l)

ICES 1990 PAPER

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C.M. 1990/C:44Ref. E

Hydrog~aphy Committee,Ref. MEQC

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SKAGEX 1990.Preliminary results from the' nutrient intercalibration.

by

. .Institute of Marine Research

P.O.Box 1870, 5024 Bergen, Norway.

ABSTRACTAn important part of SKAGEX 1990 was the nutrient intercalibration,which was performed to simulate ordinary work at sea. 44 watersampies of 0,5 liter were delivered to. each of the 13 participatingresearch vessels in Arendal harbour the morning .of June 6th. The,sampies were sampled during the 5th of Jurte wheri RN ~G. O. Sars" wasworking the H transect of SKAGEX. The participants should presenttheir results before noon June 7th. From the preliminary results of thetreatment of the reported data, it is demonstrated that most of thenutriertt data determined during SKAGEX may be used for the purpose ofSKAGEX.

INTRODUCTIONIn the ICES multiship study of the Skagerrak in may • june 1990, the Skagerrakexperiment· SKAGEX - (C. Res. 1989/4:1), measurements of nutrients played animportant part in the synoptic survey. The Study. Group on SKAGEX, (C.Res. 1989/2:28), indiscussion of the nutrient measurements, expressed the need for an intercalibration betweenthe participating ships during the field work. Although the results from the ICES nutrientintercalibration, where most of the participating laboratories had taken part, werepromising, the Study Group feit that there may be clearly differences in the performance ofchemical measurements during a weil organized analytical scheme at a stable platform in aland·based Jaboratory and in a shipboard laboralory working under time pressure. The

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intercalibration during SKAGEX was decided to be perlormed as close to normal shipbOardoperations as possible änd was taking place in the harbor of Arendal 6th· 7th of June 1990.

< .,-"" ,."

MATERIALS AND METHODSThe, Skagerrak experiment is presented in the "Report of the Siudy Group on SKAGEX", C.M.1990/C:31 , and the various transects workedare ~resented in Fig. 1. The nOrWegianresearch vessel "G.O. Sars" covered the western part of the area and the transect H ( Fig. 2)from Lindesnes on the nOrWegian coast to Tybor0en at the west 60ast of Jutland. 15hydrographical stations were worked in the H transect, numbered from 1 to 15 starting atthe nOrWegian coast. Stalions 1, 5, 7, 8, 11 and 15 were chosen tor water sampling tortheintercalibrations. Thestations represented the various water-masses to be tound in most ofthetransects worked during SKAGEX. Fig. 3 and Fig. 4presents the salinity arid temperatureof the transect H the day of the calibl'ation sampling.

Water was sampied from the standard depths, 0, 5, ,10, 20, 30, 50, 75, 100, 125, 150,200 meters arid 285 m as the deepest. Two 5 liter Niskin boUles were closed at eachsampling depth and the water from each depth were transferred to 10 I mixing arid storagepolyethylene cans with taps for easy transfer to the sub-samples. .

Sub-samples, 44 in all for each partlcipating ship, were tapped into 0,5 I polyethylenebOUles, marked with station number and depth, and then stored under coverage on a semi­open deck space. Of the participating SKAGEX ships, 13 were equipped tor on bOard nutrientanalyses and took part in the intercalibration in ArendaJ.

The, sampling of the water for the intercalibration was done on the last crossing. starting at .midnight from Tyborßri St. H 15 the 5th of June arid ending at undesries. St. H 1 at 1500hours the same day. After docking in Arendal in the morning of the 6th of June the sub-sampies for the participating ships were delivered on board at aach ship. CTD data from thesampled stations and torms tor plotting and reporting the data were also presented to theparticipants at the deliverY of the sampies. .

. . .The participating ships were asked to report the results tiefore noon on the 7th of June. Theresults were then briefly. preseriif~d. arid. discussed st the tollowing scientific discussion ofthe experiences after the half-run SKAGEX; .

