An input to the evaluation of NERI’s
research on marine eutrophication
Nitrat + nitrit [mikrogram N/l]
nitrat [mikrogram N/l]
Anholt øst vinterkoncentrationer i overfladevand (DMU)
(kilde: Danmarks Statistik)
lineær 1975-1984 (GÆ: 1975-1984)
lineær 1976-1978 (GÆ: 1976-1981)
01-1992 01-1993 01-1994 01-1995 01-1996 01-1997 01-1998
1970 1975 1980 1985 1990 1995 2000
NERI et al 1996:
NERI et al 1996:
“It has been shown under the
on the transport
of the Kattegat
from the German Bay.”
NERI to the Parliament 1999:
NERI to the Parliament 1999:
Normally, it is assumed that only a small
of the contribution
it is assumed
is due to
due to the
water of the
subsequent can lead to oxygen depletion.”
Great Belt January-March
Country of Fuenen data
Lineær (NERI data)
Lineær (Country of Fuenen data)
y = 0,1661x + 4,6789
y = 0,181x + 3,3146
Little Belt North 1999
0 5 10 15 20 25 30 35 40
Press release from Statistics Denmark 1999:
Press release from Statistics Denmark 1999:
The Nitrogen concentration in the Baltic Sea is in
in the Danish
than in the
Belt Sea. This
of the Baltic
Sea, but rather from
local sources to the Danish straits.”
Hereby I take the freedom to bring some aspects into consideration concerning the evaluation of the research
of NERI on marine eutrophication and its role in the recommendations for political decisions on issues on
My background for writing this document is not as scientist in marine biology, physical oceanography or
other relevant issues.
First time I was wondering over the information from NERI on the marine eutrophication issue was as newly
elected politician as county counsellor in Vestsjællands County. Using my scientific methodology I found
some statements from NERI questionable, and since then I have been studying the topic in my free time.
In September 1997 I was in a direct debate with on scientist from NERI on TV. In a situation, where the
Mariager Fiord had experienced a strong oxygen depletion with fish mortalities after two years with very
little water discharge from land, I tried to tell two messages: There have been even stronger oxygen
depletion 900 years ago, and that the continental rivers discharging to the southern North Sea is influencing
the Danish marine environment.
The day after the TV-station brought a statement from NERI and other scientific organisations, that my
point of view was incorrect. Local discharges were responsible for the eutrophication in the Danish marine
This document is based upon some central material from NERI and other sources. It is not meant as a
complete coverage of the subject. It is including some new treatments of available data from NERI and some
of the counties, which I have found on public data bases or have got from a county. It could be argued that
these analyses should have been published, but as this is not my profession, I have not been able to find the
time to do so.
From 1981 to 1987, the period of the change of paradigm. .................................................................5
The old paradigm: ............................................................................................................................5
The new paradigm presented in 1984...............................................................................................6
The German report on the Oxygen depletion and fish mortalities in 1981. .....................................7
The origin of the new paradigm. ......................................................................................................7
October 1986. .....................................................................................................................................10
The well-known media events:.......................................................................................................10
Less known information:................................................................................................................10
Conclusion on the period 1981-1987: ............................................................................................12
The programme for monitoring the marine environment...................................................................14
NERI and The Jutland Coastal Current (JCC) ...............................................................................15
Two different opinions on the origin of the inorganic Nitrogen in the Danish straits. ......................20
The graph with Swedish data but without including the Swedish arguments................................20
The misleading second graph. ........................................................................................................23
The first attempt to proof that JCC has little influence on the Danish straits by NERI and coworkers.
The conclusions drawn by NERI on basis of the report : ..........................................................28
The difference between the South North Sea water and the water from the German Bight (JCCdefinition).
The Nitrogen over-concentration theory (NERI 1997). .....................................................................36
List of references ................................................................................................................................43
In this document the change of paradigm in the Danish marine research community around 1984, dominated
by scientists’ today employed at NERI, and the importance of this change is described.
This so called new paradigm is discussed and the conclusion of this document is that the new paradigm was
not at the time of its formulation documented; neither has it later been supported by good research results.
The media events in 1986 leading to the most important political decisions related to the marine
environment in Denmark until now is shortly described, showing that the central scientist behind the new
paradigm here committed himself strongly in public to this paradigm.
Further this document discuss the monitoring program following the political decisions in 1986-1987,
pointing on the fact that the monitoring program has been insufficient to support those conclusions drawn by
NERI on the origin of inorganic Nitrogen in the Danish straits.
Two different attempts from NERI and co-workers on issues relevant for estimating the influence from
water from the southern North Sea and though from the continental rivers discharging to this ocean on the
environment of the Danish straits are discussed.
The first attempt was the so called gelbstoff theory, where central NERI scientists and co-workers based on
in reality one single cruise in the turbulent northern Kattegat and southern Skagerrak claimed to be able to
assume that the contribution to the Danish straits from the Jutland Coastal Current (JCC) should be 10-20 %
and not the 50-67 % of the water entering the Kattegat from north which was the conclusion on earlier work
from other scientists. The amount of data, the time of monitoring the data and the simple model with its
simplificated boundary conditions is discussed. It is concluded that this model is neither based upon enough
and suitable data, nor is it based upon an adequately refined model and appropriate boundary conditions to
be able to support any new conclusion on the amount of water reaching the Kattegat from the JCC.
The second attempt was the so-called over-concentration theory, where it was postulated on a simple data
analysis that there in most years are for example inorganic Nitrogen concentrations in the Danish straits
which are showing a clear influence from local sources. This theory is discussed, by applying data from the
NERI-cruises and the cruises from the Danish counties in the Danish straits. Based upon mainly public
available data it can be shown that several sources of error can explain the higher nutrient concentrations in
water with salinity in the range of 15-25 psu. Again the conclusion is that this work cannot support the socalled
Further this document reveals a few of the cases, where NERI is bringing the new paradigm into the public
discussion. One is the case, where Statistics Denmark on basis of data points from NERI concludes in
contrast to the Swedish institute SMHI that the reason to an increase in inorganic Nitrogen in the Danish
straits is the local nutrient loads, while SMHI claims it is due to water from the continental rivers
discharging to the southern North Sea. Another example is an answer, the former minister of Environment
and Energy gave in the Parliament in 1999.
The work from the NERI has played a very important role in the political decisions and on the forming of
the public opinion in Denmark on this issue. It is therefore necessary not only to evaluate, what NERI has
published internationally in the scientific community, but also it’s more popular publications in Danish with
the Danish public audience in mind as well as its role in the communication with the politicians at all
NERI was founded around 1990, DIWHU probalby the most important national political decisions on marine
environment protection had been taken (Vandmiljøplan 1 from 1987). However, major scientists within the
eutrophication field, employed at NERI since its establishment, were formerly employed at Marine Pollution
Laboratory, National Agency of Environmental Protection. Some of these scientists were in fact through the
1980’es having a very dominating role in both the forming of the theories on the cause of oxygen depletion
in the Danish marine environment and in the forming of the public opinion.
