The Harbinger Seals of San Francisco Bay

What will it mean if Harbinger seals disappear from the bay?

It’s damn cold in the foggy gray pre-dawn at the Richmond Bridge. Two women — Palma Formica and Christin Khan — are stamping their feet and rubbing their palms at the toll bridge plaza. In a cramped upstairs room hidden behind rows of old street lamps, a pile of spare parts, and scattered Caltrans gear, they suit up in orange vests and harnesses with heavy metal D-rings on the back, then drive to an access point on the bridge’s lower level. The pale green waters of the north bay fade into the silvery fog as Formica lowers their gear — camera, tripod, binoculars, logbooks, and lunch — to Khan, who stands on a platform just below the lower deck. It takes sure footing to clamber down the exterior ladder to a platform that hangs under the road face and then to squeeze first over and then under a series of bracing beams to reach the viewing platform on the opposite side of the bridge. “But this is nothing,” says Khan. “Last year in February, there was a week of nothing but rain. I would go home, turn on the heat full blast, take a hot shower, put on my robe, and drink hot tea, and I would still be cold.”

Khan and Formica reach the platform and immediately train their binoculars nearly straight down, where, about 50 meters away, a dozen plump harbor seals are perched on the tips of barely-exposed rocks in the bay just south of the bridge piers. “Remember, they can see us, so keep a low profile,” Khan warns. By mid-morning low tide, nearly 80 seals have hauled themselves out onto a string of mini-islands, known as Castro Rocks.

The seals aren’t the only action in the water: Three large barges maneuver into place at the base of the bridge’s piers, bringing construction workers and equipment as part of a massive project to retrofit the bridge for seismic safety. One worker dons a wetsuit and tank and lowers himself into the water to work at the base of the pier. A loud horn sounds, causing many of the highly sensitive seals to raise their heads in alarm.

Not long after low tide, with 59 seals still sunning themselves during this vital rest period before heading back into the chilly waters of the bay, a small yellow rowboat emerges from the south. It’s headed right for rock “F” — the farthest outcropping from the busy bridge, and thus the most popular spot for seals. From up on the bridge, the four rowers are tiny, antlike — but through binoculars they can be seen pointing toward the mossy green, seal-studded rock. With steady strokes they pass into a boat exclusion zone marked out by orange buoys. An anxious seal thrashes off her perch into the water, and a dozen others jerk their heads up — and then follow suit. By the time the sightseeing passengers have had their fill, 44 of the resting animals have slid off the rock, swimming into deeper water to find safety.

Khan and Formica exchange exasperated — and worried — looks. “With this rising tide, those seals are not coming back,” says Khan. “Most are going to give up, and that’s cutting their rest period short.” Formica scans the boat’s hull for a license number, but to no avail. “It’s illegal to do that,” she explains. “But there’s very little enforcement anyway. If we can see the boat license we can report it, but probably they’ll just get a phone call or a letter saying, ‘You shouldn’t have done that.'”

Khan and Formica, graduate students in marine biology at San Francisco State University, are part of the Richmond Bridge Harbor Seal Survey. A collaboration between Caltrans and SF State, the survey is overseen by the National Marine Fisheries Service in an effort to monitor — and, where possible, diminish — the effects of the bridge retrofit on the resident population of harbor seals who use Castro Rocks throughout the year. Harbor seals have been protected under federal law ever since the National Marine Mammal Act of 1972, and their numbers along most parts of the California coast have largely rebounded. But that’s not true in the heavily urbanized San Francisco Bay, where shoreline development has chased the seals from the quiet, secluded haul-out sites they favor. Researchers expect that the pile-driving, drilling, and just plain old hammering involved in retrofitting the Richmond Bridge is bound to scare away many, if not most, of the seals from yet another of the few remaining sites in the bay.

Given the pressing need to shore up the bridge, there’s little that can be done to prevent the damage to the seals’ well-being, aside from minor suggestions for changes in construction approaches. So wildlife experts are using the opportunity to record scientific data on aquatic mammal behavior and health before and during a major disturbance. What they’re finding is that the bay could lose its only year-round population of marine mammals. And that’s a double threat: There’s not only the risk of havoc in the ecosystem when a top predator goes missing, but there’s a host of implications for the beleaguered health of the bay. If it’s not safe for seals, how safe is it for the rest of us?

