Mullineaux 9619605 The dynamic habitats at deep-sea hydrothermal vents are temporally ephemeral and often separated from the nearest comparable habitats by hundreds-to-thousands of kilometers. Nevertheless, the physiologically unique organisms that depend on active vents not only maintain stable populations, but also colonize new vent sites within months after they appear. This paradox raises two major unanswered questions about the biology of vent animals: 1) Do larvae of vent animals disperse between distant vent sites? and 2) If so, how do they do it? These questions are central to understanding how vent populations and communities persist over ecological time and how vent species persist over evolutionary time. Presently, we know virtually nothing about how long larvae of vent species live in the plankton, how far they disperse, or what biological and physical parameters influence their dispersal ability. The three Principal Investigators will combine their expertise in cold-water larval physiology (Manahan), deep-sea larval ecology (Young) and larval dispersal models near hydrothermal vents (Mullineaux) to investigate the biological and physical factors that influence dispersal of vent larvae. This interdisciplinary study will: 1) develop methods and high-pressure equipment for rearing vent larvae at in situ pressures and temperatures; 2) measure the metabolic requirements and changes in energy content during larval development in order to estimate larval lifespans; 3) characterize the roles of vertical swimming and buoyancy in determining how larvae position themselves vertically in the field; 4) determine if the physiological tolerances for pressure and temperature change during larval development; 5) determine the distribution and abundance of larvae in the water column above vent sites; and 6) incorporate larval attributes (distributions, vertical motions, physiological tolerances, metabolic requirements and ene rgy stores) into hydrodynamic models developed by collaborating physical oceanographers to investigate the retention times, trajectories and fluxes of dispersing larvae. The studies will be the first comprehensive investigations of the larval biology of the unique hydrothermal vent fauna and will be conducted near 9N on the East Pacific Rise. This information will significantly increase our understanding of larvae in deep-sea environments, while providing data sets for comparison to larval biology in polar and temperate oceanic regions.
