From the late 1940s through the early 1970s, Southern California manufacturing firms dumped large quantities of waste laden with the pesticide DDT and the chemical PCB into the Los Angeles County sewer system that ended up in a massive sediment deposit at the end of sewer outfall pipes located off the Palos Verdes Peninsula's White's Point.
According to the U.S. Environmental Protection Agency, sediment contaminated with DDT and PCB spreads across more than 40 square kilometers. Because both of these compounds are lipophilic (are absorbed easily in fats), they don't dissolve in water and therefore, have remained concentrated in the area.
Contamination in pinnipeds including California sea lions, Pacific harbor seals and northern elephant seals living or feeding in the Southern California Bight—the Pacific Ocean near-shore area between Point Conception and the Mexico border—had not been studied, so CSULB marine biology master's student Mary Blasius and full-time lecturer Gwen Goodmanlowe published a research article in the journal Marine Pollution Bulletin demonstrating that these animals continue to be contaminated.
Goodmanlowe said the contaminants were found in the animals' blubber as a result of traveling up the marine food chain, starting with worms and other invertebrates that live in the sediment, moving to fish and finally to top-level carnivores like marine mammals.
They obtained blubber samples from two Southern California marine mammal care centers from 145 animals that had stranded on local beaches and subsequently died at the centers. Since the centers preserve tissue from dead animals, they were able to obtain samples covering a 13-year time period, from 1994 to 2006.
"We thought that there might be a difference in the amount of contaminants they have in their blubber depending on how much time they spend in the Southern California Bight," Goodmanlowe said. The researchers also wanted to look at the three species' prey, age differences among the animals, as well as contaminant levels over time since dumping ended in 1972.
DDT was higher than PCBs in all three species, especially California sea lions. Goodmanlowe said. Among sea lions, "the levels of both contaminants increased with age and then decreased again with older females," who pass along the contaminants to their offspring. The young animals lose blubber when learning how to feed, "then they build it up again throughout their lifespan, losing a little bit every time they fast."
"The elephant seal had higher levels than previously found, which is interesting because this shows that the pups and sub-adults are probably feeding in the Southern California Bight more often than was previously thought."
Finally, over the 13 years examined, contaminant levels decreased among sea lions, although remained higher than in animals previously studied from other California waters. Because domoic acid from marine diatoms causes many strandings of California sea lions in the Southern California Bight, Goodmanlowe would like to continue this study and investigate the possible causal relationship between high levels of these contaminants and of domoic acid.
