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The role of Antarctic marine protists in trophodynamics and global change and the impact of UV-B on these organisms - Voyage 3, BROKE-West, Aurora Australis 2005/2006 samples

Entry ID: BROKE-West_ASAC_40_AA0506V3

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Summary

Abstract: Locations of sampling sites for ASAC project 40 on voyage 3 of the Aurora Australis in the 2005/2006 season (the BROKE-West voyage). Samples were collected between January and March of 2008.

Three datasets are currently included in this download - an excel spreadsheet and a draft publication providing details on the methodology, etc employed, as well as two copies of corrected fluoro data for ...

Related URL

Link: GET DATA

Description: Download point for the data

Geographic Coverage

(Click for Interactive Map)

Spatial coordinates

N: -59.79

S: -69.21

E: 80.01

W: 29.93

Parent DIF

This data set description is a member of a collection. The collection is described in
ASAC_40
BROKE-West

Temporal Coverage

Start Date: 2006-01-10

Stop Date: 2006-02-27

Location Keywords

OCEAN > SOUTHERN OCEAN

GEOGRAPHIC REGION > POLAR

Science Keywords

BIOLOGICAL CLASSIFICATION > PROTISTS

BIOSPHERE > AQUATIC ECOSYSTEMS > PLANKTON > PHYTOPLANKTON

OCEANS > OCEAN CHEMISTRY > PIGMENTS > CHLOROPHYLL

ISO Topic Category

BIOTA

OCEANS

Platform

R/V AA > R/V Aurora Australis
SHIPS

Instrument

CTD > Conductivity, Temperature, Depth

HPLC > High-Performance Liquid Chromatograph

NISKIN BOTTLES

FLUOROMETERS

Quality The corrected fluorometer dataset is a 2 minute average dataset, and has been corrected to match the HPLC surface data and the interpolation includes a correction for irradiance.

Taken from the draft paper:

Materials and Methods

Oceanography

... Oceanographic profiles were collected at 120 CTD stations from RV Aurora Australis using a Seabird SBE9 plus CTD and 24 bottle rosette frame equipped with 10 L Niskin bottles, as described by Rosenberg (2006). Interpretation of oceanographic features follows Williams et al. (this issue). In this paper, the mixed layer depth is defined as the depth at which SigmaT exceeds that at 8 m by 0.02, and the pycnocline is the depth of maximum Brunt-Vaisala frequency

Sample collection

Samples were normally collected at twelve depths - 10, 20, 30, 40, 50, 60, 70, 80, 100, 120, 150, 200 metres - although this was reduced to eight depths on deeper casts when fewer bottles were available in the upper water column. Seawater (1-2 L) from Niskin bottles or the ship's clean seawater line was filtered onto 13mm Whatman GF/F filters (0.7 micron nominal pore size) using vacuum less than 0.5 atm, while protected from light. The filters were blotted dry and frozen in 1.2 ml internal thread cryotubes in liquid nitrogen for return to Australia.

HPLC analysis

The pigments were extracted by a modification of the method of Mock and Hoch (2005). Filters were extracted in the cryotube as follows: 300 micro litre dimethylformamide plus 50 micro litre methanol (containing 140 ng apo-8'-carotenal (Fluka) internal standard) were added, shaken briefly, then filters were soaked for 1 hr in the freezer (-18 degrees C) with approximately 0.6g zirconia beads (0.7mm dia., Biospec) added. Tubes were shaken for 20 sec at 4800 cycles/min (Biospec Products Mini-BeadBeater). This reduced the filter to a milky suspension. The extract was cleared of particulate matter by centrifugation, as follows: the base of the cryotube was pierced with a hot needle, the cryotube was placed on top of a second cryotube inside a 15 ml plastic centrifuge tube, and together they were centrifuged in a Heraeus Multifuge 3 in a swing-out rotor for 3 min at each of 350, 1010 and 2100x g at -9 degrees C. The supernatant was then transferred to an amber autosampler vial with a 350 micro litre micro insert. Extracts (150 micro litre) were automatically diluted to 80% with water immediately before injection to improve peak shape (Wright and Jeffrey, 1997) and analysed by HPLC (Zapata et al., 2000) using a Waters 626 pump, Gilson 233xL autoinjector (with the sample stage refrigerated to -10 degrees C), Waters Symmetry C8 column (150 x 4.6mm, 3.5 micron packing, in a water bath at 30.0 plus or minus 0.1 degrees C), a Waters 996 diode array detector and a Hitachi FT1000 fluorescence detector. Pigments were identified by comparison of their retention times and spectra with a sample of mixed standards from known cultures (Jeffrey and Wright, 1997) that was injected at the head of each daily sample queue. Peaks were integrated using Waters Empower software. All peaks were checked manually and corrected where necessary, and quantified using the internal standard method (Mantoura and Repeta, 1997). Unidentified peaks were roughly quantified using the closest match from our spectral library.

