R/V ALIS - CHEMISTRY AND NUTRIENTS DATA

M. Rodier (ORSTOM, New Caledonia)

Announced availability: 1 April 1994

Data Access

The R/V Alis chemistry data are available upon request from NOAA's National Oceanographic Data Center (NODC) in Silver Spring, MD (http://www.nodc.noaa.gov). The data are also archived at the National Center for Atmospheric Research (NCAR) in Boulder, CO (http://dss.ucar.edu/pub/toga_coare/).

Background

The oceanographic cruise EQUALIS, a joint operation between the two international projects JGOFS (Joint Global Ocean Flux Study) and TOGA COARE, was organized by the FLUPAC group of the Centre ORSTOM de Noumea, New Caledonia, with participation and collaboration of Japanese and Australian scientists.

The cruise was carried out from 3 November through 12 December 1992 (Noumea to Noumea) onboard the ORSTOM research vessel Alis and consisted of two fixed stations at 156 15E, 1 30S (12 - 22 November 1992) and 156 10E, 1 45S (27 November - 6 December 1992), interrupted for one day (27/28 November) for intercomparison of meteorological measurements with the Australian research vessel Franklin.

Nutrient (nitrate, nitrite, silicate and orthophosphate) and pigment (chlorophylls and phaeophytin) concentrations in the upper 200 m were determined for 193 casts during the Alis COARE participation. Samples were taken during each cast at 12 different water depth levels between 0 and 200 m and at 24 depth levels when two consecutive casts were made. During each cast the sampling depth was chosen according to the T/S diagram of the CTD to assure best sampling of the nitracline (N-N03(-)>0.1 uM). The instrument used was a General Oceanics Rosette system (12 bottles, 1.2 liters). Nitrate (N-NO3(-)), nitrite (N-NO2(-)) and orthophosphate (P-PO4(3-)) were measured at all levels every time a cast was made. Silicate (Si-SiO4(2-)) was only measured for the 500h, 1100h, 1700h and 2300h casts (all levels). 

Time    # of casts
(UTC)
01h00   2
04h00   1
07h00   2
10h00   1
10h00   1
13h00   1
16h00   1
19h00   2
22h00   1

Data Analysis

Samples were put into 50-ml polyethylene vials and immediately analyzed onboard the ship with an Autoanalyzer II Technicon. Nutrient analysis was done according to the procedure described by Strickland and Parsons (1972). Nitrate concentrations of less than 1.5 uM and nitrite concentrations were measured with the "high sensitivity method" described by Oudot and Montel (1988). For phosphate and silicate analyses, artificial seawater (salinity of 35) was used to determine the baseline. For nitrate and nitrite analyses, seawater taken below the surface at 15S (156E) was used as a reference since it was less concentrated than artificial seawater.

Detection limits for the different nutrients and the coefficients of variation given in the following table are based on six repetitive analyses from the same bottle of cast 232. 

Nutrient                 Detection Limit (uM)   Coefficient of Variation (%)
N-NO3(-) < or = 1.5 uM   0.005                  0.30% for 1.500 uM
N-NO3(-) >      1.5 uM   0.03                   1.10% for 3.75 uM
                                                1.21% for 8.55 uM
N-NO2(-)                 0.005                  16.5% for 0.015 uM
                                                3.76% for 0.095 uM
P-PO4(3-)                0.008                  0.30% for 0.360 uM
                                                1.12% for 0.640 uM
Si-SiO4(2-)              0.1                    0.56% for 2.0 uM
                                                0.25% for 2.9 uM
Pigment analysis was done using 100-ml samples for measurement of total chlorophyll a. Samples from almost every cast done and from all depth levels between 0 and 160-200 m were filtered through Whatman GF/F (25mm) filters. Filters were immediately stored in a deep freezer for future analysis in the lab.

Chlorophyll and phaeophytin concentrations were determined after extraction with methanol (95%) for 15 to 20 minutes with a Turner fluorometer. Sigma chlorophyll a solutions were used as a reference. Analysis was done according to the protocol described by Le Bouteiller et al. (1992). Tests made during previous missions (10 repetitive measurements) showed a 2-5% variation and that storage at -20C does not lead to a pigment loss of more than 10%.

Measurements were good and the sensitivity of the methods used allowed to describe the vertical distribution of the pigments and nutrients in a satisfactory way. It should be noted that due to some malfunctioning of the fluorometer, certain values that correspond with high percentage of phaeophytin in the surface layers should be considered with precaution.

Data File Information

Number of data files: 2 (alispf1.ros, alispf2.ros)
Dataset format: ASCII
Dataset volume: 60 KB

File Header

22 Columns: Day, month, year, station number, hour, minute, degrees of latitude, minutes of latitude, S or N, degrees of longitude, minutes of longitude, E or W, depth (meters), temperature( deg C), salinity, sigma theta (kg/m3), phosphate (uM), silicate (uM), nitrate (uM), nitrite (uM), chlorophyll (mg/m3), % of phaeophytin.

Dates and time are UTC.

The first line in the file gives the code for missing values for each parameter.

Data Example 


11 11 92   1 22 32 1 30 S     156 15 E      0 99.99 99.99 999.99 9.99 99.999 9.999 9.999 9.999 99.99
11 11 92   1 22 32 1 30 S     156 15 E      0 28.93 34.18 999.99 0.11  0.008 0.007 0.132 0.093 41.41
11 11 92   1 22 32 1 30 S     156 15 E     20 28.80 20.43 999.99 0.09  0.008 0.007 0.093 0.071 43.23
11 11 92   1 22 32 1 30 S     156 15 E     40 28.84 34.15 999.99 9.99 99.999 9.999 9.999 9.999 99.99
11 11 92   1 22 32 1 30 S     156 15 E     49 28.84 34.16 999.99 9.99 99.999 9.999 9.999 9.999 99.99
For more information, please contact:

Marie-Helene Radenac
Groupe SURTROPAC
Centre ORSTOM de Noumea
BP A5
Noumea Cedex
New Caledonia

email: radenac@noumea.orstom.nc
Phone: (68) 726 1000
FAX: (68) 726 4326

or

Martine Rodier
Groupe SURTROPAC
BP A5
Noumea Cedex
New Caledonia

email: rodier@noumea.orstom.nc
Phone: (68) 726 1000
FAX: (68) 726 4326

References

ORSTOM, 1993: Rapport de la campagne EQUALIS a bord du NO ALIS pendant la periode d'observations intensives de l'operation COARE du 3 novembre au 12 decembre 1992. Rapports de Missions, Sciences de la Mer, Oceanographie, No 4, 1993, ORSTOM, Centre de Noumea, New Caledonia, Decembre 1993, 491 pp.

Le Bouteiller, A., J. Blanchot, and M. Rodier, 1992: Size distribution patterns of phytoplankton in the western Pacific: towards a generalization for the tropical open ocean. Deep Sea Research, 39, 805-823.

Oudot, C., and Y. Montel, 1988: A high sensitivity method for the determination of nanomolar concentrations of nitrate and nitrite in sea-water with a Technicon Autoanalyzer II. Marine Chemistry, 24, 239-252.

Strickland, J., and T. Parsons, 1972: A practical handbook of seawater analysis. Fisheries Research Board of Canada, Bulletin 167, 310 pages.

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