[Water_news] 4. DWR'S CALIFORNIA WATER NEWS: WATER QUALITY -10/19/07

Harbor seals may help determine effect on humans of eating toxic fish

San Francisco Chronicle – 10/19/07

Jane Kay, staff writer

 

Harbor seals in San Francisco Bay are so contaminated with chemicals such as flame retardants and the pesticide DDT that scientists are studying whether the pollutants hurt the pups' chances of survival, data that can add to knowledge about the contaminants' effects on humans.

 

About 500 harbor seals that rest on the bay's beaches eat the same kinds of fish caught by local anglers, and the seals live in waters shared by swimmers, surfers and kayakers. What happens to these marine mammals could offer clues as to how pollution from sewage and dirty rain runoff can affect other mammals, including sea lions, otters and even people, scientists say.

 

The study, financed in part by a $100,000 grant from the National Oceanic and Atmospheric Administration, focuses on the offspring of harbor seals that rest on Castro Rocks near the Richmond-San Rafael Bridge in view of ferryboat traffic and the Chevron refinery.

 

Thirty-five pups are swimming around the bay and coastline with 11/2-inch-high, triangular, orange or yellow plastic tags glued to their heads. To help gather data about the animals in the wild, people are asked to report any sightings to the Marine Mammal Center in Sausalito.

 

San Francisco Bay seals are born with chemicals in their bodies, which they get from their mothers eating contaminated fish. Studies begun decades ago show that now-banned chemicals such as the insecticide DDT and PCBs, once used in electrical transformers, linger in the estuary. The chemicals can transfer from a mother's body across the placenta and into the baby seal's blubber. Just as in humans, the chemical levels increase when the babies nurse and as they grow to adulthood.

Studies in West Coast estuaries have found mercury in harbor seals because they eat fish contaminated by leaking mines, atmospheric pollution and discharges from sewage plants. Levels of PBDEs - the flame retardants used in soft foam furniture and carpets - have been rising in harbor seals and other organisms over the past decade.

 

In a new development, PFOS and PFOA - compounds shed from Teflon-like coatings in cookware and fabric guards - are turning up in the animals. Some manufacturers have stopped using the compounds, but they remain in the bay.

 

Harbor seals are good indicators of how contaminated food can contribute to the chemical buildup in animals and how mammals process pollutants in their bodies. The new study is striving to find out if the chemicals are affecting the seals' health and survival, said study leader and Marine Mammal Center biologist Denise Greig.

"It's possible that contaminants increase the seals' chances of contracting and succumbing to disease," Greig said. "Anyone who is eating fish from the bay is eating the same food that these seals eat."

 

The study will analyze the seals' blood for a range of pathogens, including toxoplasma, a protozoan, and the bacteria salmonella. Humans are also susceptible to the pathogens after exposure to polluted water, Greig said.

 

Harbor seals weigh around 150 pounds and are much smaller than California sea lions. In the spring, they give birth to 30-pound pups on one of eight haul-out sites: Castro Rocks, Yerba Buena Island, Corte Madera Marsh, Point Bonita at the mouth of the bay and four areas within the boundaries of the San Francisco Bay National Wildlife Refuge - Mowry and Newark sloughs, Coyote Slough at Alviso and Bair Island. Haul-out sites are spots used by the seals to lounge and give birth.

The seals feed on sole, flounder, hake, cod, herring, sardines, surfperch, sculpin, squid, salmon, rockfish, jacksmelt and anchovies.

 

In April at Castro Rocks, the study team led by Greig captured seven weaned pups and took samples of their blood to check for contaminants and signs of disease. The researchers glued to the heads of the pups bright yellow or orange "hat tags," each marked by a large number that can be seen from hundreds of feet away with binoculars. The other 28 seal pups in the study so far were tagged when they were brought to the Marine Mammal Center after they were separated from their mothers.

The tags, which the scientists insist don't influence the animals' social life, will stick on the fur until the seals molt next April when they're a year old.

 

Collaborating on the new study are two scientists who have studied the seals for more than three decades: Jim Harvey, a professor of vertebrate zoology at the Moss Landing Marine Laboratories, and Sarah Allen, a biologist at Point Reyes National Seashore.

 

"The work we've done implies that animals have high enough levels that make us suspect they are impacting the immune and neurological systems. But in the United States, very few people have done the experiments that would definitely tell us the effects," Harvey said.

 

Scientists at UC Davis and the California Department of Toxic Substances Control worked on other seal studies, confirming chemical levels that raise questions over what health effects they have on the animals. Elsewhere in the world, high exposure to PCBs have been linked to damaged immune systems, lower birthrates and central nervous system disorders in marine mammals.

 

Harvey and Greig want to expand the study to implant some radio transmitters beneath the skin so they can monitor them for four to five years. If they obtained funding, they could learn about the seals' survival into adulthood.

 

The California Legislature banned two forms of PBDEs partly on the basis of harbor seal tests in San Francisco Bay in 2002 showing that levels in the seals had increased by 100 times in 10 years.

 

There are about 43,000 harbor seals along the California coast. The bay's population has remained about the same, leading some scientists to wonder why the population doesn't rise. Others say it's surprising that numbers haven't fallen given the rise in boat traffic, loss of habitat and bay pollution.

 

Out on the bay Thursday was Norton Bell, a Palo Alto resident who has volunteered at the wildlife refuge for 13 years, in the last eight years observing seals. He carries a cell phone and watches for any illegal activity that could harm the seals.

 

Boats must steer clear of the seals, and people are prohibited from getting out of boats near the haul-out areas. Seals frighten easily. When they jump into the water, they risk injuring pups or getting separated from them during nursing. They also use up needed energy, scientists say.

 

"Sometimes airplanes fly below the height limits. Commercial and recreational fishermen get too close to the seals. I've seen jet skiers disturb the seals. People come out and do target practice and disturb the seals," Bell said.#

http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/10/19/MN11SRS7D.DTL