Abstract
Abstract. Coccolithophores are a diverse group of calcifying phytoplankton, which are responsible for a large part of the modern oceanic carbonate production. Here, we describe novel or poorly known coccolithophores and novel life cycle combination coccospheres detected in samples collected either in the Gulf of Aqaba in the northern Red Sea or in the Gulf of Naples in the western Mediterranean. These include Syracosphaera winteri, for which detached coccoliths have previously been recorded but both a formal description and taxonomic affiliation were lacking, and five undescribed sets of combination cells linking HET and HOL forms for S. pulchra, S. mediterranea, S. azureaplaneta, S. lamina and S. orbicula. We also propose the replacement name S. kareniae for the fossil species Deutschlandia gaarderae. We describe a new species of the genus Ophiaster, O. macrospinus, displaying a unique morphological and ecological distribution as well as putative combination cells of two variants of the deep-dwelling Florisphaera profunda, which provide new insights on the affiliation of this genus within the Calcihaptophycideae. Additionally, in the family Papposphaeraceae we detected a new species, Pappomonas vexillata, and combination cells of Picarola margalefi and of a species resembling Papposphaera arctica. Finally, we detected three novel, unpaired holococcolithophore forms (Calyptrosphaera lluisae, Calicasphaera bipora and one form designated as Holococcolithophore A). Overall, this set of novel observations and ensuing discussions provide further insights into the diversity, evolution and life cycle complexity of coccolithophores in the oceans.
Highlights
Coccolithophores are calcifying protists that characteristically produce an exoskeleton made of multiple calcium carbonate scales called coccoliths (Young et al, 1999)
We describe a new species of the genus Ophiaster, O. macrospinus, displaying a unique morphological and ecological distribution as well as putative combination cells of two variants of the deep-dwelling Florisphaera profunda, which provide new insights on the affiliation of this genus within the Calcihaptophycideae
Coccolithophores intracellularly produce a high amount of dimethylsulfoniopropionate (DMSP) that is the precursor of the volatile gas dimethylsulfide (DMS), which can act as condensation nuclei that increase cloud albedo and impact climate (Charlson et al, 1987; Franklin et al, 2010)
Summary
Coccolithophores (class Prymnesiophyceae, subclass Calcihaptophycidae) are calcifying protists that characteristically produce an exoskeleton (the coccosphere) made of multiple calcium carbonate scales called coccoliths (Young et al, 1999). Coccolithophores are a major component of phytoplankton communities in the oceans and significant contributors to marine primary productivity (e.g., Okada and McIntyre, 1979; Poulton et al, 2017). Due to calcification, coccolithophores influence seawater alkalinity and act as ballast in faecal pellets of zooplankton and in marine aggregates, enhancing the export of biogenic matter to the deep ocean and sediments (e.g., Milliman, 1993; Poulton et al, 2007; Ziveri et al, 2007; Broecker and Clark, 2009). Coccolithophores intracellularly produce a high amount of dimethylsulfoniopropionate (DMSP) that is the precursor of the volatile gas dimethylsulfide (DMS), which can act as condensation nuclei that increase cloud albedo and impact climate (Charlson et al, 1987; Franklin et al, 2010)
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