The Richmond Bridge is a two-tiered cantilever and truss structure with 143 spans covering just over four miles of bay between Richmond and San Quentin. When the $66 million bridge was completed in 1956, it was one of the largest bridges in the world; it currently hosts an average of 60,000 commute trips each day. Although the bridge has withstood a number of boat collisions — including, on a single day, a World War II vintage warship and a Navy radar ship — it is nearing the end of its current design life. In a construction project costing about $500 million, all sections of the bridge will be strengthened with seismic retrofit. The bridge’s concrete trestle will be completely replaced; thirteen-foot-diameter piles will be driven into pier foundations below the water line; and all of the bridge’s rivets and most of its steel superstructure will be replaced with stronger components. “We have work on every pier, on every piece of steel,” says Caltrans senior environmental planner Chuck Morton. “It’s the largest construction contract that Caltrans has ever let.”

Adds Morton, “At Caltrans, one of our large roles is being a steward of the environment; we don’t want our projects to affect the environment — or if they do, in the least amount possible.” The agency is spending an unprecedented $2 million on the harbor seals survey — an unusually large sum for a biological assessment, allocated under pressure from environmental groups such as the Earth Island Institute, Baykeeper, the Bay Chapter of the Sierra Club, and the Conservation Law Project, which threatened legal action when Caltrans originally proposed only limited mitigation measures for the seals. When Caltrans’ original Environmental Impact Report speculated that the seals were “likely to acclimate to construction activity” and would probably return after the retrofit, environmentalists successfully pointed out that only a thorough, ongoing monitoring of the site during and after construction would be able to track seal response one way or the other.

Previous studies had already demonstrated that the stakes are high. “Since 1976, four years after the marine mammal protection act, populations on the coast have grown fourfold,” says Sarah Allen, a science adviser at Point Reyes National Seashore and one of the Bay Area’s resident experts on harbor seals. “But in the bay, it’s flattened out.” While some seals will travel extensively throughout the bay and along the central California coast from year to year, a core group of seals have always been permanent year-round residents of San Francisco Bay. In the early ’90s, Professor Jim Harvey of Moss Landing Marine Labs worked with harbor seal researcher Dianne Kopec on early studies of seals in the bay. “That work gave us an indication that things were not all great with harbor seals in San Francisco Bay,” he says. “If you look at the counts of harbor seals in the bay over the last fifteen years, there hasn’t been much of a change — but on the coast, numbers have grown six percent per year over the last twenty years. So clearly there’s something wrong there.”

The loss of seal haul-out sites to rapid shoreline development is widely posited as a key factor. Unlike their brassier cousins, sea lions (which you’re likely to see at Pier 39), harbor seals are shy and skittish on land. They need a quiet, sheltered place to rest during each tidal cycle and reoxygenate their blood. “If they don’t spend as much time resting on shore, then they’re not as healthy as animals that can,” says Harvey. “And if females aren’t as healthy, they may not have pups some years, and the population will have a reduced number of pups. Or you might see pup mortality.”

Researchers note that seals are highly individualized, and while some may have a high tolerance for nearby human activity, others simply won’t approach a site if they’ve been scared off it too many times before. Strawberry Spit, once a popular destination for seals in the north bay’s Richardson Bay, was abandoned after homes were built nearby and residents began walking their dogs within view of the seals. Now, even after one project aimed to entice the seals back to the site, none have returned. “There was one woman who let her dog run loose,” remembers Allen. “If they’re harassed day after day by that sort of thing, they might shift somewhere else temporarily, and try to come back, but eventually they give up. If you were woken up every night, night after night, what would you do?”

Humans also interfere directly with seals, thinking they are rescuing abandoned babies who in reality have been carefully stationed by mother seals who have gone out to hunt. “They’re about two feet long, they’re white and furry, and they sound like they’re saying ‘Ma, Ma,'” explains Sarah Bockhorst of Sausalito’s Marine Mammal Center. “But 25 percent of all pups brought here are illegal pick-ups.” Mother seals seem to remember the exact beach where they’ve left their young, and may listen for the individual cry of the pup when they return. “San Francisco Bay is a sub-optimal environment for seals,” says Harvey. “These animals are inhabiting a highly modified environment. Humans have changed it pretty dramatically, and made it difficult for them to live in it.”

