Niskin bottle

A Niskin bottle (a next generation water sampler based on the Nansen bottle) is a cylindrical, non-metallic water collection device with stoppers at both ends. The bottles can be attached individually on a hydrowire or deployed in 12, 24, or 36 bottle Rosette systems mounted on a frame and combined with a CTD. Niskin bottles are used to collect discrete water samples for a range of measurements including pigments, nutrients, plankton, etc.

R/V Thomas G. Thompson

1995-01-08

Purpose: Process Cruise #1 (Late NE Monsoon)

Methods & Sampling
PI: Lou Codispoti of: Old Dominion University dataset: Temp, salinity, nutrients from Niskin bottles dates: January 08, 1995 to February 01, 1995 location: N: 22.483 S: 9.9826 W: 57.2999 E: 68.75 project/cruise: Arabian Sea/TTN043 - Process Cruise 1 (Late NE Monsoon) ship: Thomas Thompson Final Corrections performed at US JGOFS DMO October 28, 1996 From: Lou Codispoti Subject: Final Corrections Dear JGOFS investigator, This is to inform you that some minor corrections were made to the JGOFS Arabian Sea nutrient data after the 1996 meeting in New Hampshire. It is doubtful that any of these corrections will alter any of your hypotheses, but they may have some significance in documenting changes over long periods of time, and in WOCE-style investigations. The need for these corrections arose, as a consequence of post-cruise re-calibration of pipets, and because we did not properly account for the nutrient content of our low nutrient sea-water. The corrections have already been applied to the US JGOFS Arabian Sea nutrient data collected with the hydrographic rosette, by personnel at WHOI who maintain the US JGOFS data. I list them here for your information. 1) All ammonium and nitrite data from Thompson leg TN053 were multiplied by 0.997. 2) All ammonium and nitrite data from ALL US JGOFS Arabian Sea cruises (TN039, 043, 045, 049, 050, 053 and 054) were multiplied by 0.995. 3) ALL phosphate data from ALL US JGOFS Arabian Sea cruises (TN039, 043, 045, 049, 050, 053 and 054) were multiplied by 0.992. Corrections 2) and 3) should probably be applied to the ONR data as well, but I will leave this up to Burt Jones, as I am not exactly sure how he did his standardizations. Basically, corrections 2) and 3) arise from a failure to take into account dilution of the Low Nutrient Sea Water signal by standards in cases where the LNSW contains appreciable quantities of nutrients. The above corrections are pretty minor within the scheme of nutrient analyses, but we should always attempt to eliminate such systematic errors. George and Chris have made these corrections on the US JGOFS Arabian Sea nutrient data collected from the hydrographic rosette. Trace metal rosette data and experimental data have not yet been corrected. Cheers, Lou Codispoti -- +---------------------------------+------------------------------------------+ | Louis Codispoti | Center for Coastal Physical Oceanography | | Research Professor | Old Dominion University | | lou@ccpo.odu.edu | Norfolk Virginia, 23529 USA | | http://www.ccpo.odu.edu/ | PH: 804-683-5770 FAX: 804-683-5550 | +---------------------------------+------------------------------------------+ The depth values in the bottle file have been calculated from pressure using the algorithm below. The US JGOFS Data Management Office is the source of the calculations. The latitude used in computation was the lat_begin of the bottle file. The CHECKVALUE was used to verify the accuracy of the computation. The stated accuracy of this algorithm is 0.1 meters Thanks to Edward Peltzer (MBARI) for supplying the algorithm and for discussions regarding the computation. function DEPTH=depth(P,LAT); DEPTH Computes depth given the pressure at some latitude D=DEPTH(P,LAT) gives the depth D (m) for a pressure P (dbars) at some latitude LAT (degrees). Fofonoff and Millard (1982). UNESCO Tech Paper #44. Notes: (ETP3, MBARI) This algorithm was