首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Lignin phenols were measured in the sediments of Sepitiba Bay, Rio de Janeiro, Brazil and in bedload sediments and suspended sediments of the four major fluvial inputs to the bay; São Francisco and Guandu Channels and the Guarda and Cação Rivers. Fluvial suspended lignin yields (Σ8 3.5–14.6 mgC 10 g dw−1) vary little between the wet and dry seasons and are poorly correlated with fluvial chlorophyll concentrations (0.8–50.2 μgC L−1). Despite current land use practices that favor grassland agriculture or industrial uses, fluvial lignin compositions are dominated by a degraded leaf-sourced material. The exception is the Guarda River, which has a slight influence from grasses. The Lignin Phenol Vegetation Index, coupled with acid/aldehyde and 3.5 Db/V ratios, indicate that degraded leaf-derived phenols are also the primary preserved lignin component in the bay. The presence of fringe Typha sp. and Spartina sp. grass beds surrounding portions of the Bay are not reflected in the lignin signature. Instead, lignin entering the bay appears to reflect the erosion of soils containing a degraded signature from the former Atlantic rain forest that once dominated the watershed, instead of containing a significant signature derived from current agricultural uses. A three-component mixing model using the LPVI, atomic N:C ratios, and stable carbon isotopes (which range between –26.8 and –21.8‰) supports the hypothesis that fluvial inputs to the bay are dominated by planktonic matter (78% of the input), with lignin dominated by leaf (14% of the input) over grass (6%). Sediments are composed of a roughly 50–50 mixture of autochthonous material and terrigenous material, with lignin being primarily sourced from leaf.  相似文献   

2.
On average, five to six storms occur in the Qiongzhou Strait every year, causing significant damage to coastal geomorphology and several property losses. Tropical Storm Bebinca is the most unusual and complex storm event that has occurred in this region over the last 10 years. To detect the high-frequency beachface responses to the storm, a pressure sensor was deployed in the surf zone to record the free sea surface height, and the heights of grid pile points on the beachface were measured manua...  相似文献   

3.
Mar泣.H州门】气口Notable Feat盯es of the Mixing in the Lingdingyang Bay·“····一·······”···················……‘”二”·… …’二”·‘’·.”…’二’二’············“”···········”…Y细92五if“(应  相似文献   

4.
Procedures are described to extract, fractionate and analyze organic pollutants in environmental samples. The methods are based on organic solvent extraction to isolate the pollutants, liquid-solid adsorption chromatography to separate the various pollutants into four fractions, and analyses of the fractions using glass capillary gas-chromatography. Based on a number of considerations, the procedures were found suitable for the analyses of trace level organic pollutants in a variety of sample types. The data from these studies has provided important information on the biogeochemistry of organic pollutants in the aquatic environment.  相似文献   

5.
A new conservation measure aimed at protecting the larger broodstock (females with a carapace length between 115 and 129 mm, i.e., window‐size females, WSF) to enhance egg production was implemented in 2003 for the American lobster (Homarus americanus) fishery in the southern Gulf of St. Lawrence, Canada. To assess the effectiveness of this new measure, a tagging project was carried out between 2004 and 2007 in the Hillsborough Bay area with the collaboration of local harvesters. Based on a single mark‐recapture Petersen model, the estimated catch rates of WSF not carrying eggs under the abdomen in the study area varied between 40% and 53%. The catch‐per‐unit‐effort (animals per 100 traps) of both berried (egg‐bearing) and non‐berried WSF increased from 0.2 to 0.8 and 1.0 to 1.6, respectively, between 2004 and 2007. Based on the estimated number of non‐berried WSF in the population observed during the spring fishery between 2004 and 2007, the potential total egg production for WSF was estimated at 1.1 billion in the study area. From this total, 515 million eggs would have been produced by WSF directly protected by the conservation measure, i.e., females that would have been harvested if not for the new regulation. Finally, the contribution of berried WSF to the annual egg production in the study area increased from 4% to 23% between 2003 and 2007 based on the at‐sea sampling programme and the fecundity curve. WSF that represented 10% of the total berried female population in 2007 contributed 23% of the annual egg production. Hence, the protection of WSF seems to be an effective conservation measure to increase egg production based on the catch‐per‐unit‐effort and egg production.  相似文献   

