Distribution Of Salt Marsh Foraminifera In Jiaozhou Bay And Its Environmental Implication

The continuous rising of sea level has become a global environmental problem that influences the sustainable development of human society, and as a result relative scientific problem has become the hotspot of the research on changes of global climate and environment system. Reconstructing past sea-level changes accurately is significant for studying the history of sea level changes, summarizing the law of fluctuation and predicting the future trend. In 1970's, it was found that salt marsh foraminifera's vertical distributions are closely related to tidal level in certain tide regime, which indicated that this character of salt mash foraminifera could be a effective method for the reconstruction of past sea level changes. Consequently, the study of using salt marsh foraminifera as a potential effective tool to reconstruct past sea-level changes has been carried out. Vertical distribution of salt marsh foraminiferal has been studied in many coastal marshes around the world, and furthermore, regional sea-level transfer function based on foraminifera has been developed in some area and has been used to reconstruct past sea-level changes and its precision is proved higher than many traditional methods. However, there are not enough researches carried out in China, even existing research remains in a relatively low level and present achievement are of significant limitations. Along the east Chinese coastline, there are many salt marshes that have developed extensively, which has created favorable environment for the study of coastal salt marsh foraminifera. The surveys and researches on salt marsh foraminifera in China could increase the information of primary regional data of the worldwide distribution of salt marsh foraminifera, which will be helpful for summarizing the rule of foraminiferal distribution around the world, comparing foraminiferal assemblage in different areas and reconstructing local history of sea-level fluctuation. Presently, the impact of global sea-level change on our coast area has become more and more severe, while salt-marsh foraminifera, as proxy of paleo-elevation in salt marshes, could provide accurate record of regional sea-level change , which could help predicting the local sea level change and consequently developing proper and effective coastal area protection. Therefore the research work of this thesis also has important practical significance.The work of the thesis was supported by the research program "Demonstration report- and project implementation plan on establishment of the special marine reserves of coastal wetland in Jiaozhou Bay" (No.HB2005003) funded by Qingdao Municipal Bureau of Ocean and Fisheries. Research project was carried out in two phases: firstly, salt marshes in Jiaozhou Bay were surveyed extensively, primary research on salt-marsh foraminifera distribution being carried out ,more than fifty field samples being obtained, based on which five favorable sites were selected; Secondly, transects were designed in each selected study site and sampling were undertaken in detail on each transect. There are more than 100 samples taken quantitatively in the field; in each sampling site, both elevation and distance have been surveyed. During above two phases, following laboratory work were carried out: live and dead foraminifera were systemic processed, identified and counted respectively, and the sediment grain size, water content and organism content of each sample were measured.Research work is focused on following contents: Based on vegetation, landform and sediment property salt marsh characters were studied. Based on the component of live and dead foraminifera, the assemblages and distribution of salt-marsh foraminifera in Jiaozhou Bay was studied, and the influence of environment variable on foraminifera distribution was discussed. And the environmental characters (elevation, distance from bank, shape of sediments, etc.) were summarized. Finally transfer functions were established based on foraminiferal data of five salt marshes, and the questions that how to select appropriate model and training sets and how to screen out immoderate sample could improve the performance of transfer function were discussed.Conclusions drawn from this research are presented as follows:1. Salt marshes in Jiaozhou Bay are located in diverse sedimentary settings. The Nvgukou, Daguhe and Yanghe salt marshes have developed on estuary tidal flat, Hongshiy marsh is situated on the open coast tidal flat, and Shanjiaodi marsh is located on the sandy river flat of convex bank. The five salt marshes all develop in recent decades with narrow spatial extent and monospecific vegetation community are their common characteristics.2. The living foraminifera mainly consist of salt-marsh species, while the dead assemblages contain mixture of salt-marsh species and the allochthonous subtidal species and salt-marsh species, thus, living assemblage can provide exact information of foraminiferal distribution of salt marsh. Living in strictly limited environment, the salt-marsh assemblage is obvious different from adjacent inter-tidal or subtidal species, and as a result salt-marsh foraminifera could be used as a precise indicator of . environment.3. Most of the agglutinated species of the salt-marsh foraminifera in Jiaozhou Bay are cosmopolitan, while the calcareous ones mainly consists of the species mostly distributed along the east coast area of China, which indicates that salt-marsh foraminifera in Jiaozhou Bay not only have the common character of foraminifera assemblage, but also have obvious local character.4. The environment difference caused the diversity of salt-marsh foraminifer's zonations. Hongshiya and Daguhe marsh both possess gentle slope and considerable elevation difference, in which foraminiferal populations show vertical zonations, indicating elevation is the effective factor. However Nvgukou and Shanjiaodi marsh are relatively flat but possesses a more variable microtopography, and no zonations present there. Yanghe marsh is divided by creeks, which complicates the simple vertical subdivision of foraminiferal assemblages.5. Transfer functions were calculated respectively based on foraminiferal data of each salt marshes. Performance of transfer functions of Hongshiya marsh is favorable with precise prediction which is comparable with temperate salt marsh reports in other regions of the world. Foraminiferal data of Jiaozhou Bay has the potential utility in paleo-environment study and sea-level reconstruction.