Biomanipulation of large moderately eutrophicated Lake Lappajaervi

摘要

Despite considerable decrease in point load during the last decades, the eutrophication of inland waters is still a severe European problem. Excessive external nutrient loads from catchments trigger eutrophication of lakes (Vollenweider & Kerekes 1982), and subsequent changes in the ecosystem and the deterioration of the sediment will further increase internal load. Internal load may be far more important than external load, effectively diminishing the effects of water protection measures. Dense cyprinid-dominated fish stocks especially deteriorate lake status by accelerating nutrient cycling (Persson & Hamrin 1994). A widely used measure to restore internally loaded lakes is intensive removal of coarse fish. Successful results have been obtained in many cases but not in others (Jeppesen & Sammalkorpi 2001).