By Julia Scott
SCOTT: This is the story of a murder mystery, and how one woman solved it.
MILLER: can I grab a scalpel and a knife and stuff? So I am gonna open up her chest here.
SCOTT: Dr. Melissa Miller sees a lot of bodies. Her job is to determine cause of death. Sometimes the culprit is a little… unusual.
MILLER: What we see in the center of the laceration on her arm is fragment of a tooth. The obvious cause of death for this otter is shark bite.
SCOTT: There are no human victims at this lab. Miller is a medical examiner for sea otters at the Marine Wildlife Veterinary Care and Research Center in Santa Cruz. And until five years ago, she thought she’d seen it all.
That’s when dead sea otters starting coming in with symptoms Miller had never seen before. First just a few, from around Monterey Bay.
A Rash of Symptoms Prompt Further Investigation
MILLER: And when I was looking at them externally they were bright yellow. The whites of their eyes, instead of being a nice healthy color, they were yellow.
SCOTT: Then, more sea otters, all with liver failure. By the end of 2007, there were 12 altogether. By 2008, that number nearly doubled. The California sea otter is a threatened species, with a population of 2,800 animals. Losing so many of them got everyone’s attention.
MILLER: What scares people like me is when I start to see lots of those otters dying and I’m seeing something that I haven’t recognized before as a cause of death.
SCOTT: Unbeknownst to Miller, the summer of 2007 also brought one of the worst reported algal blooms in the United States. It was in Pinto Lake in nearby Watsonville. But no one had made the connection – yet. Back at the lab, Miller couldn’t figure out the otters’ liver problems. So she sat down and made a list of murder weapons.
At the top of the list was a bacterial infection that affects California sea lions.
MILLER: I was so sure that it had to be that, that I actually did every test for this bacterium.
SCOTT: She was wrong. The tests came back negative. Next, she considered really unlikely suspects – like poison mushrooms and the possibility that the sea otters were struck by lighting.
MILLER: So that only left me with one thing. And the one thing at first seemed so farfetched that I didn’t believe myself.
Cyanobacteria Becomes Prime Suspect
SCOTT: That one thing was a kind of blue-green algae known as cyanobacteria. One common form of blue-green algae produces a kind of toxin, called microcystin, which attacks the liver.
Algal blooms are common. But this kind of toxin had never been found in an ocean environment, nor detected in any marine mammal, ever – including sea otters. But when Miller ran the test for microcystin, the sea otters tested positive. All of them.
Twenty-two miles away, that same year, Robert Ketley with the City of Watsonville was getting really worried about thick green pond scum on Pinto Lake. It was producing toxic bacteria he’d never heard of, and he didn’t know what to do about it.
KETLEY: I had a number of concerns that there was a potential human health problem.
Making the Local Connection
SCOTT: For her part, Miller had no idea how a bacteria normally found in farm ponds could be killing sea otters in Monterey Bay. On a hunch, she called a friend, who remembered hearing ab out an algae problem in Pinto Lake. Then she sent a colleague to take a look.
MILLER: Once she got out there she called me on her cell phone and her first comment to me was ”this is gnarly.”
SCOTT: It IS gnarly. In summertime, the water is bright green and smells like old gym socks.
KETLEY: I think the best way to describe it is like automobile antifreeze with chunks of steamed broccoli floating in it.
SCOTT: Fed by phosphorous and sunlight, it thickens in summer and washes away in the October rain.
Miller and some colleagues at the University of California, Santa Cruz decided to follow the microcystin trail. It wasn’t long before they found it at the mouth of the Pajaro River, downstream from Pinto Lake. That’s where sea otters feed on what Miller thinks is poisoned shellfish.
MILLER: These toxins are strong enough and potent enough that they can cause death within 24 to 48 hours.
SCOTT: This problem goes way beyond the Central Coast. Water officials are finding toxic cyanobacteria in other California lakes and reservoirs. Which means more wildlife could be affected – birds or fish, or even another group of sea otters.
WARD: It seems as though the more researchers look, the more they find them.
SCOTT: That’s Kim Ward, an environmental scientist at the State Water Resources Control Board.
Not Unique to Pinto Lake
WARD: This affects the San Francisco Estuary. There are areas of Southern California that have similar problems. South Africa, Japan, China, Brazil, Europe. You name it, everybody’s looking at it.
SCOTT: Scientists aren’t sure whether the cyanobacteria may have been there all along, or it it’s getting worse. Ward says dozens of California water bodies could be affected, including reservoirs we count on for tap water.
WARD: What worries me is that other toxins are out there that we’re simply just not able to test for yet.
SCOTT: Ward wants to develop a statewide monitoring program. But removing the toxin is tricky. Ketley’s office is building a lab at Pinto Lake to test out different treatment technologies. But he says whatever they choose will only be a Band-Aid solution.
KETLEY: It’s sort of like a big vat of Miracle Gro. The plant, in this case the cyanobacteria, thrives regardless of what you do with it.
SCOTT: To really solve the problem, scientists will need to figure out what’s boosting phosphorous and nitrogen in lakes and reservoirs covered with blue-green algae.
KETLEY: Even if we were to shut down most of the inputs from the watershed, the lake itself has sufficient nutrients internally to continue to bloom.
SCOTT: Pinto Lake lies in valley below old farms and ranches. Manure and fertilizer are possible culprits, but so are the houses that surround the pond: Ketley worries about things like lawn fertilizer and leaky septic tanks.
Or it could be something in the pond already. If humans are the problem, finding solutions may be an even greater challenge than solving the mystery of what’s killing the sea otters – because it goes back to the source. And if more Pinto Lakes exist than we know of, more sea otters may be affected in the years to come. For KUSP, I’m Julia Scott.