It's been a struggle for the furry, button-nosed critter to make
a comeback since being hunted nearly to extinction along
They get chomped by great white sharks. They must scrounge in
overexploited waters to find enough shellfish to eat. Their immune
systems are weakened by polluted runoff and under attack by
parasites that wash into coastal waters from the feces of domestic
cats and opossums.
Now it turns out that some of these playful marine mammals are
also being poisoned by an ancient microbe ---- a type of
cyanobacteria ---- that appears to be on an upsurge in warmer,
polluted waters around the world.
The discovery was made by Melissa Miller, a state wildlife
veterinarian and scientific sleuth investigating the multitude of
things killing otters faster than they can reproduce. The southern
sea otter population has dropped for two years in a row, the U.S.
Geological Survey announced last month. An estimated 2,711 otters
remain in central and southern California waters.
The first clues came when nearly a dozen otters mysteriously
died in Monterey Bay in 2007. Their carcasses were taken to the
California Department of Fish and Game laboratory in Santa Cruz,
where Miller and others do postmortem analyses.
"I started getting otters that were clearly jaundiced, with
bright yellow gums and yellow in the whites of their eyes," Miller
Performing necropsies, she found swollen livers that fell apart
in her hands. She initially suspected a bacterial infection,
leptospirosis, known for outbreaks in sea lions and found
occasionally in sea otters as well. Yet all the tests turned up
"I sat down and said, 'I'm seeing a new problem. I've got to
back to the basics.'" She began to rule out potential causes.
Poisonous mushrooms? No. Poisonous plants? No. Iron toxicity? No.
Drug overdose? None of these made sense.
Then she dredged something out of her memory from veterinary
school. The damaged livers were like those of a dog or a cow that
died after drinking out of a scum-choked farm pond. The culprit in
those cases was a toxin, microcystin, produced by a type of
cyanobacteria called Microcystis.
She found a lab to run tests and, sure enough, the liver sample
tested positive for the Microcystis toxin. Yet it raised a
question: How could a toxin produced in fresh water poison a sea
Miller called the State Water Quality Control Board and learned
that Microcystis blooms seemed to be occurring more often in lakes
and estuaries. One was Pinto Lake, about five miles inland from
Monterey Bay, where some of the yellow deceased otters had been
"I sent a lab tech to look at this lake," Miller said. "She
called me on her cell and said, 'This is gnarly. I'm going to take
pictures.'" She also took some samples.
"The best way to describe it? The lake turns the color of
automobile antifreeze with chunks of broccoli floating in it," said
Robert Ketley, water quality manager for the nearby city of
Watsonville. "It's that grotesque. When the scum dries, it has a
turquoise color to it."
The city owns much of the 100-acre lake and used to draw on it
for water ---- but no longer. Ketley now posts signs warning people
to avoid contact and to keep their pets away.
The city is investigating what's prompting the toxic bloom. A
nearby pig farm is gone. Yet other farm fields drain into the lake,
which also has shoreline homes that rely on septic tanks for sewage
Wayne Carmichael, professor emeritus of aquatic biology and
toxicology at Wayne State University, calls Microcystis a premier
organism. "We find it everywhere you have nutrient enrichment:
nitrogen and phosphorous in warm, stagnant water. It's been
documented in every country in the world."