Orie set 6f sub-samples were anaiyzed as pari of the ordinary nutrient measurement aftersampling on board "G.O. Sars" and ttie resiJlts are repoi'ted as G.O. Sars, S, in table 1.

. .RE5ULT5 AND DI5CU5510NAll the reported data are presented in table 1. The participants were asked to repori theirresults both as vertical station plots and plotted with drawn iso-Iines tor the wholetransect, and in tables as weil. At the brief discussion in Arendal the vertical plots from theparticipants were copied tor "overhead" projectiori and the plots from the various stations .and parameters were presented.· The similarity of the profiles was promising. Fig. 5, 6 and7 presents the combined results from the participating ships of the values of nitrate.phosphate and silicate in water from si. H 1. . .•

The figures 5 io 7 show that most of, the participaÜng ships are performing wilhin ,reasonably good agreement. Some ships fall clearly out of the pattern and indicate analyticalproblems. This is most pronounced for silicate. but bOth for phosphate and nitrate there are

,;..u,

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c ,0 ' .' . '",,, ..,also some analytical disturbances.

", " • -, ."', "", ,;".' ~ , ."" "'- " , ... .' ., ' • ,,_,. ,.-.' •.:, ..... , J .\ '. "., • ';'"

By looklng at all the vertlcal profiles, the ships that do not perform according to theaveragepattern, can be removed before further calculations are done. This subjective method iscertainly an easy way out, hut in a preliminary 'treatment of the data it may weil bejustified.

Ba~ed on ltie remainlng ships the average values are calculated. Each ship may then beplotted against the average value and the corresponding regression line calculsted. This givea possibility to recalculate the various ships values according to the average values from the

. intercalibration. Examples of these plots are presented figs. 8, 9 and 10. For some ships ttieanalytical performance on some of the nutrients iridicate that their results on theseparameters should not be used in SKAGEX..

The storage of the water for more than 24 hours without any conservation chemicals added,was 60risidered as a possible problem. But, since the .aim of ttie intercalibration exercisewas to .establish the relationship belween the values from the participatingships, it wasassumed th~it the water sampies iNould betiave more or less the same in all the boUles andth,erefor possible changes in the nutriant content due to biological activity could be ignored.

As mentioned above one set of sampIes was analyz~d durlng the sampling on board~G.6.Sars". Figs.11, 12 and 13 presents the two "G.O. Sars" set of nutrients values. 80th fornitrate and silicate there is a gocid correlation between the values from the !Wo separate setof analyses, arid there are almost negligeable differences in the values from the two set ofsampies. "G.O. Sars",a, was analyzed as part of the routine work when working the transectarid "G.O. Sars", b, as part of the intercalibration exercise.

Our analytical performance on phosphate determinations on board.~G.O. Sars" the day of thesampling was unfortunately not satisfactorilyas is clearly shown in fig. 12.Duringtheintercalibration, however, our auto-analyzer seemed to,have hehaved weil. As. it is thevalues fram the first set of sampIes, Le. rio storage, that are not eonsisteni, there is reason

, to conclude that for the phosphl:lte as weil, there may have been only negligeablEi changes duete the storage.

Although there is a need for staUstical work on the data from the intercalibration, theresults so far strongly indicate that for the purpose of the SKAGEX most of the i'lUtrientvalues determined during the synoptic surveys are cOmparable after adjustments accordingto a specific correction facter tor each ship.

The SKAGEX iniercallbratien e~ercise have aiso demonsirated that this type of exerciseshould be conducted whenever more ships are working in the same area. This exercise hasalso clearly demonstrated the need for a common nutrient standard. Most of the discrepancyhetween the various ships seems to bedue to slight differences in the standards that areuSed.

CONCLUSIONThe SKAGEX intercalibraiion exerdse:

.; confirrris that most of the nutrient data determined during SKAGEX can be used for thepurpose öf SKAGEX. .demoristrates the need for a comnlon nutrient standard.indicates a necessary caution in the use of nutrient data as absolute figures.

