http://lod.bco-dmo.org/id/dataset/823190
eng; USA
utf8
dataset
Highest level of data collection, from a common set of sensors or instrumentation, usually within the same research project
Biological and Chemical Oceanography Data Management Office (BCO-DMO)
Unavailable
508-289-2009
WHOI MS#36
Woods Hole
MA
02543
USA
info@bco-dmo.org
http://www.bco-dmo.org
Monday - Friday 8:00am - 5:00pm
For questions regarding this resource, please contact BCO-DMO via the email address provided.
pointOfContact
2020-09-03
ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data
ISO 19115-2:2009(E)
An investigation into the characteristics of the reactive pools of Mississippi River plume sediments collected August to September of 2016 and May 2017 aboard the R/V Pelican.
2020-09-04
publication
2020-09-04
revision
Marine Biological Laboratory/Woods Hole Oceanographic Institution Library (MBLWHOI DLA)
2020-09-09
publication
https://doi.org/10.26008/1912/bco-dmo.823190.1
Rebecca A. Pickering
Dauphin Island Sea Lab
principalInvestigator
Jeffrey W. Krause
Dauphin Island Sea Lab
principalInvestigator
Kanchan Maiti
Louisiana State University Dept. of Oceanography and Coastal Science
principalInvestigator
Biological and Chemical Oceanography Data Management Office (BCO-DMO)
Unavailable
508-289-2009
WHOI MS#36
Woods Hole
MA
02543
USA
info@bco-dmo.org
http://www.bco-dmo.org
Monday - Friday 8:00am - 5:00pm
For questions regarding this resource, please contact BCO-DMO via the email address provided.
publisher
Cite this dataset as: Pickering, R., Krause, J., Maiti, K. (2020) An investigation into the characteristics of the reactive pools of Mississippi River plume sediments collected August to September of 2016 and May 2017 aboard the R/V Pelican. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2020-09-04 [if applicable, indicate subset used]. doi:10.26008/1912/bco-dmo.823190.1 [access date]
Methods and Sampling: <p><strong>Core Sampling</strong></p>
<p>Briefly, samples were acquired from the study area using an Ocean Instruments MC-900 Multi-corer, which preserved the sediment-water interface during recovery. Overlying bottom water was removed, cores were sectioned into 1cm slices, homogenized, packed under N<sub>2</sub> gas and frozen at -20<sup>o </sup>C for further analysis. On select cores, pore waters were collected prior to core sectioning using Rhizons (0.15 μm pore size; Rhizosphere Research Products) attached to syringes, and inserted into the core (1-cm sediment intervals) through pre-drilled holes. Porewater nutrients were analyzed at the Dauphin Island Sea Lab Analytical Laboratory, via a Skalar San<sup>++</sup> Auto Analyzer based on standard Environmental Protection Agency methodologies, including dSi, nitrate plus nitrite (NO<sub>3 </sub>+ NO<sub>2</sub>), soluble reactive phosphate (PO<sub>4</sub>) and nitrite (NO<sub>2</sub>) (μmol L<sup>-1</sup>).</p>
<p><strong>Operational Definitions </strong></p>
<p>Operational reactive Si pools have previously been defined by Rahman et al. (2016) but for consistency and clarity with previous literature (DeMaster, 1981; Michalopoulos and Aller, 2004; Qin et al., 2012; Wang et al., 2015; Rahman et al., 2016; Krause et al., 2017) it has been restated here. Therefore we use the following nomenclature;</p>
<ol>
<li>1.&nbsp;&nbsp; &nbsp;Si-HCl: Mild acid-leachable pre-treatment; Highly reactive silica associated with authigenic clays and metal oxide coatings (Michalopoulos and Aller, 2004).</li>
<li>2.&nbsp;&nbsp; &nbsp;Si-Alk: Mild alkaline-leachable digestion completed after acid pretreatment; Frees reactive silica associated with the biogenic silica pool (Michalopoulos and Aller, 2004).</li>
