Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Program Information
• Funding

Seawater sampling occurred during October 1-25 2011 onboard the R/V Kilo Moana during the METZYME expedition (Saito et al., 2014). Seawater samples for trace metal analyses were collected using a trace metal clean rosette consisting of X-Niskins on a trace metal clean (Amsteel) winch line. Following seawater collection, X-Niskins were brought into a fabricated shipboard class-100 clean room and pressurized with filtered high purity nitrogen gas. Seawater was filtered through 47mm 0.2 µm Supor membranes to remove the particulate fraction.

METZYME seawater was acidified to pH 1.8 using hydrochloric acid (Optima grade, Fisher Chemical). Seawater preconcentration was performed using an automated solid phase extraction system, seaFAST pico, run in offline concentration mode.  Following offline seaFAST preconcentration, the multi-element quantitative analysis was performed using an iCAP Q inductively coupled plasma-mass spectrometer (ICP-MS) (Thermo Scientific). Concentrations of Fe, Mn, Zn Ni and Cd were determined using a six-point external standard curve with a multi-element standard (SPEX CertiPrep), diluted to range from 1-10 ppb in 5% nitric acid. Indium standards (SPEX CertiPrep) were similarly added to these standard stocks, diluted to 1, 2, 3, 4 and 10ppb. Instrument injection blanks consisted of 5% nitric acid in Milli-Q. Standard curve R² values were ≥0.98 for the metals monitored.

Quality flags follow the SeaDataNet schem as per the GEOTRACES recommendations: https://www.geotraces.org/geotraces-quality-flag-policy/

Flag definitions:
1 = good quality; 
2 = probably good;
3 = probably bad;
4 = bad;
6 = below detection;
9 = missing data.

BCO-DMO Processing:
- renamed fields;
- added date/time fields in ISO8601 format;
- formatted flag columns as integers;
- replaced values of 0.00 with 'nd' for sample 1226558 because it was not run (quality flag of 9).
Version history:
- 2021-07-09 (v2; current) - published version 2, which includes corrections to data and flags.
- 2021-01-15 (v2) - version 1 published.

MetZyme project researchers will determine the role of enzymatic activity in the cycling of trace metals. Specifically the research will address the following questions: (1) degradation of sinking particulate organic material in the Tropical North Pacific can be influenced by the ability of microbes to synthesize zinc proteases, which in turn is controlled by the abundance or availability of zinc, and (2) methylation of mercury is controlled, in part, by the activity of cobalt-containing enzymes, and therefore the supply of labile cobalt to the corrinoid-containing enzymes or co-factors responsible for methylation. To attain their goal, they will collect dissolved and particulate samples for trace metals and metalloenzymes from three stations along a biogeochemical gradient in the Tropical North Pacific (along 150 degrees West from 18 degrees North to the equator). Sinking particles from metal clean sediment traps will also be obtained. The samples will also be used to carry out shipboard incubation experiments using amendments of metals, metal-chelators, B12, and proteases to examine the sensitivity and metal limitation of heterotrophic, enzymatic degradation of organic matter within the oceanic "Twilight Zone" (100-500 m). This study will result in a novel metaproteomic/metalloenzyme datasets that should provide insights into the biogeochemical cycling of metals, as well as co-limitation of primary productivity and controls on the export of carbon from the photic zone. In addition to the final data being contributed to BCO-DMO, an online metaproteomic data server will be created so the community has access to the raw data files generated by this research.

GEOTRACES is a SCOR sponsored program; and funding for program infrastructure development is provided by the U.S. National Science Foundation.

GEOTRACES gained momentum following a special symposium, S02: Biogeochemical cycling of trace elements and isotopes in the ocean and applications to constrain contemporary marine processes (GEOSECS II), at a 2003 Goldschmidt meeting convened in Japan. The GEOSECS II acronym referred to the Geochemical Ocean Section Studies To determine full water column distributions of selected trace elements and isotopes, including their concentration, chemical speciation, and physical form, along a sufficient number of sections in each ocean basin to establish the principal relationships between these distributions and with more traditional hydrographic parameters;

* To evaluate the sources, sinks, and internal cycling of these species and thereby characterize more completely the physical, chemical and biological processes regulating their distributions, and the sensitivity of these processes to global change; and

* To understand the processes that control the concentrations of geochemical species used for proxies of the past environment, both in the water column and in the substrates that reflect the water column.

GEOTRACES will be global in scope, consisting of ocean sections complemented by regional process studies. Sections and process studies will combine fieldwork, laboratory experiments and modelling. Beyond realizing the scientific objectives identified above, a natural outcome of this work will be to build a community of marine scientists who understand the processes regulating trace element cycles sufficiently well to exploit this knowledge reliably in future interdisciplinary studies.

Expand "Projects" below for information about and data resulting from individual US GEOTRACES research projects.