Population dynamics of picophytoplanktons, including Prochlorococcus, Synechococcus, and picoeukaryotes, were investigated in the upstream Kuroshio. Data were collected during eight cruises between July 2007 and May 2009. Sampling stations were located along 21¢X55¡¦N and between 121¢X00¡¦E and 122¢X10¡¦E in the Kuroshio off the Southeast Taiwan. Monitoring experiments including light shadding experiment, nutrient enrichment, temperature control, and grazing experiments were conducted to better understand the mechanisms that affect the growths of the picophytoplanktons. The abundances of the picophytoplanktons were measured using a flow cytometry.Water column integrated (0~200 m) abundance of Prochlorococcus was higher (26.63 ¡Ó 3.87 ¡Ñ 1012 cells m-2) in spring than either summer (19.07 ¡Ó 4.08 ¡Ñ 1012 cells m-2), autumn (16.05 ¡Ó 2.80 ¡Ñ 1012 cells m-2), or winter (17.89 ¡Ó 5.41 ¡Ñ 1012 cells m-2). During winter, the abundance was significantly (p<0.05) higher at the offshore station (17.89 ¡Ó 5.41 ¡Ñ 1012 cells m-2) than the inshore station (3.19 ¡Ó 2.07 ¡Ñ 1012 cells m-2). The abundance of Prochlorococcus was positively related to water temperature, nitracline depth (Dni), and euphotic depth (Deu), and negatively to surface concentration of N+N or SRP. Prochlorococcus was abundant (>100 ¡Ñ 103 cells ml-1) in the upper 100-m water column. Its maximum (200~300 ¡Ñ 103 cells ml-1) often occurred at the depth shallower than 75 m. The cell density sustained at >25 ¡Ñ 103 cells ml-1 between 100~150 m and was almost nil at the depth deeper than 150 m.
There was no significant seasonal differences for either the abundances of Synechococcus (0.32~1.07 ¡Ñ 1012 cells m-2) or picoeukaryotes (0.16~0.24 ¡Ñ 1012 cells m-2). During winter, the abundances of Synechococcus was significantly (p<0.05) higher in the offshore Kuroshio water (2.94 ¡Ó 0.32 ¡Ñ 1012 cells m-2) than that of the inshore Kuroshio water. Similar trend of offshore (0.52 ¡Ó 0.05 ¡Ñ 1012 cells m-2) higher than the inshore was observed for picoeukaryotes in winter. The dynamics of Synechococcus abundance was positively related to surface SRP concentration and negatively to Dni. The picoeukaryotes abundance was positively related to surface N+N concentration, and SRP and negatively to Temp, Dni, and Deu. Vertical distribution of Synechococcus showed that the maximum abundance often occurred above 75 m, but was almost nil below 100 m. By contrast, the maximum abundance for picoeukaryotes often occurred between 50~125 m. The abundance of Synechococcus was positively related to the abundance of picoeukaryotes. And their abundance were negatively related to that of Prochlorococcus. Many environmental factors fluctualed parallelly. Dynamics of surface Temp, Dni and Deu were positively correlated to each other and either of them was negatively correlated to the dynamics of surface concentration of N+N or SRP. Surface N+N was positively correlated with surface SRP.
The result of light shadding experiment showed that Prochlorococcus and picoeukaryotes, compared to Synechococcus, were much sensitive to high intensity of light. This suggest that Synechococcus was more tolerant to high light intensity or required more light energy than Prochlorococcus or picoeukaryotes. The results of nutrient enrichment experiments showed that addition of EDTA significantly enhanced the growth of three groups of picophytoplanktons. However, there was no significant difference after addition of either nitrate, Fe, or Cu. Prochlorococcus grew better at 27 ¢XC than 30 ¢XC in the temperature experiment. But there was no difference in the growth rate between 27 ¢XC and 30 ¢XC for Synechococcus or picoeukaryotes The result of grazing experiment showed that there was no difference between the growth rate with and without grazers in the incubation for any of the three groups of picophytoplanktons.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0218111-160923 |
| Date | 18 February 2011 |
| Creators | Huang, Chien-Chih |
| Contributors | Meng-Hsien Chen, Yuh-ling Lee Chen, Kuo-Ping Chiang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0218111-160923 |
| Rights | not_available, Copyright information available at source archive |
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