Evaluation of a Sodium Hydroxymethanesulfonate Product for Reducing Total Ammonia Nitrogen in a Small-Scale Rotifer Batch Culture System

Abstract

The total ammonia nitrogen (TAN) produced as metabolic waste in rotifer batch culture systems can reach toxic concentrations as un-ionized ammonia (UIA). Sodium hydroxymethanesulfonate has been used to neutralize TAN in hauling and shipping containers for fish, crustaceans, and mollusks. The objective of this study was to determine the efficacy of a sodium hydroxymethanesulfonate product to neutralize ammonia in a rotifer batch culture system. Rotifers Brachionus rotundiformis were stocked at an initial concentration of 80 individuals/mL and were batch-cultured without water exchange for 7 d. We evaluated response variables that included TAN concentration, rotifer production, egg count, and egg : female ratio. Mean maximum TAN was 3.3 mg/L (0.08 mg UIA per liter of water) and 9.5 mg/L (0.84 mg/L UIA) for treated and control groups, respectively. Significant differences were detected in TAN, rotifer density, egg count, and egg : female ratio beginning on day 3 (P < 0.05). Beginning on day 2, mean rotifer density declined exponentially in the control group (y = 293.4 · e ^−0.249x ; R ² = 0.98) but remained constant in the treated group. Correlation coefficients indicated that TAN explained 72% of the population decrease. We conclude that the use of a sodium hydroxymethanesulfonate product as an ammonia neutralizer is effective in decreasing TAN and UIA in a small-scale rotifer batch culture system.