<li>3.&nbsp;&nbsp; &nbsp;Si-NaOH: Harsh NaOH digestion done after Si-HCl and Si-Alk (Rahman et al., 2016; Rahman et al., 2017); Associated with the reactive lithogenic Si (LSi) pool and the comparatively refractory “dark bSiO<sub>2</sub>” (e.g. sponge spicules and Rhizaria, Maldonado et al., 2019).</li>
<li>4.&nbsp;&nbsp; &nbsp;T-bSiO2: Following the traditional definition of biogenic silica (DeMaster, 1981), with no acid pre-treatment.</li>
</ol>
<p><strong>Reactive Silica Pools </strong></p>
<p>Frozen sediment samples were thawed to room temperature (22<sup>o </sup>C) and triplicate ~50-100 mg subsamples were immediately weighed into 50 mL polyethylene centrifuge tubes. Samples were never dried or ground before/during extractions. Procedural blanks were also prepared in triplicate. Additional subsamples of sediment were dried at 60<sup>o </sup>C to obtain correction for water content.</p>
<p><em>Sequential Extractions </em></p>
<p><em>Acid Leachable Silica (Si-HCl) </em></p>
<p>Sediment extractions occurred at room temperature (22<sup>o </sup>C) using Honeywell Fluka Trace SELECT 0.1 N HCl for 12 hrs, while keeping particles suspended via constant motion. Following centrifugation, the Si-HCl leachate was removed and neutralized. Remaining sediment was rinsed in triplicate with Milli-Q water to remove any residual acid (Michalopoulos and Aller, 2004). As it had previously been demonstrated by Rahman et al. (2016) that the rinses contained minor amounts of Si these rinses were discarded. A weak HCl molarity was purposely chosen to remove metal coatings, authigenic phases, and activate bSi surfaces while not affecting the sequential Si-Alk digestion (Michalopoulos and Aller, 2004).</p>
<p><em>Mild Alkaline Leachable Si (Si-Alk)</em></p>
<p>Following the acid pre-leach, the remaining sediment was sequentially digested with 25 ml Fisher Scientific Certified ACS 0.1 M Na<sub>2</sub>CO<sub>3</sub> in an 85<sup>o </sup>C water bath for a total of 5 hrs. (dry weight SSR ~1-2). Time-point subsamples were taken at 20 min., 1, 2, 3, and 5 hrs. following (DeMaster, 1981). The individual acidified Si-Alk leachates were analyzed for dSi and the intercept from a regression of individual timepoints (DeMaster, 1981) represents the bSiO<sub>2</sub> content without LSi interference. After the 5 hrs. aliquot was removed, whole samples were neutralized to stop the digestion. Following centrifugation, the leachate was removed and discarded. Remaining sediment was rinsed in triplicate with Milli-Q water to remove any residual Na<sub>2</sub>CO<sub>3</sub> and again the rinses were discarded.</p>
<p><em>Harsh NaOH Digestion (Si-NaOH) </em></p>
<p>The remaining sediment from the Si-Alk treatment was subsequently digested with Honeywell Fluka 4 M NaOH for 2 hrs in a 85<sup>o </sup>C water bath. After 2 hrs, samples were placed on ice and neutralized to stop the digestion. Following centrifugation, the Si- NaOH leachate was removed, the remaining sediment was rinsed with Milli-Q water to remove any residual leachate and this rinse was added to the Si-NaOH leachate and stored for further analysis (Rahman et al., 2016).</p>
<p><em>Traditional bSi Digestion (T-bSiO2)&nbsp; </em><em>&nbsp;</em></p>
<p>Additionally, a second treatment following the traditional definition of biogenic silica (DeMaster, 1981), with no acid pre-treatment was used. New subsamples of sediment were weighed out. 0.1 M Na<sub>2</sub>CO<sub>3</sub> was added to samples and heated in a 85<sup>o </sup>C water bath for 20 mins to remove the bSi phase. Following the 20 min timepoint, samples were placed on ice and neutralized to stop the digestion. Following centrifugation, leachate was removed and stored for further use. Similar to the Si-Alk digestions, the process was stopped after 20 mins to ensure the absence of lithogenic material.</p>
