Elemental stoichiometry of the key calcifying marine phytoplankton <i>Emiliania huxleyi</i> under ocean climate change: A meta‐analysis

Sheward, Rosie M.; Liefer, Justin D.; Irwin, Andrew J.; Finkel, Zoe V.

doi:10.1111/gcb.16807

Cited by 9 publications

(1 citation statement)

References 215 publications

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“…Many phytoplankton, including coccolithophores, have higher growth rates under higher irradiance level, longer daylength, or when continuous light is used (e.g., Chisholm and Brand, 1981;Harris et al, 2009;Sheward et al, 2023). We did not measure growth rate before the start of the experiment, so are unable to quantify the impact of the abrupt transition from a 12:12 L:D cycle to continuous light on growth rate under control conditions.…”

Section: Growth and Morphological Responses To Continuous Lightmentioning

confidence: 99%

Short-term response of Emiliania huxleyi growth and morphology to abrupt salinity stress

Sheward,

Gebühr,

Bollmann

et al. 2024

Preprint

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Abstract. The marine coccolithophore species Emiliania huxleyi tolerates a broad range of salinity conditions over its near-global distribution, including the relatively stable physiochemical conditions of open ocean environments and nearshore environments with dynamic and extreme short-term salinity fluctuations. Previous studies show that salinity impacts the physiology and morphology of E. huxleyi, suggesting that salinity stress influences the calcification of this globally important species. However, it remains unclear how rapidly E. huxleyi responds to salinity changes and therefore whether E. huxleyi morphology is sensitive to short-term, transient salinity events (such as occur on meteorological timescales) in addition longer duration salinity changes. Here, we investigate the real-time growth and calcification response of two E. huxleyi strains isolated from shelf-sea environments to the abrupt onset of hyposaline and hypersaline conditions over a time periods of 156 h (6.5 days). Morphological responses in the size of the cellular exoskeleton (coccosphere) and the calcium carbonate plates (coccoliths) that form the coccosphere occurred as rapidly as 24–48 h following the abrupt onset of salinity 25 (hyposaline) and salinity 45 (hypersaline) conditions. Generally, cells tended towards smaller coccospheres (-24 %) with smaller coccoliths (-7 to -11 %) and reduced calcification under hyposaline conditions whereas cells growing under hypersaline conditions had either relatively stable coccosphere and coccolith sizes (Mediterranean strain RCC1232) or larger coccospheres (+35 %) with larger coccoliths (+13 %) and increased calcification (Norwegian strain PLYB11). This short-term response is consistent with reported coccolith size trends with salinity over longer durations of low and high salinity exposure in culture and under natural salinity gradients. The coccosphere size response of PLYB11 to salinity stress was greater in magnitude than observed in RCC1232 but occurred after a longer duration of exposure (ca. 96–128 h) to the new salinity conditions compared to RCC1232. In both strains, coccosphere size changes were larger and occurred more rapidly than changes in coccolith size, which tended to occur more gradually over the course of the experiments. Variability in the magnitude and timing of rapid morphological responses to short-term salinity stress between these two strains supports previous suggestions that the response of E. huxleyi to salinity stress is strain specific. At the start of the experiments, the light condition was also switched from a light: dark cycle to continuous light with the aim of desynchronising cell division. As cell density and mean cell size data sampled every 4 h showed regular periodicity under all salinity conditions, the cell division cycle retained its entrainment to pre-experiment light: dark conditions for the entire experiment duration. Extended acclimation periods to continuous light are therefore advisable for E. huxleyi to ensure successful desynchronisation of the cell division cycle. When working with phased or synchronised populations, data should be compared between samples taken from the same phase of the cell division cycle to avoid artificially distorting the magnitude or even direction of physiological or (bio)geochemical response to the environmental stressor.

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Section: Growth and Morphological Responses To Continuous Lightmentioning

confidence: 99%

Short-term response of Emiliania huxleyi growth and morphology to abrupt salinity stress

Sheward,

Gebühr,

Bollmann

et al. 2024

Preprint

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Total alkalinity change: The perspective of phytoplankton stoichiometry

Wolf‐Gladrow,

Klaas

2024

Limnology & Oceanography

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Many biogeochemical processes change total alkalinity: this has been reported for carbonate precipitation and dissolution, uptake and release of various nitrogen‐containing compounds, uptake of phosphate, sulfate reduction combined with methane oxidation. However, the list is not exhaustive. Here we discuss additional processes, namely the uptake of Mg, K, Ca by phytoplankton, and calculate their contribution based on the explicit conservative expression for TA and an extended (compared to Redfield's C : N : P) stoichiometry of phytoplankton. These additional contributions are of the same order of magnitude as that of phosphate uptake and thus much smaller than the contribution from nitrate uptake and of opposite sign to the contribution by nitrate and phosphate uptake.

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Differential impacts of pH on growth, physiology, and elemental stoichiometry across three coccolithophore species

Chauhan,

Rickaby

2024

Limnology & Oceanography

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Coccolithophores are pivotal players in ocean biogeochemistry, yet the impact of changing pH on the physiology of different species remains unclear as there has been a dominant focus on Gephyrocapsa huxleyi. Meta‐analyses of existing experimental data are challenging due to the differences in multidimensional culture conditions. This study investigated the response of three species—Gephyrocapsa huxleyi, Coccolithus braarudii, and Chrysotila carterae—under varying CO2 conditions (via pH). The sensitivity to pH differed between species, but all species showed reduced growth rates under the highest CO2 (lowest pH) treatment possibly due to high [H+]‐related inhibition. Low pH impacted cellular physiology and elemental stoichiometry, while the impact of high pH was less adverse. The changes in elemental production induced by low pH could exert a negative influence on the contribution of coccolithophores to nutrient and carbon export, especially for biogeochemically relevant open‐ocean species. pH also affected coccolith formation, especially in C. braarudii, through CO2 limitation at high pH and low calcite saturation state at low pH. Contrasting species‐specific pH sensitivities highlighted the potential for species like G. huxleyi to further outperform others like C. braarudii in an acidic ocean. Literature synthesis showed that coccolithophores show a broad CO2 optimum, although growth rates and particulate inorganic carbon to particulate organic carbon ratios consistently declined with increasing CO2. Strain‐specific CO2 optima partly contributed to the variability within responses of individual species, giving the misleading perception of a broad species‐level CO2 optimum. Strain‐specific optima exist possibly due to their adaptation to carbonate chemistry conditions at the place of origin.

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Elemental stoichiometry of the key calcifying marine phytoplankton Emiliania huxleyi under ocean climate change: A meta‐analysis

Cited by 9 publications

References 215 publications

Short-term response of Emiliania huxleyi growth and morphology to abrupt salinity stress

Short-term response of Emiliania huxleyi growth and morphology to abrupt salinity stress

Total alkalinity change: The perspective of phytoplankton stoichiometry

Differential impacts of pH on growth, physiology, and elemental stoichiometry across three coccolithophore species

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