Cyanobacteria toxicity in aquaculture system and its impact on fish physiology

Abstract

Algae and some Cyanobacteria, being a core part of primary production, act as a food organism for many fishes and other aquatic organisms. But they can also be responsible for fish kill or illness. Review on Cyanobacteria effect on fish growth, survival, and recruitment is the need of the hour. The mechanisms of toxicity of cyanotoxins and their toxic metabolites in fish have been scarcely covered. The effects may be sublethal on growth, physiology, survival, recruitment, and in long run, it may have a role in the fish’s adaptive response to abiotic and other biotic stressors. Around 46 species from genera of Microcystis, Cylindrospermopsis, Synechococcus, Anabaena, Lyngbya, Oscillatoria, etc. have been shown to cause toxic effects in aquatic system. The bloom of these cyanobacteria is primarily associated with altered temperature and nutrient load in water bodies due to effluents from municipal discharge and aquaculture. Their acute or chronic toxic effects may vary depending on the species, type of toxin produced, and concentration. The various cyanotoxins are grouped as hepatotoxins like microcystin, nodularin cylindrospermopsin, neurotoxins; like anatoxins, homoanatoxins, dermatotoxins; like aplysiatoxin, debromoaplysiatoxins, lyngbyatoxins, and pyrogenic component; like lipopolysaccharides (LPS). The concentration of the specific cyanotoxin in the fish body and the water along with other factors such as the length of exposure, fish metabolic processes, water parameters like dissolved oxygen and temperature, are likely to impact cyanotoxin toxicity in freshwater fish. The impact of such toxicity may be reflected on the individual species level, ecosystem level, and even at the culture system level.