<p>A 1 ml aliquot of each resulting liquid (Si-HCl, Si-Alk, Si-NaOH and T-bSi) was analyzed for dissolved SiOH<sub>4</sub> concentration (dSi) as described by Brzezinski and Nelson (Brzezinski and Nelson, 1986) using the molybdate-blue method on a Genesys 10S UV-Vis Spectrophotometer. The remaining supernatants were stored following DeMaster (1980) in preparation for future analysis.</p>
<p><strong>Major Metal Compositions and Corrections </strong></p>
<p>Leachate supernatants were evaporated to dryness in Teflon beakers on a hotplate at 100<sup>o </sup>C and samples were reconstituted in 2% HNO<sub>3</sub> (in-house distilled). Major ion concentrations were determined on an Agilent 7700 Series ICP-MS at the Dauphin Island Sea Lab, following calibration using a blank and seven matrix-matched, mixed standards. Internal standards <sup>115</sup>In and <sup>4</sup>Be (50 μl, 10 ppm) were added to all standards and samples. Samples which could not be resolved from the blank solution were considered operationally undetectable.</p>
<p><strong>Organic Matter </strong></p>
<p>Sediment Particulate organic carbon (POC) and total organic nitrogen (PON) content were analyzed at the Dauphin Island Sea Lab using a Costech elemental combustion system (4010 ECS) following vapor phase acidification to remove carbonates. Briefly, dried sediment samples were placed in a glass desiccator and reacted with reagent-grade 12N HCl vapor for 24 hrs at room temperature. Samples were then dried at 60<sup>o </sup>C overnight to remove remaining HCl and water content before POC/PON analyses (Yamamuro and Kayanne, 1995).</p>
Funding provided by NSF Division of Ocean Sciences (NSF OCE) Award Number: OCE-1558957 Award URL: https://www.nsf.gov/awardsearch/show-award?AWD_ID=1558957
completed
Rebecca A. Pickering
Dauphin Island Sea Lab
+46 46 222 39 78
Department of Geology - Room 328 Sölvegatan 12, 223 62
Lund
Sweden
rebecca.pickering@geol.lu.se
pointOfContact
Jeffrey W. Krause
Dauphin Island Sea Lab
251-861-2141 x2289
101 Bienville Blvd
Dauphin Island
AL
36528
USA
jkrause@disl.edu
pointOfContact
Kanchan Maiti
Louisiana State University Dept. of Oceanography and Coastal Science
225-578-4531
1143 Energy Coast Env Bldg
Baton Rouge
LA
70803
USA
kmaiti@lsu.edu
pointOfContact
asNeeded
Dataset Version: 1
Unknown
Cruise_Collected
MultiCore
Station_Number
Bottom_Depth
Latitude
Longitude
Date_Collected
Sample_Depth
Nominal_Depth
Porewater_SiOH_4
Porewater_NO3_NO2
Porewater_PO4
Porewater_NO2
Porewater_NH4
Vapor_Phase_Carbonate
POC
POC_2_Stdev
PON
PON_2_Stdev
Si_HCl
Si_HCl_2_Stdev
Si_Alk
Si_Alk_2_Stdev
Si_NaOH
Si_NaOH_2_Stdev
T_bSiO2
T_bSiO2_2_Stdev
Skalar San++ Auto Analyzer
Genesys 10S UV-Vis Spectrophotometer.
theme
None, User defined
cruise name
core id
station
depth_bottom
latitude
longitude
date
depth range
depth core
No BCO-DMO term
nitrate plus nitrite
reactive phosphorus (PO4)
Nitrite
Ammonium
particulate organic Carbon (POC)
standard deviation
particulate organic nitrogen
mean
featureType
BCO-DMO Standard Parameters
Costech International Elemental Combustion System (ECS) 4010
Nutrient Autoanalyzer
Spectrophotometer
instrument
BCO-DMO Standard Instruments
PE17-20
service
Deployment Activity
Northern Gulf of Mexico Shelf
place
Locations
otherRestrictions
otherRestrictions
Access Constraints: none. Use Constraints: Please follow guidelines at: http://www.bco-dmo.org/terms-use Distribution liability: Under no circumstances shall BCO-DMO be liable for any direct, incidental, special, consequential, indirect, or punitive damages that result from the use of, or the inability to use, the materials in this data submission. If you are dissatisfied with any materials in this data submission your sole and exclusive remedy is to discontinue use.
