The international intercalibration exercise for nutrient methods

This report is concerned with the final statistical evaluation of the data obtained during the International Intercalibration Excercise organized by the ICES Working Group on Chemical Analysis of Seawater. Before coming to the specific details of this excercise it may be useful to review briefly the history of this excercise and the specific reasons why it was carried out. 

Intercalibration of chemical methods for nutrient analysis has long been the concern of an active group of chemists belonging to ICES, especially those from Baltic countries. Already in 1965 an intercalibration excercise was organized in Copenhagen between institutes in Gothenburg, Helsinki and Kiel. The results were published in UNESCO technical papers in marine science No 3. The same year a Working Group on intercalibration and standardization of chemical methods (today W. G. on Chemical Analysis of Seawater) was established (C.Res. 1965/33). In 1966 two intercalibration trials were performed i) In Leningrad in connection with the 5th Conference of Baltic Oceanographers and ii) in Copenhagen during the Annual Meeting of ICES. Again, the results were published by UNESCO as Rep. No 9.

In general, these excercises indicated that, especially in areas where many Institutions contribute to the basic data bank, intercalibration of methods is of utmost importance. In addition, especially in multiship surveys, it will be worthwhile to pay close attention to a careful inter calibration of methods, either by means of stored samples or by means of a reference station.

In order to draw attention to the intercalibration problem, SCOR 1968 suggested that a world-wide international intercalibration exercise should by organized by the Working Group. The request was accepted (C. Res. 1968/3:4) and Drs. F. Koroleff and K. H. Palmork were nominated principal organizers. Subsequently, a SCOR-sponsored meeting was held in La Jolla, in which Drs. K. Sugawara, N. Rakestraw, W. Wooster and J.Gieskes participated. At this meeting, it was recommended that standards for nitrate, nitrite, phosphate and silicate would be prepared by the Analytical Chemistry Section, Sagami Chemical Research Center, under the supervision of Professor Ken Sugawara. The collection and statistical analysis of the data would then be the responsibility of Drs. Koroleff and Palmork.

Two progress reports (C:33 and C:21) have been presented at the statutory meetings of ICES in 1970 and 1972, after which a statistical evaluation of the data was made which, due to several inadvertent delays, was finished in April, 1976. Although it has taken consider-able time to reach this final end product, it seems very worthwhile to carefully consider the results of this excercise. It has been established clearly that intercalibration of methods is of great importance, that uniformly acceptable standards should be established. and that, especially for open ocean surveys, the use of standard reference stations should be encouraged for the purpose of in situ inter calibration.