http://lod.bco-dmo.org/id/dataset/628230
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
2015-12-04
ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data
ISO 19115-2:2009(E)
Data on phytoplankton physiology and iron and temperature interactions collected in the Ross Sea during 2013 (Ross Sea Microb Ecophys project)
2015-12-08
publication
2015-12-08
revision
BCO-DMO Linked Data URI
2015-12-08
creation
http://lod.bco-dmo.org/id/dataset/628230
David A. Hutchins
University of Southern California
principalInvestigator
Andrew E. Allen
J. Craig Venter Institute
principalInvestigator
Deborah A. Bronk
Virginia Institute of Marine 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: Hutchins, D. A., Allen, A. E., Bronk, D. A. (2015) Data on phytoplankton physiology and iron and temperature interactions collected in the Ross Sea during 2013 (Ross Sea Microb Ecophys project). Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 2015-12-08) Version Date 2015-12-08 [if applicable, indicate subset used]. http://lod.bco-dmo.org/id/dataset/628230 [access date]
Phytoplankton physiology with iron and temperature interactions Dataset Description: <p>There are five species/strains of phytoplankton:<em> Pseudo-nitzschia</em> <em>subcurvata</em> LN, <em>Pseudo-nitzschia</em> <em>subcurvata</em> HN,<em> Chaetoceros</em> sp. LN, <em>Fragilariopsis cylindrus</em> HN, and <em>Phaeocystis antarctica </em>HN. The physiological response of these five species/strains to four treatments was investigated: 0°C-Fe limited (1nM),&nbsp; 0°C-Fe replete (500nM),&nbsp; 4°C-Fe limited (1nM),&nbsp; 4°C-Fe replete (500nM).</p>
<p>We report: carbon fixation rates, Fe uptake rates, Fe uptake rates to carbon fixation rates ratio; carbon quota, nitrogen quota, phosphorus quota, and silicate quota; cell volume, cell surface area to cell volume ratios; carbon quota to Chl a ratio, Chl a per cell; and Fv/Fm of <em>Pseudo-nitzschia</em> <em>subcurvata</em> LN and <em>Chaetoceros</em> sp. LN .</p> Methods and Sampling: <p><strong>Methodology:</strong></p>
<p>Strains and growth conditions: Unialgal cultures of Pseudo-nitzschia subcurvata, Chaetoceros sp., Fragilariopsis cylindrus, and Phaeocystis antarctica were isolated from the ice edge in McMurdo Sound (77.62°S, 165.47°E) in the Ross Sea, Antarctica during January and February 2013. All stock cultures were maintained in 0.2 µM-filtered seawater that was collected using trace metal clean techniques from the same locale as the culture isolates (Hare et al. 2007, King et al. 2012). Cultures were grown at 0°C in a walk-in incubator under 24 hour (h) cold white fluorescence light (80 µmol photons m-2 s-1).</p>
<p>Experiments examined interactions between temperature and iron availability under four conditions: 0°C-Fe limited (+1nM Fe, abbreviated as 0C-Fe), 0°C-Fe replete (+500nM Fe, or 0C+Fe), 4°C-Fe limited (+1nM Fe, or 4C-Fe), and 4°C-Fe replete (+500nM Fe, or 4C+Fe). Fe concentration was amended by adding EDTA chelated FeCl3 (100: 1) into 0.2 µM-filtered trace metal-clean Ross Sea seawater. The seawater was collected late in the Antarctic summer, and so the concentrations of NO3 -, PO4 3- were relatively low for this region at 6.95 µmol L-1 and 0.66 µmol L-1 respectively. Si(OH)4 and dissolved Fe concentrations were 52.91 µmol L-1, and 0.2 nmol L-1 respectively (Feng et al. 2010). Chaetoceros sp. and one strain of Pseudo-nitzschia subcurvata (P. subcurvata) were grown in this seawater medium without any added nutrients. Another isolate of P. subcurvata, Fragilariopsis cylindrus, and Phaeocystis antarctica were maintained in the same four conditions, but the seawater was enriched with chelexed nutrient stocks to 50 µmol L-1 NO3 - and 10 µmol L-1 PO4 3- to examine growth effects of these two variables at higher nutrient levels. Cultures grown at high and low major nutrient levels will be identified as HN and LN treatments, respectively.</p>
