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Venezuela struggles to remove aquatic plant faster than it spreads over nation's largest lake

Source:  Copyright 2004, Associated Press
Date:  June 17, 2004
Byline:  Alexandra Olson, Associated Press
Original URL: Status DEAD


CARACAS, Venezuela — Efforts to remove an aquatic weed from Venezuela's largest lake are barely keeping up with its growth, the environment minister said Wednesday.

The green plant, known as duckweed or lemna, covers about 12 percent of Lake Maracaibo's 13,500-square kilometer (5,400-square mile) surface, said Ana Elisa Osorio.

The lake in western Venezuela is one of South America's largest bodies of water and is an important oil-producing region. Since World War I, about 14,000 oil wells have been drilled in the lake.

Workers are removing the plant at a rate of 1,500 cubic meters (53,000 cubic feet) a day. But it can double in size every 48 hours, Osorio said, and has covered an area of 130 million cubic meters (4.6 billion cubic feet).

Crews have extracted about 43,000 cubic meters (1.5 million cubic feet) since the duckweed started burgeoning several weeks ago, Osorio said. To date, most of the work has been done manually. The government is deploying dredging machines to help.

Venezuela is spending about US$2 million a month for cleanup, Osorio said. The state-run oil company, Petroleos de Venezuela S.A., created a US$750 million cleanup fund.

A spokesman for PDVSA, who spoke on condition of anonymity, said the corporation had offered to provide money from its newly created US$2 billion Social and Economic Development Fund. But the spokesman said no specific amount of money has been set aside for the cleanup.

Duckweed feeds off nitrogen and phosphorous contained in sewage and river runoff, said Gonzalo Godoy, a marine biologist from Zulia state. As the plant dies and rots, it absorbs oxygen, killing fish and threatening the livelihood of thousands of fishers, Godoy said.

Osorio denied the duckweed has seriously affected fish. More than 3.8 million kilograms (8.4 million pounds) of fish were caught in May, compared with 2.6 million kilograms (5.7 million pounds) in May 2003, she said.

However, duckweed does entangle the propellers of fishing boats. Large oil tankers aren't affected.

Oil spills, sewage, and industrial runoff may have triggered the expansion, said Nola Fernandez, head of the Sanitary and Environmental Engineering Department of Zulia University.

"The plant grew because the lake wasn't able to continue purifying itself, so it looked for a mechanism of self-purification. It's matter of nature," Fernandez said.

Osorio said unusually heavy rains and a reduction of the lake's salt content could have contributed. Duckweed thrives in fresh water, she said.

Lake Maracaibo, about 500 kilometers (300 miles) west of Caracas, opens to the Caribbean Sea.

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