LANDING -- From basking sea lions to surfacing whales, no vacation to
the Central Coast is complete without a sighting of a marine mammal.
holiday snapshots are not the only pictures the charismatic ocean
dwellers have to offer. Scientists are increasingly finding ocean
mammals are valuable sources of information about
diseases and toxins
found in coastal waters.
The most recent research has focused on harbor seals, who live from birth to death just off shore.
view them as samplers for the environment," said Stephanie Hughes, a
recent graduate of the Moss Landing Marine Labs and marine scientist who
researches diseases in seals.
The seals, whose territory ranges
from Alaska to Mexico, live close to humans and eat many of the same
fish that people do, including sardines and salmon. They scoop up
sediment full of human contaminants when they swoop to the sea floor for
"Seals do similar things that we do, in the
same places. So if seals can get something, then people ask, 'Well, what
if I swim in the bay?'" said Denise Greig, a marine scientist who
studies chemical contamination in seals at Sausalito's Marine Mammal
In a recent study of water from San Francisco to Monterey
Bay, Greig and her colleagues found Monterey Bay seal blubber had high
levels of pesticides and other agricultural chemicals, while San
Francisco Bay seals were full of flame retardant chemicals and other
To better track the local trends, the Marine
Mammal Center plans to make "disease maps" for the California coast.
Scientists are using the past 10 years' worth of data about diseases in
stranded seals, sea lions and whales captured by mammal labs from San
Diego to Sausalito.
The center's scientists are looking at health
issues, including injury, illness and toxins from human contamination of
"The idea is to track trends and find hot spots, both
where and when. Then we can address why," said Frances Gulland, the
center's head veterinarian.
Gulland hopes the disease map will
serve as a model for similar projects around the world -- perhaps in New
England, where hundreds of harbor seals died of bird flu in 2012.
want to monitor so we don't reach that level of, 'Oh, jeez, we have
this disaster, where did it come from?'" Hughes said. "These animals are
sick, but we don't know why."
Another recent study highlighted how research on seal diseases can help protect the health of humans.
collaboration among Moss Landing Marine Labs, the Marine Mammal Center
and UC Davis tested 500 seals for Vibrio, a family of bacteria that
includes cholera and food poisoning bugs. Hughes, Greig and Gulland were
co-authors on the paper. They collected samples from seals from
California's North and Central Coasts in 2007, 2008, 2010 and 2011.
seals were infected with Vibrio, some with strains that could be
dangerous to humans. Depending on the type, said the U.S. Centers for
Disease Control and Prevention, the bacteria can cause anything from
mild food poisoning to sepsis and death -- though none of the seals had
the deadly strains.
A recent report by the CDC showed regulations
banning raw oysters fished from the Gulf of Mexico from April to October
every year has slowed Vibrio infections in humans. The regulations even
completely halted California cases of Vibrio vulnificus, the most
dangerous form of the bacteria, which recently killed people in Florida.
Vibrio study was "only four years. So it would be nice in the future to
be able to have more of a sample and say, 'Is this increasing over
time?'" said Sarah Peterson, a marine scientist at UC Santa Cruz's Long
Marine Lab. "Is there something that's changing in the environment to
cause it to be more prevalent?"
Marine scientists say it will take
more than one species to get a good picture of the coastal ecosystem.
Another marine mammal they would like to focus on is the sea otter,
which shares a similar place on the food chain as the harbor seal.
otters have been dying of everything from the drug-resistant staph
bacteria that are terrorizing hospitals, to toxoplasmosis, a parasitic
disease that makes it dangerous for pregnant women to change the litter
box. Sea lions, who swim much farther out than seals, will eventually
tell scientists about contamination in deeper water.
say as humans continue to adversely affect the seas through pollution
and global-warming emissions that raise sea levels, they need all the
help they can get.
"The environment is changing and we should be
aware of those changes," Hughes said. "Then, if something happens, we'll
have the data to know how we can mitigate it."
I've written three books about raising traditional breed poultry in small flocks, How to Raise Chickens, How to Raise Poultry, and The Field Guide to Backyard Chickens. I blog about poultry at http://poultrybookstore.blogspot.com. I'm interested in all animals and the wildlife of California's Central Coast enchants me.