title: Large variability of bathypelagic microbial eukaryotic communities across the world's oceans.
abstract: In this work, we study the diversity of bathypelagic microbial eukaryotes (0.8-20 μm) in the global ocean. Seawater samples from 3000 to 4000 m depth from 27 stations in the Atlantic, Pacific and Indian Oceans were analyzed by pyrosequencing the V4 region of the 18S ribosomal DNA. The relative abundance of the most abundant operational taxonomic units agreed with the results of a parallel metagenomic analysis, suggesting limited PCR biases in the tag approach. Although rarefaction curves for single stations were seldom saturated, the global analysis of all sequences together suggested an adequate recovery of bathypelagic diversity. Community composition presented a large variability among samples, which was poorly explained by linear geographic distance. In fact, the similarity between communities was better explained by water mass composition (26% of the variability) and the ratio in cell abundance between prokaryotes and microbial eukaryotes (21%). Deep diversity appeared dominated by four taxonomic groups (Collodaria, Chrysophytes, Basidiomycota and MALV-II) appearing in different proportions in each sample. Novel diversity amounted to 1% of the pyrotags and was lower than expected. Our study represents an essential step in the investigation of bathypelagic microbial eukaryotes, indicating dominating taxonomic groups and suggesting idiosyncratic assemblages in distinct oceanic regions.
authors.affiliation: Department of Marine Biology and Oceanography, Institut de Ciències del Mar (CSIC), Barcelona, Spain.
authors.forename: Massimo C
authors.initials: MC
authors.lastname: Pernice
authors.affiliation: Department of Marine Biology and Oceanography, Institut de Ciències del Mar (CSIC), Barcelona, Spain.
authors.forename: Caterina R
authors.initials: CR
authors.lastname: Giner
authors.affiliation: Department of Marine Biology and Oceanography, Institut de Ciències del Mar (CSIC), Barcelona, Spain.
authors.forename: Ramiro
authors.identifier: http://orcid.org/0000-0002-8213-0604
authors.initials: R
authors.lastname: Logares
authors.affiliation: Department of Marine Biology and Oceanography, Institut de Ciències del Mar (CSIC), Barcelona, Spain.
authors.forename: Júlia
authors.initials: J
authors.lastname: Perera-Bel
authors.affiliation: Department of Marine Biology and Oceanography, Institut de Ciències del Mar (CSIC), Barcelona, Spain.
authors.forename: Silvia G
authors.initials: SG
authors.lastname: Acinas
authors.affiliation: Division of Biological and Environmental Science and Engineering, Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia.|IMEDEA (UiB-CSIC), Department of Global Change Research, Institut Mediterraneo de Estudios Avanzados, Esporles, Spain.
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Duarte
authors.affiliation: Department of Marine Biology and Oceanography, Institut de Ciències del Mar (CSIC), Barcelona, Spain.
authors.forename: Josep M
authors.initials: JM
authors.lastname: Gasol
authors.affiliation: Department of Marine Biology and Oceanography, Institut de Ciències del Mar (CSIC), Barcelona, Spain.
authors.forename: Ramon
authors.initials: R
authors.lastname: Massana
mesh_terms: D044822:Biodiversity; D004275:DNA, Ribosomal / Q000235:genetics*; D017753:Ecosystem; D056890:Eukaryota / Q000235:genetics*; D005843:Geography; D056186:Metagenomics; D009792:Oceans and Seas; D016133:Polymerase Chain Reaction; D012623:Seawater / Q000382:microbiology*; D017422:Sequence Analysis, DNA
chemical_list: D004275:DNA, Ribosomal