<p>Experimental cultures were grown in triplicate 500 ml acid washed polycarbonate bottles under 24 h irradiance (80 µmol photons m-2 s-1). Semi-continuous culturing methods were used, whereby the cultures were diluted every 2 days with medium pre-acclimated to their respective temperatures. Dilution rates were based on the individually calculated growth rate of each replicate bottle (see ‘Growth rates’ section below), allowing each bottle to reach its own steady state exponential growth rate. All of the cultures were acclimated to their respective environmental conditions for 8 weeks before the commencement of the experiment. After the growth rates remained stable for at least three to five consecutive transfers, indicating steady state growth had been attained, the cultures were sampled 48 h after dilution.</p>
<p>Growth rates: Ten ml aliquot of culture samples were taken for visual cell counts directly before and after each treatment was diluted. Cell count samples were preserved with 0.5% glutaraldehyde (final concentration) and stored at 4°C for subsequent counting on a hemacytometer using an Olympus BX51 microscope (Olympus, Japan). Due to poor preservation, cell count samples of P. antarctica at 4°C for phosphorus cell quotas and Chl a per cell calculations were lost. Specific growth rates, expressed as h-1, were calculated as: µ = (ln N1 - ln N0)/t, where N0 and N1 are the cell density at the beginning and end of a dilution period, respectively, and t is the duration of the dilution period.</p>
<p>Elemental analysis: 50 ml and 20 ml culture samples of each treatment were filtered onto pre148 combusted GF/F filters (500°C for 2h) and dried in a 60°C oven overnight for particulate organic carbon/nitrogen (POC/PON) and particulate organic phosphorus (POP) analyses, respectively. POC/PON samples were analyzed using a 440 Elemental Analyzer (Costech Inc, Valencia, CA) following Fu et al. (2007) and Garcia et al. (2014). POP was analyzed using a molybdate colorimetric method according to Fu et al. (2007). A 20 ml aliquot of Chaetoceros sp. and P. subcurvata LN sample from each treatment was filtered onto 2 µm polycarbonate filters and dried in a 60°C oven overnight for biogenic silicate (BSi) analysis (Passche et al. 1973). Chlorophyll a analysis: 20 to 50 ml culture samples were filtered onto GF/F filters (Whatman) and extracted with 90% aqueous acetone for 24 h at -20°C, and measured using the non157 acidification method on a 10-AUTM fluorometer (Turner Designs, CA) (Fu et al. 2007). Cell volume and surface area: A minimum of 50 cells from each treatment were measured using an Olympus BX51 microscope (Olympus, Japan) with a coupled Excelis HD camera (ACCU8 SCOPE, NY). The length, height, or diameter of all cells were measured using ImageJ (NIH), and the volume and surface area of each cell was calculated following Hillebrand et al. (1999). Active fluorescence characteristics: A 6 ml aliquot of culture sample of P. subcurvata LN and Chaetoceros sp. LN from each treatment was dark-adapted for 5 min, and minimum fluorescence (F0) was measured using a 10-AUTM fluorometer (Turner Designs, CA). Next, maximum fluorescence (Fm) was recorded by adding 6 µl DCMU &nbsp;(dichloromethylurea) to each sample followed by shaking for 30 seconds. The quantum efficiency of photosystem II Fv/Fm was calculated according to the equation Fv/Fm = (Fm – F0)/Fm (Schreiber 2004).</p>
<p>C fixation and Fe uptake rates: To measure carbon fixation rates and iron uptake rates, a 30 ml aliquot of culture sample from each treatment was incubated with 37 kBq 14C -bicarbonate (MP Biomedicals), or ~2 kBq 55FeCl3 (PerkinElmer, 0.33 nM 55FeCl3 complexed to 120 µmol L-1 EDTA) under their respective treatment conditions. Samples were filtered onto GF/F filters after 24 h incubation. For Fe uptake rate samples, the filters were washed in oxalate reagent for 5 min to remove surface-adsorbed Fe (Tovar-Sanchez et al. 2003). To correct for filter absorption of both radiotracers, the same amount of stock solution was added to a 30 ml aliquot of sample and filtered immediately; these filter absorption count values were subtracted from reported activities. The radioactivities of 14C and 55Fe in each sample were counted in a Tri-Carb 2500TR (Packard, now Perkin Elmer). Carbon fixation rates and Fe uptake rates were calculated using the initial dissolved inorganic carbon (DIC) concentrations and initial total Fe concentrations of each bottle (1nM Fe and 500 nM for iron limited and iron replete cultures, respectively), and were normalized to cell density (Garcia et al. 2014). Because 55Fe additions were a large fraction of the total Fe present in the Fe-limited samples, these uptake values represent an upper rate estimate for this treatment.</p>
