最新刊期
期 28 ， 1987
- 摘要：The Three Gorges Dam now under planning will drastically change the seasonal distribution pattern of the runoff (it wi1l increase from January through April, and decrease in October). A multidisciplinary investigation has been conducted on the impact of its change on estuarine environment and distribution pattern of marine fishes and invertebrates. The relationship between the Changjiang (Yangtze) River runoff and the hydrographic, hydrochemical and sedimentary environments, the primary productivity, the species composition and abundance of phyto-and zoo-plankton, benthos and nekton in the Changjiang River Estuary and adjacent waters has been analysed. The in luence of environmental factors including the Changjiang runoff on the biological community and stock size of economic species has also been discussed. Results of monthly survey and data analysis showed that after completion, the Three Gorges Reservoir will store water in the rainy season to the levels of 150一180 meters and .the distributional range of the hrackish water in the Changjiang River Estuary wi1l be changed from the original 4550k㎡ to 1800k㎡and the estuarine salinity will rise by 1--4. The 30 isohaline wi1l shrink back to the mouth. The mean salinity gradient will rise simu1taneously, the contents of nutrient salts and organic compounds in the water will decrease accordingly, .and the high concentration area will also shrink back towards the estuary. The change of oceanographic environment will change the species composition, the distribution pattern and abundance of living organisms; the biological productivity will also de?rease. Results of the analysis of fish and invertebrate samples and oceanographic data showed that the change of water level of the Three Gorges Reservoir will affect the stock of important fishes and invertebrates to various extents. Caloulation showed that the stock index of marine fish will be ,reduced by about 5% to 15%. The location of the center of fishing grounds will also be changed somewhat. In the period from January to April, increasing runoff will benefit the reproduction and recruitment of fish population.关键词：THREE GORGES PROJECT,ECOLOGY AND ENVIRONMENT,CHANGJIANG RIVER ESTUARY
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发布时间：2023-04-28 - 摘要：Hydrographic characteristics in the ChangJiang River Mouth area are described for four seasons. The paper points out that there is an upwelling area off the mouth, which may be caused by upward climbing of Taiwan Warm Current along the slope bottom. By the statistics the discharges of the Changjiang River, Taiwan Warm Current and wind stress on the study area are the main factors causing the Changjiang River Diluted Water to turn to the northeast.关键词：TEMPERATURE AND SALINITY DISTRIBUTION,UPWELLING PHENOMENA,CHANGJIANG RIVER MOUTH AREA
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发布时间：2023-04-28 - 摘要：The distribution and variations of Changjiang Diluted Water fronts at the surface and bottom layers in different seasons and years are described. The front boundary between the Changjiang Diluted Water and high salinity water of the open sea is roughly along the isohaline 30, 31.The positions of the front at surface are changed in large scale with the discharge of Changjiang River Diluted Water, but at bottom layer they are less changed. Besides the above fronts，secondary fronts in the interior of Changjiang Diluted Water are often found. The variation of strength of halocline in the mouth area is discussed, from which the upwelling in this area can be proofed once more. Possible impact of the Three Gorges Project on the fronts and the area of Changjiang Diluted Water is also discussed.关键词：CHANGJIANG DILUTED WATER FRONTS, DISCHARGE ,CHANGJIANG RIVER
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发布时间：2023-04-28 - 摘要：Based on the historical runoff data of the Changjiang River and the current data from anchor stations within the Changjiang Estuary and its adjacent area since 1950s, some predictive models are established to predict discharges of the Changjiang River at Station Datong from the regulated discharges of the Changjiang River at Station Yichang according to the Three Gorges Project, and on the basis of which impacts of the Three Gorges Project on tida1 currents and residual currents off the Changjiang River mouth are also analyzed. The results show that after the discharge at Station Yichang is regulated, the discharge at Station Datong will be markedly changed and the changed discharge could reach as much as 50 per cent or more in certain months of certain years, which will have a significant influence on the ecosystem. And a secular trend of the discharge reduction at Station Datong will have even greater influence on the ecosystem.关键词：THREE GORGES PROJECT, CURRENT FIELD OFF THE CHANGJIANG RIVER MOUTH
