Compilation of Summaries 
25 
However, the determination and evaluation of suitable effect limits for marine 
ecosystems remains the subject of research and scientific discussion. Between 
2006 and 2011, the lead time series in waters far from the coast showed a 
slight but significant downward trend with already very low concentrations, 
around the expected background level. 
The spatial concentration distributions of the elements mercury, cadmium, 
lead, copper and zinc show similar patterns in surface waters of the German 
Bight. The contents decline significantly from coast towards the open sea. 
Most elevated concentrations were detected in the inner German Bight and the 
Elbe estuary and significant in the estuaries of the Weser and Ems rivers Cad 
mium, zinc and nickel show pronounced seasonal cycles with increased con 
centrations during spring and at minimums in the later summer to autumn. In 
contrast, the dissolved manganese shows a clear maximum in the summer, 
which indicates oxygen deficiency events in the water column. According to 
the current level of awareness, there is no danger to the marine ecosystem 
arising from the measured metal concentration in sea water. 
Sediment: Along the North Frisian coast, the metal pollution of the silt/clay 
fraction (< 20 pm) reaches contents in the surficial sediment which could have 
negative biological effects. Only mercury, zinc and lead exceed the effect limit 
of the six elements studied (Cd, Cu, Hg, Ni, Pb and Zn), along the North Frisian 
coast. 
Zinc and lead show increased levels throughout the entire German Exclusive 
Economic Zone; mercury is found only at enhanced levels along the North Fri 
sian coast up to the Elbe estuary. Altogether low levels of pollution are deter 
mined in the area of the White Bank; the elements cadmium and copper reach 
their background levels here in the silt/clay fraction of the surficial sediment. 
Significant temporal trends detected during the period 2001 to 2011 on the 
trend stations were all downward (White Bank (Hg), Ems (Cu), German Bight 
(Hg)). Since 2001, there has been a significant downward trend in mercury vir 
tually over the whole of the German Bight (with the exception of Ems). In the 
period between 2005 and 2010, the deposition of sediments from the dredging 
activities in the Port of Hamburg to buoy E3 led to local increased metal con 
tents in the silt/clay fraction of the surficial sediment. This was mainly the case 
for the elements cadmium, copper, mercury and zinc. After 2011, there were 
also no longer metal contents detected at this site above previous usual ranges. 
Radioactive Substances (Page 258 et seq.) 
Monitoring in the years 2008 to 2011 focused on the radionuclides 137 Cs, 90 Sr, 
tritium and the transuranic elements 238 Pu, ( 239+24 °)pu and 241 Am in the German 
Bight and North Sea. Overall, the activity concentration distributions of radio 
nuclides exhibited very minor spatial differences in the German Bight in com 
parison with previous years. The concentrations were slightly higher than those 
in the surface water of the North Atlantic, which can be attributed to the global 
fallout of atmospheric nuclear weapons testing. The slightly higher concentra 
tions of 137 Cs in the north-west North Sea, compared to the coastal zone, are 
due to re-suspended material from the highly contaminated Irish Sea sedi 
ments. It was possible to identify a characteristic freshwater inflow from the 
Elbe in the distribution of the 90 Sr concentration. The higher concentrations