Nutrient content of the aquatic macrophytesElodea canadensis andCeratophyllum in the course of the year

Summary In Lake Vechten, a sandpit near the city of Utrecht (The Netherlands), the submerged macrophyte vegetation is dominated by two species, namelyCeratophyllum demersum andElodea canadensis. In the course of the year both species are able to develop two distinct forms: the normal vegetative form in summer, the dormant form in winter.Elodea is anchored to the substrate by roots,Ceratophyllum by modified leaves, called rhizoids by GLÜCK (1906, 1911). Both species form distinct zones. The depth at which the plants occur abundantly is 0 to 3 m in the case ofElodea and from 3 to 5 forCeratophyllum.