title: Benthic protists and fungi of Mediterranean deep hypsersaline anoxic basin redoxcline sediments.
abstract: Some of the most extreme marine habitats known are the Mediterranean deep hypersaline anoxic basins (DHABs; water depth ∼3500 m). Brines of DHABs are nearly saturated with salt, leading many to suspect they are uninhabitable for eukaryotes. While diverse bacterial and protistan communities are reported from some DHAB water-column haloclines and brines, the existence and activity of benthic DHAB protists have rarely been explored. Here, we report findings regarding protists and fungi recovered from sediments of three DHAB (Discovery, Urania, L' Atalante) haloclines, and compare these to communities from sediments underlying normoxic waters of typical Mediterranean salinity. Halocline sediments, where the redoxcline impinges the seafloor, were studied from all three DHABs. Microscopic cell counts suggested that halocline sediments supported denser protist populations than those in adjacent control sediments. Pyrosequencing analysis based on ribosomal RNA detected eukaryotic ribotypes in the halocline sediments from each of the three DHABs, most of which were fungi. Sequences affiliated with Ustilaginomycotina Basidiomycota were the most abundant eukaryotic signatures detected. Benthic communities in these DHABs appeared to differ, as expected, due to differing brine chemistries. Microscopy indicated that only a low proportion of protists appeared to bear associated putative symbionts. In a considerable number of cases, when prokaryotes were associated with a protist, DAPI staining did not reveal presence of any nuclei, suggesting that at least some protists were carcasses inhabited by prokaryotic scavengers.
authors.affiliation: Geology and Geophysics Department, Woods Hole Oceanographic Institution Woods Hole, MA, USA.
authors.forename: Joan M
authors.initials: JM
authors.lastname: Bernhard
authors.affiliation: Department of Ichthyology and Aquatic Environment, School of Agricultural Sciences, University of Thessaly Volos, Greece.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Kormas
authors.affiliation: Geology and Geophysics Department, Woods Hole Oceanographic Institution Woods Hole, MA, USA.
authors.forename: Maria G
authors.initials: MG
authors.lastname: Pachiadaki
authors.affiliation: Division of Life Sciences, Hong Kong University of Science and Technology, Clear Water Bay Kowloon, Hong Kong.
authors.forename: Emma
authors.initials: E
authors.lastname: Rocke
authors.affiliation: Biology Department, Woods Hole Oceanographic Institution Woods Hole, MA, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Beaudoin
authors.affiliation: Biology Department, University of Nevada Reno Reno, NV, USA.
authors.forename: Colin
authors.initials: C
authors.lastname: Morrison
authors.affiliation: Department of Marine Sciences, University of Connecticut Groton, CT, USA.
authors.forename: Pieter T
authors.initials: PT
authors.lastname: Visscher
authors.affiliation: Geology and Geophysics Department, Woods Hole Oceanographic Institution Woods Hole, MA, USA.
authors.forename: Alec
authors.initials: A
authors.lastname: Cobban
authors.affiliation: Biology Department, Woods Hole Oceanographic Institution Woods Hole, MA, USA.
authors.forename: Victoria R
authors.initials: VR
authors.lastname: Starczak
authors.affiliation: Geology and Geophysics Department, Woods Hole Oceanographic Institution Woods Hole, MA, USA.
authors.forename: Virginia P
authors.initials: VP
authors.lastname: Edgcomb
keywords: DHABs; L’ Atalante; Urania; discovery; diversity; eukaryote; rRNA