Data on the cycling of Cu and Zn in two eutrophic lakes are presented:
Lake Greifen that becomes seasonally anoxic in its hypolimnion and La
ke Sempach that is aerated during winter and oxygenated during summer.
They suggest that hypolimnetic oxygenation 1) enhances the release of
copper from the sediment but 2) also accelerates the entrapment and d
eposition of Cu and Zn by freshly formed Mn- and Fe-oxides.