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1\&00 0700 0900 1.100 "005930 ~v:x:.~llUl'\l"';;r---L-----"""I...----';;-T~-----1''j9'0

•5700

5800

5900

5700

5800

5900

.5600..L.---------~-.....,.__--......--~:_----T.0500 0100 0900

Fig. 1 Transects during SKAGEX

10

200

100 - - - - - - - - - - - - - . - - - - - - - - _. -- •SIlIP:

DATE:

PARA"ETDl:

COl1~NTS:

,

)00

500

400

600+-------------------;

Fig.2 The depth profile of H transect with stations and samplingdepth marked. The nutrient intercalibration stations markedare St. 1, 5, 7, 8, 11 and 15.

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5

100 - - - - - - - - - - - - - - - - - - - - - - - - - -

200

35.0

$HIP: G. O. SARS.

DATE: 5 Juni 1990.

PARAMETER: S./••

COHHENTS:

80

SKAGEX SECTlON: H

60

40

400

soo

300

Fig. 3·600J-----------------------1

The salinity distribution at H transect, June 5th 1990.

100 - - - - - - - - - - - - - - - - - - - - - - - - - -

5.·.·1---4seAl!

SKAGEX SECTlON: H

8

$HIP: G. O. SARS.

DATE: 5 Juni 1990.

PAR AMH[R: t· C

COHHENTS:500

400

300

~

40

80

60

•

Fig.4600J-----------------------I

The temperature distribution at H transect, June 5th 1990.

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Nitrate, micromol pr. liter

•

108642oo

100

~ A. Velmer

Depth (m) • G.O. sars,a

• G.O. sars,b

• Hydromet

• Argos200 ~ Pr. Siediecki.. OC8anla.. A. v. Humbolt

• T. Braarud

Svanle

• Lev Tltov.. G.M. Dann.vlg.. A. Tlsellus

• G. Thorson •300

All ships St. H1.

Fig.5 The vertical profiles for l"!itrate (Jlmol N03 1- 1) values forall participating vessels of water sampled at 51. H 1.

~ A. Velmer

• G.O.5ars,aDepth (m) • G.O.5ars,b

0 Hydromet

• Argos

200 ~ Pr.Sledleckl.. Oceanla.. A. V. Humbolt

• T. BraarudSvanlc

• LevTltov

• .. G.M. Dannevlg.. A. TIselJus

• G. Thorson

"'",

•

Fig.6

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Phosphate, micromol pr. liter

0.0 0.2 0.4 0.6 0.8 1.0O.U~--'I---I..._+----lL--+-""""-~-"'----I

100

300

All ships St. H1

The vertical profiles for phosphate (J.lmol P04 1·1) values foralt participating vessels of water sampled at 81. H 1.

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Silicate, micromol pr. liter

,

o 2 3 4 5 6

Fig.7

•Depth (m)

~ G.O.sars,a

• G.O. sars,b

• Hydromet

200 • Argos

• Pr. Siediecki~ Oceanla.. A. v. Humbolt.. Svanle

• Lev T1tovG.M. Dannevlg

• A. T1sellus.. G. Thorson •300

All ships St. H1

The vertical profiles tor silicate (~mol Si 1. 1) values tor allparticipating vessels of water sampled at 81. H 1.

..

9Nltnt.

~,.-----....-----r-----....----..-----"""'---~

•at~•:>C

S!+----4-----+----+--f----+--,"""'~~:A

.+-----+----+-----+----f-:;;M't::...-+---~

/~...+----4----+-----+"7'''''''--t----....----j

./~

... •G.O. Sari, oblerv.d

GOS, corr = . 6.5372.-3 + 0.91309 GOS, obi. R"2 =1.000

Nitrat.

S!,.------..,..-----,r-----,.------,-----""7I

R"2 = 0.999

N •

Oc••nl., obl.rv.d

ac••n. corr. =1.3360.-2 + 0.99824 Oc••n. obi.

Ni------::>f'''"-----ti-----i-----+-----l

.+------+-----jt-----+---~::_:...llir:_-----l

•at•..•:>C

Nltret.

