Potentiometric determination of copper complexation by phytoplankton exudates 1

Potentiometric copper titrations were done on culture media in which eight algal species, Thalassiosira pseudonana (3H), Ankistrodesmus falcatus, Chlamydomonas sp., Pediastrum sp., Staurastrum gracile, Gloeocystis gigas, Tribonema sp., and Cyclotella cryptica were grown to cell concentrations of 105–106 cells · ml−1. The results demonstrate that only G. gigas produces extracellular organic compounds that can measurably reduce the cupric ion activity in 1 × 10−6 M total copper.