Table of Contents

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

Analysis of nutrients, Cobalt (total and labile), dissolved Iron, and dissolved Manganese of water samples drawn from Trace Metal Rosette (TMR) bottle casts. CTD dataset is combined from both sensors. Missing CTD was due to lack of sensor package on the trace metal rosette (Stations 1, 25, 27, and some repeat Station 13 casts) or technical issues (battery failure, Station 9). Selected CTD depths (usually the deepest) were not included when O2 sensor values were anomolous (i.e. negative values).

This dataset is related to the BCO-DMO Dataset Nutrients and Metals: https://www.bco-dmo.org/dataset/3233

Related Publications:
Noble, A.E, C. H. Lamborg, D. C. Ohnemus, P. J. Lam, T. J. Goepfert, C. I. Measures, C. H. Frame, K. L. Casciotti, G. R. DiTullio, J. Jennings, M. A. Saito. 2012. Basin-scale inputs of cobalt, iron, and manganese from the Benguela-Angola front to the South Atlantic Ocean. Limnology and Oceanography, 57(4) 989-1010. doi:10.4319/lo.2012.57.4.0989

Sohm, J. A., J. A. Hilton, A. E. Noble, J. P. Zehr, M. A. Saito, and E. A. Webb. 2011. Nitrogen fixation in the South Atlantic Gyre and the Benguela Upwelling System. Geophys. Res. Letters. 38: L16608, doi:10.1029/2011GL048315

Three transects were sampled using the Trace Metal Rosette (TMR) on the CoFeMUG cruise aboard R/V Knorr in 2007. Refer to Noble et al. (2012) for detailed information on acquisition and processing.

Nutrient Analyses: Technicon AutoAnalyzer II components were used to measure phophate and ammonium. Alpkem rapid flow analyzer (RFA) 300 components were used to measure silicic acid, nitrate+nitrite, and nitrite.

Cobalt Analyses: Total dissolved and labile cobalt concentrations were determined using cathodic stripping voltammetry, previously described by Saito and Moffet (2001) and Saito et al. (2004). Measurements were made using Eco-Chemie uAutolab-III systems connected to Metrohm 663 VA Stands with hanging mercury drop electrodes and Teflon sampling cups.

Iron and Manganese Analyses: Total dissolved iron and manganese concentrations were measured using inductively coupled plasma mass spectrometry (ICP-MS). SAFe seawater intercalibration standards were analyzed at the beginning of each analysis day with iron concentrations of 0.96 ± 0.095 nmol L-1 for D2 and 0.125 ± 0.046 nmol L-1 for S1 (n = 10), which are within the reported ranges of 0.91 + 0.17 nmol L-1 and 0.097 + 0.043 nmol L-1 (Johnson et al. 2007).

CTD: Two CTD packages were employed on KN-192-5, the Knorr's Seabird 911+ CTD package and the science party's Seabird-19 sensor package. The Seabird-19 was deployed on the science party's trace metal rosette for the deep casts to ~5000m, while the ship's CTD was deployed to 800m for upper water casts. The two packages were needed due to wire time constraints, as there was insufficient time to send both rosettes deep at each station. Oxygen data for the two CTD were calibrated with shipboard winkler titrations as described in Noble et al. Limnol. Oceanogr. 2012. The Seabird-19 was calibrated in the factory immediately prior to the cruise. 

References:
Johnson, K.S. et al. 2007. Developing iron standards for seawater. EOS Trans. 88: 11, 131-132. doi: 10.1029/2007EO110003

Saito, M. A., and J. W. Moffett. 2001. Complexation of cobalt by natural organic ligands in the Sargasso Sea as determined by a new high-sensitivity electrochemical cobalt speciation method suitable for open ocean work. Marine Chemistry. 75 (49-68). doi: 10.1016/S0304-4203(01)00025-1.

Saito, M. A.,  J. W. Moffett, and G. DiTullio. 2004. Cobalt and Nickel in the Peru Upwelling Region: a Major Flux of Cobalt Utilized as a Micronutrient. Global Biogeochemical Cycles. 18 GB4030, doi: 10.1029/2003GB002216.

Asterisks next to some values for Fe and Mn denote samples where contamination is suspected. Quality flags indicate values below detection limits and potentially erroneous data according to the codes below.