• •at~•:>C

S!,.-----...,...------,...------,----_...... __

.+------t------tI-----+---__-.-~:::....----_1;i!... ··· · ··············1·..····························· !f .. !.. ·..··············..····· t························ ·························t·..···········..·..····..·· '!i ! i~ i ~: : :

N+- ~'------t'-----+'-----I----~'

o •Argol, obl.rv.d

Argol, corr... • 5.7950.-2 + 1.0537 Argol obI. R"2 = 0.998

Fig.8 Nitrate values from same vessels plotted against theselected average value.

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Phosphata

..o

...

.,;'".,;

If

. !. __ _ : _ : __ _ .: :: :

j aj: :: :: :

i:!!

................................. • H .

i- i: :i i: :

~-F---_---;, --li--__--i---_---1o.,;

•.......

•aI~ ...• ..~

<C

'"..

•

..o

Jil •

..................................\ __ __.! ~.•....! ;~.) ij l.i

G.M.Oann.vlgy = 1.99488-2 + 0.90273x RA 2 = 0.986

ii!

••••__• __••_._••__ ~._••••••••••••••••••_ ••• _ •••O' _._

o "I Io-F-------+-------;---.......--+------lo.,;

....

.....•aI~ ...• ..>

<C

'"..

Oe.anlay = 1.67098-2 + 1.0351x RA2 = 0.990

•i

~l:----oo------r-,--

i

!i:

.............................__••_ _ _ _.__ u .

I I:;:+------...!------;!r--------li-------i

....

...0

•aI• ..... ..•~<C

'"0

oo

N

o...o

...o

..o

G.Thorson

y = 3.9920.·2 + 0.93386x R"2 = 0.985

Fig.9 Phosphate values trom some vessels plotted against theselected average.

----------------

,

i1 1

SIIIcU8

... ,-----...-----r------.------r----....,

• f') _ .._...... • .

a~•>, c

'"R"2 = 0.996

N G.O.Sers.bC'I

= . 1.2018e·2 + 0.98288 G.O. Sers,obs.G.O.Sers,corr•

o-F--........--+---....--I--~---+--~--+--~--io

•a•..•>C

... 4-----+-----I-----t-----t""";----;

R"2 = 0.995

'" Argos CO>

• 0.20556 + 1.0080 Argos,obs.Argos,corr. =

o+..J-=:......--+---....--1I--.....---+--....--~--......--io

"',-----...-----,..------r----"""T"-----,:>"\

•a•..•>oe

'" Oe.enle CO>

y = 0.10045 + 1.0171ll R"2 = 0.990

Fig. 10 Silicate values fram sam vessels platted against theselected average.

12~~---,-----r---r-----:-----""----.::>I

..

.&:l_

I!!•Ulcici

2t---+-_-+---~--+---.",Jlt1...--1

:!

-==:::~:.=l=o ....._--+--_-+-_-f-_-+-___._-+-~___l

o

G.O.Sars,a

y :: 2.6664.-2 + 0.993681 RA2:: 0.993

Fig. 11 Nitrate values trom RN "G.O. Sars", a values determined on board during thesampling, b values determind during the intercalibration in Arendal.

:~---,..-----:-----r---_r----""'7I

:::+----+----t----=-~f----"-~IoC_--___l: -I

.&:I o"'t----+--..:-:...:..-;.I-=-_~*:.....--_1_---~i~ - !.. io • ...:ci : ·_·····__····--··-1:·············__··,················-_.._.- __.- _ _._ .

ot---~iF----t----l---~~-----1

~f'0E;;...&....---+..----.i----..I----.----l_~---.----lo00000

G.O.Sars,ay :: 1.2841.-2 + 1.21011 RA2:: 0.910

•I;

fIIII _ ••••••_.l _ .

!i

.&:1_ ..t----+---+---..-~:::....---1----~l!!•Ulcici

Phosphate values trom RN "G.O. Sars", a values determined on board duringthe sampling, b values determined during the intercalibration in Arendal.

