<div><p>Seawater samples were collected using an epoxy coated CTD-rosette mounted with Go-Flo samplers and a Sea-Bird Electronics CTD (SBE9plus). Go-Flo bottles were transferred to a trace metal clean van for subsampling into polypropylene tubes (nutrients), polypropylene bottle (biogenic silica and particulate carbon and nitrogen) or TM acid-cleaned polycarbonate incubation bottles (Si-32 & C-14 incubation experiments).</p>
<p>Nutrient samples were filtered through 0.2 μm polycarbonate filters and frozen at -20°C. Samples for biogenic silica concentrations were size fractionated by serial filtration through 5 μm and 0.6 μm polycarbonate filters. Filters were stored frozen at -20°C. Particulate organic carbon and nitrogen were measured on samples from experiments examining the effect of added Fe and Si on carbon fixation. These samples were filtered through precombusted GFF filters placed in glass scintillation vials and frozen at -20°C.</p>
<p>Samples for silicic acid uptake profiles were spiked with the radioisotope Si-32. Nutrient limitation assays were performed on pairs of samples where rate of silicic acid uptake (Si-32) or carbon fixation (C-14 in paired light/dark bottles) were determined in unaltered controlled samples and in samples augmented with either silicic acid (20 μM) or iron chloride (1 nM). All samples were incubated on deck in simulated in situ incubators cooled with flowing surface seawater from 24 h. Profiles samples six depths from near surface to the 1% light level. Nutrient limitation assays were performed at the 40% and 10% light levels.</p>
<p>Particles from incubated samples were size fractionated by serial filtration through 5 μm and 0.6 μm 25 mm polycarbonate filters. For C-14 incubations, total radioactivity in each sample was determined by sampling 100 μl of sample seawater prior to filtration. Filters from Si-32 incubations were placed on plastic planchettes and dried before covering with mylar film and stored or analysis ashore using low level beta counters (Riso Inc). Filters from C-14 incubations were acidified in glass scintillation vials, scintillation cocktail (Ultima Gold XR) added followed by liquid scintillation counting. Total radioactivity samples received 100 μL of b-phenethylamine and 5 mL of scintillation cocktail prior to analysis at sea using a Beckman 8500 scintillation counter.</p>
<p>For more information, see the Protocol documents (under Supplemental Files).</p></div>
32Si and 14C production data (experimental)
<div><p>Depth profiles in the euphotic zone of nutrient (nitrate, silicate, phosphate) concentrations, profiles of silicic acid uptake rates and assessment of limitation by Si and Fe on both silicic acid uptake and carbon fixation.</p>
<p>See related dataset: <a href="https://www.bco-dmo.org/dataset/785856" target="_blank">https://www.bco-dmo.org/dataset/785856</a></p></div>
14C 32Si Experimental - from RR1813
<div><p>Silicon uptake was calculated as the product of the fraction of total Si-32 radioactivity taken up and the ambient silicic acid concertation. Rates of primary production were calculated as the product of the fraction of total C-14 radioactivity taken up and a DIC value of 2132 μmol kg-1 correcting for isotope discrimination (x 1.05).</p>
<p>Nutrient concentrations were adjusted using certified JAMSTEC CRMs.</p>
<p><strong>BCO-DMO Processing:</strong><br />
- formatted date to yyyy-mm-dd (was dd/mon/yy);<br />
- modified parameter names (replaced spaces and symbols with underscores, removed units);<br />
- replaced "~" and blanks with "nd" (no data);<br />
- created ISO_DateTime_UTC field.</p></div>
786013
14C 32Si Experimental - from RR1813
2020-01-06T13:15:25-05:00
2020-01-06T13:15:25-05:00
2023-07-07T16:10:26-04:00
urn:bcodmo:dataset:786013
32Si and 14C production data (experimental) from EXPORTS cruise RR1813 on R/V Roger Revelle in the Subarctic North Pacific near Station PAPA from August to September 2018
This dataset includes 32Si and 14C production data (experimental) from EXPORTS cruise RR1813. The EXPORTS field campaign in the subarctic North Pacific sampled an ecosystem characterized as high nutrient low chlorophyll (HNLC) due to low iron (Fe) levels that are primary controllers constraining phytoplankton utilization of other nutrients. It has been a paradigm in low Fe, HNLC systems that diatoms grow at elevated Si:C and Si:N ratios and should be efficiently exported as particles significantly enriched in Si relative to C. However, Fe limitation also alters diatoms species composition and the high Si demand imposed by low Fe can drive HNLC regions to Si limitation or Si/Fe co-limitation. Thus, the degree of Si and/or Fe stress in HNLC waters can all alter diatom taxonomic composition, the elemental composition of diatom cells, and the path cells follow through the food web ultimately altering diatom carbon export.
Within each ecosystem state examined in the EXPORTS program, nutrient biogeochemistry, diatom and phytoplankton community structure, and global diatom gene expression patterns (metatranscriptomics) are characterized in the lit ocean. Nutrient amendment experiments with tracer addition (14C, 32Si) are used to quantify the level of Si and Fe stress being experienced by the phytoplankton and to contextualize taxa-specific metatranscriptome responses for resolving gene expression profiles in the in situ communities.
false
Brzezinski, M., Buck, K., Jenkins, B. (2020) 32Si and 14C production data (experimental) from EXPORTS cruise RR1813 on R/V Roger Revelle in the Subarctic North Pacific near Station PAPA from August to September 2018. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2020-01-06 [if applicable, indicate subset used]. doi:10.1575/1912/bco-dmo.786013.1 [access date]
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10.1575/1912/bco-dmo.786013.1
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2020-01-06
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