Effect of phytoplankton bloom on intestinal bacterial load of Vannamei shrimps (Litopenaeus vannamei) sampled in Gwadar complex, Sistan and Baluchestan province

Abstract

Introduction: The aim of this study is to investigate the impact of phytoplankton blooms on the gut bacterial load of Litopenaeus vannamei shrimp samples collected from the Gwadar complex located in Sistan and Baluchestan province.

Materials & Methods: This study was conducted during the period of April to September 2020, corresponding to the cultivation cycle of Litopenaeus vannamei shrimp in the Shahid Sanaati Gwadar Shrimp Farm complex located in Sistan and Baluchestan province. Ten monthly samples of Whiteleg shrimp, which were cultured in ponds containing algal blooms or in natural conditions, were collected using standard sampling methods.

Results: The results indicated a significant difference in the nutrient levels measured in the water of the farms, inlet, and outlet canals (P<0.05). The outlet channel and fields had significantly higher levels of nitrite, nitrate, phosphate, and TOM than the inlet channel, likely due to the nutrition, metabolism, excrement, and physical activities of the shrimps (P<0.05). The algal bloom observed in the active farms was mostly caused by the Phormidium cyanobacterium, while the inlet channel of phase two had a Noctiluca algal bloom. The algal bloom in the outlet channel of the south phase was related to Synechococcus cyanobacterium. The study also found that the intestinal microbial flora of Vannamei shrimps is affected by probiotics and algal blooms. Shrimps fed with probiotics showed a significant increase in the total number of intestinal bacteria and a significant decrease in the bacterial load of intestinal vibrio (P<0.05). Additionally, shrimps cultured in ponds with algal blooms had significantly higher total bacterial load and Vibrio bacteria compared to those cultured in ponds without algal blooms (P<0.05).

Conclusion: In conclusion, this study highlights the significant impact of phytoplankton blooms on the intestinal microbial flora of Vannamei shrimps, particularly in relation to the use of probiotics. The results demonstrate the importance of monitoring water quality in shrimp farms and implementing measures to minimize the negative effects of algal blooms. Future research could further investigate the potential use of probiotics and other interventions to improve the health and productivity of shrimp populations in aquaculture settings.