Instrument Type: Water Temperature Sensor

The Strytan Hydrothermal Field (SHF; Eyjafjord, northern Iceland) exhibits alkaline (pH ~ 10), hot (up to 78 degrees C), submarine hydrothermal venting, resulting in the formation of numerous saponite towers. We performed a detailed geochemical and microbiological characterization of hydrothermal fluids and precipitates from the site. End-member calculations revealed elevated concentrations of many major and trace elements (e.g., 2.4 mM Na, 3 to 27 uM K, 40 to 120 uM Ca, 10 to 25 uM B, and overall high concentrations of trace elements). We hypothesize that recharge of meteoric water occurs in the mountains south of Eyjafjord, and low temperature alteration of plagioclase, pyroxene and olivine in basalt, and precipitation of calcite, occurs in a closed system. This explains the observed high pH, variable Ca concentrations, and low DIC. CH4, H2, and CO concentrations were all elevated relative to normal seawater (up to 1.41, 5.19, and 0.13 uM, respectively), and a range of δ13C-CH4 was measured. Weathering of pyroxene may produce H2, which combines with CO2 to form abiotic CH4. The abiotic production of H2 and CH4 in a site such as the SHF broadens the range of potential origin of life environments significantly. Intact polar lipids indicate Bacteria dominated all samples except one. Up to 50% of the lipids at this site were archaeal. Bacterial clone sequences were dominated by betaproteobacteria (Dechloromonas sp.), followed by deltaproteobacteria (Desulfovibrio sp.) Archaeal results indicate a dominance of Crenarchaeota, particularly Thermoproteales, followed by Desulfurococcales. More detailed analysis of microbial communities is currently underway.

The Strytan Hydrothermal Field (SHF; Eyjafjord, northern Iceland) exhibits alkaline (pH ~ 10), hot (up to 78 degrees C), submarine hydrothermal venting, resulting in the formation of numerous saponite towers. We performed a detailed geochemical and microbiological characterization of hydrothermal fluids and precipitates from the site. End-member calculations revealed elevated concentrations of many major and trace elements (e.g., 2.4 mM Na, 3 to 27 uM K, 40 to 120 uM Ca, 10 to 25 uM B, and overall high concentrations of trace elements). We hypothesize that recharge of meteoric water occurs in the mountains south of Eyjafjord, and low temperature alteration of plagioclase, pyroxene and olivine in basalt, and precipitation of calcite, occurs in a closed system. This explains the observed high pH, variable Ca concentrations, and low DIC. CH4, H2, and CO concentrations were all elevated relative to normal seawater (up to 1.41, 5.19, and 0.13 uM, respectively), and a range of δ13C-CH4 was measured. Weathering of pyroxene may produce H2, which combines with CO2 to form abiotic CH4. The abiotic production of H2 and CH4 in a site such as the SHF broadens the range of potential origin of life environments significantly. Intact polar lipids indicate Bacteria dominated all samples except one. Up to 50% of the lipids at this site were archaeal. Bacterial clone sequences were dominated by betaproteobacteria (Dechloromonas sp.), followed by deltaproteobacteria (Desulfovibrio sp.) Archaeal results indicate a dominance of Crenarchaeota, particularly Thermoproteales, followed by Desulfurococcales. More detailed analysis of microbial communities is currently underway.

The Strytan Hydrothermal Field (SHF; Eyjafjord, northern Iceland) exhibits alkaline (pH ~ 10), hot (up to 78 degrees C), submarine hydrothermal venting, resulting in the formation of numerous saponite towers. We performed a detailed geochemical and microbiological characterization of hydrothermal fluids and precipitates from the site. End-member calculations revealed elevated concentrations of many major and trace elements (e.g., 2.4 mM Na, 3 to 27 uM K, 40 to 120 uM Ca, 10 to 25 uM B, and overall high concentrations of trace elements). We hypothesize that recharge of meteoric water occurs in the mountains south of Eyjafjord, and low temperature alteration of plagioclase, pyroxene and olivine in basalt, and precipitation of calcite, occurs in a closed system. This explains the observed high pH, variable Ca concentrations, and low DIC. CH4, H2, and CO concentrations were all elevated relative to normal seawater (up to 1.41, 5.19, and 0.13 uM, respectively), and a range of δ13C-CH4 was measured. Weathering of pyroxene may produce H2, which combines with CO2 to form abiotic CH4. The abiotic production of H2 and CH4 in a site such as the SHF broadens the range of potential origin of life environments significantly. Intact polar lipids indicate Bacteria dominated all samples except one. Up to 50% of the lipids at this site were archaeal. Bacterial clone sequences were dominated by betaproteobacteria (Dechloromonas sp.), followed by deltaproteobacteria (Desulfovibrio sp.) Archaeal results indicate a dominance of Crenarchaeota, particularly Thermoproteales, followed by Desulfurococcales. More detailed analysis of microbial communities is currently underway.

