Growth response of the marine blue-green alga, Gomphosphaeria aponina, to inorganic nutrients and significance to management of Florida red tide.

A bioactive isolate from the blue-green alga Gomphosphaeria aponina is cytolytic towards the dinoflagellate, Gymnodinium breve, Florida's red tide organism. Batch and continuous cultures of G. aponina were used to determine nutrient limitation and to optimize mass-culture conditions. Iron and inorganic carbon were growth limiting; first-order saturation kinetics were observed for both substrates. For Fe3+, kinetic parameters were: Ks = 62 +/- 9 microgram 1(-1), and Ke max = 2.14 days-1. Maximum growth was observed at 150 micrograms Fe3+1(-1), with minimal growth below 10 microgram 1(-1). Cells colonized with increasing Fe3+ supplements, and time to reach maximum culture populations was inversely related to the concentration. For HCO3-,Ks = 62 +/- 4 mg1(-1) and Ke max = 1.3 day-1. Additions of NH4+ up to 200 micrograms 1(-1) were not stimulatory, whereas at 1.0 mg 1(-1) levels, Ke was 50% greater than for NO3- enriched medium. Concentrations greater than 25 micrograms PO4(3-) 1(-1) were stimulatory. However, at 1 mg1(-1), growth was less than in controls. Comparison of similar data available for G. breve would suggest that the inorganic nutrient requirements of G. aponina were minimal. Potential for natural control of G. breve by G. aponina is perhaps related to the efficiency of contact of the two organisms.