カナダ北極圏ボフォート海におけるマリンスノーフラックスおよび内部の微小生物相の変化

概要

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Seasonal changes of sinking marine snow (>0.5mm in longest dimension) flux and their composition of microorganisms associated with marine snow collected using time-series sediment traps were observed at a station (CA7; 71°N, 134°W, 501m water depth) in the Mackenzie shelf slope of the Beaufort sea from 21 September 2002 to 31 August 2003. Downward fluxes of marine snow at 69m increased in the middle of May 2003 and reached the maximum (ca. 20000m^<-2>d^<-1>) in the end of June 2003. The epifluorescence microscopic study showed that marine snow are associated with many microorganisms, such as bacteria, nano- and microflagellates, diatoms and ciliates, and they frequently included small clay-like detritus. The abundance and compositions of microorganisms in these marine snow varied seasonally with elevated primary production in spring-summer and turbid water intrusion from the Mackenzie shelf area during an open water period. The maximum flux (ca. 20mgC m^<-2>d^<-1>) appeared at 199m in the beginning of July, was about 3 times less than that at 69m in late June. The difference in occurrence of maximum flux between two depths would be explained by combined processes of particle retention within the upper water column and horizontal transport of allochthonous particles from the shallow shelf waters.