(ABC 6 News- Clear Lake) A June bloom of Curly-leaf pondweed, or Potamogeton crispus, is impacting some boating and recreation activities on Clear Lake.

According to the Iowa DNR, the species starts growing in the fall and winter, flowers in late spring, and dies in mid-summer. Curly-leaf pondweed also provides valuable waterfowl food.

Iowa DNR Fisheries Management Biologist Scott Grummer said the species has grown heavily each June for the last four years.

“It’s a fall germinator,” said Grummer. “It’s done growing for the year and it’s topped out, releasing to the surface. We’re seeing a lot because we had a very mild winter.”

The invasive species poses a hazard to boat engines, and provides unsuitable coverage for native and introduced species.

“There’s a lot of weeds,” said Clear Lake angler Dennis Mikesell.

“They’re getting chopped up by prop motors of boats, and its causing some issues but it’s good for the fish, it prevents you from catching fish.” 

“You wouldn’t want to boat through the heaviest stands of it right now,” said Grummer. “But that should really quickly improve, hopefully by July.”

While the decomposing pondweed washes ashore, the DNR is asking boaters to be cautious, and is encouraging shoreline property owners to dispose of the waste through composting.

It is illegal to transport aquatic plants and invasive species in boats and equipment.

The pondweed is one of three invasive species currently being mitigated in the lake, along with zebra mussels and Eurasian watermilfoil, which Grummer said was being treated with herbicide and frequent vegetation surveys since October.

Water equipment being improperly cleaned is a big transporter of invasive plant and animal species, and according to the Iowa DNR, all water must be drained from water-related equipment when leaving a water access (this includes live wells and bait buckets). Drain plugs, bailers and valves must remain removed or open during transport.