Contributors | Affiliation | Role |
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Valentine, David L. | University of California-Santa Barbara (UCSB) | Principal Investigator |
Treude, Tina | University of California-Los Angeles (UCLA) | Co-Principal Investigator |
Kinnaman, Franklin S. | University of California-Santa Barbara (UCSB) | Scientist |
Gosselin, Kelsey M. | University of California-Santa Barbara (UCSB) | Student |
Liu, Na | University of California-San Diego (UCSD-SIO) | Student |
Qin, Qianhui | University of California-Santa Barbara (UCSB) | Student, Contact |
Newman, Sawyer | Woods Hole Oceanographic Institution (WHOI BCO-DMO) | BCO-DMO Data Manager |
Methodology:
Sampling and analytical procedures:
Densities were calculated from CTD-measured parameters (Seabird SBE 19plusV2 Seacat Profiler system).
Methane concentrations were measured by headspace equilibration method, modified from Kinnaman et al., 2007.
Oxygen concentrations were measured by ODF Winkler titration method.
Nitrate concentrations were measured by flow injection analysis (FIA) using the QuikChem 8500 Series 2 (Lachat Instruments, Zellweger Analytics Inc.)
Fractional methane turnover rates were analyzed based on the 3H-labeled methane incubation protocol by Bussmann et al., 2015.
Methane oxidation rates were calculated assuming adherence to the first-order rate law, by multiplying fractional methane turnover rate and ambient methane concentration (Valentine et al., 2001).
Samples were collected from R/V Connell and R/V Atlantis.
Processing notes from researcher:
Time series maps were generated using Ocean Data View version 5.2.1-64 bit. Gridded fields were calculated using DIVA gridding algorithm, with X scale-length of 400 and Y scale-length of 350.
For the 8/13/19 and 8/26/19 trips, fractional methane turnover rate samples were discarded because of an apparent leaching problem with the closure tubing inside of the Niskin bottles used for sampling (leading to interference with rate measurements).
Parameter | Description | Units |
sample_datetime | UTC datetime of sample collection; the date format is YYYY-MM-DDTHH:MM:SS | unitless |
Latitude_degrees_north | latitude of sample collection; a positive value indicates North | decimal degrees |
Longitude_degrees_east | longitude of sample collection; a negative value indicates East | decimal degrees |
Station_Name | station from which samples were collected; stations are either NDRO (34.2625, -120.0313), SDRO (34.2008, -120.0417), or CalCOFI (34.2749, -120.0252 W) | unitless |
Type | sampling type; presents either as CTD or bottle | unitless |
Depth_m | depth at which sample was collected | m |
density_kg_per_m3 | density of seawater at a certain depth | kg/m3 |
density_stdev | standard diviation of seawater density | unitless |
methane_concentration_nM | methane concentration of the sampled water | nM |
methane_concentration_stdev | standard diviation of methane concentration | unitless |
methane_oxidation_rate_nM_per_d | methane oxidation rate of methanotrophs of the sampled water | nM/d |
methane_oxidation_rate_stdev | standard diviation of methane oxidation rates | unitless |
oxygen_concentration_uM | oxygen concentration of the sampled water | uM |
oxygen_concentration_stdev | standard diviation of oxygen concentration | unitless |
nitrate_concentration_uM | nitrate concentration of the sampled water | uM |
nitrate_concentration_stdev | standard diviation of nitrate concentration | unitless |
Dataset-specific Instrument Name | 6 4-liter Niskin bottles |
Generic Instrument Name | Niskin bottle |
Dataset-specific Description | Seawater sampling was performed using a rosette equipped with 6 4-liter Niskin bottles, the in-situ temperatures of the water samples were recorded by the conductivity–temperature–depth recorder (CTD), a Seabird SBE 19plusV2 Seacat Profiler system attached to the rosette.
