Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2005
Publication Date: 5/31/2006
Citation: Riche, M.A., Pfeiffer, T.J., Garcia, J. 2006. Evaluation of a sodium hydroxymethane-sulfonate product for reducing total ammonia nitrogen in a small-scale rotifer batch culture system. North American Journal of Aquaculture. 68:199-205. Interpretive Summary: The production of larval marine fish requires the use of rotifers as an initial food source, which is one of the major bottlenecks preventing the full commercialization of many farmed fish. Batch culture systems, where rotifers are reared in vessels and harvested at the end of the culture cycle, are often used for rotifer production. These systems are particularly useful for small-scale hatcheries, short-term seasonal use, or where capital, resources, and training are limited. However, over the batch culture period rotifers produce ammonia as a waste product which can reach toxic concentrations. The objective of this study was to determine the effectiveness of a chemical treatment to neutralize the ammonia in rotifer batch culture systems. The culture systems were monitored for ammonia concentrations and the effect of ammonia on rotifer population numbers and reproductive capacity. Culture systems treated with the ammonia neutralizer did not exhibit increased ammonia whereas those not receiving the treatment had significant increases in ammonia. Rotifer populations and reproductive capacity were lower in the culture vessels with high ammonia, but remained healthy in the vessels receiving the ammonia neutralizer. The use of the ammonia neutralizer will allow larval culturists to raise more rotifers in the same amount of space increasing their capacity for larval production as well as substantially reducing production costs.
Technical Abstract: Total ammonia nitrogen (TAN) produced as metabolic waste in rotifer batch culture systems can reach toxic concentrations as unionized 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/mL and batch cultured without water exchange for 7 days. Response variables evaluated included TAN concentrations, rotifer production, egg counts, and egg:female ratio. Mean maximum TAN was 3.3 mg/L (0.08 mg/L UIA) and 9.5 mg/L (0.84 mg/L UIA) for treated and control groups, respectively. Significant differences were detected in TAN, density, egg counts, and egg:female ratio beginning day 3 (P<0.05). Beginning day 2, mean density declined exponentially in the control group (y = 293.4 e-0.249(x); R2 = 0.98), but remained constant in the treated group. Correlation coefficients indicate TAN explained 72% of the population decrease. We conclude use of a sodium hydroxymethanesulfonate product as an ammonia neutralizer is effective in decreasing TAN and UIA in a small-scale batch rotifer culture system.