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Dynamics Of Picoplankton In The East And South China Seas And Some Preliminary In Situ Experiments On Nutrient Enrichment Effects

Posted on:2001-06-12Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y H YangFull Text:PDF
GTID:1100360002950477Subject:Marine biology
Abstract/Summary:PDF Full Text Request
Spatial distributions and seasonal variations of cell abundances of Synechococcus (Syn), Prochlorococcus (Pro), picoeukaryote (Euk) and heterotrophic bacteria (Bact) in the East and South China Seas, and the Jiaozhou Bay were investigated by flow cytometry. Relationships between the four groups of picoplankton and some environmental factors were discussed. In situ nutrient enrichment experiments were performed on board the investigation vessel. Attempts were made on estimating the growth rate of Prochlorococcus through the cell cycle approach, and abundance of marine virus was measured by flow cytometry. The main results are as follow: 1 In the East China Sea, picoplankton with cell size less than 2 i~ m accounted for about 40% of the bulk chlorophyll a (Chl a) biomass. Among them, Syn were the most important contributor. Cell abundance ratios of Pro : Syn were about 10. In the South China Sea, more than 70% of Chl abiomass were contributed by the picoplankton fraction. Carbon biomass of Pro accounted for about 30% of the total carbon biomass of the picoplankton community in the South China Sea. Cell abundance ratios o昮 Pro : Syn ranged between 15?60. Picoplankton community structures were different in the sea basin area from in the Nansha Islands sea area. Distribution of picoplankton and the species composition of the Iv L ttj i~I dii jfi14~ ~ picoplankton were affected by the currents, water masses and the physical and chemical features of the water column. Picoplankton were more important in the open water areas than in the nutrient repleted coastal waters. In winter, the distribution of Pro was limited mainly within the Kuroshio current area, most probably by temperature. In summer, distribution of Pro paralleled the 50m isobath, presenting in most areas of the East China Sea. From a large scale, cell abundances of Pro and Bact varied in an opposite way when going from coastal to the open sea areas. Vertical distribution patterns of picop]ankton were affected by both chemical and physical status, such as stratification of the water column. In the East China Sea where there was shallower upper mixing layer, and nitrate was detectable, the depth of the maximum layers of picoplankton followed the nitracline. Whereas in the basin area of the South China Sea, upper mixing layer was generally deeper and usually with undetectable nitrate, maximum layer of Pro seemed to have something to do with the distribution of ammonia. 2 Nutrient enrichment experiments in the South China Sea suggested that, Syn and Euk were similar ~i characteristics of high demanding for Fe and N. On the other hand, Pro responded more to Co and P than to Fe and N. In 75m in the South China Sea, Fe enriched from a large range of concentrations stimulated the growth of nanoplankton. For the picoplankton, Fe enrichment of nano-molar level increased the cell abundance of Euk, on the other hnad, Syn and Pro had significant responses to higher concentration of Fe enrichment. Although Co stimulated the growth of Pro, vitamin B,2 had little influence on Pro, indicating that Co functioned other than V~,2 synthesis in metabolism processes of Pro. Effects of...
Keywords/Search Tags:Synechococcus, Prochlorococcus, picoeukaryote, heterotrophic bacteria, virus, nutrient enrichment
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