Recruitment patterns of invertebrates at anhydrite hydrothermal vents on the Juan de Fuca Ridge, NE Pacific

Increased understanding of recruitment dynamics of vent species can provide greater insights into the variability in adult populations and aid in identifying factors, such as physical and/or environmental stressors, which may obscure the temporal history of recruitment patterns. At anhydrite vents within the ASHES vent field (Axial Volcano, Juan de Fuca Ridge) the infrastructure is unstable, fluids contain low metal but high sulphide concentrations, and temperatures range from 10 to 200 degrees C. Despite high levels of larval supply to these vents, there is a paucity of colonizing invertebrates, either because of the physical instability of the anhydrite substratum or the chemical composition of the fluid. Colonization panels were used to quantify recruitment to three anhydrite vents (Virgin, Virgin's Daughter, Marshmallow) in the ASHES vent field over different time scales (1 vs. 2 yrs). Recruitment to anhydrite habitats did occur, but at lower levels compared to other vents in the field. The most abundant taxa colonizing the panels were gastropods and polychaetes. The recruit assemblages on the colonization panels generally were similar to the established assemblages inhabiting these vents, particularly after 2-yr periods. These results suggest that environmental factors, such as the temperature and/or chemistry of the vent fluid, rather than the physical instability of the anhydrite substratum are regulating invertebrate populations at anhydrite hydrothermal. vents.