Physicochemical Process, Crustacean, and Microcystis Biomass Changes In Situ Enclosure after Introduction of Silver Carp at Meiliang Bay, Lake Taihu.

Chengjie Yin,Chunlong Yi,Leyi Ni,Longgen Guo,Congqiang Luo

doi:10.1155/2017/9643234

Chengjie Yin, Chunlong Yi + Show 3 more

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https://doi.org/10.1155/2017/9643234

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Abstract

In order to control cyanobacteria blooms with silver carp in Lake Taihu, an in situ experiment was carried out by stocking silver carp at a biomass of 35, 70, and 150 g m−3 and no carp control in waterproof enclosures. Physicochemical water parameters and biomass of plankton were measured in enclosures to evaluate the suitable stocking density of silver carp for relieving internal nutrients and constraining cyanobacteria growth in Lake Taihu. It is found that the 35 g m−3 silver carp group and 70 g m−3 silver carp group presented lower total phosphorus, lower chlorophyll-a, and higher water transparency. Increased nitrogen to phosphorus ratio, which indicated the result of algae decline in fish presence enclosures, was attributed to decline of phosphorus. Phosphorus decline also exerted limitation on reestablish of cyanobacteria bloom. Crustacean zooplankton biomass and Microcystis biomass decreased significantly in fish presence enclosures. Silver carp could be more effective to regulate algae bloom in enclosures with dense cyanobacteria. Therefore, nonclassic manipulation is supposed to be appropriate method to get rid of cyanobacteria blooms in Lake Taihu by stocking 35 to 70 g m−3 silver carp in application.

Highlights

In freshwater ecosystems, fish affect the structure and dynamics of pelagic plankton communities by trophic cascading effects [1, 2], which usually relates consumers to their environments by food web chains [3]
Removal of planktivorous fish could relieve the predation pressure on zooplankton community by top-down control; the enhancement of crustaceans zooplankton leads to decline of algal density [4, 5]
Water temperature varied from 22.1∘C to 26.2∘C. pH and total dissolved solids did not show significant different between control group and each treatment

Summary

Introduction

Fish affect the structure and dynamics of pelagic plankton communities by trophic cascading effects [1, 2], which usually relates consumers to their environments by food web chains [3]. Removal of planktivorous fish could relieve the predation pressure on zooplankton community by top-down control; the enhancement of crustaceans zooplankton leads to decline of algal density [4, 5]. This method, used to be defined as classic biomanipulation, usually malfunctions [6] because the presence of zooplankton grazing-resistant species such as frequent carpet of fetid cyanobacteria disables or weakens top-down force in nutrient enrichment lakes. As the absence of large size zooplankton such as Daphnia in these lakes, crustacean communities are not able to control algal bloom by zooplankton-target manipulation: grazing pressure by zooplankton is useless [7]

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