Using unmanned underwater vehicles as research platforms in coastal ocean studies     

Kendall L.Carder  David K.Costello 《中国海洋大学学报(英文版)》2003,2(2):211-217

The advantages of using unmanned underwater vehicles in coastal ocean studies are emphasized. Two types of representative vehicles, remotely operated vehicle (ROV) and autonomous underwater vehicle (AUV) from University of South Florida, are discussed. Two individual modular sensor packages designed and tested for these platforms and field measurement results are also presented. The bottom classification and albedo package, BCAP, provides fast and accurate estimates of bottom albedos, along with other parameters such as in-water remote sensing reflectance. The real-time ocean bottom optical topographer, ROBOT, reveals high-resolution 3-dimentional bottom topography for target identification. Field data and results from recent Coastal Benthic Optical Properties field campaign, 1999 and 2000, are presented. Advantages and limitations of these vehicles and applications of modular sensor packages are compared and discussed.  相似文献   

Natural and artificial connections between atoll islets in the pacific,their process and environmental impact     

Russell Howorth 《中国海洋大学学报(英文版)》2003,2(2):195-200

Three types of natural connection between atoll islets are described. Causeway, as an artificial way of connecting islets, makes a connection to be completed in a few months. In this case shore adjustment becomes more vigorous than that in natural conditions, resulting in lagoon shore erosion. A causeway without short bridges or culverts should be built close to the lagoon shore to reduce lagoon shore erosion. A causeway-crossing channel assemblage is the worst type among all of the connection engineering constructions because the crossing channel traps sediment and further transports it out of the channel, resulting in long period coastal erosion. Reforming Nippon Causeway in Tarawa Atoll, Kiribati by simple means will stop sand loss, reduce shore erosion and greatly upgrade its stability.  相似文献   

Pathogenicity of vibrios in fish: An overview   总被引：1，自引：0，他引：1  

Norman Y.S.Woo 《中国海洋大学学报(英文版)》2003,2(2):117-128

Bacteria of the genus Vibrio are ubiquitously distributed in the marine environment. Due to the rapid expansion of intensive mariculture and the consequent deterioration of culture conditions, more and more Vibrio spp. have been recognized as pathogenic agents in outbreaks of vibriosis, a serious epizootic disease affecting most wild and farmed fish species worldwide, which has become the most important limiting factor for the development of intensive mariculture industry. Attempts have been made to understand the pathogenicity of vibrios in host fish with the ultimate aim of elucidating the best means for disease control. After an extensive literature survey of the recent advances in the field of fish vibriosis, the pathological changes, virulence factors and associated potential pathogenic mechanisms, transmission routes and related environmental factors involved in outbreak of vibriosis, as well as the controlling strategies are reviewed in the present paper.  相似文献   

Isolation of protoplasts from <Emphasis Type="Italic">undaria pinnatifida</Emphasis> by alginate lyase digestion     

Hu?Xiaoke  Jiang?XiaoluEmail author  Guan?Huashi 《中国海洋大学学报(英文版)》2003,2(1):58-61

The aim of this study is to isolate protoplasts from Undaria pinnatifida. Protoplasts of the alga were isolated enzymatically by using alginate lyase, which was prepared by fermenting culture of a strain Vibrio sp. 510. Monofacterial method was applied for optimizing digestion condition. The optimum condition for protoplast preparation is enzymatic digestion at 28°C for 2h using alginate lyase at the concentration of 213.36 U (8 mL) every 0.5g fresh thalline with NaCl 50 and at the shaking speed of 150 r min⁻¹ during digestion. The protoplast yield can reach 2.62±0.09 million per 0.5 g fresh leave under the optimum condition. The enzyme activity is inhibited by Ca²⁺ and slightly enhanced by Fe²⁺ and Mn²⁺ at concentrations of 0.05, 0.08 and 0.10 mol L⁻¹.  相似文献   

国家之间经济发展水平比较与中国的差距     

何蕾  何百根 《世界地理研究》2003,12(3):38-43

为了促进现代化的实现,作者试图找出中国与发达国家之间的经济差距,并选取了世界银行公布数据的三个指标,代入自己设计的简便公式,测得中国与韩国、希腊的经济差距为26年(以2000年基准)。于是作者将发达国家分为一般发达国家和高度发达国家,把发展中国家分为一般发展中国家和发展中的发达国家。作者预计2020年中国将达到发展中的发达国家水平。并预测中国将在2007年经济总量超英国;中国与英国的人均水平差距约为34年。中国与美国经济总量的差距约为35年,中美之间的人均水平差距约为44年,动态差距将在50年以上。结论,中国在2030年将可达到一般发达国家水平,即可实现现代化。  相似文献   

Application of multiple sublethal stress indicators to assess the health of fish in Pamlico Sound following extensive flooding   总被引：1，自引：0，他引：1  

