Effects of Temperature on Growth, Calcification, and Coccolith Form in Coccolithus Huxleyi (Coccolithineae)

Rates of growth of Coccolithus huxleyi were determined at 7, 12, 18, 24, and 27C and found to be highest at 18 and 24C. The mean minimum doubling time was about 19 hr. The Q10 of growth rates for the interval 7–18C was 2.95. The Q10 value was 1.66 in medium lacking Na2CO3. The percentage of cells forming coccoliths was twofold to threefold greater at 18 and 24C than at 7 and 27C. Coccolith dimensions were significantly different at 12, 18, 24, and 27C. The width and length of the coccoliths and the length of the elements of the upper disc decreased progressively above 18C. In contrast, the width of the upper elements increased to a maximum at 24C. Abnormal coccoliths were produced at all temperatures and were minimal in number at 18C.