A JOINT ICES-IOC STUDY GROUP ON NUTRIENT STANDARDS
Michio Aoyama (1), Andrew G. Dickson (2), David J. Hydes(3), Akihiko Murata(4), Jae Oh(5), Patrick Roose(6),
E. Malcolm S. Woodward(7)
(1)
Meteorological Research Institute, 1-1 Nagamine, Tsukuba, Ibaraki 305-0052, Japan, Email: maoyama@mrijma.go.jp
(2)
Scripps Institution of Oceanography, University of California at San Diego 341 Endurance Hall, 9500 Gilman Drive,
La Jolla, CA 92093-0212, USA, Email: adickson@ucsd.edu
(3)
National Oceanography Centre, Southampton, European Way, Southampton SO14 3ZH, UK, Email:
djh@noc.soton.ac.uk
(4)
Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka-shi, Kanagawa, 237-0061,
Japan, Email: murataa@jamstec.go.jp
(5)
IAEA-Marine Environment Laboratories, Monaco, 4 Quai Antoine 1er B.P.800, MC 98000 Prinicipaute de Monaco,
Email: j.oh@iaea.org
(6)
MUMM, 3de en 23ste Linieregimentsplein B-8400 Ostend, Belgium, Email: P.Roose@mumm.ac.be
(7)
Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH, UK, Email: emsw@pml.ac.uk
ABSTRACT
Improved comparability and traceability of data for
nutrients in the world's oceans are needed to improve
our knowledge of change in the deep oceans, and for
studies of global change. In particular this is necessary
to reliably investigate, changes in the distribution of
concentrations of nutrients in the ocean, and the
tightness coupling between the nitrogen, phosphorus
and carbon cycles. A Joint IOC-ICES Study Group on
Nutrients Standards (SGONS) is now working to enable
better comparability between data sets measured at
different times, and by different laboratories.
1.
INTRODUCTION
The comparability and traceability of nutrient data in the
world’s oceans are fundamental issues in marine
science, and particularly for studies of global change.
The oceanography community is working to improve
the comparability of nutrient data in many ways,
including international inter-laboratory comparison
exercises and the development of nutrient reference
materials. However, as Climate Change 2007 – The
Physical Science Basis (IPCC2007) [1] report stated,
adequate comparability and traceability have not yet
been achieved.
In 1993 the IOC-IAEA-UNEP Group of Experts on
Standards and Reference Materials (IOC-IAEA-UNEP,
1993, IOC Workshop Report 112) [2] drew attention to
an urgent need for the development of certified
reference seawater for dissolved nutrients. Dickson [3]
also pointed out the need to develop a certified
reference seawater that can cover several determinands
all in one bottle.
In the 1990s a number of studies were organized under
the ICES umbrella. These studies were well documented
by UNESCO [4, 5]; ICES [6, 7]; Kirkwood [8]; Aminot
et al., [9], Aoyama, [10]). In Europe, this led in 1993 to
the establishment of the Quality Assurance of
Information for Marine Environmental Monitoring in
Europe [11]. QUASIMEME has since evolved into a
self sustaining proficiency-testing scheme (PTS) that
supports individual laboratories in validating and
maintaining the quality of their procedures for a wide
range of determinands. However, QUASIMEME
samples are not meant to be used as long-term reference
materials, such as those needed to support the
traceability and to link measurements from day to day.
This is needed in order to improve the overall precision
within a laboratory, and to assess differences between
laboratories in order to achieve a higher level of
comparability. Various efforts have been made to
change it, but these have been on too small a scale to
meet the needs of the global community in measuring
nutrients in seawater. For example in 2000 and 2002,
the National Oceanic and Atmospheric Administration
(NOAA), USA and the National Research Council of
Canada (NRC) conducted two inter-laboratory
comparison exercises to certify MOSS-1 [12,13] .
However, this developemnt was not followed through
and despite such efforts, adequate comparability and
traceability of nutrient data have not yet been achieved.
In 2003 Aoyama of the Meteorological Research
Institute (MRI), Japan, organized an inter-laboratory
comparison study that included 18 laboratories [10, 14].
In 2006, Aoyama, working with Hidekazu Ota of the
General Environmental Technos Co., Ltd. (KANSO),
Japan, organized a second inter-laboratory comparison
study that included 55 different laboratories world-wide
[15]. Both inter-laboratory comparison studies clearly
show that the global use of reference materials for
nutrients in seawater could greatly improve the
comparability of nutrients data in the world’s oceans.
