Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2006
Publication Date: 12/28/2006
Citation: Ludwig, G.M., Hobbs, M.S., Perschbacher, P. 2006. Ammonia, pH and plankton in sunshine bass nursery ponds: The effect of inorganic fertilizer or sodium bicarbonate. North American Journal of Aquaculture. 69:80-89. Interpretive Summary: High photosynthesis rates and low buffering capacity in culture ponds often result in high pH levels. In sunshine bass fingerling production ponds high pH levels often occur during the first phytoplankton bloom after ponds are filled and fertilized. Food-wise, it is usually optimal for stocking fry into ponds because it is at the beginning of a rapid increase in the concentration of rotifers, a zooplankton that is the fry’s first food. High stress and low fry survival is often the result of high pH levels. Sodium bicarbonate has been used by baitfish farmers and it reportedly reduces pH levels. Another technique, reducing the amount of inorganic fertilizer may also reduce pH and additionally reduce the mortality risk presented by high un-ionized ammonia. Ammonia is often a constituent of inorganic fertilizer and it becomes lethal under conditions of high pH. This experiment examined the effect of applying sodium bicarbonate at three levels to ponds fertilized with published recommendations for inorganic and organic fertilizer. It also examined the effect of eliminating the inorganic fertilizer. Results after two weeks showed that the sodium bicarbonate reduce pH slightly but not significantly and did nothing to lower ammonia.. Eliminating inorganic fertilizers resulted in a significant reduction in the magnitude and frequency of high pH levels and high concentrations of un-ionized ammonia.
Technical Abstract: High pH often develops just at the time recommended for stocking 5-day-old fry when sunshine bass fingerling production ponds are filled and fertilized according to recommended practices. Decreased survival of striped bass and its hybrids with white bass is often the result of high pH and/or high un-ionized ammonia concentrations. Unionized ammonia levels resulting from fertilizer and high pH may also reach unhealthy concentrations. Anecdotal evidence suggests that using only organic fertilizers results in lower pH levels in their ponds. Similar evidence from bait-fish farmers suggests that sodium bicarbonate will reduce the effect of pH spikes. An experiment was performed that compared the effect of using sodium bicarbonate at 56.5, 113, and 226 kg/ha or eliminating the use of inorganic fertilizers on pH and other water chemistry variables and on concentrations of chlorophyll a, phytoplankton, primary productivity, and zooplankton during 12 days after ponds were filled and fertilized. Fry are usually stocked within that time period. Control ponds were fertilized with organic and inorganic fertilizers at published amounts. Ponds were 0.04 hectares. Sodium bicarbonate use resulted in a nominally lower pH on all days of the experiment; however ponds that only received organic fertilizer had pH values significantly lower than the other treatments 75% of the days. Chlorophyll a, TAN and un-ionized ammonia concentrations were also significantly lower in organic-only fertilized ponds than in the other two treatments on most days and well below sunshine bass fry tolerance limits. For most water chemistry variables tested, use of sodium bicarbonate resulted in a slight but not statistically significant (at p=0.05) improvement while use of only organic fertilizer significantly improved water quality. Although total nutrient input was lowest in the organic-only fertilized ponds, rotifers, copepod nauplii, copepods and cladocerans, the food base for sunshine bass fry were not significantly reduced. The experiment suggests using lower amounts of fertilizer in older ponds would be safe for sunshine bass fingerling culture.