Marine Chemistry 
System Nordsee 
33 
verse impacts on living organisms were to be expected. That is the conclusion from an 
evaluation of cadmium, lead, mercury and nickel concentrations based on the WFD 
environmental quality standard AA-EQS. Copper and zinc were evaluated according to 
the water quality standard (WQS) of the US Environmental Protection Agency (EPA). 
Background values of metals (dissolved) were found only in the outer parts of the EEZ, 
but only for the elements cadmium and nickel. Also close to the coast, in water bod 
ies with salinities > 28, effects limits values were not reached anywhere. It should be 
taken into account, though, that the determination and evaluation of suitable effects 
limit values for marine ecosystems still are subject to research and scientific debate. 
Between 2003 and 2007, time series of the elements copper and nickel (dissolved) 
in coastal waters showed significant upward trends but levels nevertheless remained 
very clearly below the effects limits. 
Spatial concentration distributions of the elements mercury, cadmium, lead, copper, 
and zinc in surface water of the German Bight show similar patterns. Their levels de 
crease markedly from the coast toward the open sea. The highest pollution levels are 
found in the inner German Bight and Elbe estuary, but elevated concentrations have 
also been found in the estuaries of the rivers Weser and Ems. 
Cadmium, zinc, and nickel show marked seasonal cycles, with elevated levels in 
spring and minima in late summer to August. By contrast, dissolved manganese had 
a pronounced maximum in summer, which points to an oxygen deficiency situation in 
the water column. 
According to present knowledge, metal concentrations currently measured in sea wa 
ter do not pose a hazard to the marine ecosystem. 
Along the North Frisian coast, metal concentrations in fine-grained surface sediment 
(< 20 pm) have reached levels capable of causing adverse biological effects. Of the 
six elements investigated (Cd, Cu, Hg, Ni, Pb, and Zn), five (nickel being the only 
exception) reached effects levels off the coast of Sylt. Zinc levels are elevated along 
the entire German coast, whereas elevated mercury levels have been measured only 
along the North Frisian coast, up to the Elbe estuary. Lead is the only element exceed 
ing the effects limit in the entire area of the German EEZ. The lowest levels are found 
in the area of the White Bank, where concentrations of the elements cadmium and 
copper drop to background values in fine-grained surface sediment. The method used 
in this assessment is based largely on the OSPAR assessment method. The ERL 
guideline values for effects limits issued by the National Oceanic and Atmospheric 
Administration (NOAA) were used in the assessment. 
All significant temporal trends in the period from 1998 to 2007 were downward trends 
(White Bank (Cu), Ems (Zn, Pb), German Bight (Hg)). Mercury levels since 1997 have 
shown a significant downward trend almost throughout the German Bight. However, 
the waters south-east of Helgoland in the inner German Bight constitute an exception. 
Changes taking place in this area have led to a clearly higher variability in mercury 
levels since 1999, which is definitely not attributable to higher emissions from the river 
Elbe but probably to local redisposition processes on the seabed which have brought 
deeper, more polluted sediment horizons to the surface. 
Independent of these changes observed since 1999, sediment dredged from Ham 
burg harbour and dumped near buoy E3 has led to a local increase in metal levels in 
fine-grained surface sediment, mainly cadmium, copper, mercury, and zinc.