Copper ions as poison in the sea and in freshwater

TLDR: It has recently been shown that ocean water in the centres of upwelling becomes suitable for plankton growth only after the addition of a chelator, suggesting that a large part of the Cu found in the subsurface waters of the oceans is present in ionic form.

Abstract: Copper in ionic form is found to be very poisonous for photosynthesis and growth of unicellular algae at concentrations of Cu usually found in natural waters. This indicates that Cu is ordinarily not present in ionic form but is complexed by organic matter such as polypeptides. The affinity of Cu to diethyl-dithiocarbaminate is very much higher than to the organic matter which complexes Cu in nature. Thus, it is not possible to distinguish the two forms of Cu during analysis. Complexed Cu is not poisonous to algae. It has recently been shown that ocean water in the centres of upwelling becomes suitable for plankton growth only after the addition of a chelator. This suggests that a large part of the Cu found in the subsurface waters of the oceans is present in ionic form. Some manufactures of C14 ampoules have used ordinary distilled water which often has a content of about 250 μg Cu/l. Thus, it is very likely that some productivity measurements have been influenced. A likely example is mentioned.