Native macrophytes in the lower Spree River (Germany)
After years of absence, macrophyte vegetation gradually has increased from the mid-1990s. In recent years, submerged and floating-leafed macrophytes (mostly Sagittaria sagittifolia, Potamogeton pectinatus and Nuphar lutea) attained a wet weight of 700-800 tons in a 30-km river section. With the development of macrophyte biomass, the water level rose by 20-50 cm, causing problems for farmers and residents. Therefore, about 250-600 tons are mechanically removed each year.
Mowing the aquatic vegetation has, however, impaired water quality in the downstream river sections and of lakes in the Berlin region. This river section is intensely used for recreation, and the Spree is a main source of drinking water for Berlin. The stakeholder involved is the agency responsible for landscape management (Wasser- und Landschaftspflegeverband Untere Spree).
River Spree (top left; photo S. Hilt) with dense macrophyte stands of Sagittaria sagittifolia and Potamogeton perfoliatus (top right; photo F. Wieland), and Nuphar lutea (middle, left) and Ranunculus fluitans (bottom, left) covering the entire water body. As a result, plants have been removed since 2005 by mechanical mowing and removal (middle right, photos J. Köhler).