Hélène Launay: Metabolism_epiphyte_PNBA

Hélène Launay 

 

Mission summary

Metabolism_epiphyte_PNBA

Contribution of benthic and epiphytic microalgae to the carbon cycle in the Banc d’Arguin National Park (PNBA)

Our ‘Mobility 2025’ expedition and the one planned for 2026 aim to quantify the contribution of benthic and epiphytic micro-organisms to the carbon cycle in the Banc d’Arguin National Park (PNBA). The sediments contain a large quantity of benthic diatoms, and the vast seagrass beds (and areas of macroalgae) are covered with epiphytic diatoms. Microscopic observations and physico-chemical parameters (O₂ levels, pH) of the sediments indicate high biological activity, with energy metabolism (as indicated by O₂ levels) varying from one part of the park to another. This variation appears to correlate with the stability of the mudflats, as well as with the presence of seagrass cover. Although the same species are found at all the surveyed sites, the intracellular organisation of the diatoms differs, as does their ability to produce lipid droplets. These photosynthetic lipids form the basis of the park’s food chain. H. Launay’s 2026 outgoing research project aims to complete the survey of PNBA sites that were inaccessible under the 2025 logistics arrangements, in particular the park’s oldest mudflat (Mamghar Bay) and the one currently forming (which appeared in 2013, the Bellat breach). The sample collection will also be optimised (using Lugol’s solution) for high-resolution observation of intracellular organisation. The aim of Mr V. Sidi Boune’s incoming mobility project is to analyse the photosynthetic lipids in the PNBA food chain.