The biotic and abiotic controls on the Silicon cycle in the northern Gulf of Mexico
https://osprey.bco-dmo.org/project/712667
The biotic and abiotic controls on the Silicon cycle in the northern Gulf of Mexico
<p><em>NSF Award Abstract:</em><br />
The Louisiana Shelf system in the northern Gulf of Mexico is fed by the Mississippi River and its many tributaries which contribute large quantities of nutrients from agricultural fertilizer to the region. Input of these nutrients, especially nitrogen, has led to eutrophication. Eutrophication is the process wherein a body of water such as the Louisiana Shelf becomes enriched in dissolved nutrients that increase phytoplankton growth which eventually leads to decreased oxygen levels in bottom waters. This has certainly been observed in this area, and diatoms, a phytoplankton which represents the base of the food chain, have shown variable silicon/nitrogen (Si/N) ratios. Because diatoms create their shells from silicon, their growth is controlled not only by nitrogen inputs but the availability of silicon. Lower Si/N ratios are showing that silicon may be playing an increasingly important role in regulating diatom production in the system. For this reason, a scientist from the University of South Alabama will determine the biogeochemical processes controlling changes in Si/N ratios in the Louisiana Shelf system. One graduate student on their way to a doctorate degree and three undergraduate students will be supported and trained as part of this project. Also, four scholarships for low-income, high school students from Title 1 schools will get to participate in a month-long summer Marine Science course at the Dauphin Island Sea Laboratory and be included in the research project. The study has significant societal benefits given this is an area where $2.4 trillion gross domestic product revenue is tied up in coastal resources. Since diatoms are at the base of the food chain that is the biotic control on said coastal resources, the growth of diatoms in response to eutrophication is important to study.</p>
<p>Eutrophication of the Mississippi River and its tributaries has the potential to alter the biological landscape of the Louisiana Shelf system in the northern Gulf of Mexico by influencing the Si/N ratios below those that are optimal for diatom growth. A scientist from the University of South Alabama believes the observed changes in the Si/N ratio may indicate silicon now plays an important role in regulating diatom production in the system. As such, understanding the biotic and abiotic processes controlling the silicon cycle is crucial because diatoms dominate at the base of the food chain in this highly productive region. The study will focus on following issues: (1) the importance of recycled silicon sources on diatom production; (2) can heavily-silicified diatoms adapt to changing Si/N ratios more effectively than lightly-silicified diatoms; and (3) the role of reverse weathering in sequestering silicon thereby reducing diffusive pore-water transport. To attain these goals, a new analytical approach, the PDMPO method (compound 2-(4-pyridyl)-5-((4-(2-dimethylaminoethylamino-carbamoyl)methoxy)phenyl)oxazole) that quantitatively measures taxa-specific silica production would be used.</p>
CLASiC
largerWorkCitation
project
eng; USA
oceans
Northern Gulf of Mexico Shelf
-91.60927
-89.57833
28.49563
29.01
2016-08-28
2017-05-11
Northern Gulf of Mexico, specifically the Louisiana Shelf region dominated by the discharge of the Mississippi River on the western side of the delta
0
BCO-DMO catalogue of parameters from An investigation into the characteristics of the reactive pools of Mississippi River plume sediments collected August to September of 2016 and May 2017 aboard the R/V Pelican.
