URLhttps://www.bco-dmo.org/dataset/551080
Download URLhttps://www.bco-dmo.org/dataset/551080/data/download
Media Typetext/tab-separated-values
CreatedFebruary 18, 2015
ModifiedAugust 19, 2016
StateFinal no updates expected
Brief DescriptionTemperature profile along transect at shallow-water hydothermal vent site in Paleochori Bay, Milos Island, Greece

Processing Description

Temperature measurements were conducted in situ by Scuba diving at different locations along the transect from the hottest part of the venting area towards the unaffected, colder sediments, i.e., at 0 cm, 50 cm, 100 cm, 150 cm, 200 cm, and 300 cm, at 5 cm intervals to a maximum sediment depth of 30 cm with a digital thermometer in a custom underwater housing.

Instruments

Digital thermometer [Water Temperature Sensor]
Details
Instance Description (Digital thermometer)

Digital thermometer in custom underwater housing

General term for an instrument that measures the temperature of the water with which it is in contact (thermometer).

Parameters

location [region]
Details
location
sampling location

geographical area of sampling

lat [latitude]
Details
lat
latitude; north is positive

latitude, in decimal degrees, North is positive, negative denotes South; Reported in some datasets as degrees, minutes

lon [longitude]
Details
lon

longitude; east is positive

longitude, in decimal degrees, East is positive, negative denotes West; Reported in some datsets as degrees, minutes

site [site]
Details
site
sampling site number
Sampling site identification.
depth [depth]
Details
depth

depth of temperature

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.

distance [unknown]
Details
distance

distance along transect

association with a community-wide standard parameter is not yet defined
Details
temp
temperature
water temperature at measurement depth

Dataset Maintainers

NameAffiliationContact
Stefan M. SievertWoods Hole Oceanographic Institution (WHOI)
Nancy CopleyWoods Hole Oceanographic Institution (WHOI BCO-DMO)

BCO-DMO Project Info

Project TitleAutotrophic carbon fixation at a shallow-water hydrothermal system: Constraining microbial activity, isotopic and geochemical regimes
AcronymHydrothermal Autotrophic Carbon Fixation
URLhttps://www.bco-dmo.org/project/473892
CreatedJanuary 8, 2014
ModifiedJune 3, 2015
Project Description

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.

Project Maintainers
NameAffiliationRoleContact
Costantino VetrianiRutgers UniversityCo-Principal Investigator
Stefan M. SievertWoods Hole Oceanographic Institution (WHOI)Co-Principal Investigator
Dionysis I. FoustoukosCarnegie Institution for Science (CIS)Co-Principal Investigator
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