originally compiled by RP @ WHOI. It was copied from the UNESCO technical report. The algorithm was endorsed by SCOR Working Group 51. The equations were originally developed by Saunders and Fofonoff (1976). DSR 23: 109-111. The parameters were re-fit for the 1980 equation of state for seawater (EOS80). CHECKVALUE: D=9712.653 M FOR P=10000 DECIBARS, LAT=30 DEG CALCULATON ASSUMES STD OCEAN: T = 0 DEG C; S = 35 (IPSS-78) X = sin(LAT/57.29578); X' = X*X; GR = GRAVITY VARIATION WITH LAT: ANON (1970) BULLETIN GEODESIQUE GR = 9.780318*(1.0+(5.2788E-3+2.36E-5*X')*X') + 1.092E-6*P D = DEPTH BEFORE GRAVITY CORRECTION D = (((-1.82E-15*P+2.279E-10)*P-2.2512E-5)*P+9.72659)*P DEPTH = D/GR Cast specific comments, quality assessment, analytical methods as prepared by L. Codispoti All stations See Codispoti documentation regarding data quality see section on DATA QUALITY below. Station 2 cast 4 From 911.2 to 3.1 decibars bottle (autosal) salinities and comparison CTD scan salinities only agree within 0.010 to 0.029. Station 5 cast 3 From 908.8 to 2.5 decibars Niskin bottle (autosal) salinities and companion CTD scan salinites only agree with 0.01 to 0.022. Station 7 cast 5 Ammonium values are questionable and were deleted Station 7 cast 14 From 2022.5 to 2.6 decibars Niskin bottle (autosal) salinities and CTD scan salinites only agree within 0.01 to 0.023. L. Codispoti, Hydrographic data Station 9 cast 3 Niskin bottle (autosal) salinities and companion CTD scan salinities agree to only 0.012 at 2021.5 decibars, 0.014 at 1714.5 decibars and 0.011 at 707.3 decibars. Station 10 cast 1 Phosphate, silicate, and ammonium values for Niskin bot. 21 at 13.4db are questionable. Station 11 cast 4 All salinities are questionable. Disagreements between Autosal bottle values and CTD scan are as great as 0.032. Station 13 cast 11 Possible 3% "carryover" in nitrate channel. Station 17 cast 5 Between 507.4 and 255.4 decibars, several Niskin bottle (autosal) salinities and CTD scan salinities agree to only 0.011. Station 20 cast 2 The companion deep cast "TN04302002" has not been reported because of uncertain depths due to CTD spiking problems. Station 21 cast 10 Possible 3% "carryover" in nitrate. DATA QUALITY JGOFS Arabian Sea Cruise TN043 READ ME FILE FOR THE HYDROGRAPHIC BOTTLE DATA L.A. Codispoti (lou@ccpo.odu.edu) Old Dominion University, July 1995 General Comments: This "readme" file pertains to the salinity, dissolved oxygen, and nutrient data taken from sampling bottles with the hydrographic rosette that was typically equipped with 24 10-liter Niskin type bottles during RV T.G. Thompson cruise TN043. This cruise was the first JGOFS Arabian Sea Process Leg and took place between 8 January and 5 February 1995. Dr. M. Roman of the University of Maryland's Horn Point Laboratory was the chief scientist. DATA TAKEN WITH THE CLEAN ROSETTE USED FOR OBTAINING PRIMARY PRODUCTION AND OTHER TYPES OF BIOLOGICAL SAMPLES ARE NOT INCLUDED IN THIS REPORT. Because the JGOFS data base system does not have a system for "flagging" questionable data, some questionable data are not included in this report when the values appeared to be in significant error. These data are available by sending an Internet message to No units are given for salinity in this report because the most recent definitions of salinity define it as a dimensionless number. To accommodate every preference, Winkler oxygen values are reported in ml/l, micromolar and micromoles per kg. The latter values can only be calculated with a knowledge of the oxygen sample temperatures when the samples were drawn. These "draw temperatures" are not reported here, but can be obtained by contacting lou@ccpo.odu.edu. Nutrient values are reported in micromolar. They can be converted to micromoles per kg, by combining lab. temperature on the Thompson (approx. 23.5 deg C) and the salinity of the sample to compute density and then dividing the value in micromolar by this number.

