Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Biogeosciences, 13, 2743-2755, 2016
https://doi.org/10.5194/bg-13-2743-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
10 May 2016
Change in coccolith size and morphology due to response to temperature and salinity in coccolithophore Emiliania huxleyi (Haptophyta) isolated from the Bering and Chukchi seas
Kazuko Saruwatari1,a, Manami Satoh1,2, Naomi Harada3, Iwane Suzuki1,2, and Yoshihiro Shiraiwa1,2 1Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, 305-8572, Japan
2CREST, Japan Science and Technology Agency (JST), Tsukuba, 305-8572, Japan
3Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, 237-0061, Japan
anow at: GIA Tokyo Godo Kaisha, Yamaguchi Building 7, 11F, 4-19-9 Taito, Taito-ku, Tokyo, 110-0016, Japan
Abstract. Strains of the coccolithophore Emiliania huxleyi (Haptophyta) collected from the subarctic North Pacific and Arctic oceans in 2010 were established as clone cultures and have been maintained in the laboratory at 15 °C and 32 ‰ salinity. To study the physiological responses of coccolith formation to changes in temperature and salinity, growth experiments and morphometric investigations were performed on two strains, namely MR57N isolated from the northern Bering Sea and MR70N at the Chukchi Sea. This is the first report of a detailed morphometric and morphological investigation of Arctic Ocean coccolithophore strains. The specific growth rates at the logarithmic growth phases in both strains markedly increased as temperature was elevated from 5 to 20 °C, although coccolith productivity (estimated as the percentage of calcified cells) was similar at 10–20 % at all temperatures. On the other hand, the specific growth rate of MR70N was affected less by changes in salinity in the range 26–35 ‰, but the proportion of calcified cells decreased at high and low salinities. According to scanning electron microscopy (SEM) observations, coccolith morphotypes can be categorized into Type B/C on the basis of their biometrical parameters. The central area elements of coccoliths varied from thin lath type to well-calcified lath type when temperature was increased or salinity was decreased, and coccolith size decreased simultaneously. Coccolithophore cell size also decreased with increasing temperature, although the variation in cell size was slightly greater at the lower salinity level. This indicates that subarctic and arctic coccolithophore strains can survive in a wide range of seawater temperatures and at lower salinities with change in their morphology. Because all coccolith biometric parameters followed the scaling law, the decrease in coccolith size was caused simply by the reduced calcification. Taken together, our results suggest that calcification productivity may be used to predict future oceanic environmental conditions in the polar regions.

Citation: Saruwatari, K., Satoh, M., Harada, N., Suzuki, I., and Shiraiwa, Y.: Change in coccolith size and morphology due to response to temperature and salinity in coccolithophore Emiliania huxleyi (Haptophyta) isolated from the Bering and Chukchi seas, Biogeosciences, 13, 2743-2755, https://doi.org/10.5194/bg-13-2743-2016, 2016.
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Coccolithophore Emiliania huxleyi (Haptophyta) strains collected from the subarctic North Pacific and Arctic oceans during the R/V MIRAI cruise in 2010 (MR10-05) were established as clone cultures. This is the first report of a detailed morphometric and morphological investigation of Arctic Ocean coccolithophore strains. Taken together, our results suggest that calcification productivity can be used to predict future oceanic environmental conditions in the polar regions.
Coccolithophore Emiliania huxleyi (Haptophyta) strains collected from the subarctic North...
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