These flowering, green aquatic plants float on or just below the surface of fresh water and wetlands. They are seemingly throwing a duckweed reunion in Grand Haven, and nobody seems to know exactly why.
Small concentrations of duckweed started surfacing in the channel earlier this summer. Recently, the aquatic weed has spread upstream, invading the Government Basin and Municipal Marina, and stretching beyond the U.S. 31 drawbridge.
Tony Groves, the water resource practice leader for Progressive AE in Grand Rapids, said the plant typically prefers calm water. But the Grand Haven channel, with boat traffic and recent storms and high winds, hasn't exactly been a quiet place to hang out.
“I'm a little bit surprised,” Groves said of the duckweed invasion. “You usually don't see it growing that heavy. It makes me think this will be a short-lived thing.”
Kari Strait, a dock hand for the Municipal Marina, said she's lived in Grand Haven all of her life and doesn't recall seeing duckweed in the channel.
“There's a lot of it,” she noted. “It's a natural thing, so there's really nothing you can do about it.”
Strait said boaters have definitely noticed, but they're not complaining.
“They just say, 'This duckweed is crazy,'” she said. “It's gotten worse in the last week or so. It's in our slips. A little under half of our slips are covered in green. We could blow it out of our slips, but the current would take it right back into our slips.”
Groves said duckweed is not usually a plant that persists for a long time, but according to those who frequent the channel, it seems to be growing more plentiful in recent weeks.
“It's unusual to see it that heavy, but I contribute that to the weather,” he said. “I guess time will tell if it persists or not. If conditions are right, certain plants will really proliferate and take off. It appears conditions are favorable for that plant at the present.”
Duckweed is not known for becoming a chronic problem, Groves said. It also has no toxic or allergic effects for swimmers, and he said he has never heard of any boat mechanical issues due to duckweed.
Groves said he doesn't believe the duckweed came from Wisconsin or another coastal inland lake because Lake Michigan's wave action would have broken it up long before it got to the Grand Haven pier heads.
“Mother Nature is cyclical,” he said. “Things like this happen where you'll get a bloom of a particular plant. This should be a short-term thing.”