Processing Description
Methods: In general, the methods employed for the bottle Salinity, Winkler dissolved oxygen, and nutrient analyses did not differ significantly from those described in the JGOFS protocols that were distributed in June, 1994. Minor differences included the following: 1) Sea Bird CTD systems and bottle carousels were employed (SBE- 9+ underwater units, SBE-11 deck units, SBE-32 carousels). These units represent a newer generation of equipment than the units described in the JGOFS protocols. 2) The weights of the salts used for primary standards for dissolved oxygen and nutrients were not adjusted to an "in vacuo" basis as suggested in the protocols. It is unlikely that this departure from procedure would cause significant errors. Our calculations suggest that the maximum differences arising from our decision to not correct to an "in vacuo" basis would range from 0.02% (oxygen standards) to 0.06% (ammonium standards). 3) The protocols give one a choice of adjusting nutrient methods so that calibration curves are strictly linear, or opting for more response and taking into account non-linearities. We choose the latter method. 4) No corrections were made for "carryover" between nutrient samples run on the Technicon Autoanalyzer. Data from this cruise suggest that carryover effects in our nutrient analyses are generally less than 2% of the concentration difference between adjacent samples. When cases of a larger carryover effect could be determined, they are noted in the cast specific comments. Examination of cases where more than one sample was taken from a depth at which there was a significant increase in nutrient concentrations will help the user determine the carryover effect for many individual casts. 5) Calibration and re-calibration of volumetric ware were not exactly as described in the JGOFS protocols, but this was largely compensated for by comparing independent standards diluted with independent volumetric ware, and by re-calibration of some of the volumetric ware after cruise TN045. 6) Duplicate oxygen samples were not drawn from every Niskin or Go-Flo bottle, but there were several comparisons of bottles tripped at the same depth. 7) Azide was added to the Winkler oxygen pickling reagents to destroy nitrite that can be present in relatively high concentrations in the Arabian Sea. Temperature: The temperature data associated with each bottle depth were taken by the CTD system during the bottle tripping process. Consult the companion CTD data report for this cruise to learn more about the CTD system. Sampling: The samples in this report were taken from 10 liter Niskin bottles. Because there is little or no lag time between triggering a bottle and bottle closure with the new SeaBird rosette systems, bottles were generally held at the sampling depth for at least 20 seconds before tripping. This value was based on data obtained during TN039 when the rosette was equipped with fewer electronic packages. During this cruise (TN043), a decision was made to increase soak times to 30 seconds or until the deck read-outs stabilized because differences between bottle salinities and the values obtained by the CTD when the bottles were tripped were, in some cases, larger than anticipated. The bottles were probably flushing relatively rapidly but it was noted that the companion CTD data sometimes continued to change for periods longer than 20 seconds. This was probably because of the additional equipment mounted near the CTD sensors during TN043. This equipment can act as a heat source/sink and interfere with flushing and equilibration of the CTD sensors on the up cast. This adjustment was made approximately mid-way through TN043. Whether 20 second soak times were the cause of some of the differences has not been determined. The cast specific comments notes those instances where agreement between bottle and CTD salinities was greater than expected. NOTE THAT THE MID-POINT OF THE SAMPLING BOTTLES WAS ONE METER ABOVE THE CTD SENSORS. THE DATA HAVE NOT BEEN CORRECTED FOR THIS ONE METER OR 1.1 DECIBAR DIFFERENCE BETWEEN CTD SENSOR AND SAMPLING BOTTLE POSITIONS. Salinity: Salinities were run on almost every bottle sample with new vials of standard sea-water used before and at the end of every run (12-36 samples). Agreement between bottle salinities and the recently calibrated sensors on the Sea Bird CTD systems was usually better than 0.01 except in regions of strong gradients and in the cases that have been noted above and mentioned in the headers for individual casts. More information on the quality of the salinity data are given in the companion CTD report. Dissolved oxygen: The Winkler dissolved oxygen set-up was built and supplied by the SIO/ODF group. This system is computer controlled and detects the end-point photometrically. Temperature of the thiosulfate and standard solutions is automatically monitored by this system. An independent "Sagami" standard was compared with a SIO/ODF primary standard. The agreement between these standards was +-0.02 per cent. These standards were made up at sea with independent volumetric ware. The linearity of the "Dosimat" automatic buret was also checked during this cruise. NOTE THAT THE TWO LAST DECIMAL PLACES ARE MEANINGLESS IN THE COLUMNS THAT EXPRESS DISSOLVED OXYGEN IN mM and in mM/kg. Nutrients: Note that the terminology used to describe nutrients has become somewhat loose over the years and that silicate=silicic acid, and phospate=reactive phosphorus. Nutrient analyses were performed on a 5-channel Technicon II AA system that was modified and provided by the SIO/ODF group. In assessing the nutrient standard comparisons outlined below, note that the full-scale ranges for nutrients were as follows: Ammonium =0 to 5 micromolar Nitrate =0 to 45 " Nitrite =0 to 5 " Phosphate =0 to 3.6" Silicate =0 to 180 " These ranges were arrived at after an Internet pole of PI's and cover the full depth concentration range for the Arabian Sea. On the set-up and calibration cruise (TN039), the SIO/ODF nitrate and nitrite standards and standards from the National Institute of Oceanography in India (provided by S.W.A. Naqvi) were compared with the following results: NIO Nitrate Std.= 22.6 micromolar; SIO/ODF= 22.5 micromolar NIO Nitrite Std.= 2.42 micromolar; SIO/ODF = 2.50 micromolar As can be inferred from the above, the nitrate plus nitrite values were almost identical in the mixed standards; 25.02 (NIO) vs 25.00 (SIO) micromolar. On TN039 Lou Codispoti prepared independent primary nitrate, nitrite, silicate and phosphate standards with SIO/ODF primary standards, and made dilutions using glassware entirely independent of the SIO/ODF glassware. The results were as follows: Codispoti SIO/ODF Nitrate 26.96 micromolar 26.85 micromolar Nitrite 2.90 " 2.86 " Silicate 86.4 " 85.8 " Phosphate 2.36 " 2.36 " All of the above results are within plus or minus 0.5% of the full scale values, and with the exception of nitrite, the rest are within plus or minus 0.2% of the full scale values. On TN043 the volumetric equipment used for making routine nitrate and phosphate standards was checked against volumetric ware calibrated by LAC. The average of the results agreed to within +-0.1% of the full scale value for phosphate and +-0.2% of the full scale value for nitrate. The three Eppendorf maxipettors used to make the routine standard dilutions were calibrated at Old Dominion University after cruise TN045. For the three maxipettors and three tips that were returned for re-calibration, the largest departure from the nominal values was 0.5% at 2.50 ml. For the 5.00ml range, used to make the working standards, the "worst" of these maxipettors (with its companion tip) was "off" by 0.2%, and the agreement between dialed and calibrated values for all three instruments/tips was better than 0.1% at the 7.50 and 10.00 ml settings. The 2.50, 7.50 and 10.00 ml settings were used for weekly determinations of the linearity of each nutrient analysis. Because nitrite values in the suboxic waters of the Arabian Sea can attain values of approximately 5 micromolar, we kept track of the efficiency of the Cd column that reduces nitrate to nitrite in the nitrate analysis towards the end of the cruise. The efficiencies were all greater than 96.7% and frequently close to 100%. Corrections have been made that should reduce any errors in nitrate arising from deviations in cadmium column efficiency to less than 0.1 micromolar in nitrite even for cases where nitrite concentrations concentrations were maximal and Cd column efficiencies were minimal. The ammonium results are the least precise of all the nutrient results. On TN039 three primary standards were compared with agreement of about plus or minus three per cent of the full-scale value. These standards may have agreed within the precision of the method, but we found a significant salinity effect on the ammonium results that might explain some of these differences since the salinities of the comparison standards varied a bit. Experiments on this first JGOFS Arabian Sea process study cruise (TN043) suggest that the ammonium signal decreases by approximately 3.5% for a salinity increase of 1.00. Comparisons of an independent standard compared by LAC with the SIO standard on this cruise (TN043) when corrected for salinity differences between the standards agreed to ~ + -0.1% of the full-scale value. The largest absolute difference was 0.025 micromolar and the average difference was 0.013 micromolar for six comparisons between 1-3 micromolar. Thus, the average difference between these two independent standards was + -0.006 micromolar. These results tend to confirm the need to take salinity differences between samples and standards into account when calculating the final ammonium concentrations. THE AMMONIUM VALUES IN THIS REPORT HAVE BEEN CORRECTED FOR THIS EFFECT.