Biological and Chemical Oceanography Data Management Office (BCO-DMO)
Unavailable
508-289-2009
WHOI MS#36
Woods Hole
MA
02543
USA
info@bco-dmo.org
http://www.bco-dmo.org
Monday - Friday 8:00am - 5:00pm
For questions regarding this resource, please contact BCO-DMO via the email address provided.
pointOfContact
http://lod.bco-dmo.org/id/dataset-parameter/823254.rdf
Name: Cruise_Collected
Units: unitless
Description: <p>Crusie name and year of collection</p>
http://lod.bco-dmo.org/id/dataset-parameter/823255.rdf
Name: MultiCore
Units: unitless
Description: <p>Multicore identifer for corresponding cruise</p>
http://lod.bco-dmo.org/id/dataset-parameter/823256.rdf
Name: Station_Number
Units: unitless
Description: <p>Station identifier for corresponding cruise</p>
http://lod.bco-dmo.org/id/dataset-parameter/823257.rdf
Name: Bottom_Depth
Units: Meters
Description: <p>Largest veritcal distance below the surface</p>
http://lod.bco-dmo.org/id/dataset-parameter/823258.rdf
Name: Latitude
Units: Decimal Degrees
Description: <p>Decimal Degrees</p>
http://lod.bco-dmo.org/id/dataset-parameter/823259.rdf
Name: Longitude
Units: Decimal Degrees
Description: <p>Decimal Degrees</p>
http://lod.bco-dmo.org/id/dataset-parameter/823260.rdf
Name: Date_Collected
Units: yyyy-mm-dd
Description: <p>When was the core collected</p>
http://lod.bco-dmo.org/id/dataset-parameter/823261.rdf
Name: Sample_Depth
Units: centimeters
Description: <p>Subsection used for analysis</p>
http://lod.bco-dmo.org/id/dataset-parameter/823262.rdf
Name: Nominal_Depth
Units: centimeters
Description: <p>Depth used for data plots</p>
http://lod.bco-dmo.org/id/dataset-parameter/823263.rdf
Name: Porewater_SiOH_4
Units: micromoles per liter
Description: <p>Concentration of dissolved silica acid in porewater collected</p>
http://lod.bco-dmo.org/id/dataset-parameter/823264.rdf
Name: Porewater_NO3_NO2
Units: micromoles per liter
Description: <p>Concentration of dissolved nitrate-nitrite in porewater collected</p>
http://lod.bco-dmo.org/id/dataset-parameter/823265.rdf
Name: Porewater_PO4
Units: micromoles per liter
Description: <p>Concentration of dissolved phosphate in porewater collected</p>
http://lod.bco-dmo.org/id/dataset-parameter/823266.rdf
Name: Porewater_NO2
Units: micromoles per liter
Description: <p>Concentration of dissolved nitrite in porewater collected</p>
http://lod.bco-dmo.org/id/dataset-parameter/823267.rdf
Name: Porewater_NH4
Units: micromoles per liter
Description: <p>Concentration of dissolved ammonium in porewater collected</p>
http://lod.bco-dmo.org/id/dataset-parameter/823268.rdf
Name: Vapor_Phase_Carbonate
Units: %
Description: <p>% of Carbonates present in the sediment sample via vapor phase acidification</p>
http://lod.bco-dmo.org/id/dataset-parameter/823269.rdf
Name: POC
Units: %
Description: <p>Particular Organic Carbon</p>
http://lod.bco-dmo.org/id/dataset-parameter/823270.rdf
Name: POC_2_Stdev
Units: dimensionless
Description: <p>2 standard deviations of sample variation</p>
http://lod.bco-dmo.org/id/dataset-parameter/823271.rdf
Name: PON
Units: %
Description: <p>Particular Organic Nitrogen</p>
http://lod.bco-dmo.org/id/dataset-parameter/823272.rdf
Name: PON_2_Stdev
Units: dimensionless
Description: <p>2 standard deviations of sample variation</p>
http://lod.bco-dmo.org/id/dataset-parameter/823273.rdf
Name: Si_HCl
Units: micromoles per gram dry sediment umol/g
Description: <p>Average Si released (n=3) for each corresponding reactive Si Pool</p>
http://lod.bco-dmo.org/id/dataset-parameter/823274.rdf
Name: Si_HCl_2_Stdev
Units: dimensionless
Description: <p>2 standard deviations for the corresponding reactive Si Pool</p>
http://lod.bco-dmo.org/id/dataset-parameter/823275.rdf
Name: Si_Alk
Units: micromoles per gram dry sediment umol/g