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发布时间：2023-04-28 - 摘要：The current structures of the Changjiang River Plume in the flood, dry and transitional seasons are briefly analyzed by using data from anchor stations obtained since 1950s. The main results are as follows: (1)In the flood season, there exists a jet-like flow area off the North Passage, where the maximum speed of the observed residual current could reach 103cm/s at the surface layer and the Changjiang Diluted Water( CDW)goes in such a way that it usually runs southeastward to eastward nearby the river mouth at first and then diverts to the northeast. (2) In the dry season the CDW is confined to a narrow band west of 122°33'E, extends to the south or southeast off the South Passage, and at the surface layer behaves like a quasi-geostrophic current instead of a jet-like current.(3) In the transitional seasons (spring and autumn) the main current speeds within the CDW are much less than that in the flood and dry seasons and its behaviour seems to be unstable. (4) The difference of the current structures for different seasons owes its origin to the seasonal differences of the monthly averaged discharge of the Changjiang River and its partitions in three branches-North Passage North Channel and South Channel. (5) The instability of the current structure in the nearshore section is caused by interaction between local wind field. coastal current. the Taiwan Warm Current and particularly, monthly averaged discharges in the above three branches over the complex topography.关键词：CHANGJIANG RIVER MOUTH,CURRENT STRUCTRES,THEIR SEASONAL VARIATIONS
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发布时间：2023-04-28 - 摘要：In order to estimate the influence of the Three Gorges Project on the deposition and geochemistry characters in the river and its adjacent waters, we have carried out 5 investigations on sedimentation, suspended samples, shallow stratum measurement, etc. during 1985-1986 in flood and dry seasons, and studied depositional structure and geochemistry characters.关键词：THREE GORGES PROJECT,DEPOSITIONAL STRUCTURE,GEOCHEMISTRY CHARACTERS ,CHANGJIANG RIVER ESTUARY
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发布时间：2023-04-28 - 摘要：Based on the investigations of the nutrients in the Changjiang River Estuary and its adjacent waters during Aug. 1985 to Jul. 1986, the spatial-temporal distributions and changes of the nutrients (P, Si and N )and their removal processes in the estuary and the relationship among the nutrients, the flow of the Changjiang River and phytoplankton are discussed. The relation equations between the transports of the nutrients from Changjiang River water into sea and the flow of the Changjiang River are presented. The annual transports of the PO4-P, SiO3-Si, and total inorganic N from Changjiang River water into the sea are estimated to be 1.4×104, 204.4×104 and 88.8×104 tons respectively. The effects of the Three Gorge Project on the distributions and changes of the nutrients in the Changjiang River Estuary and its adjacent waters are forecasted.关键词：CHANGJIANG RIVER ESTUARY, NUTRIENTS,THREE GORGES PROJECT
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发布时间：2023-04-28 - 摘要：The distribution and variation of particu late organic carbon(POC) and dissolved organic carbon (DOC) in and around the Changjiang River Estuary are studied from summer in 1985 to spring in 1986, for the first time. The concentrations of POC and DOC were affected by the freshwater of the Changjiang River, so POC and DOC are directly proportional to salinty. The determined concentrations of POC and DOC are in the range of 0.5-1.4mgC/L and 2.1-5.6 mgC/L repectively. The average concentrations of POC and DOC are 3-4 times and 30-40 times higher than that in deep waters. There is a correlation between DOC or POC and temperature to some extent, higher in summer and lower in winter.关键词：CHANGJIANG RIVER ESTUARY,PARTICULATE ,DISSOLVED ORGANIC CARBONS