S.?Marshall?AdamsEmail author  Mark?S.?Greeley  J.?McHugh?Law  Edward?J.?Noga  Judith?T.?Zelikoff 《Estuaries and Coasts》2003,26(5):1365-1382

Multiple indicators of sublethal stress (bioindicators) were used to assess the health and condition of two important estuarine fish species in the Pamlico Sound estuary following extensive flooding from three sequential hurricanes that occurred during early fall 1999. Bioindicators ranging from the biochemical to the reproductive and organism-level were used to assess the health of southern flounder and spot in Pamlico Sound compared to the health of these same species sampled from a relatively unaffected references site in lower Core Sound. Many of the physiological, reproductive, immunological, histopathological, and general condition indices suggested that both species, and particularly spot, in Pamlico Sound were sublethally stressed and in poorer condition than fish sampled from Core Sound. The major environmental stressors causing these sublethal stress responses in Pamlico Sound fish appears to be those related to episodic hypoxic exposure or a combination of effects associated with hypoxic conditions such as alterations in preferred habitat and food availability. Although fish populations in Pamlico Sound do not appear to be severely damaged or impaired at this time, organisms that are sublethally stressed can incur increased vulnerability to additional or future stressors such as modified physicochemical regimes, changes in food and habitat availability, and increases in infectious pathogens. Because of the low flushing rate (～1 yr) of Pamlico Sound, recovery rate may be exceptionally slow, prolonging any adverse effects of altered nutrient regimes (such as hypoxia) on the health and fitness of resident fish populations. Flooding from the 1999 hurricanes may have contributed to the short-term health and condition of finfish species in Pamlico Sound and also influenced longer-term recovery and ecological status of this system. Longer-term manifestation of effects from flooding may be of particular concern as the frequency of hurricanes is expected to increase over the next few years and the accelerated uses of the coastal zone places further stress on estuarine resources.  相似文献   

Effects of common reed (<Emphasis Type="Italic">Phragmites australis</Emphasis>) expansions on nitrogen dynamics of tidal marshes of the northeastern U.S.     

Lisamarie?WindhamEmail author  Laura?A.?Meyerson 《Estuaries and Coasts》2003,26(2):452-464

Several recent studies indicate that the replacement of extant species withPhragmites australis can alter the size of nitrogen (N) pools and fluxes within tidal marshes. Some common effects ofP. australis expansion are increased standing stocks of N, greater differentiation of N concentrations between plant tissues (high N leaves and low N stems), and slower whole-plant decay rates than competing species (e.g.,Spartina, Typha spp.). Some of the greater differences between marsh types involveP. australis effects on extractable and porewater pools of dissolved inorganic nitrogen (DIN) and N mineralization rates. Brackish and salt marshes show higher concentrations of DIN in porewater beneathSpartina spp. relative toP. australis, but this is not observed in freshwater tidal marshes whenP. australis is compared withTypha spp. or mixed plant assemblages. With few studies of concurrent N fluxes, the net effect ofP. australis on marsh N budgets is difficult to quantify for single sites and even more so between sites. The magnitude and direction of impacts ofP. australis on N cycles appears to be system-specific, driven more by the system and species being invaded than byP. australis itself. WhereP. australis is found to affect N pools and fluxes, we suggest these alterations result from increased biomass (both aboveground and belowground) and increased allocation of that biomass to recalcitrant stems. Because N pools are commonly greater inP. australis than in most other communities (due to plant and litter uptake), one of the most critical questions remaining is “From where is the extra N inP. australis communities coming?” It is important to determine if the source of the new N is imported (e.g., anthropogenic) or internallyproduced (e.g., fixed, remineralized organic matter). In order to estimate net impacts ofP. australis on marsh N budgets, we suggest that further research be focused on the N source that supports high standing stocks of N inP. australis biomass (external input versus internal cycling) and the relative rates of N loss from different marshes (burial versus subsurface flow versus denitrification).  相似文献   

Variation in surface turbulence and the gas transfer velocity over a tidal cycle in a macro-tidal estuary   总被引：2，自引：0，他引：2  

Christopher?J.?ZappaEmail author  Peter?A.?Raymond  Eugene?A.?Terray  Wade?R.?McGillis 《Estuaries and Coasts》2003,26(6):1401-1415