<p>Statistical analysis: All statistical analyses, including student t-tests, ANOVA, Tukey’s HSD test, and two-way ANOVA were conducted using the open source statistical software R version 3.1.2 (Systat Software, CA).</p>
<p><strong>References:</strong></p>
<p>Feng Y, Hare CE, Rose JM, Handy SM, DiTullio GR, Lee PA, Smith WO, Peloquin J, Tozzi S, Sun J, Zhang Y, Dunbar RB, Long MC, Sohst B, Hutchins, DA (2010) Interactive effects of iron, irradiance and CO<sub>2</sub> on Ross Sea phytoplankton. Deep-Sea Res I 57: 368–383 <a href="http://dx.doi.org/10.1016/j.dsr.2009.10.013" target="doilink">doi:101016/jdsr200910013</a></p>
<p>Garcia NS, Fu F, Sedwick PN, Hutchins DA (2014) Iron deficiency increases growth and nitrogen-fixation rates of phosphorus-deficient marine cyanobacteria.&nbsp;ISME J 2015(9): 238–245</p>
<p>Hare CE, DiTullio GR, Riseman SF, Crossley AC, Popels LC, Sedwick PN, Hutchins DA (2007) Effects of changing continuous iron input rates on a Southern Ocean algal assemblage. Deep-Sea Res I 54: 732-746</p>
<p>Hillebrand H, Dürselen CD, Kirschtel D, Pollingher U, Zohary T (1999) Biovolume calculation for pelagic and benthic microalgae.&nbsp;J Phycol&nbsp;35(2): 403-424</p>
<p>King AL, Sañudo-Wilhelmy SA, Boyd PW, Twining BS, Wilhelm SW, Breene C, Ellwood MJ, Hutchins DA (2012) A comparison of biogenic iron quotas during a diatom spring bloom using multiple approaches.&nbsp; Biogeosciences 9: 667–687</p>
<p>Paasche E (1973) Silicon and the ecology of marine plankton diatoms. I. Thalassiosira pseudonana (Cyclotella nana) grown in a chemostat with silicate as limiting nutrient.&nbsp;Mar Bio&nbsp;19(2): 117-126</p>
<p>Schreiber U (2004) Pulse-amplitude-modulation (PAM) fluorometry and saturation pulse method: an overview. In:&nbsp;Chlorophyll a Fluorescence, Springer Netherlands, p279-319</p>
<p>Tovar-Sanchez A, Sañudo-Wilhelmy SA, Garcia-Vargas M, Weaver RS, Popels LC, and others (2003) A trace metal clean reagent to remove surface-bound iron from marine phytoplankton.&nbsp;Marine Chemistry&nbsp;82(1): 91-99.</p>
Funding provided by NSF Office of Polar Programs (formerly NSF PLR) (NSF OPP) Award Number: PLR-1043748 Award URL: https://www.nsf.gov/awardsearch/show-award?AWD_ID=1043748
completed
David A. Hutchins
University of Southern California
213-740-5616
Department of Biological Sciences 3616 Trousdale Parkway, AHF 20
Los Angeles
CA
90089
USA
dahutch@usc.edu
pointOfContact
Andrew E. Allen
J. Craig Venter Institute
858-200-1826
4120 Capricorn Lane
La Jolla
CA
92037
USA
aallen@jcvi.org
pointOfContact
Deborah A. Bronk
Virginia Institute of Marine Science
207-315-2567
60 Bigelow Drive
East Boothbay
ME
04544
USA
dbronk@bigelow.org
pointOfContact
asNeeded
Dataset Version: 2015-12-08
Unknown
species_strain
treatment
growth_rate
growth_rate_sd
Cfix
Cfix_sd
Fe_uptake
Fe_uptake_sd
Fe_C
Fe_C_sd
POC
POC_sd
PON
PON_sd
POP
POP_sd
BSI
BSi_sd
Vol
Vol_sd
surf_area_vol
surf_area_vol_sd
POC_chla
POC_chla_sd
chla_cell
chla_cell_sd
Fv_Fm
Fv_Fm_sd
theme
None, User defined
species scientific name (binomial)
treatment
growth
standard deviation
No BCO-DMO term
particulate organic Carbon (POC)
particulate organic nitrogen
particulate organic phosphorus
biogenic silica concentration
volume
chlorophyll a
featureType
BCO-DMO Standard Parameters
Camera
Elemental Analyzer
Fluorometer
Liquid Scintillation Counter
Microscope - Optical
instrument
BCO-DMO Standard Instruments
helicopter_Allen
service
Deployment Activity
Ross Sea
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.