CHEMTAX analysis

Nine taxa were chosen for CHEMTAX analysis, based on microscopy (Davidson et al.., this issue) and previous experience in the region (Wright and van den Enden, 2000a; plus unpublished work). The list of lists pigments and their abbreviations is presented in Table 1. Two types of diatoms were defined: Type A, containing typical diatom pigmentation (Chls c1, c2, FUCO, diadinoxanthin), and Type B, where chl c3 replaces chl c1 (typified by Pseudonitzschia sp., which were commonly observed). Similarly, two types of dinoflagellates were defined initially: Type A, containing peridinin (unambiguous marker), and Type B, containing gyroxanthin diesters and fucoxanthin derivatives (the latter was changed as described below). Prasinophytes and cryptophytes were recognized by the unambiguous markers prasinoxanthin and alloxanthin, respectively. However we cannot distinguish free-living cryptophytes from the ciliate Myrionecta (Mesodinium) rubrum, which appropriates cryptophyte chloroplasts (Hibberd 1977) and is common in the Antarctic SIZ (Bathmann et al. 1997). A chlorophyte category was included due to the presence of lutein, but may include some prasinophytes that lack prasinoxanthin.

Categorisation of taxa containing FUCO, 19'-HEX and 19'-BUT was somewhat problematic due to the multiple possibilities (eight types of haptophytes, pelagophytes, some dinoflagellates (Zapata et al., 2004; Wright and Jeffrey, 2006), coupled with the inability to identify many of the taxa containing such pigments by light microscopy. After several trials of different models, two types of haptophytes were defined, Types A and B, and allowed to find their own level. These contained a mixture of Haptophyte types 6, 7, 8, as defined by Zapata et al. (2004), while types 1, 2 and 4 would appear as diatoms, since they lack acyloxyfucoxanthins. Comparison with microscopic results suggested that haptophytes-A mainly reflected Phaeocystis numbers, whereas haptophytes-B probably included Phaeocystis gametes and Parmales, although neither of these categories can be regarded as exclusive, and both probably include other haptophytes. The group originally defined as dinoflagellates-B was based on pigments of the dinoflagellates Karlodinium venificum, Takayama tasmanicum, and Karenia brevis from Southern Ocean isolates (Wright and de Salas, unpublished), all of which contain fucoxanthin and its derivatives, plus three gyroxanthin esters rather than peridinin. Such 19'-HEX containing dinoflagellates were found to be dominant by Gall et al. (2001). Late in the analysis it became apparent that the dinoflagellate-B category also corresponded to the abundance of Phaeocystis antarctica. This species was dominant through all regions of the survey (Davidson et al., this volume) and its abundance could only be explained by summing the groups Haptophytes-A, -B and Dinoflagellates-B. Thus we re-named the final category as Hapto/Dino-B. The pigment content of P. antarctica varies between strains (Zapata et al. 2004), and it appears that CHEMTAX mainly tracked the variants of this dominant species rather the intended targets.

Sixteen pigments were chosen for CHEMTAX analysis (Table 1a). Other identified pigments, including major pigments such as chl c2 and diadinoxanthin, were excluded after multiple trials showed they contributed no power to the analysis. Up to 50 randomised pigment tables were tried with each scenario to avoid the possibility of poor starting choices producing unrepresentative results. These tables were produced by randomly adjusting each of the pigment ratios in Table 1a by up to plus or minus 70% of the original ratio.

Data were split into five bins according to sample depth to allow for variation of pigment ratios according to irradiance. The depth bins and sample numbers in each bin were 0-15m [129], 15-31m [143], 31-56m [169], 56-92m [282], greater than 92 m [405] (Total = 1128). Each bin was processed separately using CHEMTAX v1.95 (obtainable from the senior author). Table 1b lists the same ratios for the 0-15m bin after optimisation by CHEMTAX from a randomised matrix.

Figure 2 shows variation in Pigment : Chl a ratios for various taxa in other depth bins. Ratios not shown in Figure 2 did not change down the water column, presumably because the parent taxon was not sufficiently abundant for its pigments to affect the analysis.

Access Constraints These data are publicly available for download from the provided URL.

Use Constraints This data set conforms to the PICCCBY Attribution License
(http://creativecommons.org/licenses/by/3.0/).

Please follow instructions listed in the citation reference provided at http://data.aad.gov.au/aadc/metadata/citation.cfm?entry_id=BROKE-We... when using these data.

Ancillary Keywords

CAROTENOIDS

PIGMENTS

Data Set Progress

COMPLETE

Data Center

Australian Antarctic Data Centre, Australia

Data Center URL: http://data.aad.gov.au

Data Center Personnel
Name: DATA OFFICER AADC Phone: +61 3 6232 3244 Fax: +61 3 6232 3351 Email: metadata at aad.gov.au Contact Address: Australian Antarctic Division 203 Channel Highway City: Kingston Province or State: Tasmania Postal Code: 7050 Country: Australia

Distribution

Distribution Media: HTTP

Distribution Size: 3.34 MB

Distribution Format: excel, word, csv

Fees: free

Personnel

SIMON WRIGHT

Role: INVESTIGATOR

Role: TECHNICAL CONTACT

Role: DIF AUTHOR

Phone: +61 3 6232 3338

Fax: +61 3 6232 3351

Email: simon.wright at aad.gov.au

Contact Address:

Australian Antarctic Division

203 Channel Highway

City: Kingston

Province or State: Tasmania

Postal Code: 7050

Country: Australia

Creation and Review Dates

DIF Creation Date: 2008-07-18

Last DIF Revision Date: 2012-10-18

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