COLLABORATIVE RESEARCH: Integrated Studies of Biological Community Structure at Deep-Sea Hydrothermal Vents

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This ivestigation represent an integrated program designed to assess factors responsible for biological community structure at hydrothermal vents in the area between 9'49.6 1' and 9'5 0.3 6'N (known as the Biologic?Geologic Transect) along the crest of the East Pacific Rise (EPR). The objective of this multi?disciplinary effort is to gain a fundamental new understanding of the biological, chemical, and physical characteristics, variability, and processes affecting organism community structure (from microbes to megafauna) in deep?sea vent systems. Study sites have been selected that should maximize integration with a variety of geophysical (e.g., seismic) and geochemical (e.g., major element) studies being proposed by other workers. This project will address the following broad hypotheses: (1) Dramatic changes in biological community structure at vents are correlated with seismic, tectonic and/or volcanic activity within the region; (2) Vent fluid chemistry (principally sulfide speciation and concentration) is the predominant factor controlling the structure of vent communities; and (3) The structure of microbial communities associated with diffuse flows varies with time, temperature, and in response to differences in oxygen, iron, manganese and sulfur speciation. At several of the 9'50N vent sites that formed during an April 1991 eruptive event in the area, mussels now dominate the faunal assemblages, while other habitats within the region are dominated either by Tevniajerichonana or Riftiapachyptila. The present approach builds upon the extensive data sets obtained at these sites over the past decade and proposes a series of in situ measurements, sampling approaches and manipulative experiments conducted using the deep submergence vehicle AIvin to gain a more detailed understanding of factors controlling biological community structure in these hydrothermal ecosystems. To this end, in situ voltarnmetric sensor packages will be used to measure chemicals, oxygen, pH and temperature over time in a variety of vestimentiferan and mussel microhabitats from which fluid samples will be obtained for microbiological characterization. Manipulative experiments will focus on removal and subsequent exclusion of mussels from selected regions of mussel?dominated assemblages, coupled with detailed geochernical and microbiological characterization of associated microhabitats before and after mussel removal. Subsequentrecruitment and colonization within exclusion cages in denuded areas, as well as in "control" areaswithin adjacent regions of the population, will be followed through successive removal and analysisof deployed basalt blocks over time. Concomitant chemical, physical and microbiological analysesof fluids will permit correlation of these parameters with temporal changes in community structure. All of the investigators are committed, as they have been in recent years, to active involvement in a myriad of educational and public outreach activities. An integral part of our proposed effort will be to closely coordinate the proposed studies with, formal and informal education and outreach activities associated with an IMAX film (Volcanoes of the Deep Sea), scheduled soon for release (fall 2003). In conjunction with Stephen Low Productions (the company producing the film) they will put together a formal Teacher's Guide and create a film?associated website www.volcanoesofthedeepsea.com), for which the domain has already been secured. An integral part of the subject matter of the film focuses on changes in biological community structure that have occurred over the past decade in the vicinity of 9'50'N. During the course of each of the proposed cruises to the area, they plan to involve museums and aquaria (i.e., those public education institutions having IMAX theaters) throughout the country, together with science educators and the network of NSF COSEE Centers (Centers for Ocean Sciences Education Excellence) directly through "real time" satellite networking tied directly to the website, providing daily data logs, images, streaming video, etc. This initiative will be closely coordinated with the Ridge 2000 Education and Outreach Program.