R/V Thomas G. Thompson

1995-04-10

R/V Thomas G. Thompson

1995-08-15

R/V Thomas G. Thompson

1995-09-15

R/V Thomas G. Thompson

1995-11-26

R/V Thomas G. Thompson

1995-12-28

R/V Thomas G. Thompson

1994-09-18

Intercalibration and Training Cruise

Methods & Sampling
PI: Lou Codispoti dataset: Temp, salinity, nutrients from Niskin bottles project/cruise: Arabian Sea/TTN039 - Intercalibration Cruise ship: Thomas Thompson Codispoti TN039 comments and methodology Cast specific comments, quality assessment, analytical methods as prepared by L. Codispoti All stations See Codispoti documentation regarding data quality see section on DATA QUALITY below. Station 1 cast 1 This station was taken on the way to the Arabian Sea from Singapore near Sri Lanka to the South of the Bay of Bengal. Station 5 cast 1 This station was designed to check the flushing characteristics of the 10 liter Niskins on the hydrographic rosette. The rosette was pulled through a strong gradient into a fairly uniform layer and bottles were fired immediately, after 21 sec, etc. until 149 seconds. Based on these data, it was decided that a 20 second soak time was ample for flushing the 10 liter Niskin bottles. On later cruises, longer flushing times than would be suggested by the data were used. This is because the CTD sensors are surrounded by additional sensors added for other JGOFS investigators. Station 6 cast 1 This cast was made with the large bottle rosette for special chemical samples. The rosette was equipped with a mixture of bottles. Only salinities and Winkler O2's on selected bottles, no nutrients. The three replicate Oxygens near the surface agreed well, but one of the two oxygens at 28-29 decibars is suspect. Station 6 cast 3 This was a large bottle rosette cast for special chemistry samples. The data from bottle 23 (Seq.23) were deleted because this bottle appeared to be a mis-trip. Station 6 cast 4 Another large bottle rosette cast for special chemistry samples. As usual, the large bottles were paired with 10 L Niskins from which the samples for the chemical data were taken. CTD "spiking" problems occured which could compromise the data, particularily the depths of bottles 13 and 15. Station 7 cast 1 All oxygen samples were drawn by trainess from Oman and Pakistan. Bubbles were noted in flasks from bottles 18-24. These questionable data have been deleted. Station 8 cast 1 We had "spiking" problems with the CTD/rosette that could have caused mis-trips at this station, but the depths seem o.k. The higher colorimetric oxygens seem to be systematically lower than the Winklers which probably means that they were outside the high range for accuracy with the colorimetric method. These values have been deleted. The elevated NH4 value at 1514.7 db occurred on several casts. Competing hypotheses for this peak are contamination from the Niskin bottle or a concentration of zooplankton activity in this layer. Station 8 cast 4 Casts 02 and 03 at Station 008 were too badly comprimised by electrical "spikes" to make it worthwhile to collect water. This shallow cast was taken because it was orginally thought that the shallow values from cast 01 were comprimised by spiking. We believe that the depths for samples for casts 01 and 04 are o.k. but there is a possibility that that they are in error because of the spiking problem. Station 9 cast 1 No significant problems on this cast, but some questionable oxygens are not reported. Station 10 cast 1 The Silicate (Silicic Acid) from bottle 3 is probably incorrect and was deleted. Station 11 cast 1 The surface oxygen saturation at this station was 125% which is possible given the relatively high nutrients at the sea surface. The salinity at 252.3 db is questionable and was deleted. Station 12 cast 1 Another station with appreciable nutrients and O2 supersaturation at the surface. Station 18 cast 1 Special Chemistry cast with large bottle rosette and mixture of bottles. All Winklers questionable and have been deleted because flasks were only shaken once before running. All data from bottle 13 are questionable because of leaking Niskin bottles. Station 18 cast 3 Special Chemistry cast with large bottle rosette and mixture of bottles. Station 18 cast 5 Another special chemistry cast. Station 18 cast 6 Another special chemistry cast with large bottle rosette. Station 18 cast 9 The bottles were not tripped in order of their sequence on the rosette. Station 19 cast 1 Electronic spiking in CTD/rosette system make depths between 26.8 and 454.4 db somewhat uncertain. The depths