This study reports the first sediment trap mooring results obtained under the SIBEX program (South China Sea Integrated Biogeochemical Experiments). Two strings of sediment traps were deployed respectively at M1 located to the southwest of Taiwan, and M2 in the northern basin of the South China Sea (SCS). Box cores were also taken at several sites to the south of M2. The main purposes are to measure settling particulate fluxes at various depths for the studies of temporal and spatial variations of the particulate flux and 210Pb activity. The box cores were used to determine the sedimentation rates. These are to enhance our understanding of the characteristics of the particulate distribution and the roles the particulate matter plays in the biogeochemical processes in the SCS. Particulate fluxes measured from different depths at M1 and M2 generally increase with depth. In temporal variation, M1 has higher amplitudes than M2, with highest amplitudes at 948 m where highest flux (2025 mg/m2/d) was observed. The particulate flux at 948 m has higher values than at 248 m, probably due to lateral transport. At M2, the particulate flux at 240 m has higher values with greater amplitudes than at greater depths, i.e. 1240 m, 2240 m and 3240 m, where their particulate fluxes show a synchronous trend with small amplitudes in temporal variation. The time-averaged particulate flux for each trap ranges from 199 to 554 mg/m2/d, consistently higher than previous observations (76~104 mg/m2/d). However, our values are comparable to the mean particulate flux (280 mg/m2/d) estimated from terrigenous inputs. The apparent changes in particulate flux in the SCS over the past ten years warrants further investigations. The temporal variations of Pb-210 show a synchronous trend and a rapid increase with depth as observed at M1 and M2. This rapid increase of Pb-210 with depth reflects effective scavenging by sinking particulates although particulate concentrations are low. The loss on ignition (L.O.I.) at M1 and M2 was inversely correlated with Pb-210, indicating that Pb-210 was expelled from biogenic particulates or organic matter. The particulate fluxes around 240 m at M1 and M2 were generally positively correlated with the L.O.I., suggesting that the high particulate fluxes are probably contributed by biogenic particulates or organic matter. The sedimentation rates as determined from excess Pb-210 profiles range from 9.01~23.13 cm/100yr. These rapid sedimentation rates reflect the effect of mixing and additional sediments accumulated through lateral transport. The surface layers of these cores were subject to perturbation and mixing, based on the penetration depths of the excess Pb-210. The Pb-210 flux estimated from the inventory of excess Pb-210 in the sediments is much greater than that observed from the traps, suggesting that additional Pb-210 has been accumulated via lateral transport and slumping of nearby surface sediments. Based on the mean particulate flux observed, one may roughly estimate the corresponding sedimentation rate of about 10 cm/ka, which is an order of magnitude lower than those determined by the excess Pb-210 method. Because the upper layers of the sediments have been strongly disturbed and mixed with the additional sediments accumulated through lateral transport, the sedimentation rates as determined by the excess Pb-210 method are probably over-estimated by a factor of 10 to 20.

The time-series sediment traps were deployed in the northern South China Sea (NSCS) to collect settling particles to study the spatial and temporal variations of particle fluxes, particle sources and particle compositions. Each recovered sample was analyzed to determine the particle flux, major compositions (OM, Carbonate, opal and lithogenic materials) and trace metals (Al, Fe, Mn, Cd, Zn). The data were employed to elucidate the biochemical processes in controlling particle and chemical fluxes. The results show that the particle fluxes vary significantly in time and space, and were apparently related to terrestrial inputs and monsoon-effected processes. Episodic events such as typhoon and earthquakes also effected the fluxes considerably. Vertical fluxes generally decreased with depth for biogenic components (POC, carbonate, opal) but increased with depth for the lithogenic component. Most lithogenic fluxes below the surface were likely derived from lateral transport and decreased with distance away from Taiwan Island. Biogenic fluxes in surface layers were generally higher in winter than in otherseasons, which may be resulted from the elevated primary production in winter. Typhoons also enhanced biogenic fluxes in surface layers but biogenic fluxes were diluted in deep layers by strong lithogenic fluxes. Carbonate dominated the biogenic fluxes in the upper layer and may play as the major ballast in the transportation of biogenic materials through the water column. The C/N ratios of organic matter increased generally with depth implying that nitrogen was preferentially decayed over carbon through the water column. Lithogenic elements such as Al, Fe, Mn were closely correlated and increased in fluxes with depth. However, microelements associated with biogenic materials (Cd, Zn) displayed a significant decrease in content with depth, showing a rapid recycling in water columns.

