The development of submerged macrophytes in Lake Ringsjön after biomanipulation

The maximum water depth of submerged vegetation and the number of sites colonized by submerged macrophytes in Lake Ringsjön were studied in 1992, 1993 and 1996, and compared with data from 1947 and 1988, in order to investigate the development of submerged macrophytes after the biomanipulation of the lake (completed 1992). The submerged vegetation has declined considerably since 1947, both in species number and outer water depth. The submerged macrophytes in Lake Ringsjön did not show any clear improvement in outer water depth or number of sites colonized after biomanipulation. The lack of any larger increase in Secchi depth after biomanipulation along with a shortage of suitable habitats (i.e. substrate), waterfowl grazing and species composition of the macrophyte populations are discussed as possible reasons for the poor development of submerged macrophytes in Lake Ringsjön.[PUBLICATION ABSTRACT]