TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 66 (No. 6), pp. 873-883, 2010

Short Contribution

Microbial Dynamics in an Oligotrophic Bay of the Western Subtropical Pacific: Impact of Short-Term Heavy Freshwater Runoff and Upwelling

An-Yi Tsai1*, Gwo-Ching Gong1, Robert W. Sanders2, Chien-Fu Chao3 and Kuo-Ping Chiang1,3

1Institute of Marine Environmental Chemistry and Ecology, National Taiwan Ocean University, of China
2Biology Department, Temple University, Philadelphia, PA 19122, U.S.A.
3Institute of Environmental Biology and Fishery Science, National Taiwan Ocean University, Keelung 202-24, Taiwan, Republic of China

(Received 11 March 2010; in revised form 14 September 2010; accepted 4 October 2010)

Abstract: This two-year study investigates the possible factors that determine spatial and temporal dynamics of picoplankton (heterotrophic bacteria, autotrophic picoplankton—Synechococcus spp., Prochlorococcus, and picoeukaryotes) and nanoflagellate abundance in the subtropical Ilan Bay, Taiwan, where the inner bay is affected by freshwater run-off from the Lanyang River and the eastern outer bay by the Kuroshio Current. In the inner bay, there was more rain and freshwater discharge in 2005 than in 2004 during the warm season (>24°C, June-September). The abundance of bacteria, Synechococcus spp., Prochlorococcus, and picoeukaryotes and the percentage contributions of pigmented nanoflagellate (PNF %) were two- to eight-fold greater during this period (July in 2005) than for other sampling periods. Relatively low abundance of heterotrophic nanoflagellates (HNF) in the presence of abundant picoplankton prey suggests that top-down control determined HNF abundance in the Ilan Bay, Taiwan.

*Corresponding author E-mail: anyitsai@mail.ntou.edu.tw

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