INSTITUT FRANCAIS DE RECHERCHE POUR L'EXPLOITATION DE LA MER

Wave-modulated Arctic Air-sea eXchanges and Turbulence (WAAXT) is a project designed to improve our understanding of ocean boundary layer processes in a changing Arctic Ocean. Sea ice extent in the Arctic Ocean has been decreasing since the beginning of the satellite era, meaning that open-water, as opposed to under-ice, oceanographic processes are becoming increasingly important for Arctic dynamics. One of the most fundamental differences between the open and ice-covered oceans is the presence of surface waves. Surface waves and wave-driven processes drastically alter air-sea fluxes, upper-ocean turbulence, and the dominant dynamical balance in the upper ocean. WAAXT will be based on a series of field experiments to study the small-scale processes associated with this emerging wave climate, with a particular focus on near-surface turbulence. Three major effects of wave processes will be targeted: 1) Modification and suppression of ice formation by wave motions and the associated elevated near-surface turbulence. 2) Physical breakup of sea ice by wave motions, and the associated contributions to the modification of air-sea fluxes, upper-ocean structure, and melt rates. 3) Interactions between wave-driven turbulence, especially breaking and Langmuir circulations, with the unique salinity-based stratification in the Arctic basin. A key aspect of these processes is their horizontal variability, which will be captured using a multi-platform approach. Experimental work will begin in a natural laboratory in the Saint Lawrence Estuary and move to the Arctic as scientific and technical capacity is developed. The long-term goal for WAAXT is to produce the data and parameterizations needed to understand climate-scale feedbacks associated with the emerging wave climate in the Arctic basin.

The deep-sea covers about two-thirds of the world’s ocean bottoms; yet, it is one of the least known environments of the planet. Given its harsh environmental conditions, life in high depths requires several specific metabolic adaptations. Surprisingly, little is known about the molecular mechanisms underlying adaptation to such environments. Which and how many genes are involved in adaptation? What is the extent of convergent evolution across distantly related taxa? Brittle stars (Ophiuroidea) are a useful group of marine invertebrates to study for this purpose, as they are abundant in the deep-sea and they colonized this environment several times independently, thus highlighting their strong adaptive abilities. Here, I intend to investigate deep-sea adaptation using a comparative genomics approach and state of the art analytic tools. I will first use an existing dataset to examine adaptive protein evolution (genealogical discordance and positive selection), by comparing 400 genes across 800 species of shallow- and deep-water brittle stars spanning the entire Ophiuroidea diversity. I will then focus on five cryptic species complexes representative of the major bathymetric transitions, by analyzing >10,000 genes generated from exon-capture and focusing on specific candidate genes. Finally, I will investigate allele frequency shifts among depths for two species displaying a wide bathymetric range using a genome scan approach (generation of two high-quality reference genomes; whole genome resequencing for 120 individuals). With these three approaches spanning a wide phylogenetic range, I intend to decipher the molecular mechanisms underlying deep-sea adaptation. This is of high importance because deciphering mechanisms of stress-driven adaptation may provide hints on the resilience of deep marine biodiversity to the ongoing environmental changes. Keywords: deep-sea; adaptation; phylogenomics; genome scan; positive selection; exon capture; Ophiuroidea; echinoderms