The Strytan Hydrothermal Field (SHF; Eyjafjord, northern Iceland) exhibits alkaline (pH ~ 10), hot (up to 78 degrees C), submarine hydrothermal venting, resulting in the formation of numerous saponite towers. We performed a detailed geochemical and microbiological characterization of hydrothermal fluids and precipitates from the site. End-member calculations revealed elevated concentrations of many major and trace elements (e.g., 2.4 mM Na, 3 to 27 uM K, 40 to 120 uM Ca, 10 to 25 uM B, and overall high concentrations of trace elements). We hypothesize that recharge of meteoric water occurs in the mountains south of Eyjafjord, and low temperature alteration of plagioclase, pyroxene and olivine in basalt, and precipitation of calcite, occurs in a closed system. This explains the observed high pH, variable Ca concentrations, and low DIC. CH4, H2, and CO concentrations were all elevated relative to normal seawater (up to 1.41, 5.19, and 0.13 uM, respectively), and a range of δ13C-CH4 was measured. Weathering of pyroxene may produce H2, which combines with CO2 to form abiotic CH4. The abiotic production of H2 and CH4 in a site such as the SHF broadens the range of potential origin of life environments significantly. Intact polar lipids indicate Bacteria dominated all samples except one. Up to 50% of the lipids at this site were archaeal. Bacterial clone sequences were dominated by betaproteobacteria (Dechloromonas sp.), followed by deltaproteobacteria (Desulfovibrio sp.) Archaeal results indicate a dominance of Crenarchaeota, particularly Thermoproteales, followed by Desulfurococcales. More detailed analysis of microbial communities is currently underway.

In this project we studied the shallow-water hydrothermal vent sites at Milos Island (Greece) to better understand the extent of autotrophic carbon fixation and its chemical and isotopic signature along environmental (redox/thermal) gradients. This was a 12-day long expedition (May 18 to 30, 2012) to sample vent fluids, gases and retrieve sediment cores at Paleochori Bay by using SCUBA diving at 8-10 m depth. In addition to the submarine vent sites, two subaerial locations of venting were identified at 36o 40′ 28″N – 24o 31′ 14″ E and 36o 40′ 25″ N – 24o 30′ 44″ E. Both the subaerial and submarine sites are located on the same fracture zone that likely controls the hydrothermal circulation of evolved meteoritic water and seawater within the magmatic zone of Milos Island. To this end, the geochemistry of the fluids and gases emitted from subaerial sites provide important information towards identifying the linkage between the subaerial and submarine magmatic activity and provide insights on the metabolic functions (e.g. H2 oxidation, Fe(III) reduction, C and S cycling) of the subsurface microbial community. 

Abstract:
Currently, there is only limited information on the identity and activity of the microorganisms carrying out CO2-fixation in situ, despite the fact that these organisms form the basis of their respective ecosystems. Representatives that are able to grow autotrophically are known to exist in almost all major groups of prokaryotes, and these organisms play essential roles in ecosystems by providing a continuous supply of organic carbon for heterotrophs. Microorganisms present in extreme environments utilize CO2- fixation pathways other than the Calvin-Benson-Bassham (CBB) cycle. At present, five alternative autotrophic CO2 fixation pathways are known. Different carbon fixation pathways result in distinct isotopic signatures of the produced biomass due to the isotopic discrimination between light (12C) and heavy (13C) carbon by the carboxylating enzymes. Thus, inferences about the carbon fixation pathway predominantly utilized by the microbial community can also be made based on the stable carbon isotopic composition of the organic matter, in extant systems as well as in the geological record. However, at present little is known about the systematics and extents of fractionation during carbon fixation by prokaryotic organisms, and to our knowledge no studies exist that have systematically studied the relationship between the operation of different carbon fixation pathways and how this is reflected in the stable carbon isotopic composition in a natural system. This is a 2-year interdisciplinary, international research program that employs a powerful combination of cutting-edge research tools aiming to improve our understanding of autotrophic carbon fixation and its chemical and isotopic signature along environmental gradients in a natural hydrothermal system. The following hypotheses are addressed:

1. The diversity of microorganisms present along a thermal and redox gradient, and rates of CO2 fixation, will reflect adaptation to in situ temperatures and geochemical conditions