It is clear that when a group of scientists are so deeply and directly involved in a public discussion and in the
forming of a political decision, as in this case, bringing a controversial hypothesis out in the public, then
they will have difficulties in having a balanced view on the field thereafter.
Therefore an evaluation of NERI in this case must take into consideration what happened in the 1980’ies
even though it was before NERI was established.
In this case there was a clear line from 1981 till the decisions taken by the Danish Parliament under severe
media pressure in 1986-1987. Vandmiljøplanen (the Plan for the Aquatic Environment) was decided after a
period with strong media focus especially on the marine environment. The overall goal was defined to be a
reduction in nutrient loads of 80 % for Phosphorous and 50 % for Nitrogen.
It can be argued that things happening before the establishing of NERI is not relevant for the actual
evaluation. It is however in my opinion relevant due to two reasons:
• As mentioned above some of the central employees at NERI since its establishing were active in this
period, bringing themselves into a position, where the had a strong personal commitment to the new
paradigm, which was established in 1984
• As a second consequence of this fact, none of these scientist can argue, that they were not aware of
the knowledge before the new paradigm.
From 1981 to 1987, the period of the change of paradigm.
In 1981, the National Agency of Environmental Protection published a summary report on the research
performed in the preceding research: “The Belt Project, Evaluation of the Physical and Biological
Measurements" . This report described, what can be called “the old paradigm”. With a solid list of
references, this report described the research over a century.
Here I will draw your attention to some of the central statements concerning the type of waters, as well as
the results and conclusions.
In this report on page 1 under “Background” is summarized that ³WKH'DQLVKVWUDLWVLHWKH6RXQGWKHEHOW
Further on page 3 the influence of nutrient from the North Sea is summarized: ³*HQHUDOO\WKHVDOLQH
Further on page 3 are summarized the development in oxygen concentration: ³'HWHUPLQDWLRQVRIWKHR[\JHQ
And further on the phosphate content: ³7KH3KRVSKDWHFRQWHQWKDVEHHQUHFRUGHGVLQFHEXW
And on Nitrogen content: “$QDO\VHVRIWKHZDWHUVFRQWHQWRI1LWURJHQKDYHRQO\EHHQVWDUWHGLQUHFHQW
The latter statement is discussed more in details, talking about large variations from year to year.
Finally I will draw your attention to the last sentence of the report in the conclusion on page 118:
Concerning the authors, I will draw your attention the first author: Gunni Ærtebjerg Nielsen. This author is
playing perhaps the most central role in the debatable change of paradigm following shortly after the
publication of this report, as well as in the communication to the public over a long period. And he has been
a central scientist at NERI through all the years since then 1 .
1 An evidence of his central position could be seen in DMU Nyt nr. 1/98, (NERI news no. 1/98)  where it is
announced that Gunni Ærtebjerg had been nominated to a prize from the Baltic Sea Foundation:
Short before the report  was published in November 1981, oxygen depletion was observed in the Danish
straits, as well as in the south-eastern North Sea and in Kiel Bay. This event became a point of discussion in
Denmark, and a new report was written (in Danish): "Iltsvind og Fiskedød 1981, Omfang og årsager"
(Oxygen depletion and fish mortalities 1981, Extend and reasons), . This report was also published by the
National Agency of Environmental Protection, but had no formal authors. Gunni Ærtebjerg was, however
amongst the people involved in the formulation of the report.
The time between the publication of the two reports  and  is maximum 3 years. Only very few new
data on Nitrogen and oxygen were collected in this short time span, and consequently there were still not
enough data to draw solid conclusions on any development in these consentrations over time. Actually the
most important new information compared to  seems to be an undocumented statement about an interview
of 9 old fishermen from Fyn (Funen) ( page 10).
Nevertheless, this report suddenly led to the opposite conclusion of . This conclusion was mainly based
upon the following elements of the new paradigm:
• Although it was clearly stated in , that: ³$QDO\VHVRIWKHZDWHUVFRQWHQWRI1LWURJHQKDYHRQO\
YDULDEOHRQWKHEDVLVRIWKHPDWHULDOFROOHFWHGVRIDU´ and although it was stated in  that there
are large variations from year to year,  is concluding on a few more years of data sampling, that
there was a clear trend towards an increasing concentration of Nitrogen in the Danish straits, 
• Although it was clearly stated in , that ³WKH'DQLVKVWUDLWVLHWKH6RXQGWKH%HOW6HDDQGWKH
strong influence from the North Sea on the Danish straits was practically totally neglected.
The scientific background for this fundamental change in paradigm seems very questionable. The short
period (9 years) of data sampling, combined with the fact that for most of the years only 1 or 2 monitoring
cruises were performed in these transient waters per year in the period of the year, where the origin of the
WLOGHOHSULVHQWLO*XQQL UWHEMHUJIUHPK YHU‘VWHUV¡IRQGHQRJVnDWGHWYDU*XQQL UWHEMHUJRJKDQV
inorganic nutrient can be estimated, makes it impossible to support the statement of the increased Nitrogen
The oxygen depletion and fish mortalities in 1981 were not only observed in Danish waters, but also in the
adjacent German waters. And therefore a report was also drawn up in Germany .
This report was published in 1990 based upon 21 reports from a special 4.5 years research programme on
“Eutrophication of the North Sea and the Baltic”, initiated in 1983.
The abstract of this report, written on the report cover sheet, is:
It can be concluded, that the oxygen depletion and fish mortalities was not an isolated local problem in the
Danish straits, but a common problem for the region.
And it can be concluded that there is a good correlation between the evaluation of the situation in the Danish
straits in  and in Kiel Bay , while the conclusions in  are fundamental different.
Further, in , the newest results from Danish research were cited several times. A difference in the Danish
and the German observations of inorganic Nitrogen in the Kiel Bay waters were discussed.  states (page
211-212) that while the German scientists in the period 1964-1984 has observed little variation in surface
inorganic Nitrogen between the years, Gunni Ærtebjerg et. al. had published an increase in the period 1975-
Thus it is clear that despite the Danish research is building upon the new paradigm, this is not accepted by
As stated above, there were no official authors of . However, as mentioned above  is pointing at Gunni
Ærtebjerg as the “father” of this new paradigm. This is further supported by  cited above and looking into
Danish technical technical magazines, one of the key papers seems to be .
In  (and in  page 158-162) some graphs were shown to support the hypothesis of an increasing
Nitrogen concentration in different positions in the Danish straits.