listed are our present "best guess". Station 21 cast 1 Spiking problems could have caused mis-trips, but depths look o.k. Because of the problems two bottles were tripped at 1014.5 db. Station 21 cast 2 Another special chemistry cast. Air leak at top of bottle 9 and relatively high result makes Winkler values questionable. Spiking problems occurred which makes bottle mis-trips a slight possibility. Station 21 cast 4 Slight possibity of mis-trips due to electrical spliking in CTD/rosette system, but data look good. Station 22 cast 1 Once again, electrical spiking in the CTD/rosette system introduces a possibility of mis-trips, particularly between 26-300db. Bottle 1 was definitely a mis-trip and the data have been eliminated. The bottle 5 "hung up". Station 23 cast 1 Another special chem. cast with large bottle rossette. Station 23 cast 2 The bottle 1 mis-tripped again. Station 23 cast 3 Another special chemistry cast with the large bottle rosette. Station 23 cast 4 Another special chemistry cast with the large bottle rossette. The bottle 9 leaked but the data look o.k. Station 23 cast 6 This is another special chemistry cast with the large bottle CTD/rosette. DATA QUALITY JGOFS Arabian Sea Cruise TN039 (Set-up and Calibration Cruise) Sept-Oct. 1994: QA/QC Report for the Niskin and Go Flow Bottle Data (Bottle Salinities, Oxygens and Nutrients) L.A. Codispoti (lou@ccpo.odu.edu) Old Dominion University, May 1995 General Comments: This "readme" file pertains to the salinity, dissolved oxygen, and nutrient data taken from sampling bottles during RV T.G. Thompson cruise TN039. This cruise took advantage of the sampling and training opportunities provided by the Thompson's transit leg from Singapore to Oman. The purposes of this cruise included: 1)testing equipment and methods that would be used on the subsequent JGOFS Arabian Sea process cruises, 2)finalizing the hydrographic and data-processing protocols that would be used on subsequent JGOFS Arabian Sea process cruises, 3)training participants from Pakistan and Oman, 4)collecting as much data as possible to extend the temporal and spatial coverage of the time-series observations included in the JGOFS Arabian Sea process study. Because the JGOFS data base system does not have a system for "flagging" questionable data, no questionable data are included in the files sent to the JGOFS Data Management Office. These data are available by sending an Internet message to "lou@ccpo.odu.edu". No units are given for salinity in this report because the most recent definitions of salinity define it as a dimensionless number. To accomodate every preference, Winkler oxygen values are reported in ml/l, micromolar and micromoles per kg. The latter values can only be calculated with a knowledge of the oxygen sample temperatures when the samples were drawn. These "draw temperatures" are not reported here, but can be obtained by contacting lou@ccpo.odu.edu. Nutrient values are reported in micromolar. They can be converted to micromoles per kg, by combining lab. temperature on the Thompson (approx. 23.5 deg C) and the salinity of the sample to compute density and then dividing the value in micromolar by this number. Methods: In general, the methods employed for the bottle Salinity, Winkler dissolved oxygen, and nutrient analyses did not differ significantly from those described in the JGOFS protocols that were distributed in June, 1994. Minor differences included the following: 1) Sea Bird CTD systems and bottle carousels were employed (SBE- 9+ underwater units, SBE-11 deck units, SBE-32 carousels). These units represent a newer generation of equipment than the units described in the JGOFS protocols. 2) The weights of the salts used for primary standards for dissolved oxygen and nutrients were not adjusted to an "in vacuo" basis as suggested in the protocols. It is unlikely that this departure from procedure would cause significant errors. Our calculations suggest that any differences arising from our decision to not correct to an "in vacuo" basis would range from 0.02% (oxygen standards) to 0.06%(ammonium standards). 3) The protocols give one a choice of adjusting nutrient methods so that calibration curves are strictly linear, or opting for more response and taking into account non-linearities. We choose the latter method. 4) No corrections were made for "carryover" between nutrient samples run on the Technicon Autoanalyzer. Data from this cruise and a subsequent cruise suggest that carryover effects in our nutrient analyses are generally less than 1-2% of the concentration difference between adjacent samples. 