Today, Castro Rocks is one of only three haul-out sites in the bay that hosts more than forty animals during breeding and molting seasons; when baby seals are born in the spring, as many as 200 seals — out of a total bay population of 400 to 500 — use the area as home base. The string of six outcroppings is inaccessible by land, and seals have accustomed themselves to the huge container ships that slip by in the shipping channel nearby, but even here seals are not immune to frights. “We’ve had people on jet skis come by,” says Debbie Green of the Richmond Bridge Harbor Seals Survey. “People know the seals are here, so they come to see the animals. But a lot of people don’t realize that if you do change their behavior, you’re in violation of the Marine Mammal Act.”

Environmentalists point to Red Rock, a dome-shaped island just west of the Castro Rocks, as a potential sign of things to come. Seals no longer use Red Rock, despite its relatively sizable beach. (Adventurers who have come to climb the red dome may have long since driven the mammals away.) Red Rock is privately owned — and up for sale. Real estate agent Rosemarie Delson of San Jose listed the island — at $10 million — early this year, hoping to lure a heady dot-commer eager to build a trophy castle on the only bit of land still up for grabs in San Francisco Bay. “It strikes me as nuts,” says Golden Gate Audubon Society Executive Director Arthur Feinstein. “Water birds use it extensively now, and it’s a great opportunity to provide habitat that’s not disturbed by people. But if it’s developed, that stops.” Audubon has joined with the California Department of Fish and Game in a plan to buy the island (at much less than asking price) hoping to use money from the Cape Mohican oil spill settlement — but, says the department’s Paul Kelly, “The whole thing hinges on the seller’s willingness to arrive at an equitable price.”

Aas the Richmond Bridge retrofit project drew nearer, the National Marine Fisheries Service sided with environmentalists and issued a revised permit that requires Caltrans to fund the comprehensive harbor seal survey, and also set up construction guidelines: no work on the piers nearest Castro Rocks during the pupping and molting season (from February to August), and no boats in the exclusion zone now marked out by buoys. “We worked out ways they could still do their work and yet allow seals to not be disturbed during critical times of the year,” says NMFS fisheries biologist Christina Fahy. “It’s part of the Marine Mammal Protection Act to allow for harassment of marine animals so long as they get a permit, but when we issue that permit, we require mitigation, monitoring, and reporting — that’s why people want to get away without having to get a permit. But if we know there’s going to be harassment, we at least try to get more information out of it, so that when it comes up again, we’ll know more, and they’ll know more.”

The resulting harbor seal survey combines direct, five-times-a-week observation of seals and disturbances viewed from the platform under the bridge with videotape data, noise recordings from both above and below water level, and monitoring of the bay’s two other main haul-out sites. A set of seals from Castro Rocks has been tagged for tracking. Data from all these observations will be combined and cross-referenced to help answer a host of questions: What kind of construction noises consistently cause seals to panic? Over time, do the seals get accustomed to those noises? If seal counts go down at Castro Rocks, are they going up at other sites around the bay — or are seals leaving the bay altogether?

Aa major delay in construction has turned out to be an boon for researchers. “When we first started, we expected to go to construction in late 1998,” explains Morton. “But due to engineering changes and other delays, construction didn’t begin until January of this year. So we had three years of baseline data. Normally when scientists get called in, it’s, ‘Well, we’re going to start construction tomorrow, could you give us baseline data now?’ So the fact that we have almost three total years of baseline data is very unusual.”

“Usually what happens is, they do construction and then afterwards realize the wildlife has been affected, and send someone in to fix it,” says Debbie Green, the survey’s project manager. “This is a more proactive approach.” Green, along with field coordinator Emma Grigg, had recently finished a master’s thesis at SF State when she was offered the opportunity to head up this project. Working under two key Bay Area marine mammal experts — Professor Hal Markowitz at SF State and Sarah Allen of Point Reyes National Seashore — Green and Grigg coordinate a bevy of graduate students who helped collect field data and mapped out a pattern of “normal” seal behavior at the rocks. “The most important thing is to find out how many seals are using the haul-out site,” says Grigg. “We have a lot of data for that, and we’ve now got an idea of how many animals are using the site at various times of the year, and enough data to take weather and tides into account.”

