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Holo-heterococcolithophore life cycles: An ecological strategy?

AuthorsCros, Lluïsa ; Estrada, Marta
Issue Date28-Nov-2013
CitationIntegrating New Advances in Mediterranean Oceanography and Marine Biology. Meeting program: 36 (2013)
AbstractCoccolithophores are haptophytes that present complex haplo-diploid life cycles and, in some stage of their life cycle, produce calcium carbonate platelets, the coccoliths; they are an important ocmponent of marine phytoplankton and play a significant role in the marine biogeochemistry of carbon-carbonate cycle. Coccolithophores tend to occupy ecological environments with an intermediate degree of fertility, midway between the extremes represented by turbulent, nutrient-rich waters, which favour diatom growth, and stratified, nutrient-poor waters, where dinoflagellates and other flagellates tend to dominate. Two structurally different types of coccoliths, heterococcoliths (formed of variable shaped crystal units) and holococcoliths (formed of numerous minute crystallites), are recognizable among the coccolithophores. Many families of coccolithophores, including Helicosphaeraceae, Syracosphaeraceae, Rhabdosphaeraceae, Coccolithaceae, Calcidiscaceae, Papposphaeraceae and Pontosphaeraceae have a life cycle with holococcoliths in the haploid phase and heterococcoliths in the diploid phase. Detailed taxonomic studies of the distribution of holococcolithophores in the field are not common, in part because holococcolithophores degrade easily in water samples and most of them cannot be reliably identified with standard optical microscopy. In this work, we present a study of holo-and heterococcolithophore distributions in the Catalano-Balearic Sea during two different periods of the year, emphasizing the comparison between holo- and heterococcolithophore stages of the same species, and propose a numerical index (Index HOLP) as a tool to evaluate the general prevalence of the holococcolithophore phase in the water column. We found that the haploid holococcolithophores showed a preference for shallower nutrient-poor waters, while the diploid heterococcolithophores tended to inhabit relatively rich deeper waters. This segregation suggests that haploid and diploid cells may exploit different ecological niches; the smaller genome size of the haploid holococcolithphore stage, and in many cases the presence of mixotrophy, could represent an advantage in oligotrophic environments
DescriptionSymposium on Integrating New Advances in Mediterranean Oceanography and Marine Biology, 26-29 November 2013, Institut de Ciències del Mar (CSIC), Barcelona, Catalunya, Spain
Publisher version (URL)http://www.icm.csic.es/bio/medocean/information.htm#schedule
Appears in Collections:(ICM) Comunicaciones congresos
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