The prokaryotic component of the global bathypelagic ocean: abundance, activity and diversity

Aquatic Sciences Meeting, Aquatic Sciences: Global And Regional Perspectives - North Meets South, 22-27 February 2015, Granada, SpainKnowledge on deep ocean microbes is limited, restricted to relatively few sites. We sampled the bathypelagic waters of the Indian, Atlantic and Pacific Oceans during the global Malaspina expedition and used common methods and Illumina tag-sequencing to describe the general patterns in biomass, activity and diversity of this habitat. We describe the depth change in biomass and activity in the different basins, we identify the dominant prokaryotes, as well as the general trends in alfa and betadiversity at a depth of 4,000 m. The deep ocean is composed by only few thousands of likely specialized prokaryotes, representing only a small fraction of the numbers reported for the surface ocean. Global oceanic circulation and deep-sea orography act as the main ecological forces determining community structure. We also describe the free-living (FL) and particle-attached (PA) communities and show that most bathypelagic prokaryotes live either attached to particles or free-living but rarely in both habitats. These two lifestyles are deeply conserved through their phylogeny and, consequently, PA and FL communities have clear alpha and betadiversity differences that exceed the global-scale geographical variationPeer Reviewe