As an example, I have taken one graph. This was winter concentrations of nitrate in surface water from the
position Anholt East. Through ”Statistics Denmark” I got assess to the data from some of the major
measuring positions where first the Marine Pollution Laboratory and later NERI through the years has
collected data on the water. From these data, I could reconstruct the graph from , but furthermore, I was
able to include newer data expanding the sampling period to the whole period 1975-1997.
In Figure 1 is shown these data. Still it should be remembered, that this is normally only based upon 1-2
measurement per winter in one position in waters, where salinity and concentrations of nutrients can vary
lineær 1975-1984 (GÆ: 1975-1984)
lineær 1976-1978 (GÆ: 1976-1981)
1970 1975 1980 1985 1990 1995 2000
In Figure 1 is shown 3 trend lines: 2 from , covering data from 7 and 3 years respectively plus one
covering data from 20 years. It is unclear, why the trend line named 1976-1981, and which were only
including data from the 3 years 1976-1978 was shown in the figure in .
This shows clearly that it was correct, when it was stated in , that the concentration of nutrients were
varying from year to year and that data from 3-4 years were insufficient ³«WRHVWDEOLVKWUHQGVLQWKH
From figure 1 it can further be concluded that even data from 7 years were insufficient.
Even at the time of publishing  it was clear that the climate had changed from the 1970’ies to the
1980’ies. Even now – after 20 years of data collection, no clear conclusions on a trend in the Nitrogen
concentration can be drawn.
The story about October 1986 is of course very important to understand, what has happened with the
 is describing the central week (page 31-35). However  is missing some central information, which I
have found through personal research, and which recently has been verified by Gunni Ærtebjerg :
In 1986, Denmark had only one TV-channel, which had an enormous impact on the public opinion. This
TV-channel took by some reasons in October 1986 the lead in forming the public opinion. The event, which
was the starting signal for an intense media campaign, followed up by a political process, was a well
remembered TV-spot in the evening news, where a fisherman were landing some dead lobsters in Gilleleje
Harbour. This happened shortly before the annual assembly of the Danish Society for the Conservation of
Nature, which was a very aggressive organisation at that time. In the campaign the message brought on the
TV was supported by the expert from the Marine Pollution Laboratory, Gunni Ærtebjerg.
The major TV-events were:
• Tuesday, October 7: the famous TV-spot, where a fisherman presented his catching of dead lobsters.
• Thursday October, 9. TV-news had a spot with Gunni Ærtebjerg on the deck of the vessel from the
Marine Pollution Laboratory. He confirmed that there was oxygen depletion in the southern Kattegat, and
that this was due to run off of Nitrogen from the Danish agriculture.
• Sunday October, 12., The Danish Society for the Conservation of Nature adopted a resolution at its
annual assembly referring to the media-events, requiring the government to take immediate actions to
protect the water environment.
• Sunday October, 19. Her there was a long directly transmitted debate in Sunday TV-news with the
president of The Danish Society for the Conservation of Nature, David Rehling, and the minister for
fishery, Lars P. Gammelgaard. Here the minister was brought into great troubles by a very well prepared
president for the Danish Society for the Conservation of Nature and an aggressive journalist .
From this point the government (a minority government) was under extreme political pressure.
• The fisherman and Gunni Ærtebjerg are brothers.
• Monday October, 6, the day before the first TV-event, Gunni Ærtebjerg made an internal report to the
National Agency of Environmental Protection on observation of dead lobsters, based upon a telephone
conversation with “a fisherman”, his brother.
• According to Gunni Ærtebjerg, then the National Agency of Environmental Protection made a press
release based upon this report on Wednesday October, 8. According to Gunni Ærtebjerg, this press
release was initiating the media events. However, the media events started the day before. A request to
the National Agency of Environmental Protection according to Danish law of puclic insight in
administration on both the report from Gunni Ærtebjerg of October 6, and the press release from the
agency of October 8, resulted in that I got the first document. The press release was, according to the
answer from the agency, disappeared.
Almost immediately after Monday October 6, the Marine Pollution Laboratory did send its vessel out in
southern Kattegat under the scientific management of Gunni Ærtebjerg. The ship turned back into a harbour
picking up the TV-team, which made the TV-spot from Thursday October, 9. After the cruise, a report was
The conclusion of this report is:
(QVWLJHQGHEHODVWQLQJDI.DWWHJDWRJ% OWKDYHWPHGLV UNY OVWRIQ ULQJVVDOWHKDU
It should be emphasized that the oxygen depletion was occurring in the open waters of the southern
Kattegat. The conclusion here is in my mind very doubtful, as the water exchange is very strong in this
strait, and the nutrient inflow from the adjacent seas is dominating the nutrient and oxygen concentration.
Furthermore, at stated above, there were in fact no clear background to conclude that the increasing load of
Kattegat and the Belt Sea with mainly Nitrogen had resulted in any significant increase in Nitrogen
concentrations in these open waters.
The conclusion of this report became, however, the “only truth” in Danish public opinion, in Danish politics
and in Danish marine science since then.
The Parliament adopted on its meeting on November 18, 1986 an agenda requesting the government to work
out a plan aiming towards reducing the outputs of Nitrogen with 50% and with Phosphorous with 80%
within 3 years.
These goals for reduction of nutrient output have been the turning point in the Danish plans for water
environment since then. And there is no doubt that the paradigm shift by the marine scientists from the
Marine Pollution Laboratory, described above and its presentation for the public in October 1986 played a
very important role in this decision.
Emphasize in the evaluation of the research within this field by NERI should be put on the fact, that the
have been repeated in NERI communications since then.
In the general terms of definition in the Danish scientific and public communication the above loads means
loads from local sources. This should be compared with the statement from :
Here is said: There is a well documented increase in river runoff from the Rhine, the Elbe and the other
rivers discharging to the southern North Sea. This combined with the other part of the statement saying that
in Kiel Bay hydrographical and geochemical processes predominantly control nutrient concentrations in
winter water, says that local discharge from the catchments area to the Danish waters cannot to any great
extend affect the winter nutrient concentration in the Danish straits.
As described above then there was made a dramatically change in paradigm on the theory on eutrophication
in the Danish straits around 1984. This change led to a number of political discussions in Denmark,
culminating in October-November 1986.
The Marine Pollution Laboratory, and especially its probably most recognized marine scientist, Gunni
Ærtebjerg, were deeply involved, not only on the scientific scene, but also on the public scene.
By making such statements in those situations on the only TV-channel, these statements had an important
impact on some much questioned political decisions. The paradigm, established by this group of scientists,
became thereafter by the Parliament regarded as the truth.
It could be argued that these events were before the forming of NERI, and though not a subject for
consideration in the context of the actual evaluation. It is, however, to great extend the same scientists, who
have been dominating the work from NERI since its establishing, and NERI has never revised the paradigm
defined in 1984.
