Response of phytoplankton to silver carp, Hypophthalmichthys molitrix (Val.), stocking under phosphorus fertilization: a case study in a large reservoir in central China

Phosphorus fertilization is employed in some reservoirs to increase fish production. To clarify whether silver carp regulate phosphorus (P) concentration or if fertilizing leads to phytoplankton blooms, a 6-week experiment was conducted with 18 enclosures in Nanwan Reservoir, central China. Treatments were three levels of P concentration (low: 45 μg/L; medium: 90 μg/L; high: 180 μg/L) with or without silver carp stocking (10 g/m3). The effect of silver carp stocking on phytoplankton community changed with P fertilization in the water column. No significant fish effect was observed on total phytoplankton biomass at the low P level, while the chlorophyll a concentration, total phytoplankton biomass, and biomass of phytoplankton > 30 μm were enhanced significantly by silver carp at the medium P level. In addition, at the medium P level, the biomass of Bacillariophyta was significantly greater, whereas the biomass of Chlorophyta was significantly lower in the enclosures with silver carp stocking. Potentially,...