Hand-held temperature probe
|Created||January 13, 2014|
|Modified||August 19, 2016|
|State||Final no updates expected|
Concentrations of anions, cations, and trace elements/metals from vents near Milos I., Greece.
Fluid samples were collected from the water column close to the shallow-water venting sites and from the interstitial waters of all cores at 2 cm intervals. Fluids and gases were also sampled from the subaerial sites. Samples returned to the Geophysical Lab were analyzed to determine dissolved concentrations of: organic acids and a range of major anions/cations species (e.g. SO42-, PO42-, SNH3, NO3-, Cl-, Na+, K+, Ca2+, and Mg2+) including trace elements and metals. We used ion chromatography (Metrohm “MIC-3 Advanced IC, Metrosep A supp 7-250/16-250; C4- 250 columns). Fluids were analyzed for metal and trace element concentrations at the MC-ICP-MS facility of Prof. Michael Bizimis at the University of South Carolina.
Mustafa Yücel, Stefan M. Sievert, Costantino Vetriani, Dionysis I. Foustoukos, Donato Giovannelli, Nadine Le Bris. Eco-geochemical dynamics of a shallow-water hydrothermal vent system at Milos Island, Aegean Sea (Eastern Mediterranean). Chemical Geology 356 (2013) 11-20.
latitude, in decimal degrees, North is positive, negative denotes South; Reported in some datasets as degrees, minutes
longitude, in decimal degrees, East is positive, negative denotes West; Reported in some datsets as degrees, minutes
Observation/sample depth below the sea surface. Units often reported as: meters, feet.
When used in a JGOFS/GLOBEC dataset the depth is a best estimate; usually but not always calculated from pressure; calculated either from CTD pressure using Fofonoff and Millard (1982; UNESCO Tech Paper #44) algorithm adjusted for 1980 equation of state for seawater (EOS80) or simply equivalent to nominal depth as recorded during sampling if CTD pressure was unavailable.
unique sample identification or number; any combination of alpha numeric characters; precise definition is file dependent
Ammonium and ammonia concentration parameters in any body of fresh or salt water.
Nitrate concentration in the water column
Orthophosphate (phosphate, reactive phosphorus), Various units.
Concentration of sulfate (SO4) per unit volume
Cesium ion concentration as measured by the USC lab
Ba (Barium). May be reported in parts per million, nanomoles per Liter, or other units. Refer to dataset metadata for units.
Iron (Fe). Concentrations may be reported in parts per million, nanomoles per liter, or other units. Refer to dataset metadata for units.
|Dionysis I. Foustoukos||Carnegie Institution for Science (CIS)||✓|
|Nancy Copley||Carnegie Institution for Science (CIS)||✓|
BCO-DMO Project Info
|Project Title||Autotrophic carbon fixation at a shallow-water hydrothermal system: Constraining microbial activity, isotopic and geochemical regimes|
|Acronym||Hydrothermal Autotrophic Carbon Fixation|
|Created||January 8, 2014|
|Modified||June 3, 2015|
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.
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.