The aquatic macrophytes of Lake Vechten. Species composition,spatial distribution and production

The macrophytic species compositions in Lake Vechten of 1963 and 1979–80 were compared and showed a considerable change. The main vegetation types were mapped in 1973, 1978, 1979 and 1980. All macrophytic communities, i.e. submerged, floating-leaved and emergent vegetation types, declined mainly due to increasing water turbidity, increasing tree-shading and, from 1978 onwards, grazing and trampling by cattle.Production rates, derived from different combinations of measurement and calculation, were compared. The macrophytes contributed only about 7% to the total lake production in 1980.