Abstract
Coccolith mass is an important parameter for estimating coccolithophore contribution to carbonate sedimentation, organic carbon ballasting and coccolithophore calcification. Single coccolith mass is often estimated based on the ks model, which assumes that length and thickness increase proportionally. To evaluate this assumption, this study compared coccolith length, thickness, and mass of seven Emiliania huxleyi strains and one Gephyrocapsa oceanica strain grown in 25, 34, and 44 salinity artificial seawater. While coccolith length increased with salinity in four E. huxleyi strains, thickness did not increase significantly with salinity in three of these strains. Only G. oceanica showed a consistent increase in length with salinity that was accompanied by an increase in thickness. Coccolith length and thickness was also not correlated in 14 of 24 individual experiments, and in the experiments in which there was a positive relationship r2 was low (<0.4). Because thickness did not increase with length in E. huxleyi, the increase in mass was less than expected from the ks model, and thus, mass can not be accurately estimated from coccolith length alone.
Highlights
Anthropogenic emission of CO2 into the atmosphere is increasing CO2 levels in both the atmosphere and ocean at an unprecedented rate [1]
Mean E. huxleyi coccolith length ranged from 2.5 μm to 3.4 μm, while mean length of G. oceanica ranged from 4.5 μm to 5.1 μm (Table 3)
This study found that salinity affects E. huxleyi coccolith morphology in terms of length and mass, but not thickness
Summary
Anthropogenic emission of CO2 into the atmosphere is increasing CO2 levels in both the atmosphere and ocean at an unprecedented rate [1] This rapid increase of CO2 is affecting the carbon chemistry of the surface ocean, leading to a pH decrease through a process called ocean acidification [2]. Ocean acidification may affect calcification in several marine organism groups Coccolithophores are an important marine group of single celled calcifying algae characterized by the production of calcitic plates called coccoliths. As both primary and calcite producers, coccolithophores play a dual role as a CO2 sink and source in the ocean surface [7,8,9].
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