The gradient flux technique, which measures the gas transfer velocity (k), and new observational techniques that probe turbulence in the aqueous surface boundary layers were conducted over a tidal cycle in the Plum Island Sound, Massachusetts. Efforts were aimed at testing new methods in an estuarine system and to determine if turbulence created by tidal velocity can be responsible for the short-term variability ink. Measurements were made during a low wind day, at a site with tidal excursions of 2.7 m and a range in tidal velocity of nearly 1 m s⁻¹. Estimates ofk using the gradient flux technique were made simultaneously with the Controlled Flux Technique (CFT), infrared imagery, and high-resolution turbulence measurements, which measure the surface renewal rate, turbulent scales, and the turbulent dissipation rate, respectively. All measurements were conducted from a small mobile catamaran that minimizes air- and water-side flow distortions. Infrared imagery showed considerable variability in the turbulent scales that affect air-water gas exchange. These measurements were consistent with variation in the surface renewal rate (range 0.02 to 2 s⁻¹), the turbulent dissipation rate (range 10⁻⁷ to 10⁻⁵ W kg⁻¹), andk (range 2.2 to 12.0 cm hr⁻¹). During this low wind day, all variables were shown to correlate with tidal speed. Taken collectively our results indicate the promise of these methods for determining short-term variability in gas transfer and near surface turbulence in estuaries and demonstrate that turbulent transport associated with tidal velocity is a potentially important factor with respect to gas exchange in coastal systems.  相似文献   

HCl emissions at Soufrière Hills Volcano,Montserrat, West Indies,during a second phase of dome building: November 1999 to October 2000     

Marie?EdmondsEmail author  David?Pyle  Clive?Oppenheimer 《Bulletin of Volcanology》2002,64(1):21-30

HCl:SO₂ mass ratios measured by open path Fourier transform spectroscopy (OP-FTIR) in the volcanic plume at Soufrière Hills Volcano, Montserrat, are presented for the second phase of dome building between November 1999 and November 2000. HCl:SO₂ mass ratios of greater than 1 and HCl emission rates of greater than 400 t day^–1 characterise periods of dome building for this volcano. The data suggest that chlorine partitions into a fluid phase as the magma decompresses and exsolves water during ascent. This is substantiated by a correlation between chlorine and water content in the melt (derived from the geochemical analysis of plagioclase melt inclusion and matrix glasses from phase I and II of dome growth). The matrix glass from the November 1999 and March 2000 domes indicate an open system degassing regime with a fluid-melt partition coefficient for chlorine of the order of 250–300. September 1997 glasses have higher chlorine contents and may indicate a switch to closed system degassing prior to explosive activity in September and October 1997. The OP-FTIR HCl time series suggests that HCl emission rate is strongly related to changes in eruption rate and we infer an emission rate of over 13.5 kt day^–1 HCl during a period of high extrusion rate in September 2000. A calculation of the HCl emission rate expected for varying extrusion rates from the open-system degassing model suggests a HCl emission rate of the order of 1–4 kt day^–1 is indicative of an extrusion rate of between 2 and 8 m³ s^–1. Monitoring of HCl at Soufrière Hills Volcano provide a proxy for extrusion rate, with changes in ratio between HCl and SO₂ occurring rapidly in the plume. Order of magnitude changes occur in HCl emission rates over the time-scale of hours to days, making these changes easy to detect during the day-to-day monitoring of the volcano. Mean water emission rates are calculated to range from 9–24 kt day^–1 during dome building activity, calculated from the predicted mass ratio of H₂O:HCl in the fluid at the surface and FTIR-derived HCl emission rates.  相似文献   

Permian radiolarians,chert and basalt from the Daxinshan Formation in Lancangjiang belt of southwestern Yunnan,China   总被引：2，自引：0，他引：2  

Qinglai?FengEmail author  Shangyue?Shen  Benpei?Liu  Dietrich?Helmcke  Xianggui?Qian  Weiming?Zhang 《中国科学D辑(英文版)》2002,45(1):63-71

The stratigraphical sequences composed of chert and basalt were found in the Daxinshan area of Simao and the Manbie area of Jinghong, southwestern Yunnan. The Middle Permian to ealiest Late Permian radiolarians, such as Follicucullus and Pseudoalbaillella, have been identified from the chert. The chert from the Manbie area of Jinghong is characterized by high SiO₂content (over 92%), large ratios of MnO/TiO₂ (2.15) and low ratios of Al/(Al+Fe+Mn) (≤0.1) and Ce/Ce*(0.4), which indicate that the chert was deposited in pelagic basin. The chert from the Daxinshan area of Simao, however, is characterized by low SiO₂ content, low ratios of MnO/TiO₂ (0.27) and high ratios of Al/(Al+Fe+Mn) (0.49) and Ce/Ce*(0.88), which imply that the chert was deposited in continental margin basin. The basalts from the both areas belong to tholeiite series, and the chemical compositions of their major, rare earth and trace elements show the characteristics of MORB. These results evidence that there are volcanic rocks and chert sequences representing pelagic basin and oceanic basin near continent. These sequences and the formerly reported island-arc volcanic rock sequences imply that the Daxinshan Formation in the Lancangjiang belt represents a sedimentary assemblage formed in active continental margin basin.  相似文献