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Getting to the bottom of a fish die-off in Southern California

[ 2011-03-15 14:15]     字号 [] [] []  
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Getting to the bottom of a fish die-off in Southern California

This is the VOA Special English Agriculture Report.

People in a community on the Pacific coast in Southern California awoke last week to a sea of dead fish. About 850 sailboats and powerboats come and go from the marina at King Harbor in the city of Redondo Beach. But the sardines that swam into the marina never swam out. Estimates put the number of dead fish in the millions.

Local resident John Archibald described the smell this way.

JOHN ARCHIBALD: "Not bad. But I would not be ordering any pizzas around here lately."

Reporter Pete Demetriou from KNX Newsradio in Los Angeles also spoke to another man who has lived in the area for 26 years.

MAN: "The die-off was as bad as I've ever seen, but they cleaned up pretty quick, so there's not too much smell."

REPORTER: "Well, you've got a few fish on the top here but they're concerned that a lot of it may still be down there on the bottom. What do you do, do you try to clean it up or let it just basically decompose?"

MAN : "No, you just let it go. The crabs will get it."

He remembered that about five years ago there was another serious kill-off of fish in King Harbor. It was caused by a harmful algae bloom, a so-called red tide of microscopic organisms that spread from time to time. But this time scientists found no toxic algae in King Harbor, so it was a mystery.

On Friday a scientist at the University of Southern California released findings of continuing research in his laboratory. Professor David Caron said fish collected on March 8th, the day of the kill, tested "strongly positive" for domoic acid in their stomach contents. Domoic acid is a powerful neurotoxin produced by one kind of microalgae.

Fish such as sardines and anchovy can get poisoned when they eat plankton that have eaten the algae.

Researchers from USC confirmed that plankton collected about 20 kilometers southwest of Redondo Beach the next day had very high levels of domoic acid. This would support a theory that the fish became poisoned in coastal waters before entering the harbor.

High levels of domoic acid in the sardines may have worsened the effects of oxygen loss in the water as the fish crowded into a limited space. Or the domoic acid may help explain why they entered the marina. Professor Caron said research shows that domoic acid poisoning can cause abnormal swimming in some kinds of fish.

Harmful algae blooms are a common cause of fish kills. Domoic acid can also cause neurological disorders and death in animals that eat fish poisoned with the neurotoxin.

And that's the VOA Special English Agriculture Report, written by Jerilyn Watson. If you ever miss one of our programs, go to voaspecialenglish.com to find transcripts and MP3s of all of our reports. I'm Karen Leggett.

marina: a specially designed harbour for small boats and yachts 小船坞;游艇停靠区

algae bloom: 赤潮

domoic: 软骨藻

anchovy: a small fish with a strong salty flavour 鯷(咸水小鱼)

plankton: the very small forms of plant and animal life that live in seas, rivers, lakes, etc. 浮游生物

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(来源:VOA 编辑:崔旭燕)