Abstract
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.
Highlights
I T is generally accepted that diatoms are the main producers of the mucilage polysaccharide matrix in the seawater.[1,2,3] The massive appearance of the mucilage in the northern Adriatic in summer of 2001 and 2002 was characterized by the domination of the epipelic diatom Cylindrotheca closterium.[4]
These results suggest that diatoms inhabiting aggregates can contribute to cycling of carbon through extracellular polymeric substances (EPS) production especially under nutrient limitation
In these samples there was no difference in SAS between original non-filtered and filtered samples, except in sample analyzed after 10 days of incubation when maximum of exponential growth was recorded (Figure 1) and maximal concentration of SAS (0.327 mg L–1 eq T-X-100) was measured in the filtered samples
Summary
I T is generally accepted that diatoms are the main producers of the mucilage polysaccharide matrix in the seawater.[1,2,3] The massive appearance of the mucilage in the northern Adriatic in summer of 2001 and 2002 was characterized by the domination of the epipelic diatom Cylindrotheca closterium.[4].
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