Synergistic Effects of Iron, Carbon Dioxide and Temperature on the Fate of Nitrate: Implications for Future Changes in Export Production in the Southern Ocean
https://osprey.bco-dmo.org/project/626702
Synergistic Effects of Iron, Carbon Dioxide and Temperature on the Fate of Nitrate: Implications for Future Changes in Export Production in the Southern Ocean
<p><em>Description from NSF award abstract:</em><br />
This award provides support for "Collaborative Research: Synergistic Effects of Iron, Carbon Dioxide, and Temperature on the Fate of Nitrate: Implications for Future Changes in Export Production in the Southern Ocean" from the Antarctic Organisms and Ecosystems program in the Office of Polar Programs at NSF. The project will use a novel combination of research approaches to evaluate the effects of temperature, carbon dioxide, and iron on three ecologically- and biogeochemically-critical Southern Ocean phytoplankton functional groups: Large centric diatoms, small pennate diatoms, and Phaeocystis antarctica.</p>
<p>The Southern Ocean around Antarctic is undergoing several changes including increased temperature and carbon dioxide content, as well as changing levels of biologically available iron. The project goals are to understand how the individual and combined influences of these three variables affect Southern Ocean phytoplankton community structure, and to determine how these assemblage-level responses are linked to fundamental cellular responses at the levels of nutrient physiology and gene expression. The research team will focus on three different types of marine algae: large and small diatoms, and the prymnesiophyte, Phaeocystis antarctica. Shifts between these three major algal groups have very different consequences for nutrient and carbon biogeochemistry in the rapidly changing Antarctic marine environments. However, the mechanistic underpinnings of these environmentally-driven community shifts are not known. The project includes a US-based laboratory component with Antarctic isolates, field study at McMurdo Station, and then a cruise of opportunity in the upwelling areas directly south of the Antarctic Circumpolar Current. The study also includes collection and analysis of environmental gene expression data, or meta-transcriptomics, both from the field and experimental settings. The transcriptomes will be generated under environmentally relevant conditions and will thus contain information critical for decoding the genomes of several newly sequenced polar phytoplankton species in addition to the three groups highlighted above.</p>
<p><em>Related publications:</em><br />
Bertrand, E.M., McCrow, J.P., Moustafa, A., Zheng, H., McQuaid, J., Delmont, T., Post, A.F., Sipler, R., Spackeen, J.L., Xu, K., Bronk, D.A., Hutchins, D.A., Allen, A.E. 2015. Phytoplankton-bacterial interactions mediate micronutrient colimitation at the coastal Antarctic sea ice edge. Proceedings of the National Academy of Sciences. <a href="http://dx.doi.org/10.1073%2Fpnas.1501615112" target="_blank">10.1073/pnas.1501615112</a></p>
Ross_Sea_Microb_Ecophys
largerWorkCitation
project
eng; USA
biota
oceans
Ross Sea
2015-12-08
McMurdo Sound of the Ross Sea
0
BCO-DMO catalogue of parameters from Data on phytoplankton physiology and iron and temperature interactions collected in the Ross Sea during 2013 (Ross Sea Microb Ecophys 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
http://lod.bco-dmo.org/id/dataset-parameter/638128.rdf
Name: species_strain
Units: unitless
Description: <p>species and strain; whether grown in high (HN) or low nutrients (LN)</p>
http://lod.bco-dmo.org/id/dataset-parameter/638129.rdf
Name: treatment
Units: unitless
Description: <p>temperature and iron exposure</p>
http://lod.bco-dmo.org/id/dataset-parameter/638130.rdf
Name: growth_rate
Units: growth/day
Description: <p>Specific growth rate</p>
