Diversity of Meiofauna from the 9°50′N East Pacific Rise across a Gradient of Hydrothermal Fluid Emissions

Abstract

BackgroundWe studied the meiofauna community at deep-sea hydrothermal vents along a gradient of vent fluid emissions in the axial summit trought (AST) of the East Pacific Rise 9°50′N region. The gradient ranged from extreme high temperatures, high sulfide concentrations, and low pH at sulfide chimneys to ambient deep-sea water conditions on bare basalt. We explore meiofauna diversity and abundance, and discuss its possible underlying ecological and evolutionary processes.Methodology/Principal FindingsAfter sampling in five physico-chemically different habitats, the meiofauna was sorted, counted and classified. Abundances were low at all sites. A total of 52 species were identified at vent habitats. The vent community was dominated by hard substrate generalists that also lived on bare basalt at ambient deep-sea temperature in the axial summit trough (AST generalists). Some vent species were restricted to a specific vent habitat (vent specialists), but others occurred over a wide range of physico-chemical conditions (vent generalists). Additionally, 35 species were only found on cold bare basalt (basalt specialists). At vent sites, species richness and diversity clearly increased with decreasing influence of vent fluid emissions from extreme flow sulfide chimney (no fauna), high flow pompei worm (S: 4–7, H'loge: 0.11–0.45), vigorous flow tubeworm (S: 8–23; H'loge: 0.44–2.00) to low flow mussel habitats (S: 28–31; H'loge: 2.34–2.60).Conclusions/SignificanceOur data suggest that with increasing temperature and toxic hydrogen sulfide concentrations and increasing amplitude of variation of these factors, fewer species are able to cope with these extreme conditions. This results in less diverse communities in more extreme habitats. The finding of many species being present at sites with and without vent fluid emissions points to a non endemic deep-sea hydrothermal vent meiofaunal community. This is in contrast to a mostly endemic macrofauna but similar to what is known for meiofauna from shallow-water vents.

Rapid colonisation by nematodes on organic and inorganic substrata deployed at the deep-sea Lucky Strike hydrothermal vent field (Mid-Atlantic Ridge)

“…Cephalochaetosoma and Halomonhystera, reported as the dominant genera in the nematofauna associated with mussel beds in the MAR (Sarrazin et al in press), dominated slate and bone recovered after 9 months (Table 4). Nematodes reported from the MAR (Zekely et al 2006a;Cuvelier et al 2014;Sarrazin et al in press), the North Fiji Basin (Vanreusel et al 1997), and other Pacific hydrothermal sites (Flint et al 2006;Zekely et al 2006a;Gollner et al 2007Gollner et al , 2010b were dominated by few nematode taxa. The richest nematode diversity was reported in soft sediments associated with Bathymodiolus mussels from the North Fiji basin with over 30 genera identified (Vanreusel et al 1997).…”

“…The ovoviviparous reproductive mode has already been described for Monhysteridae living in harsh environmental conditions (Van Gaever et al 2006), but it is being reported for the first time for deep-sea HVs. Nematode studies at the EPR revealed that the diversity of nematodes changed along a gradient of fluid emission (over a temperature gradient of >50°C; Gollner et al 2010b), emphasizing the role of environmental conditions. In this study, we observed that after 9 months, nematode communities were mainly influenced by the type of substratum and that environmental conditions appeared to play a minor role (Fig.…”

“…Several HV habitats, from inactive bare basalts (Gollner et al 2010b) and sediments (Vanreusel et al 1997) to diffuse flow areas colonized by macrofaunal assemblages (Zekely et al 2006a, c), host meiofaunal communities characterized by low abundance and diversity, linked with the abiotic and biotic conditions of the habitat (Gollner et al 2010b;Zekely et al 2006a, c;Degen et al 2012). In most cases, nematodes and copepods are the most abundant meiofaunal organisms (Vanreusel et al 2010;Zeppilli et al submitted).…”

“…In some hydrothermal vents such as at the North Fiji Basin (Vanreusel et al 1997) and IzuOgasawara Arc in the western North Pacific Ocean (Setoguchi et al 2014), none of the nematode species found in hydrothermal sediments occurred in the surrounding abyssal areas. Conversely, at the EPR, several nematode vent species have been found in abyssal sediments surrounding hydrothermal vent fields (Gollner et al 2010b(Gollner et al , 2015.…”

The nematode assemblage of a coastal lagoon (Lake Varano, southern Italy): ecology and biodiversity patterns

“…It is also well known as tolerant to a variety of natural and anthropogenic stressors (e.g. Armenteros et al 2009, Gollner et al 2010, Guilini et al 2012. The physiological and behavioural adaptations of T. longicaudata to poorly oxygenated environments include a low respiratory rate and slow movement (Warwick andGee 1984, Guerrini et al 1998).…”