6.
MarineHydrologyN .- p1- 1…………………………………PracticalimplementationofHilbert HuangTransformalgorithmHuangDaji,ZhaoJinpingandSuJilan2 - 15 1………………………………Three dimensionalhydrodynamicmodelofXiamenwatersWenShenghui,CaiSong ,TangJunjianandCaiQifu2 - 171………………………………InfragravitywaveswithinternalwavecharacteristicsinthesouthoftheBohaiSeaofChinaFanZhisong ,GaoGuoping ,YinXunqiang ,FanYuandWuWei2 - 179………………………………Spatialandtemporalvariabilityofhea…  相似文献   

7.
  相似文献   

8.
Marine Hydrologyl············……Fronts and transport of suspended matter zn the Ha叩见hou浅y Su Jiza,(苏纪兰),Wa,9 Ka、那ha,(王康塔)andL,Ya。(李炎)1,············……Hydrographie features of the plume front in the Hangzhou翔y 环几王n君Ka,gsha二(王康塔)and Su了ttan(苏纪兰)2,1··········,··…Residual eurrents in plume front zone of the Hangzhou枷yche,w‘i(陈伟),月“angD‘户(黄大吉)andya,92人a阅Ing(杨昭庆)39··,·········……Suspended sediment tra…  相似文献   

9.
《Oceanology》2011,51(3):541-542

Chronicle

Boris Vasil’evich Shekhvatov (May 2, 1924 to January 20, 2011)  相似文献   

10.
Distinctly different water masses are to be found near the sea surface within 40 km of the coast off Otago Peninsula, south‐eastern New Zealand (45° 50’ S, 170° 45’ E). Although the hydrological regime is complex in this area, the three water masses have a stable relationship to one another: neritic water close to shore, then modified Subtropical Water, and Subantarctic Water off shore. Quantitative zooplankton samples from the upper 150 m were taken from a four‐station, 50‐km latitudinal transect at monthly intervals over 15 months, October 1966‐December 1967. Data were analysed by group‐average sorting methods into a hierarchical classification of 37 components, identified to species where practicable. Each species group was clearly associated with particular stations and from this hydrological affinities were deduced. The classification recognised a primary division between “neritic” and “oceanic” groups of zooplankton, each of which contained further subdivisions. “Neritic” zooplankton contained “coastal” and “shelf” subgroups; “oceanic” plankton contained “transitional” and “subantarctic” subgroups. Zooplankton from Otago waters had hydrological affinities which were consistent with their wider distributions. Presence of subtropical zooplankton in Otago waters helps to resolve confusing differences between various interpretations of surface circulation in the southern Tasman Sea.  相似文献   

11.
Mangroves are an attractive fish habitat because they provide shelter and food for juvenile fishes. However, because mangroves are almost always located in shallow water and in sheltered (i.e., lagoonal, estuarine or bay) environments, the degree to which the latter two factors contribute to the attractiveness of mangrove prop-roots as a fish habitat is unknown. Artificial Mangrove Units (AMUs) were placed at multiple depths and along a gradient from an embayment to, and including, the coral reef. Total fish density and species richness in AMUs placed in the embayment was lower at 1 m depth than at 2 and 3 m depth, suggesting that shallow water is not a prerequisite for the attractiveness of mangrove prop-roots as a fish habitat. Total fish density and species richness were equal or greater in AMUs on the coral reef than in the embayment, suggesting that placement of mangroves in a sheltered lagoonal environment is not solely responsible for the attractiveness of mangrove prop-roots either. After 3 weeks, removal of AMUs did not have a negative effect on total fish density or species richness. However, within the embayment AMU removal resulted in the complete collapse of the assemblage component comprised of species that use mangroves as juvenile habitats, highlighting the need for a species-based approach towards assessing the benefits provided by the presence of mangrove root structure for fishes.  相似文献   

