@booklet {sheward_short-term_2024,
	title = {Short-term response of Emiliania huxleyi growth and morphology to abrupt salinity stress},
	year = {2024},
	month = {feb},
	publisher = {Biogeochemistry: Open Ocean},
	type = {preprint},
	abstract = {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{\textendash}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{\textendash}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.},
	keywords = {RCC1232},
	doi = {10.5194/egusphere-2024-349},
	url = {https://egusphere.copernicus.org/preprints/2024/egusphere-2024-349/},
	author = {Sheward, Rosie M. and Geb{\"u}hr, Christina and Bollmann, J{\"o}rg and Herrle, Jens O.}
}
@article {gebuhr_strain-specific_2021,
	title = {Strain-specific morphological response of the dominant calcifying phytoplankton species Emiliania huxleyi to salinity change},
	journal = {PLOS ONE},
	volume = {16},
	number = {2},
	year = {2021},
	note = {Publisher: Public Library of Science},
	month = {feb},
	pages = {e0246745},
	abstract = {The future physiology of marine phytoplankton will be impacted by a range of changes in global ocean conditions, including salinity regimes that vary spatially and on a range of short- to geological timescales. Coccolithophores have global ecological and biogeochemical significance as the most important calcifying marine phytoplankton group. Previous research has shown that the morphology of their exoskeletal calcified plates (coccoliths) responds to changing salinity in the most abundant coccolithophore species, Emiliania huxleyi. However, the extent to which these responses may be strain-specific is not well established. Here we investigated the growth response of six strains of E. huxleyi under low (ca. 25) and high (ca. 45) salinity batch culture conditions and found substantial variability in the magnitude and direction of response to salinity change across strains. Growth rates declined under low and high salinity conditions in four of the six strains but increased under both low and high salinity in strain RCC1232 and were higher under low salinity and lower under high salinity in strain PLYB11. When detailed changes in coccolith and coccosphere size were quantified in two of these strains that were isolated from contrasting salinity regimes (coastal Norwegian low salinity of ca. 30 and Mediterranean high salinity of ca. 37), the Norwegian strain showed an average 26\% larger mean coccolith size at high salinities compared to low salinities. In contrast, coccolith size in the Mediterranean strain showed a smaller size trend (11\% increase) but severely impeded coccolith formation in the low salinity treatment. Coccosphere size similarly increased with salinity in the Norwegian strain but this trend was not observed in the Mediterranean strain. Coccolith size changes with salinity compiled for other strains also show variability, strongly suggesting that the effect of salinity change on coccolithophore morphology is likely to be strain specific. We propose that physiological adaptation to local conditions, in particular strategies for plasticity under stress, has an important role in determining ecotype responses to salinity.},
	keywords = {Calcification, Carbonates, Ecophysiology, Marine ecology, Marine geology, Morphometry, Paleoclimatology, rcc1210, RCC1232, rcc1824, rcc868, RCC904, salinity},
	issn = {1932-6203},
	doi = {10.1371/journal.pone.0246745},
	url = {https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0246745},
	author = {Geb{\"u}hr, Christina and Sheward, Rosie M. and Herrle, Jens O. and Bollmann, J{\"o}rg}
}
