Effect of adding microalgae to whiteleg shrimp culture on water quality, shrimp development and yield

This study investigated the effects of microalgae addition on the water quality, accumulation of Vibrios in the water and sediment, and growth performance of whiteleg shrimp (Litopenaeus vannamei) in the intensive culture system. To evaluate the effects of two monospecific microalgae in whiteleg shrimp culture, an 84-day experiment was performed in concrete tanks seeded with Nannochloropsis oculata and Thalassiosira pseudonana at a density of 10 × 104~80 × 104 cells/mL. The results showed that adding T. pseudonana treatment significantly decreased the levels of nitrite-N, nitrate-N, orthophosphate-P, total ammonia nitrogen and suspended solids during the intermediate and the later culture tank. Additionally, the two added microalgae kept pH steady and increased dissolved oxygen (at daytime) in the culture water. We also found that the concentration of Vibrios in water and sediment from adding microalgae treatments was significantly reduced compared to control groups. Moreover, the highest mean weight gain (1.49 ± 0.056 g/week), the growth rate (1.50 ± 0.067 g/week) and the lowest feed conversion rate (1.42 ± 0.023) were observed in T. pseudonana treatment, which were significantly better than that of the control group (F (2, 6) = 13.77, P = 0.006). Productivity in the treatment of T. pseudonana was 3.65 ± 0.095 kg/m3, which was 25% higher than in the control group (2.92 ± 0.065 kg/m3, F (1, 4) = 143.58, P < 0.0001). These results for shrimp growth, including the yield and feed conversion rate, suggested that the addition of T. pseudonana was more suitable for whiteleg shrimp production. In summary, adding T. pseudonana to Whiteleg shrimp intensive culture system can effectively improve the water quality, preventing the accumulation of Vibrios in the water and sediment, resulting in the better growth performance.