Production of Surface Active Organic Material and Reduced Sulfur Species During the Growth of Marine Diatom Cylindrotheca closterium

Electrochemical methods at the mercury electrode were used for monitoring production of surface active substances (SAS) and reduced sulfur species (RSS) during growth of marine diatom Cylindrotheca closterium isolated from the Adriatic Sea in the laboratory conditions. In the same culture samples, production of particulate and dissolved organic carbon (POC, DOC) was followed by high temperature catalytic oxidation method (HTCO). The culture growth curve obtained by microscopically counted phytoplankton cells showed an exponential growth phase that lasted 10 days, transition phase until 14 days and stationary phase until 21 days. In these time periods twofold increase of SAS and DOC was followed, while POC increased 41 times. Detail analyses of a.c. out of phase voltammetric curves recorded in original and in acidified phytoplankton culture samples indicate transformation of organic material during growth, from more anionic (negatively charged) to less anionic polymeric surface active material. In culture samples presence of non-volatile RSS were confirmed.