Seaweed Gracilaria changii as a bioremediator agent for ammonia, nitrite and nitrate in controlled tanks of Whiteleg Shrimp Litopenaeus vannamei

Abstract

Intensive shrimp cultures are characterized by high stocking densities and use large quantities of artificial feed. The artificial feed was consumed only a small part by shrimp, while the rest decomposes in ponds and produces inorganic nitrogen compounds such as ammonia, nitrite, and nitrate, which are poisonous to shrimp and decrease water quality. One alternative that can be applied to improve water quality in the shrimp pond is the use of bioremediation agents. One of the bioremediation agents is seaweed Gracilaria changii. The study was designed using a Completely Randomized Design consisting of three treatments, namely (A) shrimp culture without seaweed as bioremediator; (B) shrimp culture with seaweed as bioremediator in the middle of the treatment (starting from fifth week), and (C) shrimp culture with seaweed as bioremediator since the beginning of the treatment. Each treatment was repeated three times each. During the study, ammonia, nitrite, and nitrate were measured every week. t-test is used to compare the average values of ammonia, nitrate, and nitrite. This study aims to analyze the potential of G. changii as bioremediator agents in the cultivation of whiteleg shrimp Litopenaeus vannamei in controlled tanks. This study indicated that seaweed G. cangii was an effective bioremediator for shrimp P. vannamei culture because seaweed could reduce ammonia that is toxic for shrimp. Seaweed was effective as bioremediator until the ninth week, and after the effectiveness decrease indicated by increase the nitrate consentration. Seaweed could be a shelter for shrimp during molting that indicated by higher survival rate at the treatments with seaweed. It is recommended to harvest seaweed at the ninth week, then proceed with the second seaweed culture cycle, so there will two cycles of seaweed culture every one shrimp culture cycle.