Seasonal dynamics of biodegradation activities for dimethylarsinic acid (DMA) in Lake Kahokugata.
The microbial activities in aquatic environments significantly influence arsenic cycles such as the turnover between inorganic arsenic and organoarsenic compounds. In Lake Kahokugata, inorganic arsenic was detected at concentrations ranging from 2.8 to 23nM in all seasons, while the concentrations of dimethylarsinic acid (DMA) produced by microorganisms such as phytoplankton changed seasonally and showed a peak in winter. The changes in the concentrations of methylarsenic species did not correlate with the changes in phytoplankton abundance (chlorophyll a contents), suggesting that DMA-degradation is related to this inconsistency. DMA (1microM) added into the lake water was converted to inorganic arsenic at 20 degrees C only under anaerobic and dark conditions, while DMA degradation was diminished under aerobic or light conditions. Moreover, DMA added to the lake water samples collected through four seasons was degraded at the same rates under anaerobic and dark conditions at 20 degrees C. However, at 30 degrees C, 1microM of DMA in the summer lake water samples was rapidly degraded in 7 and 21d. In contrast, DMA degradation was diminished in the winter lake water samples at 4 degrees C of incubation. Presumably, DMA-biodegradation activities are mainly controlled by changes in the water temperature in Lake Kahokugata, where the arsenic concentrations change seasonally.
Maki
Teruya
T
Kanazawa University, Kakuma-machi, Kanazawa-shi, Japan. makiteru@t.kanazawa-u.ac.jp
Hirota
Wakana
W
Ueda
Kaori
K
Hasegawa
Hiroshi
H
Azizur Rahman
Mohammad
M
D002101:Cacodylic Acid / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D005618:Fresh Water; D007564:Japan; D012621:Seasons; D013696:Temperature; D014867:Water / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000378:metabolism
D014874:Water Pollutants, Chemical; D014867:Water; D002734:Chlorophyll; D002101:Cacodylic Acid; D000077194:Chlorophyll A