Biological manipulation of eutrophication in West Yangchen Lake

This paper aims to share findings on nonclassical biomanipulation from a field study on eutrophic West Yangcheng (WY) Lake. In the forty years before 2009, cyanobacteria frequently bloomed in WY Lake, an event which has not occurred since 2009. The stocking density of filter-feeding carp was estimated to be more than 50 g/m3 in July after 2009, approximately double the amount observed before 2009, and the ratio of silver carp to bighead carp (SBR) increased from 0.8 to more than 1.6. Compared with the water quality between 2004 and 2007, the total nitrogen (TN) and the chlorophyll-a (Chl-a) concentration decreased while total phosphorus (TP) and transparency (SD) increased significantly after 2009 (P 0.05). A significant negative correlation was observed between fish yield and SD (P