Environmental controls on the elemental composition of a Southern Hemisphere strain of the coccolithophore <i>Emiliania huxleyi</i>

Abstract

Abstract. A series of semi-continuous incubation experiments were conducted with the coccolithophore Emiliania huxleyi strain NIWA1108 (Southern Ocean isolate) to examine the effects of five environmental drivers (nitrate and phosphate concentrations, irradiance, temperature, and partial pressure of CO 2 (pCO 2 )) on both the physiological rates and elemental composition of the coccolithophore. Here, we report the alteration of the elemental composition of E. huxleyi in response to the changes in these environmental drivers. A series of dose-response curves for the cellular elemental composition of E. huxleyi were fitted for each of the five drivers across an environmentally representative gradient. The importance of each driver in regulating the elemental composition of E. huxleyi was ranked using a semiquantitative approach. The percentage variations in elemental composition arising from the change in each driver between present-day and model-projected conditions for the year 2100 were calculated. Temperature was the most important driver controlling both cellular particulate organic and inorganic carbon content, whereas nutrient concentrations were the most important regulator of cellular particulate nitrogen and phosphorus of E. huxleyi. In contrast, elevated pCO 2 had the greatest influence on cellular particulate inorganic carbon to organic carbon ratio, resulting in a decrease in the ratio. Our results indicate that the different environmental drivers play specific roles in regulating the elemental composition of E. huxleyi with wide-reaching implications for coccolithophore-related marine biogeochemical cycles, as a consequence of the regulation of E. huxleyi physiological processes.

Full annual monitoring of Subantarctic Emiliania huxleyi populations reveals highly calcified morphotypes in high-CO2 winter conditions

“…A wide range of environmental parameters including salinity, irradiance, temperature and CO 2 and macronutrient concentrations (mainly nitrate and phosphate) are known to influence the physiology (i.e. growth, photosynthetic and calcification rates) of isolated E. huxleyi strains 28,30,59,60 . However, the ecological effect of changing environmental factors on the makeup of coccolithophore communities in their natural habitat is largely unknown.…”

Effects of multiple drivers of ocean global change on the physiology and functional gene expression of the coccolithophore Emiliania huxleyi

“…The PIC content was calculated as the difference between PTC and POC values. POP samples were filtered and digested as described in Feng et al (2018), and then analyzed with the molybdate colorimetric method (Solozano & Sharp, 1980). The photosynthetic and calcification rates were determined using the 14 C uptake technique (Paasche, 1964;Paasche, Brubak, Skattebol, Young, & Green, 1996) and the specific growth rate (μ) was calculated using in vivo Chl-a fluorescence daily according to the following equation:…”

“…On the x-axes, T, P, N, and I denote temperature, phosphate, nitrate, and irradiance, respectively. "*" represents significant difference with the control treatment based on one-way ANOVA [Colour figure can be viewed at wileyonlinelibrary.com] TA B L E 2 Rankings of the observed effects (in percentage changes relative to the present day conditions in the Chatham Rise area) of each single environmental drivers (data from Feng et al, 2017Feng et al, , 2018, and the two-way and multiple driver interactions on the rate processes (growth, photosynthetic, and calcification rates) and elemental composition (cellular POC, PIC, PON, and POP) of Emiliania huxleyi. T, P, N, and I denote temperature, phosphate, nitrate, and irradiance, respectively.…”

“…The combinations of present day and projected conditions for the year 2100 in the oceanic waters of the Chatham Rise, east of New Zealand, were used to provide an environmentally relevant experimental design. The results from the two-way factorial and MED effects on E. huxleyi physiological metrics were compared semiquantitatively to the calculated multiplicative effects based on a suite of single drivers from prior studies on the same E. huxleyi strain (see Section 2; Feng, Roleda, Armstrong, Boyd, & Hurd, 2017;Feng et al, 2018). In addition, changes in gene expression related to calcification and inorganic carbon acquisition processes were examined using quantitative real-time polymerase chain reaction (qRT-PCR) to understand the molecular mechanisms underpinning the physiological responses to MEDs.…”

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

“…Climate-driven changes such as ocean warming alter the productivity and composition of marine phytoplankton communities, thereby influencing global biogeochemical cycles (Boyd et al, 2018;Hutchins and Fu, 2017;Thomas, et al, 2012). Increasing sea surface temperatures have been linked to global declines in phytoplankton concentration (Boyce et al, 2010), changes in spring bloom timing (Friedland et al, 2018) and biogeographic shifts in harmful algal blooms (Fu et al, 2012;Gobler et al, 2017). Warming and acidification may drive shifts away from dinoflagellate or diatom dominance and towards nanophytoplankton (Hare et al, 2007;Keys et al, 2018).…”