EFFECTS OF TEMPERATURE ON GROWTH, CALCIFICATION, AND COCCOLITH FORM IN COCCOLITHUS HUXLEYI (COCCOLITHINEAE)

Abstract

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 Qlo of growth rates for the interval 7-l% was 2.95. The Qlo value was 1.66 in medium lacking Na2COs. 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 1%.

Phosphorus limitation and heat stress decrease calcification in <i>Emiliania huxleyi</i>

“…Although a similar decrease in growth rate was not observed in batch culture, measurements of growth rate in semi-continuous cultures are more robust because growth rate is measured as an average of numerous dilution cycles. The doubling in coccolith malformations provides further evidence that 24 • C cultures were heat-stressed (Watabe and Wilbur, 1966;Langer et al, 2010;Milner et al, 2016).…”

“…In all of the above studies, however, growth rate increased from low to high temperature and none of the tested temperatures were therefore above the optimum for growth (Eppley, 1972). To our knowledge, this study is the first to show that heat stress is not only detrimental for coccolith morphology (Watabe and Wilbur, 1966;Langer et al, 2010;Milner et al, 2016) but also for coccolith production in E. huxleyi. Certainly, the potential for long-term adaptation needs to be considered, as temperature increases are unlikely to occur on timescales short enough to preclude adaptation in a rapidly growing species.…”

“…Only a few studies have specifically dealt with the effect of temperature on the occurrence of coccolith malformations. These studies suggest that higher than optimum temperature leads to an increase in malformations (Watabe and Wilbur, 1966;Langer et al, 2010). Although the effect of temperature on carbon production in E. huxleyi has been addressed in numerous studies (Sorrosa et al, 2005;Feng et al, 2008;Satoh et al, 2009;De Bodt et al, 2010;Borchard et al, 2011;Sett et al, 2014;Matson et al, 2016;Milner et al, 2016;Rosas- Navarro et al, 2016), none of these studies tested the effect of above-optimum temperature.…”

“…Despite the high percentage of partially dissolved coccoliths in Plimited batch culture, the detrimental effect of heat stress on morphogenesis is evident. As all E. huxleyi strains tested so far show this response, it could be widespread if not ubiquitous (Watabe and Wilbur, 1966;Langer et al, 2010; this study). Interestingly, we observed similar malformations e.g.…”

“…In addition, coccolith ballast can accelerate the removal of organic carbon from upper water layers and aid long-term burial of carbon (Ziveri et al, 2007). Many studies have therefore addressed the production of organic and inorganic carbon (calcite) in E. huxleyi, as well as its modification by environmental factors such as carbonate chemistry (Riebesell et al, 2000;Meyer and Riebesell, 2015), nutrient availability (Paasche and Brubak, 1994;Langer and Benner, 2009), temperature (Watabe and Wilbur, 1966;Langer et al, 2010), salinity (Paasche et al, 1996;Green et al, 1998) and light (Paasche, 1968(Paasche, , 1999.…”