Distribution of microbial eukaryotes living as epibiota on tube worms (Ridgeia piscesae) in hydrothermal fluid flow and vent plumes at Axial Seamount

Abstract

Hydrothermal vents are deep-sea environments characterized by high temperature, low pH, low oxygen concentration and high chemical concentrations with a chemosynthesis based ecosystem. Microbial eukaryotes (protists) live in the water column and attached to hard substrates in the vent environment, feeding on chemosynthetic prokaryotes and detritus. A proportion of these protists are endemic to the vent environment, while other taxa are cosmopolitan. I hypothesized that protists living attached to tubeworms in hydrothermal flow would possess adaptations that allow them to survive vent conditions, leading to a lower community diversity and species richness in these communities than in the water column above the vent. Paired microbial samples were collected from the exterior of tube worms and the water column at active venting sites at Axial Seamount. Sample DNA was amplified using universal eukaryotic and metazoan-excluding primer sets and the v4 hypervariable region of the 18s gene was sequenced. Non-metazoan primers amplified prokaryotic sequences and comparatively fewer protists than universal primers, while universal primers were able to amplify more protist sequences from worm samples than non-metazoan primers suggesting that they can be effectively implemented to amplify epibiotic sequences. Higher species richness and diversity was observed in the water column samples than tube worm samples using both sets of primers, suggesting higher rates of endemism living on worms in direct hydrothermal flow as hypothesized.