Fig. 12

..oiW..&---.j------..,I----._---l~---.---l---_lo

G.O.Sar_,a

y.. • 8.3054.·3 + 0.988551 R·2:: 0.990

Fig. 13 Silicate values trom RN ·G.O. Sars·, a values determined on board during thesampling, b values determined during the intercalibralion in Arendal.

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Tabel 1.

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All the reported values from the nutriEimt intercalibration.

•

, AlB' , C" 0," E ., •. F I G I H'" , ". J I . K I- L -,IM ,. N ,. 0 I· P

·~·!·~·Y·~!!!~tg,g,~Y!Y.~·!!!!!!!!t~t~:~!~~!~!:l~!.t::~~~.~Ixl'\I:.~!!!!!r·~·~t~l':~~i·~·!"~·.1!~!?l!f-·~'·~·~rM!~~!!!!~·l~~i~~·t§~'~"

..!!:.9.!!..~....9.:.1.9.....L.l,l.:9.LL..9.:9.~ ....9.:9.~L....l,l.:9.l,l......L.9.:9.~ .......l,l.:~.~......L..9.:.~~ ....L9.:!?~.~ ...9:.9.~ ....!......!?:~l.......L..9.:.9.~....~....9.:9..L.~ ..!?:~.~...!.......9.:~.l ...5.00; 0.10 ; 0.06 ; 0.02 0.061 0.00 ; 0.02 '0.37 i 0.57 10.031 0.07 i 0.05 i 0.07 1 0.01 : 0.11 i 0.17 ..

..1.9.:.l,l.9..j....!?:!!!? ...i ..!!:.~!! ..i ...!?:.~z. .. !?:.~~i .....!?:.?9......~..!?:.?~.......!?:.~.~.....~...9.:~.~....~.!?:.~!!..i ....9.:~J ....~......9.:1.~ ......~....9.:!l.~ ....i....!?:.~~ ...J...9.:~.~ ..i ......!?:.l.~ ..20.00; . 3.60 : 3.85 ; 3.38 3.52; 3.36 ! 3.44 3.30 ; 3.05 : 3.09 ; 3.27; 3.25 ! 3.82 I 3.28 I 3.40; 0.24

...~9.:.9.!?: 7.:.!!!? ~..!!:.?.!?..i !!:.l.~ ~:.~!!i !!:.9.!! ~ ..!!:.9.!! !.:J.!! ~ §.:!.L.i.!!.,?~ ..L..~:~.l,l ~ ~:.?g ~ ~.:~.9. L..!!:.9.~ L.?:~.? ..i !!:.~L ..75.00: 9.30 : 10.25; 8.03 8.70; 9.65 ! 9.57 8.94: 7.30': 7.61 I 6.94 : 10.02 ; 7.68 ; 9.58'; 8.74: 1.11

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Tabel 1 continued

lAB I eiD LE I F I G I H I I I J I K I l I M I N I 0 P---+-) 1;. ; ~ ;. ;.. " ~ •••

•.•_l!...9.!1;_.__..i ..9.:.9.Li.._!1...9.L !1...~~i_._!1 ...??._.i..!1...9.~_ _ !:.9.?._.~__i.!1.,1.!!..LJ.:ZJ_~_.9.:.1.~.__;"".9.:!1.~._.L!1:.9.!1._.i ...9.:~.~_i._ ...!1...~L:..10.00: ~ 0.83 i 0.01 1.0g~...&~!1 1.55' : 0.75; 2.85' 0.90 • o.:..~.o ; 0.46 ; 1.00: 0.72

.._~.9.:!1.9';'_. U.:!1.(LL9.:~.L .?&!.i_1.:~.~ .._.U.&L _~.,!!."._l ; 1·~Li_.~:.~Ll_!,,!!~_.L..~:.9.~-l-1:.~.Li ..! ...~~...L....9.:Z.L...30.00· ; 2.37 ; 0.36 2.6'; 2.27 ; 2.18 3.05! ; 1.80: 3.04! 2.36 ; 2.40 I 1.80 ; 2.20! 0.74

,