Changes of Phytoplankton and Water Quality under the Regulation of Filter‐Feeding Fishes and Submerged Aquatic Plants in a Large‐Scale Experiment

Biological regulation means to inhibit proliferation of harmful phytoplankton by adjusting the community structure of the lake ecosystem and to rebuild a stable and healthy one using the self-regulating ability of the lake; but its effectiveness is still controversial. Two ways of biological control (i.e., a combination of filter-feeding fishes plus submerged plants and submerged plants alone) were tested in a large-scale in situ enclosure experiment, carried out at Gonghu Bay of Taihu Lake, China. Changes of both phytoplankton flora and water quality under two experimental conditions were dynamically monitored. The results showed that (1) filter-feeding fishes decreased the phytoplankton density and promoted phytoplankton biodiversity, while submerged plants inhibited phytoplankton only in spring and showed no significant effect on phytoplankton biodiversity. (2) Submerged plants improved the water quality, however, filter-feeding fishes had adverse impact on it. Thus, we tentatively concluded that filter-feeding fishes is more effective than submerged plants in regulating phytoplankton flora, while submerged plants play an important role in improving water quality.