Duckweed (Lemna) Invasion

Paper Summary:

This paper explains that, in 2004, an invasion of the aquatic plant, Lemna oscura, also known as duckweed or 'lemna' in Spanish, was recorded in Venezuela's Lake Maracaibo, covering now about 18% of the lake's surface and altering the habitat by blocking the photosynthesis process and asphyxiating the fish, which are the main source of income. The author points out that there is some mystery as to how the plant came to Lake Maracaibo where the plant does not normally grow; a government research group hypothesized that the plant was carried from ponds on the edges of the lake to the main body of Lake Maracaibo on stronger than normal currents caused by increased rain. The paper reports that, as the environmental authorities and experts are debating how to eliminate the weed, citizens are organizing in groups to take out the duckweed with rakes and poles, but with little improvement. Color illustrations.

From the Paper:

"Currently it covers an area of 130 million cubic meters (Fig 2), and approximately 43.000 cubic meters have been extracted. The invasion of the aquatic weed is changing the lake. It absorbs many nutrients from the lake, and creates a solid cover that shades the water column and prevents photosynthesis by submerged species. The floating plant reduces the area of contact between the water and the atmosphere, reducing oxygen from entering the lake. In addition, the lemna sheds dead roots, leaves and other organic debris into the water which is decomposed by aerobic microbes, depleting the oxygen levels."

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