Although hydrothermal plumes, over time, have had a significant impact on ocean chemistry, much remains unknown about the chemical and biological processes that occur in rising vent plumes where most mineral precipitation and redox chemistry occurs. This research addresses the abiotic and biological factors in early-stage hydrothermal vent plume processes and the impacts of these processes on particle formation, microbial community composition and structure, and chemical scavenging and transport by both organic material and mineral precipitates. Vent fluids, associated precipitated minerals and microbial samples that were collected on a cruise to the Eastern Lau Spreading Center in 2009 will be analyzed using state-of-the-art mineralogical and molecular biological techniques. These include synchrotron radiation X-ray adsorption and diffraction using the Advanced Light Source in Berkeley and metagenomics. Goals of the research are to determine the microbiological communities inhabiting the rising plumes, the role of plume-living/generated microbes and organic matter in particle formation and aggregation, chemical trends in plume chemistry from the vent to the top of the plume and its influence on the distribution of microbial species, and if particle aggregates influence the subsequent chemical evolution and fate of the particles. Models of mineralogical and biological interactions will be developed and coupled with those simulating hydrodynamics of the rising plume in order to simulate vent plume processes. Broader impacts of the work include support of three early career scientists, one of whom is from a gender under-represented in the sciences. The integration of teaching and learning which includes incorporating research into classes and working to include results into a summer camp for high school students and teachers. Two undergraduate summer students from under-represented minorities will also be involved in the research.
This project investigated the interactions between microbiology and geochemistry at deep-sea hydrotheraml vents. In particular, we investigated how the chemistry of five different deep-sea hydrotheraml vents along the Eastern Lau Spreading Center (ELSC) in the western Pacific Ocean influences microbial communities in hydrotheramal plumes. Overall, this is important in terms of understanding the relationships between biology and geology in the deep sea. Major questions addressed by our research were: what is the source of microorganisms in deep-sea hydrotheramal plumes? What are the forces that influence the composition of microbial communities in plumes? We found that plumes across the ELSC were derived from a mixture of seafloor microbial communities and background seawater. However, the plume microbial communities were by far more similar to the surrounding background seawater, and they were quite similar between the different hydrothermal vents. Many of these microorganisms are capable of using inorganic compounds such as sulfur and hydrogen as energy sources for chemosynthesis, and the abundance of microbial metabolisms correlated well with predictions of the amount of energy available from various chemicals in the hydrothermal fluids. These results showed that sulfur is the main source of energy for microbial metabolism at ELSC, and that other differences in iron and manganese geochemistry between vents are not a primary control on microbial community composition. A major discovery was that viruses in the ELSC plumes contain genes for sulfur oxidation. This was unexpected because viruses do not have their own energy metabolism; instead, they rely on the energy metabolism of their bacterial hosts. We conclude that these viral sulfur oxidation genes are for enhancing the oxidation of elemental sulfur, which is stored in the bacterial hosts of the virus. This viral maniuplation of host metabolism may provide more resources for viral replication. These results show for the first time that viruses participate directly in the biogeochemical cycling of sulfur. Our results also suggest that viruses may serve as an agent of evolution for sulfur-oxidizing bacteria by tranfersing sulfur oxidation genes between different species.
