METHYL-CHLORIDE (CH3CL) PRODUCTION IN PHYTOPLANKTON CULTURES

Unialgal nonaxenic cultures of seven species of phytoplankton, including both warm- and cold-water organisms, were examined under halocarbon-clean conditions for the production of CH3Cl. Incubations of all species showed CH3Cl increases significantly greater than in the control medium. The magnitude of increase varied with the phytoplankton species present and in some cases also with growth stage. Longer time series showed that CH3Cl continued to increase after the death of all the phytoplankton cells. Although direct production as a by-product of phytoplankton metabolism cannot be ruled out earlier in the time series, indirect chemical and (or) biotic reaction of algal-associated organic matter is required to explain this continued increase. Characterization of the role of bacteria in both pre- and postsenescent stage CH3Cl production will require comparable experiments carried out under axenic conditions.