The dynamics of marginal seas is complex in terms of carbon dioxide absorption and release. This thesis analyzes data collected in the southern Taiwan Strait and in the South China Sea. In order to deduct the influence of temperature on the fCO2, fCO2 is normalized to the average water temperature (fCO2 mean). In the spring of 2008, in the Taiwan Strait, when salinity was smaller than approximately 33.8, measured fCO2 mean and salinity had a negative correlation; but when the salinity was higher than approximately 33.8, the correlation was positive. When salinity was smaller than apprx. 33.8, fCO2 cal. mean correlated slightly negatively to chlorophyll. This indicates that the low fCO2 cal. was not only caused by the increase of the CO2 solubility at lower temperatures, but also by the biotic photosynthesis. On the contrary, when the salinity was higher than apprx. 33.8, fCO2 cal. mean and the chlorophyll held positive correlation. It indicates that the influence of photosynthesis was reduced. In this case, the primary factor of fCO2 cal. change was due to the mixing of the high normalized dissolved inorganic carbon (NDIC=35¡ÑDIC/S) China Coastal Current with low NDIC seawater. With a raise of seawater temperature, then a decrease of the CO2 solubility, seawater became a source of carbon dioxide. In the summer of 2008, the northern South China Sea was influenced by Pearl River plume, resulting in lower fCO2 and salinity. The fCO2 of the China coast was influenced not only by the Pearl River plume, but also by the Jiulong River plume and upwelling. The Taiwan Strait water mass mainly contains the South China Sea water, a Kuroshio branch and the China Coast Current. During an El Niño year, the monsoon weakens, so that the volume of Kuroshio entering the South China Sea increases. However, for La Niña years, the monsoon strengthens, therefore the volume of the Kuroshio entering the South China Sea decreases. As a result, the Taiwan Strait water changes interannually due to different mixture of seawater of the Kuroshio and the South China Sea. The southern Taiwan Strait could be divided into the Penghu Channel and the western strait. During an El Niño summer, the Penghu Channel is occupied by waters with high temperature, salinity and pH, but low NDIC and nutrients. This is because more Kuroshio waters enter the South China Sea, then move northward to the southern Taiwan Strait. The hydrology in the Penghu Channel in normal years shows different result from season to season. In the summer, the Penghu Channel contains low temperature, salinity and pH water. In winter, waters with high salinity and pH, but low AOU, NDIC and nutrients prevail. This indicates that less Kuroshio waters enter the South China Sea in summer than in winter. The hydrology of the Penghu Channel changes decidedly from season to season in a normal year but spring, summer and fall have no clear change in the El Niño period, because more Kuroshio waters enter the South China Sea in summer. The wind effect during the El Niño period becomes weakened, have the hydrology during summer monsoon is similar to the hydrology in spring and summer. The waters of the Penghu Channel reach the highest pH, but the lowest AOU, NDIC and nutrients in winter. Older waters from upwelling move to the north in the western Strait during spring and fall in a normal year. However, during the El Niño period, possibly due to the weaker monsoon, such upwelling signal is reduced. Waters of the western strait in winter have higher temperature, salinity and pH, but lower NDIC during the El Niño period compared to a normal year. This indicates that the El Niño influences not only the Penghu Channel but also the entire southern Taiwan Strait in winter.

A previously un-described filamentous non-heterocystous cyanobacterium was isolated from the South China Sea. Molecular phylogenetic analyses together with morphological observations suggested that this organism should be assigned a new specific epithet. It was designated as Leptolyngbya nodulosa Li et Brand. Filaments were enclosed in a sheath, and were unusual in their flattened appearance as seen in cross section and in the frequent occurrence of a void space (as seen by transmission electron microscopy) between the trichome and the sheath. A distinctive feature of L. nodulosa was the presence, under low light intensities, of previously un-described multicellular structures (nodules). A L. nodulosa nodule consists of a portion of a filament folded and twisted into a distinct unit surrounded by a firm continuous sheath. Nodules were highly variable in size and shape, and occurred at irregular intervals along the filament. They disappeared from filaments of cultures grown at relatively high light intensities. L. nodulosa cultures could be grown indefinitely in media devoid of any source of combined nitrogen. Acetylene reduction assays showed that L. nodulosa cultures fix dinitrogen in the dark period of a diurnal cycle under microoxygenic conditions. The addition of DCMU ([3-(3,4-dichlorophenyl)-1,1-dimethylurea], an inhibitor of Photosystem II) to a culture of L. nodulosa induced much higher rates of dinitrogenase activity and altered the cycle of activity such that most acetylene reduction occurred during the light. Measurements of dinitrogenase activity in the presence of chloramphenicol (an inhibitor of protein synthesis) indicated that dinitrogenase is synthesized in darkness and destroyed in the subsequent light period. In the presence of DCMU, a much higher dinitrogenase activity is measured, but in this case only in the light. Neither the dark-mediated dinitrogenase in the absence of DCMU nor the light-mediated activity in the presence of DCMU could be sustained for more than two days without a photoperiodic light/dark cycle. Dinitrogenase activity occurred only in non-axenic cultures of L. nodulosa. A single nifH gene, with an identical sequence in axenic and non-axenic cultures, was isolated. The requirement of heterotrophic bacteria for dinitrogenase activity in L. nodulosa is not yet understood.