12.
Fishery managers are faced with the challenge of maintaining sustainable fisheries at the lowest possible cost while conforming to international and national obligations. Given that fisheries range from low to high value, there is a real need to understand how to trade ecological and economic risks, and the various costs associated with their management, against the benefits from catch. Key to this is an understanding of (a) the costs corresponding to a given level of acceptable risk, or conversely, (b) the change in risk given a change in cost investment. This paper first defines biological, economic and ecosystem risk at a whole-of-fishery level, and then develops a simple model to quantify the trade-offs between risk, cost and catch. Using as case studies Australia's federally managed fisheries that range from data-rich to data-poor, risk was quantified for target species in terms of both their limit and target reference points (defined as “biological risk” and “economic risk”, respectively), and for ecosystems in terms of overall ecological impact (defined as “ecosystem risk”). A statistical linear model was used to quantify the risk–cost–catch frontier for each of the three forms of risk. The most parsimonious models were statistically significant for each. However, the management and research costs were mostly positively correlated with risk, indicating that these tended to be reactive to risk, as opposed to risk decreasing in response to increased costs. The only model where this was not the case was for the ecosystem risk, which is probably because these risks have only recently been assessed and the management response to these risks across all the fisheries has so far been limited. For target species risks, it was not possible to develop a model for proactive use. However, the method itself has merit and, if the costs were defined to a greater level of resolution, and/or a time-dynamic modelling approach considered, these issues could potentially be addressed.  相似文献   

13.
Hydrographic observations on the Svinøy section, which runs NW from about 62°N on the Norwegian coast to 64°40′N on the prime meridian, have been used to investigate variations in the Atlantic inflow to the Nordic Seas. The data are from the winter 1955 to 1973 and from the spring and the summer 1978 to 1996. The observations show that in the summer there exist two cores of water with salinity above 35.25 at about 100 m depth, but in the spring and the winter the core furthest offshore is less distinct. Geostrophic calculations show that, for all data sets, there are two kernels with northward currents in the Svinøy section: one over the inner part of the continental slope (over 600–800 m depths) and one further offshore (over 1400–2500 m depth). The mean volume transports of Atlantic water in the section are 4.5, 5.0 and 5.6 Sv in spring, summer and winter, respectively. Results from an Empirical Orthogonal Function analysis of the summer data indicate that there is a dual structure in the section when interannual variations are considered. In the western part of the section the temperature and salinity are negatively correlated with the winter North Atlantic Oscillation index, but in the eastern part of the section they are weakly positively correlated. This is not found in the winter data from 1955 to 1973. The geostrophic volume transport in the summer through the Svinøy section is positively correlated with the NAO indices for winter and spring, where the March NAO index gave the best correlation. Also, the summer volume transports west and east in the section seem to be in opposite phase. From the summer data 1978 to 1996 there is a positive linear trend for the eastern transport (+2.4 Sv), but there is a negative linear trend for the western transport (−2.0 Sv). The transport through the whole section has increased by 1.1 Sv during the same similar period. The atmospheric conditions were different in years with relatively low temperatures and salinities in the western part of the section compared to those years with relatively high temperatures and salinities. It is proposed that interannual variations of temperature, salinity and volume transport in the Svinøy section are controlled mostly by a large-scale variable pressure system (i.e. the North Atlantic Oscillation index).  相似文献   

14.
Marine Hydrologyl···························……Estjmatjon of water volume transPQrts through the main straits of the East China Sea z加0 Ba,e:(赵保仁)andFa即Gooho叩(方国洪)15··········……、··········……The effect of internal tides on the vertical structure of tjdal eurrent in the North Huangha1S比 z俪了。:s加二,(赵俊生),‘e叩sh”、,,(耿世江),s。二万朋,l二二夕(孙洪亮)andz加即z,l:(张自历)37··················……,··……Sur…  相似文献   