Researchers have determined that the Castro Rocks seals are already a little abnormal — unlike seals at other popular haul-out sites, Castro Rock seals crowd their site at night. Observations at other bayfront sites had already suggested that seals at disturbed sites will switch to nighttime haul-outs before abandoning the site altogether; if ambient traffic noise from the bridge makes Castro Rocks less appealing to seals during the day, their food intake could already be compromised.

The construction delay at the Richmond Bridge also allowed researchers to conduct baseline studies on seal movements around the bay. In January, the survey team — assisted by Moss Landing’s Harvey and the Marine Mammal Center’s lead veterinarian, Frances Gulland — set out to capture seals as they left the rocks. Normally, capturing marine mammals means dragging a net between two boats that approach the haul-out quickly, causing a flush into the nets. But the many rocks and shallows around Castro Rocks meant that seals could be seriously hurt with this method, so instead nets were strung between rocks and left in place until the next high tide, when seals floating off their perches unwittingly swam into them. “We preferred this method anyway because it’s less aggressive,” says Grigg, “but it’s tricky. They wise up pretty quickly.” All the seals caught in the nets were fitted with bright green, numbered flipper tags so that they can be easily identified when they show up at a haul-out like Castro Rocks; some also had radio or satellite transmitters and antennas glued to the fur on their heads or their sides. (These more expensive tags often fall off or stop transmitting, and they are shed in late summer during the molting season.)

The pilot tracking projects last winter found a marked consistency on the part of the seals that were tagged. They hauled out on Castro Rocks every day and foraged in the deep shipping channel that runs past the rocks and into the north bay. “They feed nearby, so if we do this major retrofit, how will it impact their feeding?” wonders Grigg. “Will it push them to overlap with one another?”

Researchers admit that the data they’ve compiled from tracking these animals involves such a small set that it’s hardly conclusive. Now that a new group of animals has been tagged, graduate student Barry Nicols, who specializes in tracking the seals tagged at Castro Rocks, may find new complications.

To experience the daily life of a seal, Nicols heads out into the bay in an open nineteen-foot craft skippered by a fellow student. He mans a radio receiver, tuning to one of two radio frequencies — corresponding to the two transmitters currently on seals — and rotating in 360º circles to listen for an initial reading. When, on a bright September day, he picks up a signal from a female seal heading for the deep water between Angel Island and the Bay Bridge — right into the strong ocean winds blowing through the Golden Gate — he’s surprised. “Generally what we’ve found is they’re specific to certain areas,” he says. “But at this time of year they tend to move a lot more. The male tends to move a lot more than the female, too — this is the most we’ve seen the female move.”

Nicols uses a handheld global positioning device to record the position of the seal each time it bobs to the surface. After a few hours, during which the seal comes up for air for about twenty to forty seconds between dives lasting up to five minutes, the GPS read-outs show that it’s moving in circles. “We can infer that it’s foraging now,” Nicols explains. After about six hours, the seal heads to a cove at Angel Island to rest by “bottling” — floating vertically in the water with its head in the air — rather than hauling out, which it’s likely to wait for a return to Castro Rocks to do. Here in the cove, protected from the winds and far from human traffic, several seals share the calm with a blue heron or two. None of the other animals seem to notice that one seal has an odd-looking contraption (the antenna) sticking up from the top of its head — nor that it’s the intense subject of scrutiny by the researchers in the boat moored a distance away.

Another graduate student thesis project engendered by the Richmond Bridge Harbor Seal Survey is that of Amy Bohorquez, who is monitoring pupping levels in the bay. Researchers have found that the population of bay seals as a whole has not risen, but the reasons why are unclear. Are fewer pups being born? Are more pups choosing to migrate far from their birth site? Are more pups dying before they reach maturity? “I started my pupping study the year after El Niño, so I expected that a decrease in food during the storm year might affect pupping,” Bohorquez explains. But there are other mysteries.

One of Bohorquez’s most striking findings was a pattern that correlated with the color of seals’ fur. Some seals have a condition known as “red coat,” which researchers suspect is a result of metal pollutants in the water. Harvey explains: “Our hypothesis is that the animals may be carrying some sort of pollutant, like selenium, that’s affecting their hair shafts, and that degrades the hair shafts, causing brittleness, and that allows iron oxides to attach.” The bay is known to be chock-full of metal pollutants from mining and other industries, and red coat shows up in higher incidents — up to forty percent more — in bay seals than in seal populations elsewhere. “Red-coated animals were another indication that something is amiss,” Harvey says.