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发布时间：2023-04-28 - 摘要：Investigations on distribution patterns and variation of dissolved oxygen (DO) were carried out around the Changjiang River Estuary in August and November of 1985 and in January and May of 1986. The results showed that there was a significant negative correlation between DO and temperature in autumn and winter. DO was supersaturated in spring and summer due to high content of phytoplankton with average oxygen saturabilities of 105% and 112%, separately. The maximum value of DO (15.32mg O2/L)was found in the middle part of the area during summer with oxygen saturability of 221%, phytoplankton content of 7.82×107 cells/m3, and chlorophyl-a concentration of 38.3 mg/m3, correspondingly.关键词：CHANGJIANG RIVER ESTUARY,DISSOLVED OXYGEN
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发布时间：2023-04-28 - 摘要：The construct of the Three Gorges Project will have a great effect on ecology and environment of the Changjiang River. Estuary. In order to understand the present environmental state of the Estuary before the construct of the Project, five cruises in different seasons were carried out in 122°-124°E, 30°45′-32°00'N sea areas and the river sections affected by tides The surveys indicate that COD average concentration reachs a maximum of 2.73m /L in May, nd a minimum of 1.18mg/L in October. By the results of the surveys the paper discusses the characterestics of COD distribution in the Changjiang River Estuary.关键词：CHEMICAL OXYGEN DEMAND,CHANGJIANG RIVER ESTUARY
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发布时间：2023-04-28 - 摘要：In the paper, investigations of 30 stations in the Changjiang River Estuary and the inshore (122°-124°E，30°45′-32°00′N) were made in Aug.and Octr 1985, and Jan. 1986. The determinations of Zn, Cd, Pb and Cu in surface wate were done using the method of inverse polarography with anti-adsorption physically coated mercury film electrode system.关键词：TRACE METALS,CHANGJIANG RIVER ESTUARY
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发布时间：2023-04-28 - 摘要：During the period of 1985-1986, the annual average of chlorophyll-a contents of sea water and phytoplankton cells in the estuarine area of the Changjiang River were 3.3mg/m3 and 3×107 cells/m3, respectively. The tendencies of the horizontal distribution and seasonal variation of the chlorophyll-a were very similar to those of the phytoplankton. In the flood season (from June to September) the phytoplankton patch of the largest range and the greatest density of cells occurred in the middle part of the investigated area and only a small patch whose cell density was one fifth of that of the flood season occurred near the estuary in the other months. In summer, the composition of the phytoplankton was very complex, the fresh-water species,Scenedesmus spp. and Pediatrum spp., speared in the estuary, the eurythermal and low saline species such as Skeletonema costatum(Grev.)Cleve occupied the mddle part and some tropical species, Hemidiscus hardmannicnus(Grev.) Mann and Amphisolenia bidentata Schroeder, etc, appeared in the southeastern and northeastern parts of the investigated area. The distribution patterns of the above phytoplankton species of different ecological natures showed the dynamic state of the different water masses in the investigated area. The main factor on the variation of phytoplankton cell numbers is the flow capacity of the Changjiang River. The phytoplankton peak(108 cells/m3) often occurred in the months with flow capacity of 34,000 to 40,000m3/s. When the flow capacity is more than 45,000m3/s, the transparency of the sea water falls to less than 0.5m, and becomes the limiting factor to the phytoplankton growth, although a great deal of nutrients were carried into the estuarine area by flood, yet those rich nutrients were not beneficial to the phytoplankton growth.关键词：PHYTOPLANKTON,CHANGJIANG RIVER,QUANTITATIVE VARIATION ,ECOLOGICAL ANALYSIS
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发布时间：2023-04-28 - 摘要：In the estuarine area of the Changjiang River, the primary productivity is rather high, being 1,062mg C/(㎡?d) in average, and has a very large seasonal fluctuation range. It reaches maximum, 3,670. 2 mgC/(㎡?d), from June to September and decreases to 150mgC/(㎡?d) from April to May and October to November, 24.7mgc/ C/(㎡?d)in January. The annual average of the primary production is about 359.34gC/㎡.It increases gradually eastwards from the Changjiang Estuary to 123°30′E(the middle part of the investigated area), then decreases to the east boundary of the investigated area (124°00'E). Obviously, the runoff of the Changjiang River is the main factor for the dynamics of the primary productivity, and the upwelling of the Zhejiang Coast and the runoff of the Qiantang River cannot be neglected.关键词：PRIMARY PRODUCTIVITY,CHANGJIANG RIVER ESTUARY