15.
Explosion for the treatment of underwater soft foundation is a technique newly developed in China. This paper describes the application of the method of explosion to underwater soft foundation treatment of the Great-West Dyke, Lianyungang Port, including the technical characteristics and the effect, selection of explosion parameters, workmanship of construction, requirements of quality and inspection, and the like.  相似文献   

16.
  相似文献   

17.
In two recent studies (Tian et al., Deep-Sea Res. I 43 (1996) 723–738; Campos et al., Deep-Sea Res. II 43 (1996) 455–466), in order to explain the observed temporal variations in the distributions of the dissolved iodine species at the time-series stations in the Mediterranean Sea, the North Atlantic and the North Pacific, diverse assumptions were invoked on the relationships between changes in the speciation of dissolved iodine in the surface oceans and biological production such that the surface enrichment of I− was linked to both regenerated production and primary production while the surface depletion of [IO3−+I−] was linked to “new” production. However, while some of the major conclusions in these studies are critically dependent on these assumptions, the validity of the assumptions has yet to be verified with experimental evidence. On the other hand, while there are still significant unknowns in the understanding of the cycling among dissolved iodine species in the surface oceans, presently available data from laboratory cultures and field observations are consistent with an alternative conceptual model in which IO3− and NO3− are taken up at some ratio to each other during NO3− uptake and almost all of the IO3− taken up is exuded as I−. Thus, the depletion of IO3− and the enrichment of I− in the surface water are linked to NO3− uptake. This alternative model is also consistent with the data sets presented by Tian et al. (1996) and Campos et al. (1996). By linking the surface depletion of IO3− to NO3− uptake, significantly different biogeochemical behavior of the marine dissolved iodine system may be inferred. The extent to which I− may be oxidized to IO3− within the euphotic zone during the residence time of the water in the surface ocean is still an open question.  相似文献   

18.
This study addresses the composition of biogenic matter and the metabolic activity of coastal waters of the eastern Brazilian shelf, bordered by small river–mangrove systems. Oceanic Brazil Current waters induce oligotrophic and near to homogeneous conditions of chemical constituents along the inner shelf. The impact of small river–mangrove systems upon coastal waters is minor and of local nature. Bottom topography, coral reef habitats, and local upwelling also induce minor local spatial variability of dissolved inorganic and organic nutrients and O2 and CO2 saturation levels in the coastal waters. Metabolic activity during the daylight period, inferred from O2 and CO2 saturation levels, varied from slightly autotrophic to heterotrophic.  相似文献   

19.
《Marine Policy》1999,23(3):259-270
Australia’s experience with bycatch policy has been both brief and varied. By far the greatest governmental effort has been devoted to developing policy in relation to the bycatch of dolphins and albatrosses. Although four main factors were common to the development of policy in both examples, the relative influence exerted in each case differed because of the characteristics of dolphin and albatross bycatch. International and domestic influences were equally significant in the development of bycatch policy toward both species. The greatest difference was observed in the relationship between science and NGOs, though. Albatross bycatch policy in Australia was most influenced by science, whereas environmental NGOs were instrumental in action to protect dolphins from driftnet fishing. One implication from this observation is that policy development catalysed by NGO action is less likely to achieve a consensus resolution than policy driven by science.  相似文献   

20.
Tiomin Resources Inc. (“Tiomin”), the proponent of the Kwale Mineral Sands Project in Kenya, presents a response to the article authored by J. O. Z. Abuodha and P. O. Hayombe, entitled “Protracted Environmental Issues on a Proposed Titanium Minerals Development in Kenya's South Coast”, published in Volume 24, Number 2, April–June 2006. This article contains a series of inaccuracies, some grossly misleading and many statements relate to outdated information. Tiomin is greatly concerned at the publication of such a misleading report and is obliged to state the facts correctly. This response seeks to identify the misrepresentation of statements and/or facts in the article and present a correct and accurate perspective on the environmental issues of the project.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号