Case Study: Sea Lions and DDT

Michael Williamson (
Mon, 11 Nov 1995 03:57:08

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From: Michael Williamson <WHE_WILLIAM@FLO.ORG>
Subject: Case Study: Sea Lions and DDT
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Subject:      Sea Lions-DDT
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Sea Lions-DDT
 AP Science Writer
   LOS ANGELES (AP) -- Two decades after DDT dumping ended in
Southern California waters, sea lions have dramatically lower
levels of the pesticide and their population has more than doubled.
   The huge decline of the pesticide in the sea lions' fatty tissue
represents the greatest reduction observed in any animal
population, according to researchers at the University of
California, Santa Cruz.
   California sea lions once had the highest body fat
concentrations of DDT of any marine mammal ever studied by the
National Oceanic Atmospheric Administration.
   DDT, a powerful pesticide that causes premature births in sea
lions, has been banned in this country since 1972. Montrose
Chemical Co., once the nation's largest DDT producer, dumped the
pesticide off the Palos Verdes Peninsula from 1947 to 1971.
   From 1975 to 1993 the sea lion population at San Nicolas, San
Miguel, Santa Barbara and Santa Cruz islands increased from 12,000
to 28,000. Sea lions migrate each year to the Channel Islands for a
breeding season from May to August and feast from a food chain
contaminated by DDT.
   In 1970, the sea lions' blubber showed an average level of DDT --
and its more dangerous byproduct DDE -- of 760 parts per million.
   Blubber samples taken in 1988-92 showed levels had fallen to 5.2
parts per million, according to the findings published this month
in Britain's Marine Pollution Bulletin.
   The dumping, however, left an estimated 100 tons of
DDT-contaminated sediments on the ocean floor and lingering effects
of the pesticide remain unknown.
   "We're not out of the woods," said lead study author Patricia
Lieberg-Clark, a wildlife biologist at the environmental consulting
firm BioSystems Analysis Inc. "There still is that DDT deposit
that's sitting there in San Pedro Channel that will continue to be
churned up for God knows how long."
   The study was funded by the Institute of Marine Science at UC
Santa Cruz and the National Science Foundation.