Over the course of the iAtlantic project, more than 5 Tb of genomic data were obtained to study the sequence polymorphism of 10 species or species complexes (cold-water corals, vent and seep molluscs, vent shrimp) on a genome-wide scale. These data have been used in population genetics to assess the degree of past and present gene flows between a series of populations at the scale of the Atlantic Ocean, coupling it for certain species (cold seep mussels) with large-scale larval dispersal modelling. Genetic analyses have enabled connectivity maps to be drawn up for all species, establishing past and present preferential migration routes between Atlantic regions. This information is of vital importance in conservation biology and may help in the development of sustainable management tools for deep-sea benthic communities living in fragmented and locally unstable environments. The studied deep-sea species tend to be distributed in geographic isolates, possibly linked by rare and sporadic migration events on a global scale. These species also have complex demographic histories, giving rise to cryptic species complexes that can hybridise locally following secondary contacts. Isolation by distance and the establishment of hydrographic and genetic barriers up to the closing of the Panama seaway has resulted in the regionalisation of most deep-sea species, a fact that must be considered in the current and future exploitation of biological and mineral resources from the deep ocean. The main findings of this work are:
- (1) The hydrothermal vent species along the Mid-Atlantic Ridge (with the exception of Bresiliid shrimp) are distributed in different genetic units that do not exchange much along the ridge axis due to both physical and genetic barriers. These genetic units need to be managed locally, taking into account the genetic information obtained at a regional scale.
- (2) The Atlantic seep mussels are geographically structured at the scale of the Atlantic Ocean with some rare events of long-distance migration. This structure is explained by the demographic history of species. Secondary contacts are probably linked with the closing of the Panama Seaway. However, long-distance migration events are not able to ensure the genetic homogenisation of populations, possibly due to the emergence of genetic barriers.
- (3) Cold-water corals are more genetically structured than previously thought with the co-occurrence of several cryptic species in Madrepora oculata at the scale of the Northeastern Atlantic, and the presence of several distinct populations within Desmophyllum pertusum at the scale of the whole Atlantic.