Fluoride Addition Effects on Euryhaline Phytoplankter Growth in Nutrient-Enriched Seawater at an Estuarine Level of Salinity

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Abstract
The effects of 50-200 mg/l F additions to nutrient-enriched seawater, of 14-15.permill. salinity, were exymined on the growth of 5 phytoplankter species in axenic culture. The chlorophyte Dunaliella tertiolecta and the diatom Thalassiosira weissflogii were virtually unaffected in growth-rate and maximum growth density, whereas another diatom Chaetoceros gracilis appeared to be growth stimulated, with accompanying abnormal flocculation, from all the Fl concentrations. The haptophyte Pavlova lutheri was 35-50% inhibited by 150-200 mg/l F, which inhibition was partially overcome on repeated growth at these fluoride levels. The dinoflagellate Amphidinium carteri was the most sensitive to the highest F concentration, being inhibited 20-25% at 150 mg/l and more than 90% at 200 mg/l F. When this species was gradually exposed to stepwise increase in F concentration, it successfully adapted normal growth after repeated exposure to the highest F concentration. Combining these results with those previously reported for the same species examined in coastal-salinity seawater, it is concluded that euryhaline phytoplankters are fairly tolerant of high F concentrations (approaching solubility saturation) in seawater, irrespective of salinity, under nutrient-sufficient conditions.