Our Powerboats & Aquatic Plant Communities

EDITORS NOTE: This article is fourth in a seven-part series that will help readers understand the impact of motorized boats on Lake Beulah. Most information comes from the Wisconsin Department of Natural Resources (PUBL-SS-948-00)

It’s no secret the number of boats has increased on Lake Beulah over the last 20 years. So too has boat size and horsepower!! Whereas in the 1970s 100hp was considered a pretty big engine, nowadays we’re seeing 600hp boats on the lake, even pontoon boats powered by 600hp. New kinds of boats are quite common now, especially personal watercraft, and the number of wake boats goes up every year. How is all this boat traffic impacting the aquatic plants of the lake? And why should we care?

Lake Beulah has all three kinds of aquatic plants, submerged, emergent and floating leafed species. Common native submerged plants include milfoil (Eurasian milfoil is an invasive species), elodea and pondweeds. Emergents are plants like cattails and sedges. Water lilies are in the floating category. All these plants live in shallow water. Why? There isn’t enough light in the deeper waters. But because Lake Beulah has an average depth of 17 feet, most of its lake bottom is covered with plant life.

Powerboats can have a big impact on the aquatic plants of the lake. Propellers can chop off shoots, even upright whole plants. When powerboats move over the muck bottom, water turbidity increases meaning less light is available for growth. There’s also concern about powerboats bringing non-native, invasive plants to the lake such as Eurasian water milfoil.

Here are the results of several studies.

• Channels disturbed by boat traffic had different sediment chemistry, and as a result when vegetation was removed by boat traffic it took 2-3 years without disturbance for the plants to recolonize the area.

• As boat traffic increases, turbidity increases and plant life decreases.

• Waves from boat traffic limit plant growth by uprooting and damaging the plants.

• Plant biomass is inversely proportional to the amount of boat traffic. EDITOR’S NOTE: Recent weed cutting data from the LBMD shows a decline in weeds being cut.