How will the key marine calcifier <i>Emiliania huxleyi</i> respond to a warmer and more thermally variable ocean?

• Main Authors: X. Wang, F. Fu, P. Qu, J. D. Kling, H. Jiang, Y. Gao, D. A. Hutchins
• Format: Article
• Language: English
• Published: Copernicus Publications 2019-11-01
• Series: Biogeosciences
• Online Access: https://www.biogeosciences.net/16/4393/2019/bg-16-4393-2019.pdf
• ISSN: 1726-4170; 1726-4189

<p>Global warming will be combined with predicted increases in thermal variability in the future surface ocean, but how temperature dynamics will affect phytoplankton biology and biogeochemistry is largely unknown. Here, we examine the responses of the globally important marine coccolithophore <i>Emiliania huxleyi</i> to thermal variations at two frequencies (1&thinsp;d and 2&thinsp;d) at low (18.5&thinsp;<span class="inline-formula">^∘</span>C) and high (25.5&thinsp;<span class="inline-formula">^∘</span>C) mean temperatures. Elevated temperature and thermal variation decreased growth, calcification and physiological rates, both individually and interactively. The 1&thinsp;d thermal variation frequencies were less inhibitory than 2&thinsp;d variations under high temperatures, indicating that high-frequency thermal fluctuations may reduce heat-induced mortality and mitigate some impacts of extreme high-temperature events. Cellular elemental composition and calcification was significantly affected by both thermal variation treatments relative to each other and to the constant temperature controls. The negative effects of thermal variation on <i>E. huxleyi</i> growth rate and physiology are especially pronounced at high temperatures. These responses of the key marine calcifier <i>E. huxleyi</i> to warmer, more variable temperature regimes have potentially large implications for ocean productivity and marine biogeochemical cycles under a future changing climate.</p>