Shift of phytoplankton and microbial communities cause seasonal dynamics of odor compounds in Oncorhynchus mykiss cultured in a freshwater reservoir

Abstract

The presence of the odorous compounds geosmin (GSM) and 2-methylisoborneol (MIB) can cause off-flavor in aquacultural products and result in large economic losses. Here, we investigated the effects of various factors on the abundance of microorganisms that mediate the production of off-flavor compounds as well as the environmental conditions that promote the growth of these microorganisms. We monitored seasonal variation in water quality, odorous compounds, and phytoplankton and microbial communities in a cold freshwater reservoir with Oncorhynchus mykiss. All water quality parameters significantly differed among seasons with the exception of salinity and total suspended solids. The concentrations of GSM and MIB in fish varied among seasons, and the highest values were observed in the summer. Pearson correlation analysis revealed that Cyanophyta and Bacillariophyta in water were significantly related to both GSM and MIB concentrations in fish, and three genera in Cyanophyta, including Aphanizomenon, Oscillatoria, and Anabaena, were positively correlated with GSM and MIB concentrations (P < 0.05). Principal component analysis indicated that microbial communities were distinct among the four seasons. However, no significant correlations of both the order Myxococcales and phylum Actinobacteria with odorous compounds were detected (P > 0.05). Temperature, soluble reactive phosphorus (SRP), and total phosphorus (TP) were significantly positively correlated with the phyla and genera that were significantly positively correlated with GSM and MIB concentrations (P < 0.05). Various water quality parameters (SRP and TP) could be managed to reduce the presence of GSM and MIB-induced off-flavor in this reservoir as well as other cold freshwater systems used for aquaculture.