Geochemical Journal, Vol. 45 (No. 5), pp. 355-363, 2011
Sohiko Kameyama,1 Hiroshi Tanimoto,1 Satoshi Inomata,1 Koji Suzuki,2 Daisuke D. Komatsu,3 Akinari Hirota,3 Uta Konno3 and Urumu Tsunogai3
1National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan
2Faculty of Environmental Earth Science, Hokkaido University, North 10 West 5, Kita-ku, Sapporo 060-0810, Japan
3Faculty of Science, Hokkaido University, North 10 West 8, Kita-ku, Sapporo 060-0810, Japan
(Received February 16, 2011; Accepted April 9, 2011)
Emission of trace gases from the marine diatom Thalassiosira pseudonana (CCMP1335) was continuously monitored with a proton transfer reaction-mass spectrometry (PTR-MS) in an axenic batch culture system under a 13:11-h light:dark cycle. Substantial increases in the signals at m/z 49, 63, and 69, attributable to methanethiol, dimethyl sulfide (DMS), and isoprene, respectively, were observed in response to increases in cell density. Signals at m/z 69 showed diurnal variations throughout the experiment whereas those at m/z 49 were more pronounced at the beginning of the incubation. Interestingly, the signals at m/z 49 and 69 changed immediately following the light-dark and dark-light transitions, suggesting that light plays a crucial role in the production of methanethiol and isoprene. However, in the latter half of the experiment, methanethiol showed negligible diurnal variations regardless of light conditions, suggesting the production of methanethiol from enzymatic cleavage of DMS. The trend in signals at m/z 63 was similar to that of the abundance of senescent cells plus cell debris rather than vegetative cells. The results suggest that aging or death of phytoplankton cells could also substantially control DMS production in natural waters along with the other microbial processes related to bacteria and zooplankton.
Key words: dimethyl sulfide, isoprene, methanethiol, PTR-MS, Thalassiosira pseudonana, axenic culture