Dynamics of the water quality parameters in the super-intensive culture of Litopenaeus vannamei in BFT system on artificial brackish water

The study aimed to characterize the dynamics involved in the water quality parameters in a biofloc system (BFT) during the super-intensive cultivation of Litopenaeus vannamei using two levels of artificial brackish water. The test was designed with two salinity levels, T16 (16‰) and T8 (8‰), with 4 replicates, and 250 shrimps/m2 by 60 days, water analysis and animal performance were studied in each treatment. No significant differences were observed between the two salinities for biochemical oxygen demand (BOD5), total chemical oxygen demand (CODt), and fixed suspended solids (FSS). Using CODt/BOD5, it was possible to identify the water biodegradability and manage the concentration of organic and inorganic matter in the medium. Filtered chemical oxygen demand (CODf) was used to monitor the dissolved organic matter, which was higher in T16. Carbohydrate (molasses) did not control total ammonia reaching in T8 = 1.16±0.64 mg/L. This organic matter addition reduced the growth of chemoautotrophic nitrifying bacteria and interfered in the nitrogen dynamics. Regarding total solids and suspended solids, there was a significant difference between treatments, except for FSS. Dissolved oxygen (DO) and oxygen saturation (sO2) were significantly different between the treatments. The maintenance of a more neutral pH and greater alkalinity were observed, with significant differences between the treatments throughout the whole cultivation. Regarding the shrimp growth performance, the high salinity presented more weight gain, specific growth rate, feed conversion and final biomass, and lower mortality then lower salinity. These results showed that shrimps presented a higher performance in salinity 16‰.