Hydrothermal vent chimney-base sediments as unique habitat for meiobenthos and nanobenthos: Observations on millimeter-scale distributions

Hydrothermal vents are critical to marine geochemical cycling and ecosystem functioning. Although hydrothermal vent-associated megafauna chemoautotrophic prokaryotes have received extensive dedicated study, smaller eukaryotes such as meiofauna nanobiota much less attention. These communities comprise links in trophic flow carbon of other habitats, so study their occurrence role vent ecosystems is warranted. Further, an understudied habitat the thin sediment cover at base chimneys. An initial revealed that sediments chimneys Izu-Ogawasara Arc system (western North Pacific) support metazoan meiofauna, but very little known about taxonomic composition abundance meiobenthic protists nanobiota, or millimeter-scale distributions. Using Fluorescently Labeled Embedded Coring method (FLEC), we describe results on meiofaunal higher-level identifications, life positions relative abundances within from three habitats (base chimneys, inside caldera away outside caldera) Myojin-Knoll vicinity. Results suggest chimney-base community unique more abundant compared non-chimney associated eukaryotic communities. Supporting evidence (molecular phylogeny, scanning transmission electron microscopy imaging) documents first hydrothermal-vent-associated occurrences for two protist taxa. Collectively, provide valuable insights into a cryptic component ecosystem.