Ecological interaction between cyanobacterial blooms and freshwater fish

Abstract

Fish are an integral component of aquatic ecosystems and play important roles in maintaining ecosystem stability. However, fish have recently been under great threat due to the deterioration of aquatic environments and the loss of suitable habitats. Due to the intensification of global warming and water eutrophication, the frequency and duration of cyanobacteria blooms have been increasing. Cyanobacteria blooms are often accompanied by cyanotoxin and taste-and-odor substance productions which threaten fish survival and fishery economics. However, the ecological interaction between cyanobacteria and fish is multifaceted. Biomanipulation techniques using fish to regulate excessive cyanobacteria growth have achieved certain effects in the bioremediation of eutrophic water bodies. Therefore, a comprehensive assessment of the impacts of cyanobacteria blooms on freshwater fish populations and the control and driving effects of fish on cyanobacteria are necessary to protect freshwater ecosystems. This study systematically analyzes the effect of cyanobacteria blooms on freshwater fisheries, toxicological effects of harmful cyanobacteria on fish, and the ecological regulation of fish on cyanobacteria. Accordingly, we have proposed future research directions. More attention should be paid to the impacts of cyanobacteria blooms on the physiology, ecology, and behavior of fish, and other animal populations. It is necessary to further clarify whether fish miniaturization and a decline in fish species diversity are directly related to cyanobacteria blooms. Fish exposure to cyanobacteria blooms is a complex topic because aquatic animals are not only exposed to cyanotoxins but also to cyanobacterial cells and lysates which contain various compounds. Thus, the overall effect of complex cyanobacteria biomass or in situ cyanobacteria blooms on fish and the corresponding aquatic ecological risk assessment probably will be the focus of future aquatic research. Moreover, a comprehensive examination of the impact of taste-and-odor substances produced by cyanobacteria on fishery products is also required. Biomanipulation, including traditional and non-traditional techniques, is one of the effective tools to control cyanobacteria blooms. Biomanipulation for water environment restoration can be affected by several factors including geographical characteristics, lake and reservoir morphology, algal composition, stocking mode, and biological community structure. Therefore, the feasibility of implementing biomanipulation should depend on the environmental and biological characteristics of water bodies and specific practices during decision-making processes. Previous studies suggest that combining bivalve and filter-feeding fish may enhance the bioremediation effect of algae but their synergistic effects and effectiveness in natural lakes remain to be further verified. Therefore, this study aims to provide a scientific basis to assess the ecological risk of cyanobacteria blooms, protect freshwater fish, and improve aquatic environments.