Limiting concentrations of nitrogen, phosphorus, iron on growth of Oscillatoria chlorine

The proliferation of Oscillatoria chlorine will release toxins which are harmful to prawn growth in the aquaculture ponds. We investigated the limiting concentrations of nitrogen (N), phosphorus (P) and iron (Fe3+) to the growth of O.chlorine as well as the effects of different N, P and Fe3+ concentrations on chlorophyll a content and dry weight of O.chlorine. The results show that N concentration 0.06 mgL-1, P concentration 9.9310-2 mgL-1 and 1.99 mgL-1, and Fe3+ concentration 2.5810-2 mgL-1 and 51.67 mgL-1, limited the increase of chlorophyll a content; N concentration 12.361 mgL-1, P concentration 9.9310-3 mgL-1 and the Fe3+ concentration 5.1610-3 mgL-1 and 51.67 mgL-1, limited the increase of dry weight. The threshold concentrations of N, P and Fe3+ for the growth of O.chlorine were 0.06 mgL-1, 9.9310-3 mgL-1 and 5.1610-3 mgL-1, respectively. The combined concentrations which limited the increase of chlorophyll a contents and dry weight of O.chlorine were 7.42 mgL-1 of N, 4.9610-2 mgL-1 of P and 5.1610-3 mgL-1 of Fe3+, respectively. Nitrogen had the strongest effect on chlorophyll a content and dry weight, followed by Fe3+ and P. It is suggested that the rapid proliferation of the O.chlorine might be controlled through water exchange or circulation to reduce the dissolved nitrogen content in aquaculture ponds.