Description: <p>Average Si released (n=3) for each corresponding reactive Si Pool</p>
http://lod.bco-dmo.org/id/dataset-parameter/823276.rdf
Name: Si_Alk_2_Stdev
Units: dimensionless
Description: <p>2 standard deviations for the corresponding reactive Si Pool</p>
http://lod.bco-dmo.org/id/dataset-parameter/823277.rdf
Name: Si_NaOH
Units: micromoles per gram dry sediment umol/g
Description: <p>Average Si released (n=3) for each corresponding reactive Si Pool</p>
http://lod.bco-dmo.org/id/dataset-parameter/823278.rdf
Name: Si_NaOH_2_Stdev
Units: dimensionless
Description: <p>2 standard deviations for the corresponding reactive Si Pool</p>
http://lod.bco-dmo.org/id/dataset-parameter/823279.rdf
Name: T_bSiO2
Units: micromoles per gram dry sediment umol/g
Description: <p>Average Si released (n=3) for each corresponding reactive Si Pool</p>
http://lod.bco-dmo.org/id/dataset-parameter/823280.rdf
Name: T_bSiO2_2_Stdev
Units: dimensionless
Description: <p>2 standard deviations for the corresponding reactive Si Pool</p>
GB/NERC/BODC > British Oceanographic Data Centre, Natural Environment Research Council, United Kingdom
Biological and Chemical Oceanography Data Management Office (BCO-DMO)
Unavailable
508-289-2009
WHOI MS#36
Woods Hole
MA
02543
USA
info@bco-dmo.org
http://www.bco-dmo.org
Monday - Friday 8:00am - 5:00pm
For questions regarding this resource, please contact BCO-DMO via the email address provided.
pointOfContact
14501
https://darchive.mblwhoilibrary.org/bitstream/1912/26168/1/dataset-823190_characteristics-silicon-reactive-sediment-pools__v1.tsv
download
https://doi.org/10.26008/1912/bco-dmo.823190.1
download
onLine
dataset
<p><strong>Core Sampling</strong></p>
<p>Briefly, samples were acquired from the study area using an Ocean Instruments MC-900 Multi-corer, which preserved the sediment-water interface during recovery. Overlying bottom water was removed, cores were sectioned into 1cm slices, homogenized, packed under N<sub>2</sub> gas and frozen at -20<sup>o </sup>C for further analysis. On select cores, pore waters were collected prior to core sectioning using Rhizons (0.15 μm pore size; Rhizosphere Research Products) attached to syringes, and inserted into the core (1-cm sediment intervals) through pre-drilled holes. Porewater nutrients were analyzed at the Dauphin Island Sea Lab Analytical Laboratory, via a Skalar San<sup>++</sup> Auto Analyzer based on standard Environmental Protection Agency methodologies, including dSi, nitrate plus nitrite (NO<sub>3 </sub>+ NO<sub>2</sub>), soluble reactive phosphate (PO<sub>4</sub>) and nitrite (NO<sub>2</sub>) (μmol L<sup>-1</sup>).</p>
<p><strong>Operational Definitions </strong></p>
<p>Operational reactive Si pools have previously been defined by Rahman et al. (2016) but for consistency and clarity with previous literature (DeMaster, 1981; Michalopoulos and Aller, 2004; Qin et al., 2012; Wang et al., 2015; Rahman et al., 2016; Krause et al., 2017) it has been restated here. Therefore we use the following nomenclature;</p>
<ol>
<li>1.&nbsp;&nbsp; &nbsp;Si-HCl: Mild acid-leachable pre-treatment; Highly reactive silica associated with authigenic clays and metal oxide coatings (Michalopoulos and Aller, 2004).</li>
<li>2.&nbsp;&nbsp; &nbsp;Si-Alk: Mild alkaline-leachable digestion completed after acid pretreatment; Frees reactive silica associated with the biogenic silica pool (Michalopoulos and Aller, 2004).</li>
<li>3.&nbsp;&nbsp; &nbsp;Si-NaOH: Harsh NaOH digestion done after Si-HCl and Si-Alk (Rahman et al., 2016; Rahman et al., 2017); Associated with the reactive lithogenic Si (LSi) pool and the comparatively refractory “dark bSiO<sub>2</sub>” (e.g. sponge spicules and Rhizaria, Maldonado et al., 2019).</li>
<li>4.&nbsp;&nbsp; &nbsp;T-bSiO2: Following the traditional definition of biogenic silica (DeMaster, 1981), with no acid pre-treatment.</li>
