Genetic variability of the microalga Emiliania huxleyi (Haptophyta): a temporal and geographical study

Thesis

The Earth's climate is changing at a pace that was never observed before, and this may result in species migration to new habitats or, more drastically, to extinction. Nevertheless, certain species which have a fast turnover might evolve and become resilient to the effects of a rapidly changing environment. This resiliency-scenario better applies to species with large population size and rapid generation times, such as the coccolithophore Emiliania huxleyi, which plays a fundamental role in the marine ecosystem since it produces calcium carbonate coccoliths and it is responsible of circa 80% of carbonate precipitation in seawater. E. huxleyi shows both morphological and genetic intraspecific variability, with A and B being its two main coccolith morphological types, corresponding to its two main genotypes characterised by coccolith morphology motif (CMM) I & II respectively.

Here I present the results of a temporal and geographical study, aimed to investigate the extant diversity of E. huxleyi in both the Northern and Southern hemispheres and its genetic standing stock over a 6-year time period. I found that only genotypes CMM I & CMM IV persist and dominate throughout the years, and they are both representative of E. huxleyi A morphotype, which dominates North-eastern Atlantic, Western English Channel (WEC) and North Sea E. huxleyi bloom events.

Additionally, my study confirms the genetic variability in the global E. huxleyi community and reveals that the intraspecific variability is defined by geophysical features, with E. huxleyi morphotype A being dominant in temperate regions (10-18 °C), while morphotypes B & B/C as defined by CMM II & IIb, respectively, being dominant in polar regions (<10 °C).

Finally my results show that cultures maintained in laboratory collections might not be representative of real extant stocks, and therefore may not necessarily describe the genetic composition of wild biogeographic populations.

Authors: Balestreri, C

• DOI: 10.5287/ora-qmxzxgzkz
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: coccolithophore; molecular marker
• Subjects: Emiliania huxleyi; Genetic variability