Interestingly, Bohorquez found that red-coat animals actually pupped sooner — an indication of better health. “Iron oxide ends up in a lot of fertilizers which end up in the bay,” she says, “so there would be more nutrients in those areas. It might be that these seals pupped earlier because they were foraging somewhere more nutrient-rich, but the sacrifice for that is the iron oxide that is adhering to the hair shaft. Plus, the number of red coats has gone up, so either more are eating in those areas, or those areas have expanded.” Fertilizer runoff isn’t the only factor that could be affecting seals’ health. The San Francisco Estuary Institute, which measures toxics levels in the bay, has found high levels of mercury, dioxin, the pesticide DDT, and the industrial chemical PCB — all known to wreak environmental and biological havoc. Federal laws banning some toxics have slowed down contamination rates, but toxics stick around — they lodge in animals’ fat reserves and build up there, especially in animals high on the food chain. “The trends for pesticides are for slow decline,” says the Estuary Institute’s Jay Davis. “But PCBs are declining more slowly, and mercury is probably not changing much at all.”

Iit’s hardly a surprise, then, that, during her six years of research in the bay, Dianne Kopec found “wicked high levels of PCBs in the seals — levels that were comparable to those known to cause both reduced reproduction and immune suppression.” And in the early ’90s, there was good reason to worry about the immuno-suppressant effect of contaminates. “In 1987 there was a huge chemical spill on the Rhine River in Europe,” Kopec explains. “There was a huge fire, and the firemen flushed all the chemicals into the river. It almost killed all the life in the river, and that added to existing contaminate levels on the coast. The following year, there was a big die-off of seals in the ocean off Northern Europe. Whether the Rhine fire was related to the die-off is uncertain, but it was the summer after it happened.”

That summer, hundreds of carcasses of dead seals piled up along the shores of the North Sea. By the fall, 20,000 seals — more than half the area’s population — had died. Researchers identified a new distemper virus as the cause, but they also found particularly high levels of PCBs in the dead animals — while seals in less polluted waters were found to have survived the same virus. Data from other mysterious marine mammal epidemics was added to the mix — including the deaths of nearly half of all bottlenose dolphins living along the eastern coast of the US. Again, the animals were found to be carrying high amounts of PCBs, and researchers began to suspect that the chemicals had so impaired the animals’ immune functions that they were highly vulnerable to diseases they would otherwise have easily shrugged off.

More direct evidence of the disastrous effect of PCBs came from researchers in Holland who captured seal pups off the relatively clean Scottish coast and then fed half of them a diet of fish from the heavily contaminated Baltic Sea, while the other half feasted on cleaner Atlantic fish. Sure enough, the unlucky seals eating the Baltic herring — the same fish that shows up in commercial fish markets for human intake — had ten times more PCBs, and their immune systems were drastically curtailed: The contaminated seals had 25 percent fewer “killer” cells to fend off viruses, and 35 percent fewer white blood cells to fight infections and order the creation of antibodies.

Kopec worries that die-offs like those that struck Europe could happen here. “If the seals here in the bay are exposed to a similar virus, they may not be able to fight off the disease,” she says. “In that case it could be lethal.”

Nothing of that scale has happened yet (“How much of that is luck?” Kopec asks), but in 1997 Allen, observing seals at Point Reyes, saw a die-off of over 100 animals. In 2000, a similar mass mortality showed up on a smaller scale — 25 animals washed up dead. Allen identified a naturally occurring virus that had never been found in the seals before as the cause of death — but whether increased contaminate loads in the seals’ immune system made them more vulnerable to the new virus is not known.

A parallel set of warning bells went off at the Marine Mammal Center in 1998, when 90 percent of the hospitals’ harbor seal patients died. More than half succumbed to herpes — a virus that seals can normally fend off without a problem. “Stress — from factors like improper temperatures or poor nutrients — plays an important role in the manifestation of disease,” explains Marty Haulena, staff veterinarian at the MMC. “We found that the seals who died from the herpes outbreak had higher levels of hormones indicative of stress than those who survived.” The hospital embarked on an ambitious renovation program that improved the water quality and temperature controls in harbor seal pens and also minimized disturbances for the animals. Since then, the center has dramatically reversed the situation, seeing very few seal deaths from herpes in the past two years, but Haulena points out that the same kind of stressors could weaken animals in the wild. “As of yet, there’s no evidence to show that bay seals have a problem with herpes,” he says. “But there is the potential that factors which may interfere with immune response could allow herpes to cause clinical disease that it normally wouldn’t.”

