Lower Levels of Pollutants Found in Fish
When researchers try to explain why a major new study hints at an improved coastal environment, they keep coming back to the fish.
Fewer fish appear diseased, according to researchers who worked on a new study released by the Environmental Protection Agency this week. Livers of certain other sea creatures showed sharp decreases in DDT and PCB concentrations. The pollution-intolerant brittle star has become more abundant in sediments that were once heavily tainted with pollution.
In Santa Monica Bay, one of the most seriously polluted stretches of coastal waters, the evidence from the fish and mud-dwelling creatures indicate a more resilient environment than researchers might have thought.
Overall, the new study suggests that coastal waters, from Point Conception to the Mexican border, are healthier than 10 or 20 years ago.
“You really have to ask the animals how the environment is faring. When we asked the animals, we found little evidence of current impact,” said Steven M. Bay, toxicologist for the Southern California Coastal Water Research Project, which coordinated the study by the EPA and 10 other agencies.
Creatures like the brittle star are considered to be “sentinels” of marine health in a region long known for its offshore DDT and other pollution, researchers said.
Problems persist, particularly with the bay, where researchers found that mud and sand offshore continue to show concentrations of DDT, PCBs, eight trace metals, organic carbon and nitrogen that are significantly higher than in other areas.
In fact, 49% of the bay’s sediments exceeded federal thresholds for contamination. By contrast, only 7% of sediments from other regions of the coast were similarly polluted.
Yet while sediment pollution was higher in Santa Monica Bay, the health of its biological resources--the fish and mud-dwelling animals that were tested--were similar to those in other areas.
That paradox could mean that low-level effects of pollution are going undetected or that marine creatures are simply adapting to life in a contaminated environment, said Stephen B. Weisberg, executive director of the coastal project.
Further research will be needed to determine which explanation is correct, Weisberg said.
The bay sediments found to be contaminated are on the ocean floor, with concentrations increasing in deeper water, researchers said. Beach-goers are not likely to come into contact with the tainted sand and mud.
Measurements of Santa Monica Bay’s water quality--dissolved oxygen and water clarity--were similar to those from other regions. The study did not include bacterial surveys, an issue that greatly concerns swimmers and surfers. Such surveys are planned this year.
The pesticide DDT was found in 82% of coastal sediments, making it the most widespread pollutant. The highest DDT concentrations were on the Palos Verdes shelf, long known as a serious “hot spot” because of flows from a major pesticide plant near Torrance.
DDT was banned in the United States in 1972, but it degrades extremely slowly.
“That’s generally where we found the highest [DDT] levels in sediments and highest levels in fish,” Bay said.
Scientists have paid increased attention to contaminated sediment in recent years because it can poison marine life and taint fish and mussels consumed by people.
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Until further research is done, some environmentalists warn against overly optimistic conclusions based on the new findings.
“My initial impression is that no one should be surprised that the waters are cleaner than they were 20 years ago. That’s good, but it merely demonstrates the [1972] Clean Water Act is working,” said attorney David Beckman, head of the coastal water quality program at the Natural Resources Defense Council in Los Angeles.
Janet Hashimoto, chief of the monitoring and assessment office at EPA’s regional water division, found in the study a mix of encouraging news and continuing problems.
For instance, the study found a 95% decrease in DDT and PCB concentrations in the livers of certain test fish, but it also found that the chemicals were found in nearly all the tested fish livers from certain species.
The reduction in the concentration of pollutants could be a result of natural processes such as less pesticide in the food chain as DDT spreads and its concentration drops, some experts said.
“The bad news is that it’s still fairly prevalent,” said Hashimoto.
The new report is the largest environmental study ever conducted along the region’s coast, federal and state officials say. It relies on data collected in 1994 and refined and analyzed in years since.
Government regulators and environmentalists alike hailed the cooperative effort, noting that less than 5% of the region’s coast is routinely monitored, and that some areas were tested for the first time.
The study stands out from earlier efforts because it looked at areas away from known pollution sources such as sewer outfalls and then analyzed the findings regionally, officials said.
“To be quite candid, the findings were less important than that the study occurred,” said Mark Gold, executive director of the environmental group Heal the Bay, who praised the regionwide monitoring approach. “We’re ecstatic that this sort of work is being done.”
Some findings from the report are now available on the Internet at https://www.sccwrp.org
