The Mississippi River, with its many islands, sloughs and backwaters, is rich in nutrients that sustain aquatic plants which make up the bottom of the food web for living organisms in the river ecosystem. Various species of pondweed along with water milfoil, elodea, watershield, duckweed, arrowhead, bulrush, cattail, and wild rice populate backwaters and ponds. These aquatic plants serve as an important food source and provide habitat. They produce oxygen and organic material to benefit other organisms. Their leaves and stems provide spawning habitat, food, and cover for a variety of fish and aquatic invertebrates.