Toxicity tests to assess the effect of a synthetic tank liner on shrimp survival and nitrification in a recirculating superintensive production system

Episodes of shrimp mortality occurred during the growth of Litopenaeus seti ferus in a recirculating, superintensive production system, An EPDM liner t hat was used to line the shrimp tanks was suspected of being toxic to the s hrimp. This hypothesis was tested with shrimp grown in small tanks in the p resence or absence of the liner. In the presence of the liner, all the anim als died within two weeks. Control animals, not exposed to the liner, had 1 00% survival during the same period. Additionally, ammonia accumulation was noted in the shrimp production tanks which contained liner. A second test was conducted where nitrifying bacteria, in the absence of shrimp, were exp osed to the liner. In the presence of the liner, ammonia and nitrite remova l ceased completely within a few hours, whereas the controls demonstrated f ast and efficient ammonia and nitrite removal. The EPDM liner apparently re leased chemicals that were toxic to both shrimp and nitrifying bacteria. Th is resulted in shrimp mortality and elevated ammonia levels in the recircul ating shrimp production system. This paper describes toxicity tests that id entified the liner's potential danger. These tests can be applied to select nontoxic materials for use in aquaculture facilities. The work has general application to material selection and demonstrates the need to consider bo th direct and indirect effects of toxicity in recirculating systems. (C) 20 01 Elsevier Science B.V. All rights reserved.