Contaminants from years of dumping off California's coast are still affecting our ecosystem.
A new study led by San Diego conservationists found that marine mammals eaten by the critically endangered California Condors contain such high levels of now-banned contaminants it may be harming their birds' reproductive systems.
The study, led by San Diego State University (SDSU) and San Diego Zoo Wildlife Alliance (SDZWA) scientists and published Wednesday in Environmental Science & Technology, compared the diets of condors from the California coast with their cousins' in Baja California. Their research found the dead marine mammals eaten by the vulturous bird in the U.S. contain more than 400 types of halogenated organic contaminants (HOCs) and an estimtaed seven-times more DDT than their food south of the border.
“The marine mammals in the Gulf of California presumably have less DDT and other halogenated compounds because there wasn't a historic discharge or dumping off of the coast like we see in Southern California,” co-author and SDSU researcher Margaret Stack said.
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The study also found a four-times increase in the number of contaminates found in California condors' blood when compared to inland condors, which do not eat marine mammals. DDT was seven times more abundant in coastal birds.
The harmful contaminants can disrupt estrogen hormone levels and researchers said there is evidence coastal condors are experiencing eggshell thinning as a result, which could be disasterous given condors may only raise one chick every other year, according to SDZWA.
Researchers are using the study titled "Assessing Marine Endocrine-Disrupting Chemicals in the Critically Endangered California Condor: Implications for Reintroduction to Coastal Environments," to determine where to reintroduce the bird that was once on the brink of extinction.
But it also holds implications about our sea life. Although HOCs were banned decades ago when the Ocean Dumping Act was enacted, the contaminants are highly resistant to natural degradation and are found in marine food webs with the potential to harm marine life, the researchers said.
Watch the California condors nest at the San Diego Zoo Safari Park during the 2022 breeding season on this wildlife cam
California condors were nearly exinct before researchers in the 70s began collecting wild eggs to hatch at the San Diego Zoo Wild Animal Park and the Los Angeles Zoo, according to the California Department of Fish and Wildlife. By the 1980s, there were no California condors left in the wild but the conservation efforts paid off and biologists were able to reintruduce the birds into the wild by 1992. There are now more than 180 wild condors in California.
While the study was the first to examine the threat of HOCs to condors, their biggest threat remains lead poisoning, researchers said. Condors frequently ingest fragments from land animals shot with lead ammunition and California has added measures to create "non-lead" zones for hunting.