In early 2007 Aoyama visited the National
Oceanography Centre in Southampton, UK, to discuss
the results of the inter-calibration exercise with the
European participants in the inter-calibration exercise as
well as other interested nutrient chemists. As a followup to this meeting, an International Workshop on
Chemical Reference Materials in Ocean Science was
held in Tsukuba, Japan, on 29 October to 1 November
2007. It focused on the measurement of nutrients and of
ocean CO2 parameters, and the current status of
available chemical reference materials, particularly for
nutrient references in ocean science. The participants
agreed to start a collaborative programme, called the
International Nutrients Scale System (INSS), with the
aim of establishing global comparability and traceability
of nutrient data. The agreements at this workshop in
Tsukuba 2007 marked a turning point in the history of
nutrient comparability.
In February 2009, the INSS group held a workshop at
UNESCO in Paris to advance international collaboration
in establishing global comparability of nutrient data in
the world ocean and to discuss future tasks (2009
International Nutrients Scale System international
workshop, Paris, 10–12 February 2009). An
“International Nutrients Scale System (INSS)” in
seawater was agreed as the appropriate way to achieve
this goal.
2.
A JOINT ICES-IOC STUDY GROUP ON
NUTRIENTS STANDARDS
A joint ICES-IOC study group was proposed at IOCUNESCO 25th assembly to develop international
standards for nutrients to establish comparability of
nutrient data in the world oceans (IOC/INF-1260[16]).
The IOC-ICES joint Study Group on Nutrient
Standards, SGONS, is established in 2009. The
principal objective of SGONS is to establish global
comparability and traceability of seawater nutrient data
from the world’s oceans through the development of
appropriate certified reference materials (CRMs).
Specific Terms of Reference of SGONS are as follows.
(v) Complete a revised nutrients analysis manual.
(vi) Distribute 10,000 bottles of reference material for
nutrients to laboratories measuring nutrients as
part of the CLIVAR Repeat Hydrography
Programme to construct a global nutrient dataset
referenced to the new RMNS.
(vii) Promote the use of RMNS to aim for global
acceptance in order to enable reliable
comparability between global nutrient data sets,
and to investigate the feasibility of expanding
RMNS to include ammonium and dissolved
organic matter.
(viii) Collaborate with the ocean science community that
uses chemical reference materials, including
carbonate system reference material for dissolved
inorganic carbon, total alkalinity and pH, and
dissolved oxygen in seawater.
3.
In the marine chemistry community, there is expertise
that if applied by all labortaories can improve
reproducibility. In addition, now, we can use RMNS,
which has a large batch size and a long-term stability
(>3 years) to check on inter and intra laboratory
preformance. These things make it possible to improve
to comparability of measurements to level that has not
been achieved previously. For example, comparability
of nitrate concentration and nitrate/phosphate ratio at
the crossover point of P3 and P14 lines obtained by four
cruises in 1985, 1993, 2005 and 2007 had been
considerably improved by using RMNS as shown in
Fig. 1.
P3_P14_crossing stations in 1985,1993,
2005 and 2007 (24N, 180E , r=250km)
1000
2000
Develop and establish reference materials for
nutrients in seawater (RMNS) collaborating with
producers of currently available RMNS. Primary
determinands are nitrate, nitrite, phosphate and
silicate.
(ii) Collaborate with and encourage the National
Metrology Institute of Japan to complete
certification of RMNS for nitrate, nitrite,
phosphate and silicate.
(iii) Develop new sampling and measurement protocols
using the RMNS.
(iv) Carry out an international collaboration exercise to
verify the stability of the reference materials and
test the proficiency of the new protocols.
Depth / dbar
Specific Terms of Reference
(i)
PRESENT STATUS OF NUTRIENTS
COMPARABILITY
1985 without RMNS
1993 without RMNS
2005 with RMNS
2007 with RMNS
3000
4000
5000
6000
32
34
36
38
40
42
-1
Nitrate / micro mol kg
Fig. 1. Comparison of nitrate measurements between
with and without RMNS.
That is, measurements in 1985 and 1993, when RMNS
was not available, show substantial differences between
the two years larger than would be expected in deep
waters. By contrast, in 2005 and 2007, when RMNS
was available, the measurements in 2007 are consistent
with those in 2005 within the precision of the
measuremnts.
4.
INTERNATIONAL NUTRIENTS SCALE
SYSTEM
67.5
157
67.0
156
155
66.5
154
66.0
153
65.5
152
2 SI
65.0
151
5 SI
3 SI
64.5
150
64.0
149
0
5
10
15
20
25
30
Sample ordered by reported value
CONCLUSION
By the end of the next decade the aspiration of the IOCICES Study Group on Nutrients Standards is that the
quality
and
inter-comparability
of
nutrient
measurements will have been improved considerably
form the present position. This will be achieved by the
wide spread use of RMNS materials. This requires that
RMNS can be reliably produced in sufficient quantities
and that the global community develops trust in their
use along with the continued development of best
practices.
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