Growth responses to variations in temperature and specific conductance byChaetoceros muelleri(Bacillariophyceae)

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Abstract
C. muelleri Lemm. was isolated from lower Chevelon Creek, Arizona [USA] and cultured in a defined medium. Maximum division rates occurred at temperatures between 20.degree.-30.degree. C with mean doublings per day sharply decreasing above and below this temperature range. No divisions occurred at < 5.degree. C or > 40.degree. C. C. muelleri showed maximum division rates (> 1.5 divisions day-1) in solutions with specific conductance values between 3.0-20.0 mmhos cm-1 (2-12.5.permill. salinity). Division rates decreased abruptly in media with conductance values < 3.0 mmhos cm-1 with solutions of at least 2.0 mmhos cm-1 required to maintain 1.0 division day-1. No cell divisions were recorded at conductance values < 1.5 or > 33.0 mmhos cm-1 (< 1.permill. or > 22.permill. salinity). No significant differences in maximum division rates were measured in media dominated by Na+ and Mg2+ salts; division rates were significantly reduced in media dominated by Ca2+ and especially K+ salts. Comparisons in distribution and salinity requirements are made with C. elmorei Boyer.