No description available.

Graduate

China and the South China Sea region will play an important role in global and US strategic policy for the foreseeable future. Because China is an upcoming global economic power, the US and other nations must become cognizant of China's motivations in the South China Sea in order to avoid conflict, which seems inevitable. The purpose of this thesis is to examine China's conflicts/tensions in the South China Sea, specifically the Spratly Islands, Paracel Islands, Taiwan, ASEAN, and US Navy. Discussions on the evolution of the People's Liberation Army Navy (PLAN) will also provide additional insight to China's actions in the region. Understanding China's history, role, and claims in the region begins to paint a picture that the PLAN are operating under a principle very similar to the Monroe Doctrine, which allowed the US unfettered access to the Caribbean Sea and Gulf of Mexico. Lastly, the thesis will demonstrate that the Chinese version of the Monroe Doctrine as well the country's desire to establish dominance in the South China Sea, which she sees as her "lost territory", is derived from the fear of an encirclement strategy implemented by the US and a nascent US-backed collective security regime, ASEAN. / Master of Arts

This dissertation conducts a genealogy of freedom of the seas discourse in United States foreign policy in order to problematize the contemporary representation lying at the heart of American political-military strategy in the Western Pacific. This project aims to accomplish two goals. First, this project aims to show that freedom of the seas is not an enduring historical principle consistently championed by the United States, as is often claimed in contemporary governmental publications. Rather, it shows that the current understanding is a recent phenomenon that emerged after the Second World War. By highlighting the contingency of the contemporary understanding of freedom of the seas, this work seeks to show that such discourse is not a necessary foundation on which to place American political-military strategy. The second objective of this genealogical analysis is to show that the contemporary freedom of the seas discourse in U.S. foreign policy is not an altruistic principle championed on behalf of the global community, but rather facilitates American control over the global ocean space. By showing that freedom of the seas is a mechanism of sea control, this work aims to show that in an era of maritime great power competition, strategies predicated upon the discourse are more dangerous than would otherwise appear. Together, this genealogical analysis, and the two goals that are made possible by it, will make a substantive contribution to the critical strategic studies literature, in conjunction with the wider critical security studies literature, by showing that American political-military strategy in the South China Sea can and should be reconceptualized. / Doctor of Philosophy / Currently, the United States is locked in a fierce competition with China in the South China Sea. The United States believes that Chinese actions in the region, such as claiming large swaths of maritime territory, constructing militarized artificial islands, and deploying weaponry designed to endanger American forces operating in the region, violates the principle of freedom of the seas. The United States asserts that it has consistently championed the principle freedom of the seas because it is the essential foundation of international peace and prosperity. Due to this, the U.S. claims that it will continue to defend the principle of freedom of the seas against Chinese depredations. However, this dissertation argues that the United States' political-military strategy in the Western Pacific is misrepresenting the concept of freedom of the seas and therefore failing to see the dangers at stake in the regional confrontation. To show this, this work writes a history of how the concept of freedom of the seas has been used in U.S. foreign policy over the course of American history. Such a history shows that the concept of freedom of the seas has not been consistently championed by the United States and is not an altruistic principle defended on behalf of international peace and prosperity. Instead, this project shows that the concept of freedom of the seas is used by the United States to facilitate control over the world's oceans on behalf of U.S. interests. It is problematic to portray the pursuit of American national interests as a universal altruistic good because it does not leave room open for compromise. In a time where China is rapidly developing their military forces to control sea themselves, basing American political-military strategy on the concept of freedom of the seas is increasingly dangerous.

published_or_final_version / Comparative Asian Studies / Master / Master of Arts

published_or_final_version / abstract / Ecology and Biodiversity / Master / Master of Philosophy