http://lod.bco-dmo.org/id/dataset-parameter/638131.rdf
Name: growth_rate_sd
Units: growth/day
Description: <p>standard deviation of specific growth rate</p>
http://lod.bco-dmo.org/id/dataset-parameter/638132.rdf
Name: Cfix
Units: pmol/cell/h
Description: <p>Carbon fixation rate</p>
http://lod.bco-dmo.org/id/dataset-parameter/638133.rdf
Name: Cfix_sd
Units: pmol/cell/h
Description: <p>standard deviation of Carbon fixation rate</p>
http://lod.bco-dmo.org/id/dataset-parameter/638134.rdf
Name: Fe_uptake
Units: 10-18mol/cell/h
Description: <p>Iron uptake rate</p>
http://lod.bco-dmo.org/id/dataset-parameter/638135.rdf
Name: Fe_uptake_sd
Units: 10-18mol/cell/h
Description: <p>standard deviation of Iron uptake rate</p>
http://lod.bco-dmo.org/id/dataset-parameter/638136.rdf
Name: Fe_C
Units: umol: mol
Description: <p>Iron to Carbon ratio</p>
http://lod.bco-dmo.org/id/dataset-parameter/638137.rdf
Name: Fe_C_sd
Units: umol: mol
Description: <p>standard deviation of Iron to Carbon ratio</p>
http://lod.bco-dmo.org/id/dataset-parameter/638138.rdf
Name: POC
Units: pmol/cell
Description: <p>Particulate Organic Carbon</p>
http://lod.bco-dmo.org/id/dataset-parameter/638139.rdf
Name: POC_sd
Units: pmol/cell
Description: <p>standard deviation of POC</p>
http://lod.bco-dmo.org/id/dataset-parameter/638140.rdf
Name: PON
Units: pmol/cell
Description: <p>Particulate Organic Nitrogen</p>
http://lod.bco-dmo.org/id/dataset-parameter/638141.rdf
Name: PON_sd
Units: pmol/cell
Description: <p>standard deviation of PON</p>
http://lod.bco-dmo.org/id/dataset-parameter/638142.rdf
Name: POP
Units: pmol/cell
Description: <p>Particulate Organic Phosphate</p>
http://lod.bco-dmo.org/id/dataset-parameter/638143.rdf
Name: POP_sd
Units: pmol/cell
Description: <p>standard deviation of POP</p>
http://lod.bco-dmo.org/id/dataset-parameter/638144.rdf
Name: BSI
Units: pmol/cell
Description: <p>Biogenic silicate</p>
http://lod.bco-dmo.org/id/dataset-parameter/638145.rdf
Name: BSi_sd
Units: pmol/cell
Description: <p>standard deviation of Bsi</p>
http://lod.bco-dmo.org/id/dataset-parameter/638146.rdf
Name: Vol
Units: um^3
Description: <p>cell volume</p>
http://lod.bco-dmo.org/id/dataset-parameter/638147.rdf
Name: Vol_sd
Units: um^3
Description: <p>standard deviation of cell volume</p>
http://lod.bco-dmo.org/id/dataset-parameter/638148.rdf
Name: surf_area_vol
Units: unitless
Description: <p>cell surface area/vVolume ratio</p>
http://lod.bco-dmo.org/id/dataset-parameter/638149.rdf
Name: surf_area_vol_sd
Units: unitless
Description: <p>standard deviation of cell surface area/volume ratio</p>
http://lod.bco-dmo.org/id/dataset-parameter/638150.rdf
Name: POC_chla
Units: unitless
Description: <p>POC: Chl-a ratio (g/g)</p>
http://lod.bco-dmo.org/id/dataset-parameter/638151.rdf
Name: POC_chla_sd
Units: unitless
Description: <p>standard deviation of POC: Chl-a ratio</p>
http://lod.bco-dmo.org/id/dataset-parameter/638152.rdf
Name: chla_cell
Units: pg/cell
Description: <p>Chl-a per cell</p>
http://lod.bco-dmo.org/id/dataset-parameter/638153.rdf
Name: chla_cell_sd
Units: pg/cell
Description: <p>standard deviation of Chl-a per cell</p>
http://lod.bco-dmo.org/id/dataset-parameter/638154.rdf
Name: Fv_Fm
Units: unitless
Description: <p>plant stress measured as Fv/Fm</p>
http://lod.bco-dmo.org/id/dataset-parameter/638155.rdf
Name: Fv_Fm_sd
Units: unitless
Description: <p>standard deviation of Fv/Fm</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
3617
https://datadocs.bco-dmo.org/file/xooy0Qmh10MzzO/phyto_phys.csv
phyto_phys.csv
Primary data file for dataset ID 628230
download
https://osprey.bco-dmo.org/dataset/628230/data/download
download
onLine
dataset
<p><strong>Methodology:</strong></p>
