Nutritional response of a coccolithophore to changing pH and temperature

Abstract

Coccolithophores are a calcifying unicellular phytoplankton group that are at the base of the marine food web, and their lipid content provides a source of energy to consumers. Coccolithophores are vulnerable to ocean acidification and warming, therefore it is critical to establish the effects of climate change on these significant marine primary producers, and determine potential consequences that these changes can have on their consumers. Here, we quantified the impact of changes in pH and temperature on the nutritional condition (lipid content, particulate organic carbon/nitrogen), growth rate, and morphology of the most abundant living coccolithophore species, Emiliania huxleyi. We used a regression type approach with nine pH levels (ranging from 7.66 to 8.44) and two temperatures (15°C and 20°C). Lipid production was greater under reduced pH, and growth rates were distinctly lower at 15°C than at 20°C. The production potential of lipids, which estimates the availability of lipids to consumers, increased under 20°C, but decreased under low pH. The results indicate that, while consumers will benefit energetically under ocean warming, this benefit will be mitigated by ocean acidification. The carbon to nitrogen ratio was higher at 20°C and low pH, indicating that the nutritional quality of coccolithophores for consumers will decline under climate change. The impact of low pH on the structural integrity of the coccosphere may also mean that coccolithophores are easier to digest for consumers. Many responses suggest cellular stress, indicating that increases in temperature and reductions in pH may have a negative impact on the ecophysiology of coccolithophores.

Transitional traits determine the acclimation characteristics of the coccolithophore Chrysotila dentata to ocean warming and acidification

“…Although, carbohydrates are the major energy storage, Fernandez et al (1994) reported that coccolithophores under stress save more lipids as their metabolic energy reserves and utilize them as alternative carbon sources for cellular processes including protein synthesis. It is due to carbon components under OW and OA condition in coccolithophore shunt to increases more lipid which act as primary source of energy for energy utilization and cellular process (Johnson et al, 2022). Our data show larger lipid accumulation than that of carbohydrate when cells are exposed to the HTHC condition (Figure 3A,B).…”

Ocean acidification research in the Mediterranean Sea: Status, trends and next steps

“…Detrimental effects are caused by the rapid and extreme sea surface warming and the synergy with OA (Milner et al, 2016;D'Amario et al, 2017;D'Amario et al, 2020). Laboratory experiments (Fiorini et al, 2011;Milner et al, 2016;Johnson et al, 2022), long-term sediment trap series and observations in naturally high CO 2 concentration sites (CO 2 vents, off Vulcano island, Italy, Tyrrhenian sub-basin) show negative impacts of OA on coccolith weight and biodiversity (Triantaphyllou et al, 2010;Meier et al, 2014;Ziveri et al, 2014). Another study in natural CO 2 gradient sites (CO 2 vents, Aegean sub-basin) had reported increased biodiversity with high CO 2 conditions (Triantaphyllou et al, 2018).…”

Environmental Drivers of Coccolithophore Growth in the Pacific Sector of the Southern Ocean

“…High sensitivity to temperature may also expand the poleward extent of coccolithophore growth, as has been observed in the Barents Sea (Smyth et al, 2004). Growth may increase at substantially higher temperatures (K. S. Johnson, Riser, et al, 2022;R. Johnson, Langer, et al, 2022), and evolutionary adaptation of coccolithophores may increase their tolerance to higher temperatures (Schlüter et al, 2014).…”

“…High sensitivity to temperature may also expand the poleward extent of coccolithophore growth, as has been observed in the Barents Sea (Smyth et al., 2004). Growth may increase at substantially higher temperatures (K. S. Johnson, Riser, et al., 2022; R. Johnson, Langer, et al., 2022), and evolutionary adaptation of coccolithophores may increase their tolerance to higher temperatures (Schlüter et al., 2014). Temperature‐driven increases in coccolithophore growth may not necessarily drive increased surface PIC, however, as calcification may decline under higher CO 2 (Freeman & Lovenduski, 2015; Krumhardt et al., 2019) and temperatures (Rosas‐Navarro et al., 2016).…”

“…Daily gridded altimetry data are available from The Copernicus Marine Service (https://marine.copernicus.eu/) (European Union‐Copernicus Marine Service, 2017). SOCCOM float data are available at https://doi.org/10.6075/J0MC905G (K. S. Johnson, Riser, et al., 2022; R. Johnson, Langer, et al., 2022). Data from 1° CESM simulations are available at https://doi.org/10.5065/mgb4-cd43 (Long et al., 2021a, 2021b).…”