COPPER SORPTION AND RELEASE BY <i>CYCLOTELLA MENEGHINIANA</i> (BACILLARIOPHYCEAE) AND <i>CHLAMYDOMONAS REINHARDTII</i> (CHLOROPHYCEAE)¹

Abstract

ABSTRACT 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 ++ /10 6 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/10 6 cells) as compared to living cells (17.5 nM Cu ++ /10 6 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 ++ /10 6 cells and living Chlamydomonas cells sorbed 2.6 nM Cu ++ /10 6 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.