Ecology

Aquatic Macrophytes

Visible aquatic plants growing in lakes, including emergent, floating-leaf, and submersed species that provide critical habitat and help maintain water quality.

What It Means for Your Lake

Aquatic macrophytes are the visible plants growing in and around lakes, as distinguished from microscopic algae (phytoplankton). They include three main growth forms: emergent plants that grow in shallow water with stems and leaves above the surface (cattails, bulrushes, wild rice), floating-leaf plants rooted in the bottom with leaves on the surface (water lilies, pondweeds), and submersed plants that grow entirely underwater (coontail, native milfoil, elodea, chara). In Minnesota and Wisconsin lakes, a healthy and diverse native macrophyte community is considered one of the most important indicators of overall lake ecosystem health. Aquatic plants perform numerous essential functions: they produce dissolved oxygen through photosynthesis, absorb nutrients from the water column and sediments (reducing phosphorus available for algae growth), stabilize bottom sediments against wave erosion, provide spawning and nursery habitat for fish, and offer food and cover for waterfowl, turtles, and invertebrates. The littoral zone, the shallow area of a lake where light reaches the bottom and plants can grow, is the most biologically productive zone of any lake. In clear oligotrophic and mesotrophic lakes, aquatic plants may grow to depths of 15 to 20 feet, while in turbid eutrophic lakes, light limitation restricts plant growth to the shallowest 3 to 5 feet. Threats to native macrophyte communities include invasive species (especially Eurasian watermilfoil and curly-leaf pondweed), excessive herbicide treatment, mechanical removal, altered water levels, and reduced light from algae-laden water. Both Minnesota and Wisconsin DNR conduct aquatic plant surveys as part of lake assessments and regulate the removal of aquatic vegetation through permitting programs.

Frequently Asked Questions