It could further be stated that  became public after the above described events. But first, most of the
material behind  is old material, and secondly it must be concluded that  has now be public known
form many years also for NERI.
The programme for monitoring the marine environment.
Shortly after the Parliament had adopted the Vandmiljøplan, NERI was established and the Parliament
passed a large funding for research and environmental supervision, where NERI had a central role.
Furthermore the Danish counties were involved by having responsibility for some local monitoring and
reporting. A fragmented monitoring structure was the result with unclear competences at the different
political and administrative levels. Even though a county in principle were making its own political
decisions on for example goals for water quality in their part of the marine environment, their independent
right to make such decisions was very limited and to a great content controlled by the National Agency of
Environmental Protection and NERI.
Furthermore the fragmented monitoring programme resulted in many small technical and scientific weak
groups in the counties. The strongest group in this organisation was NERI (64 employees actually in the
NERI Department of Marine Ecology according to the list of staff on the internet compared to around 5-10
employees involved in marine ecology at a typical county administration. Furthermore NERI was also the
organisation having the coordination role in the program.
The reporting from NERI included a large number of reports. In the following only some central parts of the
reporting on the marine environment will be discussed.
As part of the national monitoring program, NERI conducted and conducts approximately 5 monitoring
cruises to the Kattegat, The Belt Sea and the Western Baltic every year. Normally one of the winter cruises
was enlarged including the Skagerrak and the North Sea.
In figure 2 is shown a map with the positions for data sampling for such a large winter cruise. Taking into
account the strong water exchange through the Danish straits the number of stations and the number of
cruises per year must be regarded very limited, and though conclusions based on these cruises concerning
the nutrient transportation in wintertime can be difficult.
Furthermore, the Danish counties were monitoring the nutrient concentrations at several positions close to
the coast with significantly higher sampling frequencies.
NERI had the overall responsibility for data collection ad reporting, based upon all these data. In principle
these data were available for the public, but in practice assess to these data was very limited.
After several attempts, I have got some of these data, and the following discussion is based upon:
• NERI- cruise reports from the national monitoring program from 1991
• Parts of data for the North Sea, monitored by the county of Nordjylland
• NERI-data and some county data made public via the national database for marine data (MADS)
• Some NERI-data made public via Statistics Denmark
• Data from the Swedish institute SMHI.
It could be argued from NERI that the data applied are not the total amount of data available. However, I
must assume that NERI has selected the most important data to be mad public via its homepage for MADS.
NERI has in a number of publications as well as in contributions to debate stated that the influence from the
Jutland Coastal Current (JCC) on the nutrients and on the oxygen concentration in the Danish straits was
NERI has mainly based its argumentation on their own data, more or less neglecting the data from the
counties. In figure 3 is shown the data of inorganic Nitrogen at one position at Hirtshals, i.e. at the northern
westcoast of jutland, shortly before the JCC passes Skagen.
At Hirtshals NERI has reported 5 measurements over a 6 years period (the blue squared dots). The County
of Nordjylland has been collecting data at the same position nearly every 14 days (the yellow triangles).
Assuming the concentration of the Nitrogen should be above 140 microgram per litre to identify the
influence from the German Bight, NERI has only recorded this once over a 6 years period. Nordjyllands
County on the other hand has recognized the influence from the German Bight every year.
01-1992 01-1993 01-1994 01-1995 01-1996 01-1997 01-1998
The blue dots on figure 3 are showing, when NERI performed its annual winter cruise in the North Sea and
In figure 2 is shown a map showing such cruise. This is the cruise 115 performed in the days February 10-
20, 1992. The winter cruises started in the northern and eastern Kattegat, continuing around Skagen, south
along the west coast of Jutland, passing through the Kieler channel, ending in the southern Danish straits.
The position “Hirtshals” in figure 3 and 4 is marked with a red ring. Looking on Figure 3 it can be seen, that
several of The NERI winter cruises were performed so that the major inorganic Nitrogen input from the
Jutland Costal Current into the northern Kattegat occurred DIWHU the winter cruises.
Looking on these data it is clear that by using only the NERI data, leads to an underestimate of the inflow of
inorganic Nitrogen from the North Sea to the Kattegat.
In the table below, the NERI winter-cruises in the period 1991-1997 are listed (I have only included the
period 1991-1997, as I only have data from the county of Nordjylland from this period and as the amount of
data in the NERI cruise reports after that time was reduced.)
For each cruise is summarized, whether it included Skagerrak and North Sea or not, and whether the author
(Gunni Ærtebjerg) had reported observations of Nitrogen rich water from the JCC either at Hirtshals or in
Kattegat. Comparing this table to the data from the county of Nordjylland in Figure 3, it looks logical, taking
into account the time of the occurrence of the high the inorganic Nitrogen content at Hirtshals, detected by
the county of Nordjylland.
31-12 01-03 01-05 01-07 31-08 31-10
In the table above the conclusions in the NERI cruise reports are listed. For Hirtshals, NERI in most years
concluded that the JCC was interrupted south-western for this position. I have no information indicating that
the data from NERI from Hirtshals are not correct. Therefore it cannot be denied that the JCC was
disconnected on that very day of the year, NERI was at this position, but to conclude on the background of
these few cruise reports that the JCC only exceptionally was reaching the border between Skagerrak and
Kattegat those years, is simply not a reliable scientific judgement, looking on the data from the county of
It must be concluded that the number of cruises performed in the open Danish straits performed by NERI
have been too few and placed at a time of the year, which was not optimal for detecting the JCC in northern
The paradigm, defined in 1984, was, as described above, based on the hypothesis, that there had been an
increase in Nitrogen concentrations in the Danish straits since 1950’ies, caused by local loads of nutrients.
In other words then the influence of anthropogenic Nitrogen from the North Sea was assumed negligible.
The conclusions of the analysis of the data, in the cruise reports mentioned above, seemed biased towards a
support of this hypothesis.
Further to illustrate the strong water mass and nutrient concentration fluctuations in the Danish straits, data
from the winter 1995 from two positions in the Kattegat, Fladen and Læsø Rende are shown in figure 5.
Here data from both NERI (DMU) and their Swedish colleagues, SMHI, are shown. The plots data from all
depths from each monitoring cruise, plotted as salinity/Nitrate-plots. In general SMHI is performing more
cruises than NERI. The analysis shown in this figure is not performed systematic on all dataset from the two
institutions, it is however my impression that the large fluctuations are often seen in the datasets. This
underlines the argument that the frequency of the data sampling from NERI is too small to support
conclusions on the inflow from the JCC.
Two different opinions on the origin of the inorganic Nitrogen in the Danish straits.
