific "distinct population segment."

The future of the San Gabriel River turtles remains unclear. The power plants are expected to cease dumping warm water into the river soon, and nobody knows to what extent the turtles rely on that warm outflow. "I am not expecting the turtles to leave," says Lawson, which could explain why he's hoping to have the area designated as "critical habitat" for the Endangered Species Act-listed species, a move that would impose some limits on certain kinds of federal activities.

And while the turtles enjoy a fair amount of protection in US waters, they face greater uncertainty elsewhere. Egg poaching is a serious threat to many species of sea turtles, and when combined with entanglement in fishing gear, sea level rise that threatens their historic nesting sites, and plastic pollution, they're clearly not out of the woods yet. The good news, however, is that NOAA has just proposed that the entire Eastern Pacific distinct population segment be uplisted from "endangered" to "threatened," a reflection of improved protection efforts and local breeding success.

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