Recherche - Observatoire océanologique de Banyuls sur mer
Laboratoire Arago

Présent au laboratoire dans le cadre du programme Assemble, Declan SCHROEDER, propose un séminaire portant sur le thème :

Molecular Ecology of Boom and Bust-effect of Adaptive Evolution on Biogeochemical Cycles

webs, underpinning the bulk of primary production. Moreover, microbes have a central role in controlling ocean biogeochemical processes. They are the main producers of particulate and dissolved organic carbon (DOM) that fuel the complex food webs up the trophic food chain. A significant amount of DOM is produced in the upper Ocean due to cell caused by death, feeding, and viral infections of phytoplankton and heterotrophic bacteria. The sheer abundance of viruses (~1030) in seawater results in around 1023 virus infections per second, which in turn has a dramatic impact on biogeochemistry by diverting carbon away from the classically understood food web, towards microbe-mediated recycling processes.

The predicted net effect of viral activity is increased system respiration that shifts carbon from biological organisms to a DOM form. Perhaps more importantly, viral activity also exerts adaptive pressure on biological organisms, i.e. the “Arms Race”, a subject area not well addressed to date. Ultimately, microbial interactions play crucial roles in biogeochemical cycling of climatically active gases (e.g. dimethyl sulfide (DMS), CO and CO2, which in turn have important feedbacks to the climate system.

In principle, microbes should be able to adapt to rapidly changing environments  over relatively short time-scales (decades?) due to their large population sizes and rapid generation times (as can be seen by numerous microbe blooming events), so that the genetic variation required for adaptive evolution can be readily supplied. Using a combination of novel molecular assays and the Continuous Plankton Recorder (CPR), the longest running program for monitoring distribution and abundance of planktonic organisms, I will present evidence linking biotic (e.g. viruses) and abiotic (e.g, increasing sea-surface temperatures) drivers to genetic  selection within phytoplankton populations that will ultimately influence biogeochemical cycles.