In some situations the interpretation of the data by institutions in Denmark and Sweden differs. One example
is from 1999. Here Statistics Denmark (Danmarks Statistik) made a press release on August 1999 [DS]:
Citation in Danish:
0 meter 12 mdr. gennemsnit 1983-1987
jan-94 jul-94 jan-95 jul-95 jan-96 jul-96 jan-97 jul-97 jan-98 jul-98 jan-99
2SO¡VWXRUJDQLVNNY OVWRIGYVVXPPHQDINY OVWRILQLWUDWQLWULWRJDPPRQLXPVW\UHU
NY OVWRIDIJ¡UHQGHIRULOWVYLQGHWLGHLQGUHGDQVNHIDUYDQGH-RPLQGUHNY OVWRILVHQYLQWHUHQ
% OWKDY'HWWHW\GHUSnDWIRUXUHQLQJHQPHGRSO¡VWXRUJDQLVNNY OVWRILGHLQGUHGDQVNH
This press release support the paradigm, established in 1984. Please note, that nothing is mentioned about
inflow to the Kattegat from north.
Interesting is it to look on the graph and look on where and when the data was collected. The data are from
the Sound, more precisely near the Swedish island Ven. The last datapoint is from February 1999.
According to my analysis, there were performed no Danish monitoring there at that time. SMHI, however
reported data from that position and that time period [smhi]. And while Statistics Denmark concluded that
the increased Nitrogen in the Danish straits were due to runoff from Denmark, The cruise report from SMHI
had another opinion, which can be seen on its front page:
Looking on the graphs in Figure 7, which are the data from this SMHI-cruise, the normal situation, where
the Nitrogen concentration in the water is decreasing in the whole water column from north to south is seen.
And also as normal the Nitrogen concentration as well as the salinity is largest in the bottom water. In this
graph the JCC water is clearly identified at 15-40 meters at Fladen, and there even might be an influence at
Anholt. It also shows a strong stratification in the Sound.
On this background I recommend the evaluation committee to read and compare the cruise reports from
NERI and SMHI.
Looking further carefully on the press release from Statistics Denmark, cited above, it is furthermore
including one more graph.
mg O 2
1975 77 79 81 83 85 87 89 91 93 95 97
The title is: “Minimum oxygen concentration close to the bottom in Kattegat at Anholt Rev 1975-
There is no text in the press release directly refering to this graph.
Even though no linear trend curve is included, it looks as the oxygen concentration is decreasing through the
period covered by the graph. (See the same curve with trend curve in figure 9).
The data from this monitoring station, received from Statistics Denmark, is resulting in the following table
on minimum oxygen concentration measurements near the bottom:
In the table is shown the oxygen concentration near bottom ordered in month and year. In the column at
right is the numbers, used by Statistics Denmark in Figure 7. Please note that for 1978, the data point used
by Statistics Denmark is from January! For 1981 the value, Statistics Denmark applied was from October
but from the depth 20 m. while all data in my table is from near the bottom (55 m).
0 2 4 6 8 10 12
As seen from this table, then there hasn’t been performed so systematic monitoring in the first years. It
should be noticed that, as described before, then there is only one measurement behind each number.
In figure 8 is shown these data plotted in the annual cycle, where the well now yearly variation is shown.
In figure 9 is shown again the graph published by Statistics Denmark. And in Figure 10 is shown the data
from August, September and October month in the period. Furthermore the trends in each month are shown.
Taking the uncertainty due to the fact that only one cruise were performed per year in each month, it is not
possible to draw the conclusion from the data, that there is a trend towards a lower oxygen concentration,
which is clearly shown in figure 9 (the graph published by StatisticsDenmark).
1974 1979 1984 1989 1994 1999
It should be noted that under the graphs in the press release is written: ³.LOGH%HUHJQLQJHUXGI¡UWDI
'DQPDUNV6WDWLVWLNPnOHSXQNWHUIUD'08´, translation: ³6RXUFH &DOFXODWLRQVSHUIRUPHGE\6WDWLVWLFV
It can be argued, that this is a little error. Unfortunately such errors supported the paradigm from 1984. And
the public believed of course in this information, where two national public authorities are behind.
The first attempt to proof that JCC has little influence on the Danish straits by NERI
As mentioned before, the paradigm from 1984 and the Vandmiljøplan from 1987 was based upon the
hypothesis, that the water from the North Sea in general and the JCC in particular play no role in the Danish
straits. For people believing in this hypothesis or building their career on it, it would be convenient with
some sort of scientific proof. In the beginning of the 1990’ies a scientific analysis of the contribution from
the JCC into the Danish straits was performed and published in a Danish report . It came to a new
conclusion on the relative size of the amount of water flowing into the Kattegat, which were originating
from the German Bight. This new estimate was as low as 10 % compared to, what the authors of the report
cited of old estimates, which were 50-67 %. Since then this new low estimate was used in public
information from the NERI.
It is my clear understanding, that this report became very important in the defence of the paradigm from
1984. Therefore it is important to look carefully on this report.
The work was performed in a joint research project between NERI, The Niels Bohr Institute (KU) and the
Danish Institute for Fishery Research: “Hydrografisk og biologisk beskrivelse af Skagerrak-fronten” 
(Hydrographical and biological description of the Skagerrak front”).
This report concludes then following about the influence of the JCC:
As cited above under ”Water mass classification”, this report estimated the contribution of water from the
German Bay to the Kattegat bottom water very much lower (10%) than earlier estimates (50-67%). And
furthermore it concluded that the nutrient concentration in the JCC in Skagerrak often wasn’t higher than the
background concentration of Skagerrak, and the combination of these two assumptions leads to the
conclusion: “7KH-XWODQG&RDVWDO &XUUHQWGRHVQRWVHHPWREHRIVLJQLILFDQWLPSRUWDQFHWRWKH
This conclusion supports very nicely the paradigm from 1984. But is it likely to be correct?
The water mass classification work is based upon a number of cruises. Below is listed the areas, the time
and the number of water samples taken at each cruise
Area Time Number of samples
The Sound/Kattegat May 1975 261
The Sound/Kattegat July 1975 152
Skagerrak/Kattegat May/June 1976 87
Skagerrak March/April 1979 213
Kattegat May 1979 133
Kattegat/Skagerrak March 1992 565
Kattegat/Skagerrak September 1992 694
To support the statements concerning the negligible contribution of nutrients from the JCC, only the 565
samples from the cruise in March 1992 can be used.
Below in figure 11 are shown in more details the measurements of nutrients by the County of Jutland in the
winter 1992 at 3 positions in a short transect outside Hirtshals. (Detailed data compared to Figure 3). This
position is approximately 50 km south west of Skagen. According to the report  page 15-16, the time for a
water mass to flow from this position until it reaches the area, where the data sampling were performed is
around 10 days. The cruise was performed in the days 2-12 of March 1992, and consequently This cruise
was performed before the strong contribution of Nitrogen rich water from the German Bay, detected at
Hirtshals on February 27, March 2, and March 9, could reach the Kattegat before the monitoring cruise. In
 page 58-59 is also explained that only a small amount of JCC water seemed to be detected on the last
days of the cruise.
