Effects of high temperature on water quality, growth performance, enzyme activity and the gut bacterial community of shrimp (Litopenaeus vannamei)

Gut bacterial communities play a crucial role in shrimp growth and health. However, these communities are still vulnerable to pressures (such as high temperatures) that hinder their functions. Here, shrimps were cultured for 6 weeks at three different temperatures: a variable temperature (control group, falling from 23.7 to 20.8 degrees C with ambient temperature) and two fixed temperatures (26 and 30 degrees C) to study their effects on growth, enzyme activity and gut microbes of shrimp. The results indicated that increasing temperature significantly decreased the survival rate of shrimp but had a significant rise in shrimp growth performances with the higher phosphatase enzyme activities than control group. Although the high temperature did not change the alpha diversity indexes of the bacterial communities, their compositions were significantly different, compared with that of control group. The relative abundances of the top 10 families showed a discrepancy in the dominance of the bacterial community, represented by Vibrionaceae and Mycoplasmataceae at 26 and 30 degrees C groups, and Rhodobacteraceae and Flavobacteriaceae in the control group. These results indicate that temperature changes mainly affected the compositions of bacterial community, which increased the susceptibility of shrimp to some pathogenic bacterial species, such as Vibrio, thus leading to a low survival rate of shrimp.