<p>Strains and growth conditions: Unialgal cultures of Pseudo-nitzschia subcurvata, Chaetoceros sp., Fragilariopsis cylindrus, and Phaeocystis antarctica were isolated from the ice edge in McMurdo Sound (77.62°S, 165.47°E) in the Ross Sea, Antarctica during January and February 2013. All stock cultures were maintained in 0.2 µM-filtered seawater that was collected using trace metal clean techniques from the same locale as the culture isolates (Hare et al. 2007, King et al. 2012). Cultures were grown at 0°C in a walk-in incubator under 24 hour (h) cold white fluorescence light (80 µmol photons m-2 s-1).</p>
<p>Experiments examined interactions between temperature and iron availability under four conditions: 0°C-Fe limited (+1nM Fe, abbreviated as 0C-Fe), 0°C-Fe replete (+500nM Fe, or 0C+Fe), 4°C-Fe limited (+1nM Fe, or 4C-Fe), and 4°C-Fe replete (+500nM Fe, or 4C+Fe). Fe concentration was amended by adding EDTA chelated FeCl3 (100: 1) into 0.2 µM-filtered trace metal-clean Ross Sea seawater. The seawater was collected late in the Antarctic summer, and so the concentrations of NO3 -, PO4 3- were relatively low for this region at 6.95 µmol L-1 and 0.66 µmol L-1 respectively. Si(OH)4 and dissolved Fe concentrations were 52.91 µmol L-1, and 0.2 nmol L-1 respectively (Feng et al. 2010). Chaetoceros sp. and one strain of Pseudo-nitzschia subcurvata (P. subcurvata) were grown in this seawater medium without any added nutrients. Another isolate of P. subcurvata, Fragilariopsis cylindrus, and Phaeocystis antarctica were maintained in the same four conditions, but the seawater was enriched with chelexed nutrient stocks to 50 µmol L-1 NO3 - and 10 µmol L-1 PO4 3- to examine growth effects of these two variables at higher nutrient levels. Cultures grown at high and low major nutrient levels will be identified as HN and LN treatments, respectively.</p>
<p>Experimental cultures were grown in triplicate 500 ml acid washed polycarbonate bottles under 24 h irradiance (80 µmol photons m-2 s-1). Semi-continuous culturing methods were used, whereby the cultures were diluted every 2 days with medium pre-acclimated to their respective temperatures. Dilution rates were based on the individually calculated growth rate of each replicate bottle (see ‘Growth rates’ section below), allowing each bottle to reach its own steady state exponential growth rate. All of the cultures were acclimated to their respective environmental conditions for 8 weeks before the commencement of the experiment. After the growth rates remained stable for at least three to five consecutive transfers, indicating steady state growth had been attained, the cultures were sampled 48 h after dilution.</p>
<p>Growth rates: Ten ml aliquot of culture samples were taken for visual cell counts directly before and after each treatment was diluted. Cell count samples were preserved with 0.5% glutaraldehyde (final concentration) and stored at 4°C for subsequent counting on a hemacytometer using an Olympus BX51 microscope (Olympus, Japan). Due to poor preservation, cell count samples of P. antarctica at 4°C for phosphorus cell quotas and Chl a per cell calculations were lost. Specific growth rates, expressed as h-1, were calculated as: µ = (ln N1 - ln N0)/t, where N0 and N1 are the cell density at the beginning and end of a dilution period, respectively, and t is the duration of the dilution period.</p>
<p>Elemental analysis: 50 ml and 20 ml culture samples of each treatment were filtered onto pre148 combusted GF/F filters (500°C for 2h) and dried in a 60°C oven overnight for particulate organic carbon/nitrogen (POC/PON) and particulate organic phosphorus (POP) analyses, respectively. POC/PON samples were analyzed using a 440 Elemental Analyzer (Costech Inc, Valencia, CA) following Fu et al. (2007) and Garcia et al. (2014). POP was analyzed using a molybdate colorimetric method according to Fu et al. (2007). A 20 ml aliquot of Chaetoceros sp. and P. subcurvata LN sample from each treatment was filtered onto 2 µm polycarbonate filters and dried in a 60°C oven overnight for biogenic silicate (BSi) analysis (Passche et