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发布时间：2023-04-28 - 摘要：The present paper is the result about the ecological stutides on the zooplankton in the Changjiang River Estuary(121°31'--124°E,30°45′N-32°00′N) The net samples were collected eleven times at thirty-forty one permanent stations from August 1985-july 1986. T'he total biomass of zooplankton is highest in Changjiang River Estuary. In general,it reaches a maximum in July and reduces to a minimum in April. This type of seasonal variation was essentially the same as observed in the Changjiang River, Estuary in 1958-1959, 1960 1961,1972,1973,1985-1986. The distribution zone of high biomass of zooplankton was located at the mixed place of different water masses during the period of maximum river runoff.When runoff from the river is low, the distribution zone of high biomass of zooplankton was located at the coastal water of the Changjiang River Estuary. A total about 169 species of zooplankton and 10 groups of plankton larvae were found in the investigated area. The zooplankton of the area is dominated by Copepoda and Chaetognatha, the important species of which are Calanus sinicus, Labidocer euchaeta,Acartia pacifica,Tortanus vermiculus, Schmackeria poplesia, Sagitta enflata and Sagitta nagae. Based on the relation of biological characteristic and distribution of species with the current system, the zooplankton may be divided into four ecological groups: (1)freshwater species; (2)semi-saline estuarine species, (3)low salinity neritic species,(4) warm water species.关键词：ZOOPLANKTON,CHANGJIANG RIVER ESTUARY
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发布时间：2023-04-28 - 摘要：This paper presents the results of ecological study of the macrobenthic fauna in the Changjiang River Estuary. The materials for study were collected from 35 stations west of 123°E and 30°30′-32°00′N, in April and October 1988. The distribution of species of macrobenthos and their biomass and density were described and discussed. After flood season, the center of the distribution of some species drew off shore and near the northern of the explored region, but the estuarine species, for example Heterocossura aciculata, developed again in the river mouth. The number of species and the biomass and density of macrobenthos, particularly Mollusca, decreased. The areas of high biomass and density visibly receded to the southern and northern of the explored region, particularly in the south.关键词：CHANGJIANG RIVER ESTUARY, MACROBENTHOS,SEASONAL VARIATION
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发布时间：2023-04-28 - 摘要：Based on the data of physical, chemical, geological and biological oceanographic factors and living resources obtained by Changjiang River Estuary Multidisciplinary Survey carried out in 1985-86, the changes in species diversity, abundance and distribution pattern were analysed and predicted. The change of water discharge in middle and lower reaches of the river after the Three Gorges Reservoir went into operation and the decrease of runoff in estuarine area (16% or 42% decreased in October for 150m or 180m damb height respectively) and the resulted change (increase) of estuarine water salinity will change the distribution area of most epifauna--nektobenthos which will expand their distribution area toward the coastline and river mouth. But the extent of influence will be less in rich water year than in poor water year. The increase of discharge in dry season, January-April, of 2,000-2,500m3/s will decrease the water temperature in the estuarine area and hence postpone the spawning time of certain species; but it will benefit the reproduction and recruitment of benthic population. The decrease of silt discharge to the estuarine area will increase the transparency of estuarine water, its primary productivity and the flux of organic detritus, which will benefit the herbivores and deposit feeders in benthic community. In gereral, the decrease of silt discharge into the estuarine area will change the distribution pattern of sediments and the environment, and finally the species composition and distribution pattern of benthic fauna, particularly the infauna, as well as the spawning and nursing ground of certain dominant species, especially economically important shrimps and crabs migrated into estuarine waters for feeding or reproduction. But the process of its change will be comparatively slow, not easily observable.关键词：THREE GORGES PROJECT,CHANGJIANG RIVER ESTUARY,BENTHIC FAUNA