Quality Flag Codes:
0 = no quality control = No quality control procedures have been applied to the data value. This is the initial status for all data values entering the working archive.
1 = good value = Good quality data value that is not part of any identified malfunction and has been verified as consistent with real phenomena during the quality control process.
2 = probably good value = Data value that is probably consistent with real phenomena but this is unconfirmed or data value forming part of a malfunction that is considered too small to affect the overall quality of the data object of which it is a part.
3 = probably bad value = Data value recognized as unusual during quality control that forms part of a feature that is probably inconsistent with real phenomena.
4 = bad value = An obviously erroneous data value.
5 = changed value = Data value adjusted during quality control. Best practice strongly recommends that the value before the change be preserved in the data or its accompanying metadata.
6 = value below detection = The level of the measured phenomenon was too small to be quantified by the technique employed to measure it. The accompanying value is the detection limit for the technique or zero if that value is unknown.
7 = missing = Bottle didn't trip or sample wasn't taken.

BCO-DMO Processing Notes:
-Modified original parameter names to conform with BCO-DMO naming conventions;
-Missing values (blank) were replaced with 'nd' to indicate 'no data'.

The geochemistries of dissolved cobalt (Co) and iron (Fe) in the oceanic water column share several characteristics such as extremely low concentrations, redox chemistry, low solubility,and utilization as micronutrients by marine microbes. Iron has been the subject of considerable research focus in recent years due to its role in limiting phytoplankton productivity in oceanic and coastal upwelling environments. Cobalt has been much less studied, but recent data show it may be important in influencing primary productivity or phytoplankton community composition in certain geographical areas.

The CoFeMUG project predated GEOTRACES, so while it is not formally recognized as a GEOTRACES section, it is considered a GEOTRACES-related project and the CoFeMUG data are GEOTRACES compliant.

State-of-the-art geochemical and molecular biological techniques were used to address biogeochemical questions in the South Atlantic, and focus especially on the two trace metals, cobalt and iron. The 27-day cruise in November and December 2007 to the South Atlantic was designed to study cobalt and iron biogeochemistry and focus on four major hypotheses.

(1) Large fluxes of labile cobalt are associated with upwelling systems even in Aeolian dominated environments.
(2) Cobalt and phosphate show correlations in (and only in) surface waters due to micronutrient utilization and rapid remineralization. The slope of the correlation is dependent on the chemical speciation of cobalt.
(3) The absence of Trichodesmium populations in the subtropical and tropical South Atlantic is caused by iron limitation.
(4) Based on work from the California and Peru Upwelling regimes, primary productivity in the Benguela upwelling regime off of South West Africa may be iron limited or iron-cobalt colimited.

A combination of geochemical and biological/molecular analyses were made across an oligotrophic-upwelling transition to examine how changing metal regimes affect the physiology and growth of the important primary producers Trichodesmium and Synechococcus.

CoFeMUG project results are published in:
Noble, Abigail E., Carl H. Lamborg, Dan C. Ohnemus, Phoebe J. Lam, Tyler J. Goepfert, Chris I. Measures, Caitlin H. Frame, Karen L. Casciotti, Giacomo R. DiTullio, Joe Jennings, and Mak A. Saito (2012) Basin-scale inputs of cobalt, iron, and manganese from the Benguela-Angola front to the South Atlantic Ocean. Limnology & Oceanography. Vol. 57(4), July 2012. pgs 989-1010. doi:10.4319/lo.2012.57.4.0989 (www.aslo.org/lo/toc/vol_57/issue_4/0989.pdf)

The Ocean Carbon and Biogeochemistry (OCB) program focuses on the ocean's role as a component of the global Earth system, bringing together research in geochemistry, ocean physics, and ecology that inform on and advance our understanding of ocean biogeochemistry. The overall program goals are to promote, plan, and coordinate collaborative, multidisciplinary research opportunities within the U.S. research community and with international partners. Important OCB-related activities currently include: the Ocean Carbon and Climate Change (OCCC) and the North American Carbon Program (NACP); U.S. contributions to IMBER, SOLAS, CARBOOCEAN; and numerous U.S. single-investigator and medium-size research projects funded by U.S. federal agencies including NASA, NOAA, and NSF.

The scientific mission of OCB is to study the evolving role of the ocean in the global carbon cycle, in the face of environmental variability and change through studies of marine biogeochemical cycles and associated ecosystems.

The overarching OCB science themes include improved understanding and prediction of: 1) oceanic uptake and release of atmospheric CO2 and other greenhouse gases and 2) environmental sensitivities of biogeochemical cycles, marine ecosystems, and interactions between the two.

The OCB Research Priorities (updated January 2012) include: ocean acidification; terrestrial/coastal carbon fluxes and exchanges; climate sensitivities of and change in ecosystem structure and associated impacts on biogeochemical cycles; mesopelagic ecological and biogeochemical interactions; benthic-pelagic feedbacks on biogeochemical cycles; ocean carbon uptake and storage; and expanding low-oxygen conditions in the coastal and open oceans.

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.