al. 1973). Chlorophyll a analysis: 20 to 50 ml culture samples were filtered onto GF/F filters (Whatman) and extracted with 90% aqueous acetone for 24 h at -20°C, and measured using the non157 acidification method on a 10-AUTM fluorometer (Turner Designs, CA) (Fu et al. 2007). Cell volume and surface area: A minimum of 50 cells from each treatment were measured using an Olympus BX51 microscope (Olympus, Japan) with a coupled Excelis HD camera (ACCU8 SCOPE, NY). The length, height, or diameter of all cells were measured using ImageJ (NIH), and the volume and surface area of each cell was calculated following Hillebrand et al. (1999). Active fluorescence characteristics: A 6 ml aliquot of culture sample of P. subcurvata LN and Chaetoceros sp. LN from each treatment was dark-adapted for 5 min, and minimum fluorescence (F0) was measured using a 10-AUTM fluorometer (Turner Designs, CA). Next, maximum fluorescence (Fm) was recorded by adding 6 µl DCMU &nbsp;(dichloromethylurea) to each sample followed by shaking for 30 seconds. The quantum efficiency of photosystem II Fv/Fm was calculated according to the equation Fv/Fm = (Fm – F0)/Fm (Schreiber 2004).</p>
<p>C fixation and Fe uptake rates: To measure carbon fixation rates and iron uptake rates, a 30 ml aliquot of culture sample from each treatment was incubated with 37 kBq 14C -bicarbonate (MP Biomedicals), or ~2 kBq 55FeCl3 (PerkinElmer, 0.33 nM 55FeCl3 complexed to 120 µmol L-1 EDTA) under their respective treatment conditions. Samples were filtered onto GF/F filters after 24 h incubation. For Fe uptake rate samples, the filters were washed in oxalate reagent for 5 min to remove surface-adsorbed Fe (Tovar-Sanchez et al. 2003). To correct for filter absorption of both radiotracers, the same amount of stock solution was added to a 30 ml aliquot of sample and filtered immediately; these filter absorption count values were subtracted from reported activities. The radioactivities of 14C and 55Fe in each sample were counted in a Tri-Carb 2500TR (Packard, now Perkin Elmer). Carbon fixation rates and Fe uptake rates were calculated using the initial dissolved inorganic carbon (DIC) concentrations and initial total Fe concentrations of each bottle (1nM Fe and 500 nM for iron limited and iron replete cultures, respectively), and were normalized to cell density (Garcia et al. 2014). Because 55Fe additions were a large fraction of the total Fe present in the Fe-limited samples, these uptake values represent an upper rate estimate for this treatment.</p>
<p>Statistical analysis: All statistical analyses, including student t-tests, ANOVA, Tukey’s HSD test, and two-way ANOVA were conducted using the open source statistical software R version 3.1.2 (Systat Software, CA).</p>
<p><strong>References:</strong></p>
<p>Feng Y, Hare CE, Rose JM, Handy SM, DiTullio GR, Lee PA, Smith WO, Peloquin J, Tozzi S, Sun J, Zhang Y, Dunbar RB, Long MC, Sohst B, Hutchins, DA (2010) Interactive effects of iron, irradiance and CO<sub>2</sub> on Ross Sea phytoplankton. Deep-Sea Res I 57: 368–383 <a href="http://dx.doi.org/10.1016/j.dsr.2009.10.013" target="doilink">doi:101016/jdsr200910013</a></p>
<p>Garcia NS, Fu F, Sedwick PN, Hutchins DA (2014) Iron deficiency increases growth and nitrogen-fixation rates of phosphorus-deficient marine cyanobacteria.&nbsp;ISME J 2015(9): 238–245</p>
<p>Hare CE, DiTullio GR, Riseman SF, Crossley AC, Popels LC, Sedwick PN, Hutchins DA (2007) Effects of changing continuous iron input rates on a Southern Ocean algal assemblage. Deep-Sea Res I 54: 732-746</p>
<p>Hillebrand H, Dürselen CD, Kirschtel D, Pollingher U, Zohary T (1999) Biovolume calculation for pelagic and benthic microalgae.&nbsp;J Phycol&nbsp;35(2): 403-424</p>
<p>King AL, Sañudo-Wilhelmy SA, Boyd PW, Twining BS, Wilhelm SW, Breene C, Ellwood MJ, Hutchins DA (2012) A comparison of biogenic iron quotas during a diatom spring bloom using multiple approaches.&nbsp; Biogeosciences 9: 667–687</p>
