Chapter 11: Managing Aquatic Vegetation
John D. Madsen, Robert J. Richardson, and Ryan M. Wersal
Ponds are, by their very nature, prone to grow aquatic plants either in the form of algae or larger vascular plants. Because they are shallow, much of the habitat is conducive to the growth of plants. Because ponds typically receive a large proportion of their water from runoff, they tend to be high in nutrients that plants require for growth. Some plant growth is a good thing; algae are the primary producers that form the base of the food web in aquatic systems, and adequate primary productivity will enhance pond productivity (Madsen 2009). Flowering plants provide good habitat for aquatic insects, a favored food of small fishes, and a nursery habitat for age-0 fishes of many species (Dibble 2009). Plants may also be a necessary spawning habitat for some fishes (Dibble et al. 1996; Dibble 2009).
While a moderate amount of plants may be a good thing, an overabundance of plants will impair pond uses and reduce the quality of the pond environment for fishes through reduced oxygen levels or inadequate spatial habitat heterogeneity (Lembi 2009; Madsen 2009), and may interfere with predator–prey dynamics. Often, nuisance plant problems are caused by an overabundance of nutrients, particularly nitrogen or phosphorus, though shallow pond habitats may support abundant plant growth even without added nutrients. In these cases, plant management may be necessary.
Whatever the cause, pond managers should only use techniques that are environmentally compatible, economically affordable, and legally acceptable when managing plants they consider a nuisance. Before plant management begins, some effort should be made to develop an effective management plan (Madsen 2000). If management goals are not made before implementation of management techniques, there is an increased likelihood of either selecting techniques that are contrary to long-term success, or using techniques that have negative irreversible consequences.