2. Microorganisms utilizing the CBB cycle for autotrophic CO2-fixation will represent a smaller percentage of the chemolithoautotrophic community at higher temperatures, where microorganisms utilizing alternative CO2-fixation pathways dominate

3. Isotopic values of biomass and specific biomarker molecules will vary along a thermal and redox gradient from zones characterized by a higher hydrothermal fluid flux and thus higher temperatures to the surrounding, cooler areas, corresponding to the physiology of the microorganisms utilizing different pathways for carbon fixation

The PIs will use a multidisciplinary approach to delineate the relative contribution of the different carbon fixation pathways along an environmental gradient by combining metagenomic analyses coupled with: 1) an assessment of the frequency and the expression of specific key genes involved in carbon fixation, and 2) with the measurement of carbon fixation rates. These data will be integrated with the determination of stable C isotopic composition of biomass, DIC, and specific hydrocarbons/lipids. Due to its easy accessibility, well-established environmental gradients, and extensive background information, the shallow-water vents off Milos (Greece) will be used as a natural laboratory to perform these studies.

Intellectual Merit. The data generated in this study will allow constraints on the relationship between autotrophic carbon fixation and the resulting isotopic signatures of biomass and specific biomarker molecules (e.g. CH4, C2+ alkanes, lipids) in a natural system. This has implications for assessing the importance of carbon fixation in extant ecosystems, and it will also provide a tool to improve the interpretation of isotopic values in the geological record.

In this project we studied the shallow-water hydrothermal vent sites at Milos Island (Greece) to better understand the extent of autotrophic carbon fixation and its chemical and isotopic signature along environmental (redox/thermal) gradients. This was a 12-day long expedition (May 18 to 30, 2012) to sample vent fluids, gases and retrieve sediment cores at Paleochori Bay by using SCUBA diving at 8-10 m depth. In addition to the submarine vent sites, two subaerial locations of venting were identified at 36o 40′ 28″N – 24o 31′ 14″ E and 36o 40′ 25″ N – 24o 30′ 44″ E. Both the subaerial and submarine sites are located on the same fracture zone that likely controls the hydrothermal circulation of evolved meteoritic water and seawater within the magmatic zone of Milos Island. To this end, the geochemistry of the fluids and gases emitted from subaerial sites provide important information towards identifying the linkage between the subaerial and submarine magmatic activity and provide insights on the metabolic functions (e.g. H2 oxidation, Fe(III) reduction, C and S cycling) of the subsurface microbial community. 

Abstract:
Currently, there is only limited information on the identity and activity of the microorganisms carrying out CO2-fixation in situ, despite the fact that these organisms form the basis of their respective ecosystems. Representatives that are able to grow autotrophically are known to exist in almost all major groups of prokaryotes, and these organisms play essential roles in ecosystems by providing a continuous supply of organic carbon for heterotrophs. Microorganisms present in extreme environments utilize CO2- fixation pathways other than the Calvin-Benson-Bassham (CBB) cycle. At present, five alternative autotrophic CO2 fixation pathways are known. Different carbon fixation pathways result in distinct isotopic signatures of the produced biomass due to the isotopic discrimination between light (12C) and heavy (13C) carbon by the carboxylating enzymes. Thus, inferences about the carbon fixation pathway predominantly utilized by the microbial community can also be made based on the stable carbon isotopic composition of the organic matter, in extant systems as well as in the geological record. However, at present little is known about the systematics and extents of fractionation during carbon fixation by prokaryotic organisms, and to our knowledge no studies exist that have systematically studied the relationship between the operation of different carbon fixation pathways and how this is reflected in the stable carbon isotopic composition in a natural system. This is a 2-year interdisciplinary, international research program that employs a powerful combination of cutting-edge research tools aiming to improve our understanding of autotrophic carbon fixation and its chemical and isotopic signature along environmental gradients in a natural hydrothermal system. The following hypotheses are addressed:

1. The diversity of microorganisms present along a thermal and redox gradient, and rates of CO2 fixation, will reflect adaptation to in situ temperatures and geochemical conditions

2. Microorganisms utilizing the CBB cycle for autotrophic CO2-fixation will represent a smaller percentage of the chemolithoautotrophic community at higher temperatures, where microorganisms utilizing alternative CO2-fixation pathways dominate

3. Isotopic values of biomass and specific biomarker molecules will vary along a thermal and redox gradient from zones characterized by a higher hydrothermal fluid flux and thus higher temperatures to the surrounding, cooler areas, corresponding to the physiology of the microorganisms utilizing different pathways for carbon fixation

The PIs will use a multidisciplinary approach to delineate the relative contribution of the different carbon fixation pathways along an environmental gradient by combining metagenomic analyses coupled with: 1) an assessment of the frequency and the expression of specific key genes involved in carbon fixation, and 2) with the measurement of carbon fixation rates. These data will be integrated with the determination of stable C isotopic composition of biomass, DIC, and specific hydrocarbons/lipids. Due to its easy accessibility, well-established environmental gradients, and extensive background information, the shallow-water vents off Milos (Greece) will be used as a natural laboratory to perform these studies.

