EAST GRAND RAPIDS - Recent surveys have found that Reeds and Fisk lakes are under threat from a harmful invasive species known as the European frog-bit.

The infestation is likely to impact both fishing and recreational activities on the two lakes, according to those who have been studying the threat.

"As aquatic invasive species go, frog-bit is near the top in terms of concern," said Adrian de Novato, a researcher and East Grand Rapids resident who writes the "Science Around Michigan" blog. "It grows in enormous mats along the surface, blocking native plants and sunlight from reaching below. In shallow areas with larger infestations, fish spawning is prevented."

PLM Lake & Land Management Corp., which serves as the City of East Grand Rapids lake management firm, first found the frog bit in the channel between the two lakes during a routine inspection.

Last week, experts from the West Michigan Cooperative Invasive Species Management Area (CISMA) conducted a full survey of both lakes and their connecting waterway to confirm the presence of the threatening frog-bit.

At this time there is not a specific plan for dealing with the problem, according to East Grand Rapids City Manager Brian Donovan.

"We just found out about it and are looking into it," he said. "We are exploring treatments available, trying to figure out the appropriate course of action and waiting to be updated."

Donovan confirmed that PLM regularly tests Reeds Lake and treats it for invasive species such as mil-foil. "We also need to be sure that we follow all state mandates for treatment," he said.

The risks to the lakes is huge, according to de Novato. "Growth of the frog-bit can be so immense that swimming, boating, and kayaking are no longer possible," he said. "When a large mat dies at year's end, oxygen levels fall, creating a condition we call aquatic hypoxia."

European frog-bit has small heart-shaped leaves, often described as resembling small lily pads, with a single white flower with three petals and a yellow center bloom above the water.

The infestation is to the point where hand removal is no longer an option; it is also too late in the season for an herbicide application, according to the report by Drew Rayner, coordinator of West Michigan CISMA.

A frog-bit infestation will impact both fishing and recreational activities and if allowed to spread, it will impact waterfront properties as well, said de Novato.

PLM Corp., CISMA and the Michigan Department of Natural Resources are currently discussing a course of action for the future, according to Rayner.