Some Aspects of Fluorite and Vaterite Precipitation in Marine Environments*

Abstract. Mysid shrimps of the genus Schistornysis precipitate either fluorite (CaF₂; S. spiritus) or vaterite (CaCO3; S. assimilis) for the formation of static bodies (statoliths). In S. assirnilis, 2.44 μg calcium and 3.66 μg carbonate are precipitated for each statolith. This corresponds to 69 mg or 30 mg ambient water, respectively, using the ion content of seawater for stoichiometrical comparison. Concentmtion factors of calcium or carbonate in relation to equivalent amounts of ambient water in the statocyst cavity are 760 or 3100, respectively. In S. spiritus, 3.79 μg calcium and 3.60 μg fluoride are precipitated. This corresponds to 9.3 mg or 2788 mg ambient water, respectively. Concentration factors with respect to statocyst water mass are 610 or 183.000. respectively. Ile high fluoride accumulation for the formation of statoliths alone contributes to a fluoride content of 4500 ppm with respect to body dry weight A minimum estimate for the role of mysids in the global fluoride cycle suggests that at least 62,000 tons of fluoride are bound in mysid statoliths. Due to rapid turnover of about seven days, mysid fluorite statoliths are a crucial factor by contributing to a turnover of at most 570,000 years for overall fluoride in the oceanic system.