LIU Hui1, XIE Yi-fa1, ZHANG Xiu-feng1, ZHONG Ping1, LIU Zheng-wen1,2
1. Institution of Hydrobiology, Jinan University, Guangzhou 510632, China; 2. Nanjing Institute of Geography & Limnology, Chinese Academy of sciences, Nanjing 210008, China
Fish can affect the quality of water in reservoirs.Tilapia is one of the main aquaculture fishes in southern China.This study evaluated the effect of tilapia on water quality using enclosure experiments in Dajingshan Reservoir.The results showed that fish increased the mean total nitrogen(N),total phosphorus(P) and chlorophyll a content by 42%,129% and 347%,respectively.It was likely that fish excretion increased nutrient loading and enhanced phytoplankton growth.While phytoplankton biomass increase would lead to a decrease of water transparency.The results indicate that the bottom-up control on phytoplankton through fish excretion is stronger than the top-down effects through fish grazing.
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