Biotic and Abiotic Interactions of Deep-Sea Hydrothermal Vent-endemic Fish on the East Pacific Rise

Kate L. Buckman, Ph.D., 2009
Timothy Shank, Advisor

A study of fish endemic to hydrothermal vents on the East Pacific Rise was undertaken, focusing on the bythitid Thermichthys hollisi. Gut contents indicated that T. hollisi were actively feeding upon brachyuran crabs, Alvinocaris shrimp, polychaetes, and zoarcid fish. Carbon, nitrogen, and sulfur stable isotopic measurements supported a chemosynthetically based prey source and placed T. hollisi in the uppermost trophic level. Otoliths from both species of vent fish appear to record exposure to hydrothermal fluids, most noticeably within the elevated Sr:Ca and depleted Mg:Ca ratios. Otolith chemistry suggested that Thermarces cerberus experiences greater direct exposure to diffuse fluids than does Thermichthys. hollisi. Isotopic patterns across the span of the otolith suggested that T. cerberus spends its entire life within the vent system, while T. hollisi exists outside of the influence of hydrothermal activity for some early portion of its life-cycle. Time-lapse photography and in situ electrochemistry indicated that T. hollisi are preferentially utilizing habitats containing elevated temperatures and sulfide levels, and variable oxygen levels in comparison to ambient bottom water. A fragment of Cu, Zn superoxide dismutase was successfully amplified from T. hollisi mRNA, but there were no differences in expression levels between tissue types or among individuals examined.