Comparing Contaminants In Green Sea Turtles In Urbanized California Habitats
By Daryth Morrisey

Arthur Barraza gives a fascinating talk on contaminants in
the increasing numbers of sea turtles appearing in
Southern California waters to an interested crowd at REI.
Photo by Thomas Anderson.
The Eastern Pacific green sea turtles (Chelonia mydas) have been sighted in the Bolsa Chica Wetlands, off our coast, and even in Dana Point Harbor occasionally. But did you know that there is a resident population of these turtles close by? 22 turtles were first documented in 2008. This urban population resides in Seal Beach in the San Gabriel River near the Los Cerritos Wetlands. It is one of two foraging clusters found off the coast of Southern California. The other aggregation resides in the San Diego Bay. This is the most northernmost range in the Western United States for this species. During our winter months, they have been documented warming themselves in front of the So Cal Edison Power Plant discharge pipes. Jacuzzi anyone?

Amigos de Bolsa Chica’s FLOW program and REI hosted a “Turtle Talk” on September 21 at REI in Bella Terra. We were fortunate enough to have Arthur Barraza, a graduate student at CSULB’s Shark Lab under Dr. Chris Lowe, share his and his colleagues’ research on green sea turtle contamination loads. This article is a synopsis of Arthur Barraza’s PowerPoint presentation.

Arthur began his presentation with an overview of green sea turtles. They live up to 80 years old. They are endangered worldwide and threatened in the United States. There are multiple subpopulations. We are most familiar with the Hawaiian and Eastern Pacific aggregations. The most common reasons for their Endangered/Threatened status is due to bycatch (for example, drift nets catch on average 8 other species for every one swordfish caught), egg harvesting, and pollution. The Eastern Pacific and Hawaiian populations appear to be recovering. Green turtles inhabit coastal areas to forage for long periods of time only leaving to breed and lay eggs. These areas have high human activity and are highly urbanized. This leads to turtles accumulating several anthropogenic contaminants.

The contaminants were broken down into two groups: Persistent Organic Pollutants (POPs), and trace metals. POPs comprise of: Pesticides (PCB’s and DDT’s), and Flame Retardants (PBDE’s). Trace metals occur naturally at low levels in the environment. Some are essential vs non-essential, and both can overwhelm the metabolism.

There are similarities as well as differences when comparing the Seal Beach and San Diego Bay turtles. Genetically, they are similar. They are linked to nests on Revillagigedo Islands off Michoacán, Mexico. Their diets are also similar. They are omnivorous, eating both meat and plants. Where their differences lie are primarily location, and power plant access. The power plant in San Diego closed in 2010. The turtles there surprisingly stayed.

Arthur then stated the hypothesis on his research: green sea turtles from Seal Beach and San Diego Bay will have different concentrations of POPs and trace metals. Overall, 42 turtles were captured and released, 17 from Seal Beach and 25 from San Diego (under NOAA permit #16803). Blood was drawn and sample shavings from the scute were taken. The scute is a thickened horny or bony plate on a turtle’s shell with a layer of keratin similar to fingernails. In the Seal Beach population, Selenium, Cadmium, and Mercury were most prominent. While Selenium is an essential metal and needed for survival, it can be toxic in excess. The excess can come from environmental contamination through urban runoff or agriculture. These turtles showed a much higher Selenium level than previous studies that date back to 2010. The San Diego Bay turtles had higher concentrations of PCBs, Aluminum, and Nickel in their system. The PCBs detected were those that cause neurological damage (non-dioxin-like) as opposed to cancer causing (dioxin-like). The Flame retardants were banned in 2010. They had been detected in the San Diego population prior to that, but have not been detectable after the ban. Overall, green sea turtles from each location appeared to have their own unique contaminant signature related to where they live. Future studies will need to keep in mind these contaminant signatures when studying whether these contaminants are negatively affecting these sea turtles’ health.

The research presented was extremely informative, all who were present learned so much. Follow the San Gabriel River Sea Turtle Monitoring Project on Facebook for up to date information and best places to view these turtles.