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HEIndividual fellowship2022–2024

Cocco-Next · Physiological adaptations to ecological niches in coccolithophore haplodiplontic life cycle

Horizon Europe — Marie Skłodowska-Curie Actions

Duration
2022-11-14 → 2024-11-13
EU contribution
€161,890
Participants
1
Scheme
HORIZON-TMA-MSCA-PF-EF

Lines connect the coordinator with its partners.

Results in brief

Physiological adaptations to ecological niches in coccolithophore haplodiplontic life cycle

Marine microalgae, also called phytoplankton, are crucial contributors to global carbon cycle and oceanic ecology. Indeed, they perform photosynthesis, the light-driven capture on CO2 into biomass, which is a carbon sink and a founding reaction of marine food webs. More specifically, coccolithophores are an important group of unicellular algae because they are very abundant and produce an “exoskeleton” made of calcium carbonate. In contrast with most eukaryotes (e.g. animals and land plants), coccolithophores thrive through a haplo-diplontic life cycle: both haploids and diploids (equivalent to gametes and egg cells, respectively) can undergo asexual divisions (mitosis). Moreover, within a given species, haploid and diploid cells generally form distinct extra-cellular calcareous plates. In surveys of phytoplankton spatiotemporal distribution, abundance of coccolithophore’s haploid and diploid cells are generally contrasted. It has thus been proposed that haploids and diploids display different physiological features to colonize distinct ecological niches of the ocean. The aim of this project is to challenge this hypothesis. Phytoplankton species have been relatively rarely studied in laboratory cultures because their growth is generally slow and requires highly specific conditions. I focus on the calcifying coccolithophore Calcidiscus leptoporus as a new alternative model specis and combine growth tests and measures of photosynthetic performance in strains from various locations around the globe. To gain insight at the molecular level, I also investigate the genome. Studying the life cycle of coccolithophore addresses both a fundamental topic and global ecological questions; indeed, human activities have multiple drastic effects on the ocean, and how this impacts phytoplankton, the first link in ecosystems food networks, is a major issue for biodiversity, society and economy.

Data: CORDIS, © European Union

Project objective

Human CO2 emissions are critically poisoning the earth's climate. However, sedimentation by marine primary producers contributes greatly to carbon sequestration, with coccolithophores, unicellular marine algae with cell envelopes composed of CaCO3, being the key contributors. Nevertheless, the extent of the biogeochemical impact of coccolithophores is largely unknown. They have a dual life cycle and can grow as both haploids and diploids, but past research has focused mainly on the diploid phase. Moreover, knowledge of coccolithophores is almost exclusively limited to a single species that is distributed worldwide, and can form blooms visible from space. However, this species is peculiar in many biological aspects and does not calcify in the haploid phase, therefore we need to develop more model organisms to represent impact of coccolithophores on the carbon cycle.In this action, my objective is to understand how the physiological acclimations of the coccolithophore life cycle phases allow them to inhabit different ecological niches. I will implement a multidisciplinary approach to investigate two levels of complexity: how environmental factors influence physiology and which genes contribute to distinct genetic programs. To this end, I will work on a widespread coccolithophore species that calcifies at both life cycle phases. I will characterize for the first time how photosynthesis (light-driven CO2 fixation) and photoprotection (dissipation of excess energy) differ between the two phases, and determine which environmental conditions trigger ploidy transitions. To investigate the underlying genetic factors, I will then sequence the genome and, in both phases, the transcriptome. Overall, the ambition of the Cocco-Next project is to provide important insights into the interplay between life cycles, ecological niches, and biological CO2 sequestration and beyond, create novel, interconnected and open datasets that will be invaluable to the oceanographic community.

Original text from CORDIS.

Participants

  • RUDER BOSKOVIC INSTITUTE · ZagrebCoordinatorCroatia

Links

Data: CORDIS, © European Union