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Generic Instrument Description | A Niskin bottle (a next generation water sampler based on the Nansen bottle) is a cylindrical, non-metallic water collection device with stoppers at both ends. The bottles can be attached individually on a hydrowire or deployed in 12, 24, or 36 bottle Rosette systems mounted on a frame and combined with a CTD. Niskin bottles are used to collect discrete water samples for a range of measurements including pigments, nutrients, plankton, etc. |
Dataset-specific Instrument Name | CTD Seabird 911+ rosette with 24 10-liter Niskin bottles |
Generic Instrument Name | CTD Sea-Bird 911 |
Dataset-specific Description | For BASIN19 trips, seawater sampling was performed using R/V Atlantis’ CTD (Seabird 911+) rosette with 24 10-liter Niskin bottles. In-situ temperature was recorded by CTD and in-situ oxygen concentration was recorded by an oxygen sensor that was mounted on the rosette. |
Generic Instrument Description | The Sea-Bird SBE 911 is a type of CTD instrument package. The SBE 911 includes the SBE 9 Underwater Unit and the SBE 11 Deck Unit (for real-time readout using conductive wire) for deployment from a vessel. The combination of the SBE 9 and SBE 11 is called a SBE 911. The SBE 9 uses Sea-Bird's standard modular temperature and conductivity sensors (SBE 3 and SBE 4). The SBE 9 CTD can be configured with auxiliary sensors to measure other parameters including dissolved oxygen, pH, turbidity, fluorescence, light (PAR), light transmission, etc.). More information from Sea-Bird Electronics. |
Dataset-specific Instrument Name | Seabird SBE 19plusV2 Seacat Profiler System |
Generic Instrument Name | CTD Sea-Bird SBE SEACAT 19plus |
Dataset-specific Description | Seawater sampling was performed using a rosette equipped with 6 4-liter Niskin bottles, the in-situ temperatures of the water samples were recorded by the conductivity–temperature–depth recorder (CTD), a Seabird SBE 19plusV2 Seacat Profiler system attached to the rosette.
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Generic Instrument Description | Self contained self powered CTD profiler. Measures conductivity, temperature and pressure in both profiling (samples at 4 scans/sec) and moored (sample rates of once every 5 seconds to once every 9 hours) mode. Available in plastic or titanium housing with depth ranges of 600m and 7000m respectively. Minature submersible pump provides water to conductivity cell. |
Website | |
Platform | R/V Atlantis |
Start Date | 2019-10-29 |
End Date | 2019-11-10 |
Description | BASIN Project cruise to study chemical processes that occur in oxygen-limited waters along the continental margins |
NSF abstract:
This study focuses on chemical processes that occur in oxygen-limited waters along the world's continental margins. These processes are influenced by the activities of microbes and control the fate of key elements that are deposited to sediments in these areas including carbon, nitrogen and sulfur. As a result, they are key to the health and function of the ocean. The intellectual merit of this research is to study the coupled chemical and microbial processes that occur in these environments by combining robotic technology with experiments that will be conducted at the ocean floor and in the shipboard laboratory. The broader impacts of this project will provide at-sea training and educational opportunities to undergraduate and graduate students and the results will be broadly distributed to stakeholders and interested parties. Results from this research promise to identify and quantify rates for key processes that couple carbon, nitrogen and sulfur in marine environments adjacent to the continents. The project addresses an important aspect of environmental change in the ocean (i.e., decreased oxygen due to warming and nutrient enrichment) and its influence on chemical and biological cycles and ocean ecosystems.
The dynamics of oxygen minimum zones along continental margins, and their potential for future expansion, are important because of their intersection with global biogeochemical cycles and because of their far-reaching impacts on ocean ecosystems. However, the impacts of transient deoxygenation on biogeochemical cycles of carbon, nitrogen and sulfur at the sea floor are not well established and are the focus of this study. This study will test the overarching hypothesis that deoxygenation triggers a positive feedback loop between bacterial mats at the sea floor that consume hydrogen sulfide, a sulfur species that can be toxic to higher organisms, and an underlying community of bacteria that produce hydrogen sulfide. By this hypothesis, the establishment of sea floor mats, which depend on inorganic nitrogen sources to run their sulfur metabolism, accelerates nitrogen cycling in the uppermost sediment horizon following deoxygenation. The accelerated nitrogen cycling allows for upward expansion of the sulfide-producing bacteria, which in-turn provide a shallow source of sulfide as substrate to further support nitrogen cycling in the sea floor mat. The results of this study will enable understanding of the relationship between oxygen dynamics in the water column and the biogeochemical processes at the sea floor that link the transformations of carbon, nitrogen and sulfur. The results of this study promise to define the environmental conditions under which the sulfur and nitrogen cycles are coupled and subject to strong positive feedbacks at the seafloor, as well as the conditions under which they are decoupled. This study provides training in research and innovative analytical and experimental techniques to four graduate students and several undergraduates. Undergraduates will be engaged in research at two institutions, one of which has recently been designated as a Hispanic serving institution. Approximately 10 undergraduate students (20 in total) will participate in each of the two proposed oceanographic expeditions, through an established course entitled: Field Studies in Marine Biogeochemistry. This course provides an opportunity for students to develop an independent research project in advance of the expedition, to participate on the expedition, and to conduct research projects while at sea.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
Funding Source | Award |
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NSF Division of Ocean Sciences (NSF OCE) | |
NSF Division of Ocean Sciences (NSF OCE) |