Intellectual Merit. The data generated in this study will allow constraints on the relationship between autotrophic carbon fixation and the resulting isotopic signatures of biomass and specific biomarker molecules (e.g. CH4, C2+ alkanes, lipids) in a natural system. This has implications for assessing the importance of carbon fixation in extant ecosystems, and it will also provide a tool to improve the interpretation of isotopic values in the geological record.

Deep-sea hydrothermal vents, first discovered in 1977, are poster child ecosystems where microbial chemosynthesis rather than photosynthesis is the primary source of organic carbon. Significant gaps remain in our understanding of the underlying microbiology and biogeochemistry of these fascinating ecosystems. Missing are the identification of specific microorganisms mediating critical reactions in various geothermal systems, metabolic pathways used by the microbes, rates of the catalyzed reactions, amounts of organic carbon being produced, and the larger role of these ecosystems in global biogeochemical cycles. To fill these gaps, the investigators will conduct a 3-year interdisciplinary, international hypothesis-driven research program to understand microbial processes and their quantitative importance at deep-sea vents. Specifically, the investigators will address the following objectives: 1. Determine key relationships between the taxonomic, genetic and functional diversity, as well as the mechanisms of energy and carbon transfer, in deep-sea hydrothermal vent microbial communities. 2. Identify the predominant metabolic pathways and thus the main energy sources driving chemoautotrophic production in high and low temperature diffuse flow vents. 3. Determine energy conservation efficiency and rates of aerobic and anaerobic chemosynthetic primary productivity in high and low temperature diffuse flow vents. 4. Determine gene expression patterns in diffuse-flow vent microbial communities during attachment to substrates and the development of biofilms.

Integration: To address these objectives and to characterize the complexity of microbially-catalyzed processes at deep-sea vents at a qualitatively new level, we will pursue an integrated approach that couples an assessment of taxonomic diversity using cultivation-dependent and -independent approaches with methodologies that address genetic diversity, including a) metagenomics (genetic potential and diversity of community), b) single cell genomics (genetic potential and diversity of uncultured single cells), c) meta-transcriptomics and -proteomics (identification and function of active community members, realized potential of the community). To assess function and response to the environment, these approaches will be combined with 1) measurement of in situ rates of chemoautotrophic production, 2) geochemical characterization of microbial habitats, and 3) shipboard incubations under simulated in situ conditions (hypothesis testing under controlled physicochemical conditions). Network approaches and mathematical simulation will be used to reconstruct the metabolic network of the natural communities. A 3-day long project meeting towards the end of the second year will take place in Woods Hole. This Data Integration and Synthesis meeting will allow for progress reports and presentations from each PI, postdoc, and/or student, with the aim of synthesizing data generated to facilitate the preparation of manuscripts.

Intellectual Merit. Combining the community expression profile with diversity and metagenomic analyses as well as process and habitat characterization will be unique to hydrothermal vent microbiology. The approach will provide new insights into the functioning of deep-sea vent microbial communities and the constraints regulating the interactions between the microbes and their abiotic and biotic environment, ultimately enabling us to put these systems into a quantitative framework and thus a larger global context.

Broader Impacts. This is an interdisciplinary and collaborative effort between 4 US and 4 foreign institutions, creating unique opportunities for networking and fostering international collaborations. This will also benefit the involved students (2 graduate, several undergraduate) and 2 postdoctoral associates. This project will directly contribute to many educational and public outreach activities of the involved PIs, including the WHOI Dive & Discover program; single cell genomics workshops and Cafe Scientifique (Bigelow); REU (WHOI, Bigelow, CIW); COSEE and RIOS (Rutgers), and others. The proposed research fits with the focus of a number of multidisciplinary and international initiatives, in which PIs are active members (SCOR working group on Hydrothermal energy and the ocean carbon cycle, http://www.scorint. org/Working_Groups/wg135.htm; Deep Carbon Observatory at CIW, https://dco.gl.ciw.edu/; Global Biogeochemical Flux (GBF) component of the Ocean Observatories Initiative (OOI), http://www.whoi.edu/GBF-OOI/page.do?pid=41475)