5) Calibration and re-calibration of volumetric ware was not as rigorous as described in the JFOFS protocols, but this was largely compensated for by comparing independent standards diluted with independent volumetric ware. 6) Duplicate oxygen samples were not drawn from every Niskin or Go-Flo bottle, but there were several comparisons of bottles tripped at the same depth and numerous comparisons of the Winkler and colorimetric oxygen values. 7) Azide was added to the Winkler oxygen pickling reagents to destroy nitrite that can be present in relatively high concentrations in the Arabian Sea. Cruise TN039 contains some oxygen determinations made using the colorimetric method of Broenkow in Cline (1969) which is optimized for low dissolved oxygen concentrations. This method is not described in the JGOFS protocols. Similarly, a method for the automated determination of ammonium is not included in the JGOFS protocols. The method described by Whitledge et al. (1981) as modified by K. Krogsland of the University of Washington (kkgrog@u.washington.edu) was employed for this analysis. Temperature Data: The temperature data associated with each bottle data depth were taken by the CTD system during the bottle tripping process. Consult the CTD data report for this cruise to learn more about the CTD system. Sampling Bottles: Most of the samples in this report were taken from 10 liter Niskin bottles. A few samples were taken from 20 and 30 liter Go- Flo or Niskin bottles. Information about what type of bottle a sample came from can be obtained by sending an Internet message to lou@ccpo.odu.edu. Because there is little or no lag time between triggering a bottle and bottle closure with the new SeaBird rosette systems a bottle flushing experiment was performed. The rosette was raised through a strong gradient into a mixed layer and then a sequence of bottles was tripped over about a two minute period. This experiment suggested that the bottles flushed fairly well and that a 20 second "soak time" should be sufficient before tripping a bottle at a given depth. On a subsequent cruise (TN043), it was found that bottle soak times had to be increased largely because of relatively slow response times for the CTD sensors. The bottles were probably flushing relatively rapidly but the companion CTD data for salinity showed some variation that disappeared with longer soak times. This was probably because of the additional equipment mounted near the CTD sensors during the subsequent cruises. This equipment can act as a heat source/sink and interfere with flushing and equilibration of the CTD sensors on the up cast. NOTE THAT THE MID-POINT OF THE SAMPLING BOTTLES WAS ONE METER ABOVE THE CTD SENSORS. THE DATA HAVE NOT BEEN CORRECTED FOR THIS ONE METER DIFFERENCE BETWEEN CTD SENSOR AND SAMPLING BOTTLE POSITIONS. Salinity: Salinities were run on almost every bottle sample with new vials of standard sea-water used before and at the end of every run (12-36 samples). These runs, suggested that drift during runs was usually less than 0.0005. Agreement between bottle salinities and the recently calibrated sensors on the Sea Bird CTD systems was usually better than 0.01 after final data processing. For depths greater than 500 db, the standard deviation between bottle salinities and the CTD results after final calibration was 0.002 for two of the three CTD systems. The third system that was used only to collect a few "special chemistry" samples had a standard deviation of 0.005 for this depth range. Consult the companion TN039 CTD data report for a fuller discription of these data. Dissolved oxygen: The Winkler dissolved oxygen set-up was built and supplied by the SIO/ODF group. This system is computer controlled and detects the end-point photometrically. Temperature of the thiosulfate and standard solutions is automatically monitored by this system. A primary standard provided by Lou Codispoti was compared with the SIO/ODF primary standard. The agreement between these standards was plus or minus 0.02 per cent. These standards were made up at different institutions and diluted at sea with totally independent volumetric ware. We tested the effects of using silicone vs tygon Tubing to draw dissolved oxygen samples for the benefit of Ed. Peltzer who was concerned about DOC contamination from Tygon tubing. There appeared to be no difference between the results. Because we will not have the person power to perform colorimetric dissolved oxygen concentrations