07-01 17-01 27-01 06-02 16-02 26-02 07-03 17-03 27-03 06-04
As described in  (and other literature) and as seen from figure 3, the JCC might not be permanent present
at the northern coast of Jutland.
Therefore it must be concluded, that the data applied in  are not sampled in a sufficient number at suitable
time and positions to support the very general conclusion from the report. Only data from one cruise
performed in one year in turbulent water was applied.
Looking more in details on the box model applied in conjunction to the Gelbstoff-theory, it must be
concluded that the model work is associated with very many uncertainties.
• The model is first of all applied on very few data.
• Secondly it is based upon the assumption that the water can be classified as originating from 3 types
of water with constant salinity and concentration of Gelbstoff, as shown in the table below.
Water origin Gelbstoff [absorption per meter] Salinity [psu]
Baltic surface water 0.96 8
North Sea /Atlantic Sea 0.07 35
German Bay 1.50 31
However, this statement was without documentation or references in the report. And it is very
unlikely that water from the southern part of the North Sea could be characterized as homogeneous
over time and in space. The whole Helgoland- series of data and  as well as  is saying
As an example is shown in Figure 12 an example from a recent publication, found on the internet
[xx]. The figure shows the distribution of salinity and gelbstoff in the German Bight in the end of
August 2002. The report has a number of illustrations showing the very fast variation in both
salinity and gelbstoff occurring under the high water of the Elb in summer 2002.
• Further the box model for Kattegat is very simplified, based upon rough estimates on water flow
using estimated averaged numbers, not taking annual variations in gelbstoff concentration and of
water transports in and out of Kattegat and between upper and lower layers of the water into
Taking these uncertainties into consideration, it must be concluded, that there is no clear evidence that this
scientific work with any significant strength can support any general conclusion about the little inflow of
water from the JCC and that the JCC does not seem to be of significant importance to the eutrophication
development in the Kattegat presented in the report.
In the following I will try to line up the central position this report has had in the time after.
 was one of a large number of research projects, supported under the Marine Research Program, “Hav
’90”, sponsored by the Danish Ministry of Environment and Energy during the period 1988-1994.
After this program has ended, two publications presented the major results of the program:  and .
Both  and  is referring to .
In  page 243-267, Katherine Richardsson, one of the editors of  and one of the authors of  is
discussing the influence of the JCC on the Danish straits. On page 254,  is mentioned as follows:
In , which is a popular book on Marine environment, The JCC is described at page 48. Here  is cited:
So – in , published by NERI, there is no doubt  has delivered the necessary proof of the paradigm:
There is no significant influence on the nutrients concentrations in the Danish straits from the JCC.
It must be emphasized: One report drawing a complete new conclusion on the basis of very few data and a
questionable model to analyze the data has been used as the proof of a hypothesis, which is in contradiction
to the conclusions drawn from authors in Germany.
NERI has focussed very much in the public in Denmark and in its information given to the Parliament on
arguing that the influence from the JCC is negligible . In 1999 there was relatively strong oxygen
depletion in the Kattegat. Therefore MF Hans Christian Schmidt (now Minister of Environment) asked a
question to the actual Minister for Environment and Energy. :
The answer, produced by NERI was:
'HWHUSnQXY UHQGHWLGVSXQNWLNNHPXOLJWDWY JWHWLOI¡UVOHQDIQLWUDWIUD'HQ-\VNH.\VWVWU¡PWLO
WLOJ QJHOLJWIRUGHQDOJHY NVWVRPHIWHUI¡OJHQGHNDQPHGI¡UHLOWVYLQG´
So it is clear that NERI as late as in 1999 has informed the Parliament that the influence from the JCC on the
oxygen depletion in the Kattegat is to consider almost totally negligible.
The definition of German Bight water in  seems to be based upon a narrow definition of the German
Bight as the area, located very close to the Elbe mouth.
It should however be underlined, that the paradigm from 1984 is building upon the hypothesis that the
eutrophication in the Danish straits is mainly caused by local loads and not by loads from the southern North
Sea. If this hypothesis should be correct, there should be no significant inflow of nutrient rich water from
the southern North Sea at all, independent of whether it is originating from the south eastern North Sea (the
Elbe) or the south western North Sea (the Rhine). Looking on Figure 13, the well known map over the water
flow in the North Sea from OSPAR reports, it is clear that there is a flow of South North Sea water as well
as of German Bight water along the Jutland West Coast. And from figure 14, also from OSPAR reports,
shows that all river affected currents in the southern North Sea are affected by increased Nitrogen compared
to the background concentration of the Atlantic waters. Further, in figure 15 is shown the transport of solids
and circulation pattern in the North Sea .
It sounds, however, very unlikely that the nutrient over-concentration in the southern North Sea should not
affect the Kattegat. It might be that sometimes the JCC is disrupted around Hirtshals, as stated by NERI in
its cruise reports. But even in such situations the nutrients from the JCC just cannot disappear. It will remain
in the water in the area and sooner or later, more or less diluted it will continue in the main flowing pattern
in the counter clockwise circulation in the Skagerrak.
In Figure 16 is shown another example: In the winter 1994-1995 there was a dramatic high water in the
River Rhine, due to heavy rain. The dikes in the Netherlands were close to collapse. In February the Danish
newspaper Politiken published the first satellite photo from the Danish Meteorological Institute (DMI)
(February 8, 1995). This photo and the following satellite photos (private communication with DMI) show
clearly the flow pattern in that part of the North Sea. Here it should be noted, that the transport pattern
shows that the brown water is penetrating into the western Limfjord too.
Further, looking on a new report (With Gunni Ærtebjerg as one of the authors ) satellite photos of the
North Sea shows distribution of Chlorophyll-a. In Figure 17 is shown some typical examples of these
These satellite photos make it also difficult to say, that the nutrient rich water from the southern North Sea
doesn’t reach the Skagerrak and though are affecting somehow the northern Kattegat.
The Nitrogen over-concentration theory (NERI 1997).
In  NERI is publishing a study on data from the monitoring programme arguing for a local nutrient overconcentration
in the Danish straits.
In figure 18 is shown a graph from  illustrating the theory: Here observed combinations of inorganic
Nitrogen versus salinity are plotted and an average curve is plotted. It is based upon data from NERIs
cruises and data from the Counties from January and February.
Looking more in details on the data behind this graph (MADS data-base, partly made public by NERI) it can
be seen that the data with high inorganic Nitrogen around salinity 20-25 are from the sea north and south of
Fuenen. Here data ere collected with high frequency relative to monitoring at NERI positions in the
Kattegat, which are typically data with higher salinity.
