Effect of temperature on the methyl chloride production rate in a marine phytoplankton, Phaeodactylum tricornutum

Abstract

Methyl halides such as methyl chloride (CH3Cl) are known to be important carriers of halogen from the ocean to the atmosphere, and the halogens they release into the stratosphere by photolysis catalyze ozone depletion. Marine phytoplankton have been reported as a source of CH3Cl, but the effects of environmental temperature on the CH3Cl production by phytoplankton have not been investigated. In this study, we investigated the effects of temperature on the production of CH3Cl in the culture of a marine diatom, Phaeodactylum tricornutum CCMP 630, incubated at 10, 15, 20, 25, and 30 °C. CH3Cl concentrations in cultured samples were determined using purge and trap gas chromatograph–mass spectrometry. Phytoplankton growth was monitored by measuring the chlorophyll a concentrations. CH3Cl production was observed for several weeks at four different temperatures ranging from 10 to 25 °C. The CH3Cl production from P. tricornutum was increased with increasing temperature from 10 to 25 °C, and the maximum production rate for CH3Cl was 0.21~0.26 μmol (g chlorophyll a)−1 d−1 at 25 °C, which was several times higher than that at 10 °C (~0.03 μmol (g chlorophyll a)−1 d−1). The Arrhenius equation was successfully used to characterize the effects of temperature on the production rates of CH3Cl in the culture of P. tricornutum. Our results suggest that water temperature directly affects CH3Cl production derived from P. tricornutum and that water temperature would be a significant factor for estimating the emissions of CH3Cl from marine environments.