routinely during the process legs and because of the existence of suboxic water in the Arabian Sea, we did a comprehensive comparison of colorimetric vs automated Winkler oxygen analyses. Generally, the results agreed within better than plus or minus 0.005 ml/l with perhaps a tendency for the automated Winkler to overestimate by about 0.005ml/l in the less than 0.01 ml/l (about 0.5micromolar) range compared to the colorimetric method. NOTE THAT THE OBSERVATIONS WERE MADE WITH HIGHLY EXPERIENCED ANALYSTS DRAWING THE SAMPLES AND BY ALLOWING AT LEAST THREE BOTTLE VOLUMES TO OVERFLOW THE WINKLER OXYGEN FLASK (CONSUMING ABOUT AT LEAST 0.7L OF WATER)WHEN DRAWING WINKLER SAMPLES. We performed some iodine blanks on sea-water. The results were intriguing and suggest small positive and negative blanks (about 0.5 micromolar)in the suboxic waters. Stay tuned for further developments. Nutrients: Terminology describing nutrients has become somewhat loose over the years, so it may be useful to point out that for our purposes silicate=silicic acid, and phosphate=reactive phosphorus. Nutrient analyses were performed on a 5-channal Technicon II AA system that was modified and provided by the SIO/ODF group. In assessing the nutrient standard comparisons outlined below, note that the full-scale ranges for nutrients were as follows: Nitrate =0 to 45 micromolar Nitrite =0 to 5 " Phosphate =0 to 3.6" Silicate =0 to 180 " These ranges were arrived at after an Internet pole of PI's and cover the full depth concentration range for the Arabian Sea. The SIO/ODF nitrate and nitrite standards and standards from the National Institute of Oceanography (NIO) in India (provided by S.W.A. Naqvi) were compared with the following results: NIO Nitrate Std.= 22.6 micromolar; SIO/ODF=22.5 micromolar NIO Nitrite Std.= 2.42 micromolar; SIO/ODF = 2.50 micromolar As can be inferred from the above, the nitrate plus nitrite values were almost identical in the mixed standards; 25.02 (NIO) vs 25.00 (SIO) micromolar. Lou Codispoti prepared independent primary nitrate, nitrite, silicate and phosphate standards for comparsion with SIO/ODF primary standards, and made dilutions using glassware entirely independent of the SIO/ODF glassware. The results were as follows: Codispoti SIO/ODF Nitrate 26.96 micromolar 26.85 micromolar Nitrite 2.90 " 2.86 " Silicate 86.4 " 85.8 " Phosphate 2.36 " 2.36 " All of the above results are within plus or minus 0.5% of the full scale values, and with the exception of nitrite, the rest are within plus or minus 0.2% of the full scale values. Because nitrite values in the suboxic waters of the Arabian Sea can attain values of approximately 5 micromolar, we tested the efficiency of the Cd column that reduces nitrate to nitrite in the nitrate analysis towards the end of the cruise. The efficiency was 98.3 per cent. The column may have been more efficient at the beginning of the cruise. We assumed that the column was 100% efficient. A 2% error in assumed column efficiency would in the worst case introduce an error of 0.1 micromolar in nitrite (nitrite=5 micromolar), but most of the errors would be much smaller. The ammonium results were the least precise as expected given the state of the methods available. Three primary standards were compared with agreement of about plus or minus three per cent of the full-scale value. Based on our experience, we feel that the standards probably agreed within the precision of the method, but we found a significant salinity effect on the ammonium results that might explain some of these differences since the salinities of the comparison standards varied a bit. Experiments on the first JGOFS Arabian Sea process study cruise (TN043) suggest that the ammonium signal decreases by approximately 3.5% for a salinity increase of 1.00. Thus, salinity differences between samples and standards have to be taken into account when calculating the final ammonium concentrations. The ammonium values in this report have been corrected for this effect. Acknowledgements: I thank everyone who helped me with the above work, particularly K. Krogsland, J. Kinder, R. Kohrman, D. Masten, W. Martin, S.W.A. Naqvi, R. Patrick, W. Peterson, J. Aftab, G. White, and M. Realander. References: Broenkow, W.W. and J.D. Cline (1969) Colorimetric determinaton of dissolved oxygen at low concentrations. Limnology and Oceanography, 14, 450-454. Whitledge, T.E., S.C. Malloy, C.J. Patton, and C.O. Wirick (1981) Automated Nutrient Analysis in seawater. Brookhaven National Laboratory Report 51398, 216pp.