BSH monitoring network MARNET. 
Variables obtained by remote sensing, such as radiation temperature, SPM distribution, 
phytoplankton and sea state data refer only to a thin near-surface layer. All measured data 
from deeper layers are obtained either by vessels, automatic recording stations, or drifters. On 
the whole, the data presently available are not sufficient to determine transports, frontal zones, 
thermoclines and haloclines, or to indicate the SPM concentration or turbidity. 
Climate relevant changes in the North Sea are determined by inflows and outflows through the 
English Channel and across the northern boundaries of the North Sea as well as by continental 
river runoff. Anomalies in sea surface temperature of the North Sea are closely linked to the 
so-called North Atlantic Oscillation Index (NAO index), which is a measure of the 
atmospheric heat transport to Central and Northern Europe and its impact on temperature 
conditions in the North Atlantic Ocean and North European waters. Recent investigations 
revealed that the North Atlantic Oscillation is a phenomenon in the Atlantic which is 
comparable to the El Niño Southern Oscillation in the Pacific Ocean. 
The monitoring tasks in the Baltic Sea are carried out by Institut fur Ostseeforschung 
Wamemünde (IOW, Baltic Sea Research Institute) on behalf of the BSH. We refer to the 
programme contribution of IOW on pages 41-43. 
The focus of chemical substances monitoring is on the identification of anthropogenic changes 
in the marine ecosystem on temporal and spatial scales. Nutrient concentrations in sea water 
exhibit a marked seasonal cycle. Only during the period of minimum biological production, 
i.e. in winter, are nearly all nutrients present in an analyzable form. The lowest nutrient level 
changes occur in February. Therefore, this is the most suitable month for wide-range 
monitoring cruises on vessels. 
Some organic contaminants show marked seasonal fluctuations in their concentrations. 
Lindane, for example, shows an increase in early summer and lower values in winter. By 
contrast, petroleum hydrocarbon values are 2 to 3-fold higher in winter than in summer. 
Because, of limited resources, intensive sampling on board vessels is only carried out in one 
season, while spot checks are made during the other seasons. 
Heavy metals differ considerably in their behaviour. Some of them, e.g. cadmium and zinc, 
have a clear seasonal pattern while other heavy metals hardly show any seasonal variability at 
all. A problem, in principle, in heavy metal monitoring in water is the fact that the levels of 
most heavy metals in the North Sea are only marginally above the geochemical background 
levels. The anthropogenic share of heavy metal pollution is very difficult to distinguish from 
the natural variability. Trace metal monitoring on a global basis is considered less important 
within GOOS. It only has a higher priority in the North Sea, Black Sea, and in the U.S. Great 
Lakes. Monitoring of radioactive substances, which focuses on artificial radionuclides from the 
nuclear fuel cycle, is carried out to ensure that radiologically relevant releases of nuclear 
power stations into the environment are recognized and their potential radioecological impact 
- also on long time scales - is identified in order to assess a possible radiation exposure of the 
population. 
Monitoring and investigation methods, analytical methods 
Hydrographic conditions in the German Bight and western Baltic are routinely monitored by 
the stations of the BSH‘s marine environment monitoring network MARNET. In addition, 
one-week vessel cruises into the German Bight and adjacent waters are carried out at least 
once every three months using towfish systems to cover large areas. Within the framework of 
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