In figure 19 is shown plots of MADS data for the positions Little Belt south and Little Belt north. It shows
the typical development at these positions, as shown in separate appendix on MADS data. As the NERI data
from the Kattegat are from fewer cruises per winter (typical 2) their chance of finding high concentrations of
nutrients in the turbulent water is smaller.
In Figure 20 is shown the influence from sampling frequency. 10 years data from two positions close to each
other in Great Belt, where NERI and the County of Fuenen performed data collection at different
frequencies are plotted. The linear regression lines show clearly the effect of sampling frequency. The high
frequency of the County of Fuenen leads to higher values for inorganic Nitrogen than the low sampling
frequency of NERI. In Figure 21, only data from January and February 1995, i.e. data for the same time
period as in Figure 18 is shown. This indicates that what NERI defines as over-concentration probably
mainly is due to the differences in sampling frequencies in the different regions of the Danish straits.
Further to demonstrate the fast water exchange in the Danish straits, figure 22 show the development in
salinity and inorganic Nitrogen concentration at the station Little Belt North. 1999 is selected as these data
clearly shows the fluctuation. Please note the strong change occurring from January 7 to January 12, where
the bottom inorganic Nitrogen concentration rises from 10 micromol/l to 15.7 micromol/l, while the salinity
decreases from 28.4 psu to 24.9 psu. Such fast changes cannot be caused by sudden increase in water
discharge from the small watercourses in the surrounding Danish land.
In figure 23 is sketched the principle of Figure 18 with the data structure and the average concentration line
according to NERI. Further is shown the Inorganic Nitrogen versus salinity curve for JCC-water. Two
different theoretical boundaries for inorganic Nitrogen over-concentration is shown: One following the
NERI definition, using salinity of 34 psu as representative for water entering into the Danish straits from
north, another taking the JCC water of salinity 32 psu as representing the highest level for water passing via
the northern boundary into the Danish straits.
This figure illustrates that most water masses in the Danish straits probably is a mixture of JCC-water,
Atlantic water and Baltic
T‚ˆ‡ur… Gv‡‡yyr7ry‡Aˆr r 8‚ˆ ‡’Eh Ari ('( (((
Sea water with a minor
local contribution. Looking
at figure 19, where the
development of salinity and
concentration in the Little
Belt water in 1995 is
shown, and looking on the
data for the winter period at
the same positions in other
years, it is seen that there is
only small differences in
salinity from surface to
bottom, and similar only
small differences in
In Figure 24 is shown the difference between inorganic Nitrogen concentration and salinity in surface and
bottom water for each data set in the position south of Fuenen. All data from January and February 1989-
1999 are shown. This shows that mostly the water in the bottom has the highest salinity and the highest
Nitrogen concentration than the surface water. These data does not indicate any dominating influence on the
inorganic Nitrogen concentration from local sources.
Looking more on the over-concentration theory of NERI, it should be mentioned that NERI also obtains
negative values for over-concentration in some years. The explanation for this is rather vague. The data are
form January and February, where the biological activity in these waters is rather limited.
It can be concluded that:
The over-concentration theory from NERI is based upon graphs like Figure 18 (reconstructed in figure 23).
NERI defines local over-concentration, for data points lying over the boundary for over-concentration acc.
to NERI. Here is seen data in the salinity range 15-25 seeming to represent local over-concentration. These
data are to great extend originating from around Fuenen.
However, the differences in sampling frequencies in the Kattegat and the water around Fuenen (and other
places close to the coast, where the counties are sampling data) can to some extend explain this
As stated in earlier section of this document, then the sampling frequency in the Kattegat region is far too
small to detect all inflow from the JCC. It should here be underlined that especially in the open part of the
western Kattegat, the amount of data is very limited (SMHI have only few data from here, NERI only 1-2
cruises per winter season). Taking into account that the Baltic Coastal Current is flowing northwards in
eastern Kattegat, it is clear that some southwards water flow can bring JCC-water through the western
Kattegat, which can be difficult to detect within the accomplished monitoring programs (look on Figure 25 a
typical result from the DHI simulation of the surface salinity in “Farvandsmodellen”). These flow pattern
simulations can for several years be seen as animations on the internet
Looking more on the flow situation in the Danish straits, illustrated in Figure 25, it is in general so that the
Baltic Coastal Current is a strong surface current especially passing through the Sound, but also the Great
belt, while the Baltic Coastal Current normally doesn’t flows though the Little Belt. The simulation shows
the typical situation, where the surface salinity is higher in the water north and south of Fuenen and in the
Little Belt than in the Great belt and the Sound. This indicates water flow from north to this part of the
There is no significant sign of local discharges affecting the concentration of inorganic Nitrogen in the water
masses around Fuenen, which are those water masses mainly responsible for the high over-concentration
data points in Figure 19.
There is sign of fast fluctuations in both salinity and bottom water inorganic Nitrogen concentration in the
Little Belt, which cannot be caused by sudden fast exchange in water flow and nutrient concentrations in the
Danish watercourses discharging to this part of the Danish straits.
Looking on the size and flow in the Danish watercourses and comparing this to the large continental rivers
discharging in the southern North Sea and the Baltic Sea it is unlikely that the Danish waterways to any
significant extend can affect the nutrient concentrations in the Danish straits.
It should also be underlined, that while there has been recorded a strong increase in inorganic Nitrogen
concentration in for example the river Rhine from 1960 till now, such data are not available from the small
Only one data series (Odense Aa) out of 4 data series tracing back in time shows a little increase in Nitrogen
concentration in a Danish watercourse in the past. This little increase cannot however have any significant
influence on the Nitrogen concentration in the Danish straits.
When looking on the role of NERI and its major scientists within marine environment in the forming of the
Danish politics on the marine environment it can be concluded:
In 1984 a new paradigm for marine environment research and public understanding was formed, where the
preceding organisation Marine Pollution Laboratory, National Agency of Environmental Protection, played
an important role. This new paradigm was based upon the work of one of the employees at Marine Pollution
Laboratory, since then probably the most central scientist at NERI in marine environment.
This new paradigm was excluding 100 years of knowledge on water flow in the Danish straits, building on a
wrong assumption, that the oxygen depletions in the Danish straits mainly was due to local Nitrogen
discharges. The paradigm is clearly underestimating the influence from the continental rivers on the Danish
This paradigm has been maintained by NERI since then in public and for the Parliament.
The forming of the paradigm was based upon very few data from few positions in the Danish straits,
covering a very short time period. Looking on data from the same position with the same methodology, but
over a longer time span, the weakness of this paradigm is clear.
NERI has in more than 10 years performed monitoring in the Danish straits and coordinated data treatment
from their own cruises and cruises performed by the Danish counties. NERI has neglected vital information
from these data in its conclusions on the influence of the JCC.
