WATERBURY (AP) — An invasive aquatic algae that turned up last summer in the Connecticut and White rivers and the Batten Kill has now been spotted in the Mad River, its first incursion into the Lake Champlain basin, state officials said Thursday.

Water quality scientists for the state have confirmed the presence of Didymosphenia geminata — also known as didymo, or rock snot — in an area of the river near Warren.

The algae, which tends to thrive in cold, clean waters and low-nutrient rivers, threatens aquatic insect and fish populations. It has contaminated rivers in Arkansas and Tennessee but until last year hadn't been seen in the northeastern United States.

"The discovery of didymo in the Mad River is great cause for concern," said Caitrin Noel, watershed coordinator for Friends of the Mad River.

"We are working hard to learn all we can about the extent of this, how to address it, and will continue to study this in the future. Our biggest focus right now is spread prevention and outreach. The more we can educate our community about this, the better chance we have in preventing further spread upstream and into the headwaters, or into other water bodies."

Rock snot is spread by boats, gear and fishing equipment, adhering to them and then moving as the equipment is used in other bodies of water.

Spotted first by a citizen, the algae is coating rocks and may have already spread to other parts of the Mad River, according to Leslie Matthews, a water quality scientist with the state Agency of Natural Resources.

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