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发布时间：2023-04-28 - 摘要：General characteristics of the economically important invertebrates were studied through monthly surveys with twin trawl in the period from September 1985 to August 1986. Sampling was made at each of the 33 stations. A total of about 145,000 individuals of invertebrates, belonging to 67 species, were collected and identified during the surveys. Among them, 48 species were crustaceans and 15 species were molluscs. Besides, data of fishing statistics and environmental factors were collected and analysede.The abundance and biomass of main invertebrate species in the investigated area changed seasonally. The abundance and biomass were 13, 318ind /k㎡ and 313.3kg/k㎡in summer, 12, 894 ind/k㎡and 523.4kg/k㎡ in autumn respectively,which aer much higher than 2283 ind/k㎡ in winter. The ecological characteristics and seasonal numerical distribution of some dominant species. such as the brackish water species Exopalaemon annandalei,E. cariinicauda;the catadromous freshwater species Eriocheir sinensis and the common marine species: Portunus trituberculatus, Ovalipes punctatus, Solenocera crassicornis, Trachypennaeus curvirostris, Parapenaeopsis hardwickii, P. ctlurirostris and Sepiella maindroni, were briefly dcscribcd. The main purpose of the study was to predict the impact of the Three Gorges Project the invertebrate resources. On the basis of fully understanding of the early life history of the woolly-handed crab, Eriocheir sinensis, which is one of the most important economic invertebrate in Changjiang Estuary, a conceptional model was developed. Furthermore, by stepwise regression analysis of multi-variable the relationship between the abundance of the crab seed (Megalopa )and various environmental factors, such as the monthly runoff flow of the Changjiang River and the precipitation, etc. was analysed. According to the presumable regulation of the rived runoff by the Three Gorges Project, the impact on the yield of the seed of wollyhanded crab was estimated. Similarly, the catch yields of the white shrimps and crabs were assessed. Some possible effects of the project on the resources, such as the changes of the distribution patterns of some invertebrate animals and the increase or decrease of their yield, are predictable.关键词：THREE GORGES PROJECT,INVERTEBRATE RESOURCES,CHANGJIANG RIVER ESTUARY
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发布时间：2023-04-28 - 摘要：A total of 20 orders, 80 families and 222 species of fishes have been recorded from the Changjiang River Estuary area. Among them, 167 species, belonging to 18 orders and 68 families were obtained in this survey during Sept. 1985 to Aug 1986(attached list ). Based on this data,bout 39 fish species are relatively important (IRI=0.1) and they are mostly of the Engraulidae, Sciaenidae and Stromateidae families. The abundant freshwater fish is Leiocassis longirostris only. The 176 fish species can be classified into five ecological categories,based for the most part on salinity tolerance. There were freshwater fishes(10 species), anadromous and catadromous fishes (5 species), brackish fishes(10 species ); a large number of species are marine fishes,which include two groups: the euryhaline nearshore fishes and coastal fishes. 15 species of fishes occurring around the year can be called “resident”; the others are all seasonal migratory species and can be referred to as “periodics”.In periodics the warm-season species consisting warm-temperate element and warm-season element are dominant both in number of species and abundence; the cold-season species consisting of a few cold-temperate element and some warm-temperate element are fewer. This study shows that the Changjiang River Estuary area is an importent nursery ground for juvenile of many fish species.关键词：FISHFAUNA,CHANGJIANG RIVER ESTUARY