<p>Paasche E (1973) Silicon and the ecology of marine plankton diatoms. I. Thalassiosira pseudonana (Cyclotella nana) grown in a chemostat with silicate as limiting nutrient.&nbsp;Mar Bio&nbsp;19(2): 117-126</p>
<p>Schreiber U (2004) Pulse-amplitude-modulation (PAM) fluorometry and saturation pulse method: an overview. In:&nbsp;Chlorophyll a Fluorescence, Springer Netherlands, p279-319</p>
<p>Tovar-Sanchez A, Sañudo-Wilhelmy SA, Garcia-Vargas M, Weaver RS, Popels LC, and others (2003) A trace metal clean reagent to remove surface-bound iron from marine phytoplankton.&nbsp;Marine Chemistry&nbsp;82(1): 91-99.</p>
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PI Supplied Instrument Name: PI Supplied Instrument Description:Excelis HD camera (ACCU8 SCOPE, NY) Instrument Name: Camera Instrument Short Name:camera Instrument Description: All types of photographic equipment including stills, video, film and digital systems. Community Standard Description: http://vocab.nerc.ac.uk/collection/L05/current/311/
PI Supplied Instrument Name: PI Supplied Instrument Description:440 Elemental Analyzer (Costech Inc, Valencia, CA) Instrument Name: Elemental Analyzer Instrument Short Name: Instrument Description: Instruments that quantify carbon, nitrogen and sometimes other elements by combusting the sample at very high temperature and assaying the resulting gaseous oxides. Usually used for samples including organic material. Community Standard Description: http://vocab.nerc.ac.uk/collection/L05/current/LAB01/
PI Supplied Instrument Name: PI Supplied Instrument Description:10AU fluorometer (Turner Designs, CA) Instrument Name: Fluorometer Instrument Short Name:Fluorometer Instrument Description: A fluorometer or fluorimeter is a device used to measure parameters of fluorescence: its intensity and wavelength distribution of emission spectrum after excitation by a certain spectrum of light. The instrument is designed to measure the amount of stimulated electromagnetic radiation produced by pulses of electromagnetic radiation emitted into a water sample or in situ. Community Standard Description: http://vocab.nerc.ac.uk/collection/L05/current/113/
PI Supplied Instrument Name: PI Supplied Instrument Description:Tri-Carb 2500TR (Packard, now Perkin Elmer Instrument Name: Liquid Scintillation Counter Instrument Short Name:LSC Instrument Description: Liquid scintillation counting is an analytical technique which is defined by the incorporation of the radiolabeled analyte into uniform distribution with a liquid chemical medium capable of converting the kinetic energy of nuclear emissions into light energy. Although the liquid scintillation counter is a sophisticated laboratory counting system used to quantify the activity of particulate emitting (ß and a) radioactive samples, it can also detect the auger electrons emitted from 51Cr and 125I samples.
Liquid scintillation counters are instruments assaying alpha and beta radiation by quantitative detection of visible light produced by the passage of rays or particles through a suitable scintillant incorporated into the sample. Community Standard Description: http://vocab.nerc.ac.uk/collection/L05/current/LAB21/
PI Supplied Instrument Name: PI Supplied Instrument Description:Olympus BX51 microscope (Olympus, Japan) Instrument Name: Microscope - Optical Instrument Short Name: Instrument Description: Instruments that generate enlarged images of samples using the phenomena of reflection and absorption of visible light. Includes conventional and inverted instruments. Also called a "light microscope". Community Standard Description: http://vocab.nerc.ac.uk/collection/L05/current/LAB05/
Deployment: helicopter_Allen
helicopter_Allen
McMurdo Station
laboratory
helicopter_Allen
Andrew E. Allen
J. Craig Venter Institute
McMurdo Station
laboratory