NERI has taken one piece of scientific work, which they were involved in themselves as evidence for the
little input from the JCC of nutrients to the Danish straits. This work came to a totally new conclusion
compared to former work on the estimation of the water inflow from the JCC to the Danish straits. However,
this scientific work is very questionable and clear conclusions cannot be drawn on this work. This is due to
both the fact that only very few data was applied as well as the application of a too simple box-model with
incorrect boundary conditions.
Later NERI has proposed an over-concentration theory. In this document this theory and its data is
discussed, based upon some of the data available from the monitoring program via the MADS-database. It is
shown that there is no sign of strong local influence on the inorganic Nitrogen concentration in the Danish
straits, where the so called over-concentration is originating from, but the theory is probably coming to the
wrong conclusion due to improper treatment of the data and the knowledge of the flow patterns in the
As one out of many examples of incorrect information of the public is shown a press release from Statistics
Denmark based upon data points from NERI. In this press release the statement of the origin of the increased
inorganic Nitrogen from local loads is repeated, even though the data applied in the graph in the press
release is from a SMHI cruise, where the strong inflow of continental river water is detected and described.
This press release also includes a graph where data has been applied in a very misleading way.
The document also shows that the NERI employees have been possessing information making it difficult to
say that there is little inflow of nutrients from the southern North Sea into the Danish straits.
Therefore it can be concluded that the paradigm from 1984 is not correct, and any good scientist having the
information, which have been available as public information should be able to draw this conclusion.
Furthermore, it must be concluded that a proper application of the data from the monitoring programs,
coordinated by NERI, should have supported the statement that the paradigm from 1984 was incorrect.
List of references
 Gunni Ærtebjerg Nielsen, Torben Schelde Jacobsen, Eivind Gargas og Erik Buch: "The Belt
Project, Evaluation of the Physical and Biological Measurements", Miljøstyrelsen (1981).
 DMU Nyt nr. 1/98
 "Iltsvind og Fiskedød 1981, Omfang og Årsager", Miljøstyrelsen (1984).
 Gerlach: Nitrogen, Phosphorous, Plankton and Oxygen Deficiency in the German Bight and in
Kiel Bay, Sonderheft Nr. 7, 1990, Kieler Meeresforschungen.
 Gunni Ærtebjerg: “Årsager til iltsvind i Kattegat og Bælthavet”, Vand og Miljø 2/1985 p. 59-62
 ”Vandmiljøplanens tilblivelse og iværksættelse” ATV , (1990).
 Gunni Ærtebjerg: ”Den virkelige historie om vandmiljøet”, Ingeniøren nr. 12/1999
 Gunni Ærtebjerg og Niels Kruse: “Undersøgelser af Udbredelse og Effekter af Iltsvind i det
Sydlige Kattegat 8-11. Oktober 1986”, Miljøstyrelsens Havforureningslaboratorium (1986).
 Jacobsen, F.; Ærtebjerg, G.; Agger, C. T.; Højerslev, N. K.; Holt, N.; Heilmann, J. &
Richardsson, K.: "Hydrografisk og biologisk beskrivelse af Skagerrak-fronten". Havforskning fra
Miljøstyrelsen, nr. 49. (1994).
 North Sea Task Force under Oslo and Paris Commissions: North Sea Quality Status Report 1993
 Jørgensen, B. B. and Richardsson K. (editors) "Eutrophication in Coastal Marine Ecosystems",
American Geophysical Union, (1996).
 Christensen, P. B. (Editor) "Havmiljøet under forandring?" Havforskning fra Miljøstyrelsen, nr.
 H. Nies et. Al.: „Umweltauswirkungen des Elbehochwassers vom August 2002 auf die Deutsche
Bucht”, Bundesamt für Seeschifffahrt und Hydrographie (BSH) Hamburg und Rostock 2002
 Question no. S 33, To The Minister of Environment and Energy (5/10 99) from: Hans Christian
 Kai Sørensen et. Al. (including Gunni Ærtebjerg): “Remote sensing’s contribution to evaluating
eutrophication in marine and coastal waters Evaluation of SeaWIFS data from 1997 to 1999 in the
Skagerrak, Kattegat and North Sea”, ISBN92-9167-471-0, ©EEA, Copenhagen, 2002
 Gunni Ærtebjerg et. Al. ”Vandmiljøplanens overvågningsprogram 1997, Marine områder”,
Scientific report from NERI no. 254 (1998).
ilt bund Anholt
Data fra Danmarks Statistik, statistikbank
jan feb mar apr maj jun jul aug sep okt nov dec Danmarks
1975 8,57 8,08 8,47 9,04 7,55 6,4 5,57 4,21 3,6 3,6
1976 9,74 8,2 8,25 8,48 6,88 5,61 5,37 7,43 5,37
1977 7,84 9,42 9,72 8,77 8,67 8,68 6,91 4,78 6,94 8,1 4,78
1978 6,33 8,6 6,33
1981 9,61 6,44 4,74 4,57 7,04 4,64 2,56
1982 8,27 9,74 7,85 7,63 5,04 6,67 5,04
1983 9,92 9,17 9,27 6,51 3,51 4,21 4,83 3,51
1984 9,54 8,95 7,25 5,8 4,81 3,01 6,4 3,01
1985 10,98 8,8 8,27 7,15 5,07 3,04 5,87 3,04
1986 8,51 8,51 6,98 4,86 4,05 2,61 7,05 2,61
1987 8,74 8,23 6,48 4,96 5,03 3,81 5,45 3,81
1988 8,55 9,7 7,17 5,23 1,4 4,3 6,55 1,4
1989 9,18 9,48 7,33 7,14 6 2,96 4,91 6,88 2,96
1990 7,9 9,44 8,93 8,48 7,28 5,97 3,94 2,64 5,08 6,97 2,64
1991 8,58 8,71 8,48 7,87 7,45 5,67 3,51 2,57 3,68 7,1 2,57
1992 7,88 9,08 9,02 7,58 7,14 5,26 3,3 2,26 6,57 2,26
1993 9,1 9,72 9,64 8,83 7,71 7,38 4,47 6,15 6,93 6,57 4,47
1994 8,64 8,51 9,07 8,65 8,35 6,77 4,04 5,54 3,46 6,47 3,46
1995 8,84 9,64 9,82 7,55 6,63 3,77 4,71 5,16 3,77
1996 7,8 6,9 8,05 5,14 4,34 6,53 7,01 4,34
1997 7,9 8,88 8,41 7,01 5,85 4,34 2,61 2,61
gennemsnit 8,168182 9,181176 8,9465 8 8,179091 7,776364 6,564706 4,747222 3,999444 4,46625 6,608 8,1
Table page 24