</ol>
<p><strong>Reactive Silica Pools </strong></p>
<p>Frozen sediment samples were thawed to room temperature (22<sup>o </sup>C) and triplicate ~50-100 mg subsamples were immediately weighed into 50 mL polyethylene centrifuge tubes. Samples were never dried or ground before/during extractions. Procedural blanks were also prepared in triplicate. Additional subsamples of sediment were dried at 60<sup>o </sup>C to obtain correction for water content.</p>
<p><em>Sequential Extractions </em></p>
<p><em>Acid Leachable Silica (Si-HCl) </em></p>
<p>Sediment extractions occurred at room temperature (22<sup>o </sup>C) using Honeywell Fluka Trace SELECT 0.1 N HCl for 12 hrs, while keeping particles suspended via constant motion. Following centrifugation, the Si-HCl leachate was removed and neutralized. Remaining sediment was rinsed in triplicate with Milli-Q water to remove any residual acid (Michalopoulos and Aller, 2004). As it had previously been demonstrated by Rahman et al. (2016) that the rinses contained minor amounts of Si these rinses were discarded. A weak HCl molarity was purposely chosen to remove metal coatings, authigenic phases, and activate bSi surfaces while not affecting the sequential Si-Alk digestion (Michalopoulos and Aller, 2004).</p>
<p><em>Mild Alkaline Leachable Si (Si-Alk)</em></p>
<p>Following the acid pre-leach, the remaining sediment was sequentially digested with 25 ml Fisher Scientific Certified ACS 0.1 M Na<sub>2</sub>CO<sub>3</sub> in an 85<sup>o </sup>C water bath for a total of 5 hrs. (dry weight SSR ~1-2). Time-point subsamples were taken at 20 min., 1, 2, 3, and 5 hrs. following (DeMaster, 1981). The individual acidified Si-Alk leachates were analyzed for dSi and the intercept from a regression of individual timepoints (DeMaster, 1981) represents the bSiO<sub>2</sub> content without LSi interference. After the 5 hrs. aliquot was removed, whole samples were neutralized to stop the digestion. Following centrifugation, the leachate was removed and discarded. Remaining sediment was rinsed in triplicate with Milli-Q water to remove any residual Na<sub>2</sub>CO<sub>3</sub> and again the rinses were discarded.</p>
<p><em>Harsh NaOH Digestion (Si-NaOH) </em></p>
<p>The remaining sediment from the Si-Alk treatment was subsequently digested with Honeywell Fluka 4 M NaOH for 2 hrs in a 85<sup>o </sup>C water bath. After 2 hrs, samples were placed on ice and neutralized to stop the digestion. Following centrifugation, the Si- NaOH leachate was removed, the remaining sediment was rinsed with Milli-Q water to remove any residual leachate and this rinse was added to the Si-NaOH leachate and stored for further analysis (Rahman et al., 2016).</p>
<p><em>Traditional bSi Digestion (T-bSiO2)&nbsp; </em><em>&nbsp;</em></p>
<p>Additionally, a second treatment following the traditional definition of biogenic silica (DeMaster, 1981), with no acid pre-treatment was used. New subsamples of sediment were weighed out. 0.1 M Na<sub>2</sub>CO<sub>3</sub> was added to samples and heated in a 85<sup>o </sup>C water bath for 20 mins to remove the bSi phase. Following the 20 min timepoint, samples were placed on ice and neutralized to stop the digestion. Following centrifugation, leachate was removed and stored for further use. Similar to the Si-Alk digestions, the process was stopped after 20 mins to ensure the absence of lithogenic material.</p>
<p>A 1 ml aliquot of each resulting liquid (Si-HCl, Si-Alk, Si-NaOH and T-bSi) was analyzed for dissolved SiOH<sub>4</sub> concentration (dSi) as described by Brzezinski and Nelson (Brzezinski and Nelson, 1986) using the molybdate-blue method on a Genesys 10S UV-Vis Spectrophotometer. The remaining supernatants were stored following DeMaster (1980) in preparation for future analysis.</p>
