Marine Chemistry 
System Nordsee 
31 
Riverine inflow, which influences salinity in the German Bight, far exceeded the clima 
tological monthly means in April and May 2006 due to exceptionally strong snowfalls 
during winter. The Elbe discharge volume in April was 2 1 /2 times the long-term mean. 
Because of an unusually strong storm season in autumn/winter 2006/2007, Atlantic 
water flowing in from the north spread as far as about 54.2° N in 2007. At the same 
time, a tongue of Atlantic water intruded into the southern North Sea through the 
Channel. Salinity in the North Sea was markedly lower in summer. In the surface layer, 
salinities > 35 were only found NW of the line connecting Peterhead - Fladen Ground 
- southern tip of Shetland, i. e. in the area directly influenced by the Fair Isle Current. 
Also at the bottom, the areal extent of Atlantic water decreased, with its southern 
boundary shifting more than 60 nm in NE direction. The total salt content of the North 
Sea in summer, at 1.143 x 10 12 1, about corresponded to the 10-year mean of the pre 
ceding decade. The vertical salinity gradient in the Norwegian Channel was clearly 
weaker than the year before, so that a halocline in the proper sense did not form. Total 
river runoff volumes of the river Elbe in the years 2006 and 2007, at 22 km 3 /a, were 
close to the long-term mean. 
Marine Chemistry 
Nutrients (p. 170 sqs.) 
Nutrient loads transported into the German Bight by the rivers Elbe and Weser show 
a clear downward trend, despite major interannual differences. This is also reflected in 
the long-term trend of nutrient concentrations in the German Bight. 
Nutrient levels in the winter seasons of 2006 and 2007, derived by regression from 
salinity and nutrient analyses and representative of coastal water (salinity 30) and 
sea water of the German Bight proper (S = 34), hardly differed from the concentra 
tions measured in previous years. Phosphate levels in the German Bight no longer 
exceeded the reference values from 1936 or the orientation values discussed within 
the framework of OSPAR; levels in the coastal waters exceeded these values by about 
60%. High levels of nitrogen compounds indicate that major nutrient loading is still 
taking place. Silicate concentrations, which are not much influenced by industrial or 
agricultural activities, were in the range of natural fluctuations. 
In the summer of 2006/2007, as in the years before, the North Sea surface layer was 
characterized by low nutrient levels limiting algal growth, with nitrate being the main 
limiting factor. Nutrient levels in the summer of 2007 were conspicuously high in the 
Elbe outflow area due to high runoff volumes transporting nutrients from the river Elbe 
into the German Bight. Chlorophyll levels in the central North Sea were low due to the 
observed nitrogen limitation. Chlorophyll maxima occurred only in the coastal waters, 
supported by sufficient nutrient availability due to high surface runoff and remineraliza 
tion processes. 
The Redfield ratio (N/P = 16), a parameter also used for eutrophication assessment 
within the framework of OSPAR, was outside the normal range in large areas of the 
North Sea, in part reflecting nitrogen limitation during the summer months. 
In the period under review, the distribution of oxygen saturation in bottom water was 
comparable to that in earlier years (80 - 100%). The strongest oxygen deficits, both 
in 2006 and 2007, were observed in the eastern North Sea, where less than 60% and 
locally only 53% was measured.