Aquatic plants are a valuable part of freshwater ecosystems; their presence in a pond provides many benefits:
Aquatic plants consume much of the nutrients created by the breakdown of organic matter that would otherwise turn into sludge and muck up the water. This basic function is perhaps the most overlooked benefit of aquatic plants, but it is of vital importance to a pond ecosystem’s health. For example, we have several small kiddie-pools filled with aquatic plants and no other form of filtration, and the water remains crystal-clear throughout the season because the plants consume all of the excess nitrates that would otherwise fuel algae growth.
Aquatic Plant Benefit #2: Food
Aquatic plants serve as a food-source for many animals including birds, fish, insects, and tadpoles. In particular, ducks like to eat the seeds, leaves and tubers of plants such as pondweed, duckweed and arrowhead. Turtles like to eat water lettuce and the floating pads and flowers of lilies. Larger animals may also feed on aquatic plants, and indirectly on the invertebrates that plants attract to a pond.
Aquatic plants create shade for fish and amphibians seeking to escape from the sun, and their stems and roots provide refuge from larger predators. They also serve as a home for smaller animals such as insects, snails and crustaceans. Each of these organisms plays a special role in the pond and contributes to a healthy functioning ecosystem.
Larger aquatic plants like reeds and cattails provide excellent nesting material for many species of birds and mammals. Songbirds, for instance, often use the fluff from cattails when building nests. Rodents will use the brush along the ground to make burrows near the water where food is abundant. The presence of these smaller creatures also attracts larger animals, such as fox, raccoons, snakes, bullfrogs, and possums.
Aquatic Plant Benefit #5: Shoreline Integrity
One more benefit of aquatic plants in a pond is that they help to maintain the integrity of the shoreline. Their roots from a sturdy network that holds the ground together and prevents water from eroding the shoreline. They create a natural boundary between the land and water, and serve as a perfect transition both visually and structurally.
Since we’re mentioning the various ways aquatic plants impact an ecosystem, let’s take a moment to a potential problem that plants may cause in a pond: choked water. This occurs when a system is out of balance, when there are too many plants crowding the water.
Sometimes plants will thrive and propagate until there is no more room to expand. This can be fixed by thinning out the plants and removing the excess until they cover no more than 1/3 of the water. It is best to do this in the spring and fall, before the new season of growth begins.
Aside from the poor aesthetics of a choked pond, too many plants can have other impacts on an ecosystem. When most of the water surface is covered with plants, the water flow decreases and this stagnant water can become breeding ground for mosquitoes. Too many plants can also degrade the water quality by raising pH, which means decreased oxygen and increased water temperature.
Another concern with aquatic plants deals with invasive species becoming established in native waterways. Your pond may be an isolated ecosystem, but you can’t prevent animals from spreading seeds of your exotic pond plants to native waters, where they may be considered an invasive species. The easiest way to avoid spreading invasive plants is to research which species of plants are of local concern. If you’re in NJ, you can click here to see an official list of invasive aquatic plant species.