<p><strong>Major Metal Compositions and Corrections </strong></p>
<p>Leachate supernatants were evaporated to dryness in Teflon beakers on a hotplate at 100<sup>o </sup>C and samples were reconstituted in 2% HNO<sub>3</sub> (in-house distilled). Major ion concentrations were determined on an Agilent 7700 Series ICP-MS at the Dauphin Island Sea Lab, following calibration using a blank and seven matrix-matched, mixed standards. Internal standards <sup>115</sup>In and <sup>4</sup>Be (50 μl, 10 ppm) were added to all standards and samples. Samples which could not be resolved from the blank solution were considered operationally undetectable.</p>
<p><strong>Organic Matter </strong></p>
<p>Sediment Particulate organic carbon (POC) and total organic nitrogen (PON) content were analyzed at the Dauphin Island Sea Lab using a Costech elemental combustion system (4010 ECS) following vapor phase acidification to remove carbonates. Briefly, dried sediment samples were placed in a glass desiccator and reacted with reagent-grade 12N HCl vapor for 24 hrs at room temperature. Samples were then dried at 60<sup>o </sup>C overnight to remove remaining HCl and water content before POC/PON analyses (Yamamuro and Kayanne, 1995).</p>
Specified by the Principal Investigator(s)
<p>BCO-DMO Data Manager Processing Notes:<br />
* added a conventional header with dataset name, PI name, version date<br />
* modified parameter names to conform with BCO-DMO naming conventions<br />
* blank values in this dataset are displayed as "nd" for "no data."&nbsp; nd is the default missing data identifier in the BCO-DMO system.<br />
* removed all spaces in headers and replaced with underscores<br />
* removed all units from headers<br />
* converted dates to ISO Format yyyy-mm-dd<br />
* set Types for each data column</p>
Specified by the Principal Investigator(s)
asNeeded
7.x-1.1
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PI Supplied Instrument Name: Instrument Name: Costech International Elemental Combustion System (ECS) 4010 Instrument Short Name:Costech ECS 4010 Instrument Description: The ECS 4010 Nitrogen / Protein Analyzer is an elemental combustion analyser for CHNSO elemental analysis and Nitrogen / Protein determination. The GC oven and separation column have a temperature range of 30-110 degC, with control of +/- 0.1 degC.
Skalar San++ Auto Analyzer
Skalar San++ Auto Analyzer
PI Supplied Instrument Name: Skalar San++ Auto Analyzer Instrument Name: Nutrient Autoanalyzer Instrument Short Name:Nutrient Autoanalyzer Instrument Description: Nutrient Autoanalyzer is a generic term used when specific type, make and model were not specified. In general, a Nutrient Autoanalyzer is an automated flow-thru system for doing nutrient analysis (nitrate, ammonium, orthophosphate, and silicate) on seawater samples. Community Standard Description: http://vocab.nerc.ac.uk/collection/L05/current/LAB04/
Genesys 10S UV-Vis Spectrophotometer.
Genesys 10S UV-Vis Spectrophotometer.
PI Supplied Instrument Name: Genesys 10S UV-Vis Spectrophotometer. Instrument Name: Spectrophotometer Instrument Short Name:Spectrophotometer Instrument Description: An instrument used to measure the relative absorption of electromagnetic radiation of different wavelengths in the near infra-red, visible and ultraviolet wavebands by samples. Community Standard Description: http://vocab.nerc.ac.uk/collection/L05/current/LAB20/
Cruise: PE17-20
PE17-20
R/V Pelican
Community Standard Description
International Council for the Exploration of the Sea
R/V Pelican
vessel
PE17-20
Jeffrey W. Krause
Dauphin Island Sea Lab
R/V Pelican
Community Standard Description
International Council for the Exploration of the Sea
R/V Pelican
vessel