Size matters at deep-sea hydrothermal vents: different diversity and habitat fidelity patterns of meio- and macrofauna

Abstract

Species with markedly different sizes interact when sharing the same habitat. Unravelling mechanisms that control diversity thus requires consideration of a range of size classes. We compared patterns of diversity and community structure for meio- and macrofaunal communities sampled along a gradient of environmental stress at deep-sea hydrothermal vents on the East Pacific Rise (9° 50′ N) and neighboring basalt habitats. Both meio- and macrofaunal species richnesses were lowest in the high-stress vent habitat, but macrofaunal richness was highest among intermediate-stress vent habitats. Meiofaunal species richness was negatively correlated with stress, and highest on the basalt. In these deep-sea basalt habitats surrounding hydrothermal vents, meiofaunal species richness was consistently higher than that of macrofauna. Consideration of the physiological capabilities and life history traits of different-sized animals suggests that different patterns of diversity may be caused by different capabilities to deal with environmental stress in the 2 size classes. In contrast to meiofauna, adaptations of macrofauna may have evolved to allow them to maintain their physiological homeostasis in a variety of hydrothermal vent habitats and exploit this food-rich deep-sea environment in high abundances. The habitat fidelity patterns also differed: macrofaunal species occurred primarily at vents and were generally restricted to this habitat, but meiofaunal species were distributed more evenly across proximate and distant basalt habitats and were thus not restricted to vent habitats. Over evolutionary time scales these contrasting patterns are likely driven by distinct reproduction strategies and food demands inherent to fauna of different sizes.

Endosymbionts escape dead hydrothermal vent tubeworms to enrich the free-living population

“…Tubeworms were dissected and incubated aboard the ship. To follow the symbiont escape process, we used custom-designed symbiont recruitment plates equipped with glass coverslips in high-pressure vessels to simulate deep-sea conditions of bottom water with 175 μmol·L −1 oxygen (65) and about 2-3°C at the basalt surfaces in the axial summit trough of the EPR (68). Pressure vessels for the simulated deep-sea treatments were filled with 0.2 μm sterile-filtered seawater and kept at 4°C without flow and 171.6 ± 0.…”

Characteristics of meiofauna in extreme marine ecosystems: a review

“…Species richness is inversely correlated with the intensity of vent fluid emissions (Gollner et al 2010b. In their recent study, Gollner et al (2015) showed that, unlike the majority of macrofaunal species, meiofaunal species were distributed across proximate and distant basalt habitats and were, thus, not restricted to vent habitats.…”

Hydrothermal activity lowers trophic diversity in Antarctic hydrothermal sediments

“…Hydrothermal sediments have also been suggested to act as evolutionary bridges between hard substratum vents and methane seeps (Kiel, 2016). To utilise in situ production in hydrothermal sediments, fauna must overcome the environmental stress associated with hightemperature, acidic, and toxic conditions Gollner et al, 2015). The combination of elevated toxicity and in situ organic matter (OM) production results in a different complement of ecological niches between hydrothermal and background conditions that elicits compositional changes along a productivity-toxicity gradient (Bernardino et al, 2012;Gollner et al, 2015;Bell et al, 2016b).…”

“…To utilise in situ production in hydrothermal sediments, fauna must overcome the environmental stress associated with hightemperature, acidic, and toxic conditions Gollner et al, 2015). The combination of elevated toxicity and in situ organic matter (OM) production results in a different complement of ecological niches between hydrothermal and background conditions that elicits compositional changes along a productivity-toxicity gradient (Bernardino et al, 2012;Gollner et al, 2015;Bell et al, 2016b). Hydrothermal sediments offer different relative abundances of chemosynthetic and photosynthetic organic matter, depending upon the supply of surface-derived primary productiv-ity and levels of hydrothermal activity (Tarasov et al, 2005).…”