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发布时间：2023-04-28 - 摘要：For analysing the possible effects of the Three Gorges Project on fishery resources in the Changjiang River Estuary, the fishery survey was made monthly from September 1985 to August 1986 using two-boat trawling for one hour at each of 30 stations in the surveyed water area. According to the survey data, 63,060 fish/k㎡ of mean density, 812kg/k㎡ of mean biomass and 17,054 ton of abundance in the total area were computed for each month. The seasonal changes in these quantities of fish (the highest in autumn, and the lowest in winter) were showed obviously and trended similarly. The habitat distributions of fishes were not even either,and the concentration areas of fishes often occurred in the northeast and the mouth of estuary. The estuary served as an important nursery ground where juvenile fish accounted for 60% in the yearly catch, which peaked in Aug. and Dec. (80.6% and 70.3% respectively)for 14 commercial fishes. In this paper, the abundance and distribution, the ecological habits and the resouces situation of important fishes are discussed one by one. The quality of fish resources were evaluated. The result indicated that the abundance tended towards declining and the composition of length and age tended to simplifying. The study provides a valuable baseline for analysing the effects of environment variations on fishery resources in the Changjiang River Estuary.关键词：fish community,Changjiang River Estuary
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发布时间：2023-04-28 - 摘要：From September 1985 to August 1986, the specimens of the fish community in the Changjiang River Estuary were sampled monthly at 30 stations using pair trawl, and the synchronized surveys of main environment factors were made. Studying results showed that the Changjiang River Estuary was a relatively independent brackish water system, rich in fresh runoff,silt and nutrient salts, with high primary productivity, various and abundant planktons and invertebrates, and changeable sedimentary environment, which provided fishes with complicated and variable environmental conditions and ample food foudation. The temporal and spatial distributions of fishes were controlled by the interactions of physical and biological factors.关键词：fish community,Changjiang River Estuary ,THEIR SEASONAL VARIATION,ABUNDANCE
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发布时间：2023-04-28 -
IMPACT OF THE THREE GORGES PROJECT ON THE FISHERY OF THE CHANGJIANG RIER ESTUARY AND ADJACENT WATERS
摘要：There is compelling evidence that river inflow results in considerable inputs of nutrients.It is shown that freshwater outflow to the sea is an important factor which links variations with biological productivity in coastal waters. The Changjiang River Estuary is the breeding and nursery areas for many organisms and it is also the only way of migration for anadromous and catedromous fishes. The estuary is a mixed zone of fresh and sea water,where the environmental factors are varied and complex in the form of seasonal perrodicity. The abiotic(salinity, temperature, runoff and nutrient salt, etc ) and biotic( primary productivity, phytoplankton, zooplankton and necton )environmental features in the Changjiang River Estuary have been shown in this paper. In one year, the values of factors reach the peak in summer and autumn, and lower in winter, pick up in spring. It is shown that there is obvious relationship between the Changjiang River runoff and environmental factors by regression analysis.关键词：THREE GORGES PROJECT,FISHERY- 141
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发布时间：2023-04-28 - 摘要：We established the simultaneous equations of state variables by means of stepwise regression and basing on the historical materials of hydrology, meteorology and fishery statistical figures, as a useful tool for calculation of the effects of the Three Gorges Project on Changjiang River Estuarine fishery resources On the assumption that Three Gorges Project had been built and 180m design conducted the hydrology data can be drawn up according to the design. Using this tool and the simulant data the impacts of the Three Gorge Project on the fishery resources of Changjiang River Estuary are analysed. The results indicate that, upon the whole, the construction of the Three Gorges Project will have no harmful effects on the estuarine fisheris. The draft 180m design can raise CPUE by 0.0171 t/f per year in the Changjiang River Estuary fishery resources.关键词：NUMERICAL SIMULATION,FISHERY RESOURCES, THREE GORGES PROJECT
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发布时间：2023-04-28
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