AN­CIENT THREAT

Al­ready be­sieged, many sea ot­ters are now be­ing poi­soned by an an­ces­tor of mod­ern-day bac­te­ria.

Los Angeles Times - - Latextra - Ken­neth R. Weiss

Pity the poor sea ot­ter. It’s been a strug­gle for the furry, but­ton-nosed crit­ter to make a come­back since be­ing hunted nearly to ex­tinc­tion along Cal­i­for­nia’s coast.

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 opos­sums and do­mes­tic cats.

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 said.

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 neg­a­tive.

“I sat down and said, ‘I’m see­ing a new prob­lem. I’ve got to go 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 ot­ter?

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 found.

“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

‘I started get­ting ot­ters that were clearly jaun­diced, with bright yel­low gums and yel­low in the whites of their eyes.’

— Melissa Miller,

a state wildlife vet­eri­nar­ian

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 dis­posal.

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 phos­pho­rus in warm, stag­nant wa­ter,” he said. “It’s been doc­u­mented in ev­ery coun­try in the world.”

It’s a type of cyanobac­te­ria, an an­ces­tor of mod­ern­day bac­te­ria and al­gae, which dom­i­nated the planet more than 2.5 bil­lion years ago. Sci­en­tists have found that dif­fer­ent strains are reemerg­ing with the buildup of pol­lu­tion and nu­tri­ents from ex­pand­ing agri­cul­ture and mod­ern in­dus­trial so­ci­ety.

The sam­ples col­lected by Miller’s lab tech found a su­per-bloom un­der­way in Lake Pinto, with highly toxic read­ings. Miller teamed with Fish and Game chemists and UC Santa Cruz bi­ol­o­gist Raphael Kudela to fol­low the toxic trail from Lake Pinto and other lo­cal lakes down rivers that reach Mon­terey Bay. Some of the tox­ins were also de­tected in ocean wa­ters at Santa Cruz wharf.

But the re­sults didn’t ex­plain how ot­ters might in­gest a lethal dose.

So Miller and her col­leagues de­signed a lab ex­per­i­ment to test a hy­poth­e­sis. With the lab reel­ing from state bud­get cuts, Miller shelled out money to buy six heap­ing shop­ping bags of live oys­ters, mus­sels and crabs to place in sea­wa­ter tanks. Then they added some con­tam­i­nated wa­ter from Lake Pinto.

Most shell­fish fil­ter the sea­wa­ter to feed them­selves, gath­er­ing microscopic food and any­thing else in the wa­ter. Tis­sue sam­ples re­vealed the shell­fish in the tankshad ac­cu­mu­lated the toxin in their di­ges­tive tracts at con­cen­tra­tions that were 107 times higher than in the sur­round­ing wa­ter.

The study, pub­lished by the Pub­lic Li­brary of Sci­ence’s peer-re­viewed jour­nal, doc­u­mented the first case of a fresh­wa­ter toxin poi­son­ing of a ma­rine mam­mal. The toxin was re­spon­si­ble for the death of at least 21 sea ot­ters, a species listed as threat­ened with ex­tinc­tion.

The study also sug­gests that hu­mans may be at risk if they con­sume shell­fish har­vested from river mouths, es­pe­cially af­ter the first fall rains flush tox­ins built up in the lakes. Pub­lic health of­fi­cials do not test shell­fish for fresh­wa­ter tox­ins, only for ma­rine tox­ins such as the one that causes par­a­lytic shell­fish poi­son­ing.

Carmichael, the ex­pert on Mi­cro­cys­tis, isn’t too concerned about acute hu­man poi­son­ings be­cause the dose would be too small. Sea ot­ters con­sume about 25% of their body weight a day in shell­fish, cre­at­ing per­fect con­di­tions for toxic poi­son­ing.

Lawrence K. Ho

PLAY­FUL AND IM­PER­ILED: A sea ot­ter dines on shell­fish in Mon­terey Bay. A mi­crobe threat­en­ing the mam­mal ap­pears to be on a global up­surge.

Ken­neth R. Weiss

PA­TIENT: This sea ot­ter was nursed back to health at the state Depart­ment of Fish and Game’s Ma­rine Wildlife and Vet­eri­nary Care and Re­search Cen­ter.

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