Copper Sorption and Release by Cyclotella Meneghiniana (Bacillariophyceae) and Chlamydomonas Reinhardtii (Chlorophyceae)1

Initial Cu++ sorption by Cyclotella meneghiniana Kütz. (Cu++‐sensitive) and Chlamydomonas reinhardtii Dangeard (Cu++‐resistant) was rapid in the first 5 min of Cu++ incubation with little sorption after 2 h. On a cell to cell basis, Cyclotella sorbed ca. five times more Cu++ from the medium than Chlamydomonas. In MBL medium with EDTA Cyclotella and Chlamydomonas cells sorbed 21.0 and 4.41 nM Cu++/106 cells respectively in 6 h with 0.3 mg Cu++/l in the medium. Proportionally similar quantities of Cu++ were sorbed when the cells were Cu++ incubated in MBL + citrate or filtered lake water. Cleaned cell walls of Cyclotella sorbed little Cu++ (1.7 nM/106 cells) as compared to living cells (17.5 nM Cu++/106 cells) in 3 h. Therefore, in living Cyclotella most of the Cu++ taken up must be absorbed by the protoplasm or perhaps by the organic layer surrounding the silica wall. Cleaned cell walls of Chlamydomonas sorbed 3.5 nM Cu++/106 cells and living Chlamydomonas cells sorbed 2.6 nM Cu++/106 cells. This indicates that most of the Cu++ sorbed by Chlamydomonas cells remained bound to the cell wall and probably did not readily enter into the protoplasm: When placed in Cu++ free medium after Cu++ incubation, Cyclotella and Chlamydomonas cells released 46 and 59% respectively of the Cu++ sorbed.