Benefits of a Biofilm System and Low Ammonia Levels to Decrees the Early Mortality Syndrome in Shrimp Larvae (Litopenaeus vannamei) Infected with (Vibrio parahaemolyticus)

Abstract

The world shrimp aquaculture, has faced several problems, causing severe losses in shrimp hatcheries; between the most critical has been diseases such as early mortality syndrome (EMS) caused by (Vibrio parahaemolyticus). The EMS was initially detected in Asian countries; after, it was disseminated to Mexico and other countries. In Mexico, EMS caused severe economic losses during 2013-2016; and it has not yet been eradicated. Various causes for EMS have been reported; none is entirely accurate, but water quality is essential for successful shrimp aquaculture; therefore, the aim this work was evaluate the ammonia concentration effect on susceptibility to (EMS) on post-larvae (PL-15) shrimp (Litopenaeus vannamei) infected with (V. parahaemolyticus), using a biofilm system (water with, microalgae, dinoflagellates, protozoa and other planktonic microorganisms). So series of 5 flasks each one were arranged as following: Series S; 900 ml of filtered seawater (FSW) and 10 PL-15 shrimp per flask. Series SB; 840 ml of FSW, 60 ml of biofilm and 10 PL-15 shrimp. Series E; 900 ml of FSW, infected with 2 ml (V. parahaemolyticus) 106 CFU/ ml and 10 PL-15 shrimp. Series EN; fifteen flasks with 900 ml of FSW, 10 PL-15 shrimp, added with NH4Cl (0.535 mg/ml), to get 0.5, 1.0, 1.5, 2.0 and 2.5 mg/l final ammonia concentration in 5 sub-series of 3 flasks each one. During experiment, ammonia concentration and PL-15 shrimp mortality were evaluated in all flask. Ammonia concentration was higher in series EN than in series E; the same was observed in Series S respect to SB, but at lower values. At end of experiment, mortality in series EN was 90% Vs 60% in E. Similarly, mortality in series S was 10% Vs 0% in SB. This results confirm that the ammonia increases PL shrimp mortality, and biofilm system reduce ammonia and consequently PL-15 shrimp mortality.