JOURNAL OF PLANKTON RESEARCH VOLUME 27, NUMBER 9, PAGES 881–894, 2005

1. Phytoplankton seasonal dynamics in a Mediterranean coastal lagoon: emphasis on the picoeukaryote community JOURNAL OF PLANKTON RESEARCH VOLUME 27, NUMBER 9, PAGES 881–894, 2005 報告學生: 王榮 指導教授: 蔣國平 博士

2. 已完成航次: 2007年7月 細菌(bacteria)與藍綠細菌(Synechococcus)在東海陸棚海域 成長與被攝食速率的時空分布

3. INTRODUCTION irradiance and water temperature (Kuosa, 1991; Agawin et al., 1998, Vaquer et al., 1996). Picophytoplankton (class size: 0.2–2 μm) Synechococcus and Prochlorococcus picoeukaryotic algae

4. Due to its small cell size, picophytoplankton has a competitive advantage to acquire nutrients in resource-limited environments (Raven, 1998), In contrast, under high nutrient levels, is dominated by large phytoplankton (mainly diatoms) The smallest photosynthetic picoeukaryote Ostreococcus tauri (Chre´tiennot-Dinet et al., 1995,Courties et al., 1994). diatoms, cryptophyceae, dinophyceae and small phytoflagellates (Vaquer et al., 1996,Gangnery et al., 2003). picophytoplankton escapes grazing by filter-feeding bivalves because of their small size (Dupuy et al., 2000).

5. seasonal variations in the abundances of picoeukaryotes and cyanobacteria, • the relative contribution of picophytoplankton • to Chl a biomass and primary production by means of size-fractionation (2 μm) • (iii) maximum growth rates of phytoplankton and its mortality rates due to microzooplankton grazing.

6. METHOD Water samples were collected at 8:30 AM inside oyster farming zones (Fig. 1) by immersing two 20-L polycarbonate (PC) jars to a depth of 0.1 m and were immediately brought to the shore laboratory.

7. Chl a concentration Phytoplankton primary production was estimated using the standard 14C technique (Steemann Nielsen, 1952). The biomass-specific primary productivity [P/B, mg C (mg Chl a) -1 h-1] was calculated as the carbon fixation (P) per unit of Chl a biomass (B). Phytoplankton abundances were estimated by flowcytometry

8. Dilution protocols k μ= k- g X Assumption： 1.Specific growth rate of prey is not density dependent 2.Predation is a direct linear function of prey abundance μ X <1000μm <0.2μm 100% 80% 60% 40% 20%

9. 淨成長率=原始成長率-攝食率。稀釋比 μ = k - g X K Trace Metal Solution: Enriched μMax g Unenriched The ratio μ0 /μmax is used to assess the impact of inorganic nutrient enrichment on algal growth and estimate the nutrient sufficiency for phytoplankton growth (Landry et al., 1998). k0 g0 (μ0 = k0 + g).

10. Variations of physical and chemical parameters the annual mean contribution of picophytoplankton (29%) (Courties et al., 1994; Chre´tiennot-Dinet et al., 1995; Vaquer et al., 1996), In warm and productive waters, the decreased contribution of picophytoplankton has been hypothesized to result from increased loss rates, such as strong grazing pressure (Agawin et al., 2000).

11. diatom bloom. Autotrophic picoeukaryotes numerically dominated the phytoplankton community, and represented between 55 and 99.7% of the picoplanktonic cell density.

12. Maximum growth and mortality rates based on Chl a μMax: -0.23~2.63 g: -0.28~1.13

13. total chlorophyll a (Chl a) (Chaetoceros sp. and Skeletonema costatum, respectively). > 2 μm Chl a fraction indicating that grazing pressure on larger algae was negligible in bottle incubations. < 2 μm Chl a fraction

14. Maximum growth and microzooplankton grazing rates based on flow cytometry PEUK GROWTH RATE: 0.31~2.44 CYAN GROWTH RATE: 0.42~1.64 PEUK GRAZING RATE: -0.09~1.66 CYAN GRAZING RATE: 0.25~1.17

15. Nutrient enrichment impact since nano- and micro-phytoplankton (in particular diatoms) in the Thau lagoon are mainly controlled top-down by bivalve suspension feeders (Dupuy et al.,2000), which were excluded from incubations.

16. Phytoplankton carbon assimilation

17. Factors controlling seasonal variations in phytoplankton growth the annual variations in growth rates displayed a strong seasonality which could be related to seawater temperature and/or irradiance.

18. THE END