Large-scale patterns in biodiversity of microbial eukaryotes from the abyssal sea floor

Abstract

Eukaryotic microbial life at abyssal depths remains "uncharted territory" in eukaryotic microbiology. No phylogenetic surveys have focused on the largest benthic environment on this planet, the abyssal plains. Moreover, knowledge of the spatial patterns of deep-sea community structure is scanty, and what little is known originates primarily from morphology-based studies of foraminiferans. Here we report on the great phylogenetic diversity of microbial eukaryotic communities of all 3 abyssal plains of the southeastern Atlantic Ocean-the Angola, Cape, and Guinea Abyssal Plains-from depths of 5,000 m. A high percentage of retrieved clones had no close representatives in genetic databases. Many clones were affiliated with parasitic species. Furthermore, differences between the communities of the Cape Abyssal Plain and the other 2 abyssal plains point to environmental gradients apparently shaping community structure at the landscape level. On a regional scale, local species diversity showed much less variation. Our study provides insight into the community composition of microbial eukaryotes on larger scales from the wide abyssal sea floor realm and marks a direction for more detailed future studies aimed at improving our understanding of deep-sea microbes at the community and ecosystem levels, as well as the ecological principles at play.benthic | clone library | deep sea | protists | protozoa

Analysis of the community structure of abyssal kinetoplastids revealed similar communities at larger spatial scales

“…Our results from the SouthEast Atlantic, thus, corroborate the report of Scheckenbach et al (2010) and are also in agreement with a comparable study of communities of prokaryotes from the same sampling regions also reporting of statistically indistinguishable communities from both the Angola and the Guinea Basin, as well as the Guinea Basin and the Namibia Abyssal Plain (Schauer et al, 2009). Furthermore, as the kinetoplastid-specific clone libraries from the South-East Atlantic, reported here, show the same pattern as clone libraries built with general eukaryotic primers as reported by Scheckenbach et al (2010), it is admissible to assume that the pattern reported here for both the South-East and South-West Atlantic may be similar for other groups of microbial eukaryotes. The assumption of McClain and Hardy (2010), that geographical ranges may increase with depth as environmental conditions become more constant and homogeneous, may therefore be plausible.…”

“…This may underline the constant and homogeneous conditions prevailing over large spatial distances at abyssal depths. Two previous studies already reported of similar, and even statistically not distinguishable, communities of microbial eukaryotes at larger scales from the abyssal North-West Atlantic (Countway et al, 2007) and the abyssal South-East Atlantic (Scheckenbach et al, 2010). The latter study equally reported of statistically not distinguishable communities from the Angola and the Guinea Basin, and also of statistically distinct communities from the Namibia Abyssal Plain.…”

“…An important fraction of these communities is comprised of Euglenozoa, a large group of flagellate protozoa characterized by the ultrastructure of their flagella containing a rod (called paraxonemal; Hausmann et al, 2003). This group seems to be more abundant in deep-sea clone libraries than in epipelagic waters (Countway et al, 2007) and has been reported from a wide variety of deep-sea environments (for example, Ló pez- García et al, 2001;Stoeck et al, 2003;Scheckenbach et al, 2010).…”

“…Kinetoplastids are found in almost all terrestrial and aquatic environments. A recent study of deep-sea euglenozoans revealed the presence of deep-sea specific lineages of diplonemids, a sister group of kinetoplastids (Lara et al, 2008), and studies of deep-sea kinetoplastids reported a disproportional low representation of these deep-sea lineages in public databases (Shah Salani, 2009;Scheckenbach et al, 2010). The ecological relevance of kinetoplastids, together with the potential specific deep water lineages reported, made this group an interesting subject for the study of deep-sea microbial eukaryotes.…”

Quantifying the relative roles of selective and neutral processes in defining eukaryotic microbial communities

“…So far, studies utilising these techniques are providing increasing evidence that many microbial communities are not homogenised through space, but display significant structure just like many plant and animal communities do (Martiny et al, 2006;Hanson et al, 2012;Nemergut et al, 2013). These findings have principally been based on studies examining bacteria (Fierer and Jackson, 2006;Bryant et al, 2008;Fulthorpe et al, 2008;Lauber et al, 2009;Knief et al, 2010;Ghiglione et al, 2012); the relatively fewer studies examining eukaryotic microbes also show differential patterns of community composition in space (Dumbrell et al, 2010;Scheckenbach et al, 2010;Bokulich et al, 2014;Taylor et al, 2014).…”