Wwe may soon know more about the link between contamination and seals’ ability to fight off disease. When Green, Grigg, and their Richmond Bridge Harbor Seal Survey crew capture seals for tagging, they also collect blood and tissue samples. Blood samples are being used by Jennifer Neale, a graduate student researcher at UC Davis, in a project that tests cells’ responses to contaminates. First, Neale compares the level of chemicals such as PCB and DDE (a DDT by-product) in seals from the central California coast (including the bay) to those of seals in Alaska. “Seals have a hard time metabolizing and eliminating such compounds, so over a long lifetime a seal accumulates high concentrations,” she says. Preliminary results show that the California seals have very high loads, while Alaskan seals have generally low levels — although DDE is high even in the Alaska population. “It’s especially a problem for an animal that lives a long time and lactates,” she says. “A lot of these chemicals are stored in fat, and milk has a lot of fat. I’ve found that pups have the highest loads, while mature females have the lowest, because they’ve been dumping it all through lactation.” And pups have immature immune systems — which means they’re getting high exposure to toxics right when they’re most vulnerable to disease anyway.

Next, Neale studies what happens to immune-system cells collected from the seals when those cells are doused with chemical toxics. In the lab, Neale says she’s beginning to see that exposure to some toxics may impede a cell’s ability to replicate or to communicate vital disease-fighting messages to other cells.

“Any major insult to the immune system is going to affect the seal,” Neale says. “There’s a long pathway from the cell getting exposed to the chemical directly, and seals that are chronically exposed to marine pollutants. But if we can put this together with long-term field monitoring, then the harbor seal could serve as a model for the relationship between contaminates and the immune system.”

“Seals are a sentinel species,” says Kopec. “Within the bay they’re at the top of the food web. And while we may have the option, unlike seals, of going to the store and buying alternative food sources, unless we’re able to maintain a healthy ecosystem we’re not going to be able to maintain the health of the bay itself.” The idea that the health of the bay seals is a figurative canary in the mineshaft of the bay itself is gaining ground; the San Francisco Estuary Institute, which works with regional water boards to determine the safety of seafood from the bay, hopes to begin sampling seals next year in addition to fish. “Seals would be a really good indicator for important contaminates that accumulate in food webs,” says the institute’s Davis. “They’re a good match because marine mammals are physiologically similar to humans. [We advise] people not to eat more than two fish meals from the bay each month — well, seals eat 100 meals a month from the bay. They’re constantly eating fish, so they’re very highly exposed; they accumulate really high concentrations.”

Advocates for low-income communities point out that some humans may not be all that much better off than seals when it comes to the negative effects of bay pollution. Communities for a Better Environment works with the independent fishermen who have long relied on sustenance fishing to help keep food on the table. “My parents live in Parchester Village,” says Ethel Dodson, “and the bay is in their backyard. My brothers used to cross the railroad tracks and bring back fish from the bay, and they’re still doing it. But the people who do that, they’re all sick — they have lupus, cancer, brain tumors; my father can’t walk, and my mother is almost blind. I tell them it’s not safe, but food prices are so high in the stores, and they can just go out to the bay and get it for free.”

“Our members who fish the bay for food and are really sick have been demanding for years that they be tested for the effects of pollution from the fish they eat, and their reaction to reports of [the work being done to test seals] was somewhere between despair and hilarity,” says Greg Karras, senior scientist at CBE. “Thousands of people fish the bay regularly, and most are low-income people of color. The bay shoreline is part of their community. They fish where they live, and they stay out late at night fishing if they don’t get enough food to put on the table.”

Kkarras’ group responded recently to reports of yet another pollutant that could be threatening marine life and humans alike. Polybromated Diphenylethers (PBDEs) are flame-retardant additives used widely in plastics, foams, and textiles, and can make up as much as thirty percent of electronic equipment, furniture, and children’s clothing. They’re chemically similar to PCBs, and more and more research is showing they have similar levels of toxicity — in other words, it’s likely they suppress immune functions and bio-accumulate, sticking around in the environment and intensifying up the food chain.

