Hydrodictyon

Algae

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Hydrodictyon

Hydrodictyon Roth: Water net. Hydrodictyaceae. 

Green algae. Free-floating, net-shaped structures found in clear, slow-moving water; able to coalesce into mats. Individual cells, which can be up to 0.4 in (1 cm) long, are joined together in networks or meshes to form colonies that are flat sheets or hollow cylinders. The cylinders can be up to 8 in (20 cm) long and 2 in (5 cm) wide. The meshwork can be seen when algae are floating in the water or when an individual colony is picked up. Accumulations of the algae produce extensive light- to yellow-green mats at the surface; these can trap air bubbles and look frothy. When handled, pieces of the mat do not hold together but separate out into light, airy, or fluffy smaller masses or individual nets. Hydrodictyon can reproduce rapidly, with nets enlarging and increasing in number to nuisance levels in the course of a growing season. Mats hinder swimming and fishing and can be problematic in irrigation and drainage canals. These algae are native to North America but in some places where they are introduced, e.g., New Zealand, they have become a major noxious weed.