Magazine article Science News

Algae Turn Fish into a Lethal Lunch

Magazine article Science News

Algae Turn Fish into a Lethal Lunch

Article excerpt

To sea lions, an anchovy represents little more than a bite of dinner. In a strange turn of events, microscopic algae have enabled some anchovies to bite back--albeit posthumously.

A new study establishes for the first time that fish that dine on a particular plantlike floating diatom, an alga, can become a dietary time bomb for mammals higher up the food chain.

Scientists had considered diatoms benign until a 1987 bloom of Pseudo-nitzschia australis off Canada's Prince Edward Island. Some 140 people who ate mussels that had accumulated these algae from the water fell victim to a strange neurotoxicity. Three died. Many who survived still suffer from an Alzheimer's-like loss of short-term memory.

Pathologists quickly linked this shellfish poisoning to domoic acid, an amino acid produced by the algae. Pseudonitzschia blooms were later tied to several suspicious wildlife events--from marine mammal strandings and deaths to seemingly drunk pelicans falling from the sky. No one, however, proved the alga's toxin was to blame.

Now in the Jan. 6 NATURE, Christopher A. Scholin of the Monterey Bay Aquarium Research Institute in Moss Landing, Calif., and his colleagues offer unambiguous evidence tying the toxic diatom to the deaths of more than 400 sea lions during May and June of 1998.

When the animals' initial seizures suggested a neurotoxin, Scholin's team homed in on the sea lions' diet--anchovies--and found the fish loaded with toxin-producing Pseudo-nitzschia. Autopsies showed the dead sea lions had brain lesions characteristic of mice and monkeys poisoned by domoic acid. The final link, Scholin says, was his team's documentation of the silicon-based skeletons of Pseudo-nitzschia in feces of affected sea lions and domoic acid in the animals' urine, feces, and serum.

This "is a beautiful sleuthing job," observes Pat Tester of the U. …

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