But while many countries in Europe are moving to ban the use of PBDEs, little action is being taken in the US. In fact, samples from bay seals collected by Kopec back in the ’90s were used in one of the few American studies of PBDEs. Using $20,000 in funding from the state water resources board, and working in collaboration with Myrto Petreas, who heads dioxin research at the Berkeley hazardous materials lab of the California Environmental Protection Agency, Kopec scanned tissues from eleven seals. “PBDEs were found to be doubling every 1.6 years,” she says, “and that was for samples taken from 1989 to 1998.” Who knows how high those levels have gone now? At the same time, human breast milk samples were studied at Stanford University, and PBDEs were detected in levels far exceeding even the high rates recorded in Sweden, where an exponentially increasing toxic level in milk led the Swedish EPA to ban the chemical outright.

“We knew it was happening in Europe, and we knew there was no reason to suspect it wasn’t happening here,” complains Karras. “But there is no US policy even restricting PBDEs. It’s like we’ve turned the clock backwards and are doing the PCB disaster all over again.”

In the meantime, much of the Richmond Bridge Harbor Seal Survey is focused on merely trying to minimize the effects of this specific retrofit project. The prohibition against working near the rocks during the sensitive pupping and molting seasons came to an end on August 1 — and the most potentially disruptive period of construction started rolling. “The other day, there was a dredging crane, basically in the middle of the haul-out area, so we saw a big flush of seals leaving,” says Green. “Now the interesting part begins.” Researchers are especially worried what the effect may be if Caltrans starts work at night, since nighttime sees the highest counts of seals on the rocks, enjoying the few hours of relative calm.

“Our main role is to observe and report,” says Grigg. “Caltrans is usually very cooperative, but there’s only so much you can do without calling work to a halt.” Adds Green, “There’s no way we want construction to stop — it has to happen, God knows we all want a safe bridge.”

So far, Grigg and Green have won one significant concession from Caltrans: All construction boats are now asked to approach the bridge support piers from north of the bridge, to avoid sweeping past Castro Rocks on the south side. “We talked to the Caltrans construction people, who in turn talked to the contractors and said, ‘You’ve got your little boats getting too close to the rocks. Could you not get so close?'” says Morton. “And that’s been done. But some of the other things the contractor is doing they just can’t do differently. There’s a limit to how they can change their operations.”

Field notes from project participants are already indicating the impact construction is already beginning to have on the seals. The most noticeable change during the day is that seals rarely, if ever, choose to haul out by day on the large sandy island closest to the bridge, where construction noise and action are intense.

Iit’s hard to draw any conclusions at this point, but Grigg says a rough early estimate indicates a downward trend in the number of seals on the rocks near the bridge. “It’s still very early to say — but the mean counts are down by about twenty to forty seals, out of the 150 to 170 who are normally there. And the number of disturbances during the day are way up. Normally, this is a moderately disturbed site, but this is a whole new ballgame.”

Caltrans’ Morton exalts at a recent report showing over one hundred seals still on the rocks, but Grigg questions if this is a true indicator of individual seals’ response to the added commotion. “Seals differ a lot individually, so while we may still have seals hauling out, it may be limited to the more tolerant ones.”

“Harbor seals are incredibly adaptive, but there are thresholds,” says Allen. “The question is, what are the thresholds beyond which they will no longer tolerate the disturbance?” Once those thresholds are breached, the seals will flee Castro Rocks. And while they may settle somewhere else in the bay, it’s entirely conceivable that other haul-out sites are already used at maximum comfort levels for seals — especially during pupping season. In the worst-case scenario, Castro Rocks seals would leave the bay. And if any future development scares the seals off their two other major haul-out sites at Mowry Slough and Yerba Buena Island, we would face the loss of our only year-round marine mammal neighbors — and potential ecosystem collapse. “Seals prey on fish,” says Allen. “In fact, they presently eat a lot of the exotic fish that make it to the bay — like yellow gobi. If the seals aren’t here to eat them, those introduced species might depress the native species of the bay. Or maybe the seals are a sink for certain pollutants, which would otherwise show up elsewhere. And there could be a ripple effect: That fish species the seals eat now may have a big population explosion, and that in turn could affect something that lives in the mud.

“It’s like a hanging mobile: If you dislodge one part, do the other arms go out of sync?”

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