Aquatic Macrophytes

Survey of aquatic plants (macrophytes)

Plants are described as aquatic if the plant parts involved in photosynthesis are submerged or float on the water surface either permanently or at least for several months each year. The term "macrophytes" refers to all plants large enough to be visible to the naked eye - not only flowering plants but also ferns, bryophytes and algae.

Aquatic macrophytes are an important component of many watercourses, providing a structures and abitat for fish and invertebrates, offering protection against currents and predators, and forming a substrate for the deposition of eggs. As primary producers, macrophytes represent an important food resource, and they also play a significant role in the oxygen balance and nutrient cycle of many watercourses.

In view of their varying requirements, the composition of macrophyte species in a waterbody makes it possible to draw conclusions about the local chemical and physical conditions. Species that prefer low nutrient concentrations, in particular, have become much less prevalent. Also in decline are species that are dependent on natural riverbanks with sandy and gravelly substrates. Aquatic plants are especially sensitive to changes (increases) in nutrient concentrations (notably phosphorus and ammonium) and to organic pollutants.

As part of the Modular Stepwise Procedure, a method of assessment for macrophytes is currently being discussed; however, in Switzerland, this work is still at a preliminary stage.

Photo: AWEL, Canton Zurich	Photo: EAWAG	Photo: EAWAG