武汉东湖桡足类生物量及生产量的初步研究

本文主要论述1980—1982年武汉东湖桡足类生物量及生产量的测算结果。三周年来在东湖Ⅰ、Ⅱ采样站上共观察到5种剑水蚤:广布中剑水蚤(Mesocyclops leuckarti)、近邻剑水蚤(Cyclops vicinus vicinus)、透明温剑水蚤(Thermocyclops hyalinus)、台湾温剑水蚤(Thermocyclops taihokuensis)、锯缘真剑水蚤(Eucyclops serrulatus)和5种哲水蚤:球状许水蚤(Schmackeria forbesi)特异荡镖水蚤(Neutrodiaptomus incongruens)、右突新鏢水蚤(Neodiaptomus schmackeria)、中华原鏢水蚤(Eodiaptomus sinensis)、汤匙华哲水蚤(Sinocalanus dorrii)。其总年平均生物量为321.74毫克干重/平方米。其中剑水蚤为194.70毫克干重/平方米,占60.51%;哲水蚤为127.04毫克干重/平方米,占39.49%。总年生产量为16.959克干重/平方米。其中剑水蚤为11.225克干重/平方米,占66.19%;哲水蚤为5.734克干重/平方米,占33.81%。年P/B比为52.55;其中剑水蚤为57.63,哲水蚤为46.02。各发育阶段的年平均生物量以桡足幼体最高,其次为无节幼体,卵最低。年生产量则以无节幼体最高,其次为桡足幼体,卵最低。从各种类所占总年平均生物量、年生产量的百分比值来看,广布中剑水蚤的比值最大,其次为球状许水蚤、近邻剑水蚤和特异荡鏢水蚤。       

Zooplankton composition, dominance and abundance as indicators of environmental compartmentalization in Jurumirim Reservoir (Paranapanema River), São Paulo, Brazil

Spatial and temporal patterns in the distribution of the zooplankton in a large tropical reservoir were investigated for a year. The zooplankton was sampled at 10 limnetic stations. Rotifera were richest in number of species and individuals, especially in transitional river–lake zones. They were dominant during the summer in nine sampling stations, and decreased in spring. The main species were Polyarthra vulgaris, Keratella americana, K. cochlearis and Conochilus unicornis. Polyarthra vulgaris was widely distributed. Keratella was more abundant at upstream stations, and a dense population of C. unicornis was observed in a lateral, sheltered compartment. Among copepods, Calanoida were more abundant in spring and Cyclopoida in autumn. Longitudinal gradients in the Calanoida/Cyclopoida relation were observed, with the predominance of Cyclopoida at upstream sampling stations and Calanoida in more lacustrine zones towards the dam. Notodiaptomus iheringi, Thermocyclops minutus and T. decipiens were the main species. Diaphanosoma birgei, the most abundant cladoceran, mainly occurred in lacustrine zones, while Moina minuta was more abundant at riverine sampling stations, generally in association with Bosminopsis deitersi. Peaks of tintinnid protozoans were observed in upstream zones during summer and spring.     

浙江饮用水源地浮游动物群落特征及环境响应

2010年1月至2011年10月,对浙江省16个饮用水源地(H1—H8为河网型,K1—K8为水库型)的浮游动物群落进行季节调查。共记录浮游动物优势种(属)21种(轮虫8种、枝角类5种、剑水蚤5种和哲水蚤3种),各类群第一优势种分别为针簇多肢轮虫(Polyarthra trigla)、长额象鼻溞(Bosmina longirostris)、粗壮温剑水蚤(Thermocyclops dybowskii)和汤匙华哲水蚤(Sinocalanus dorrii)。2年间,河网和水库浮游动物平均密度分别为345.2 L-1和199.4 L-1,生物量分别为0.667 mg/L和0.421mg/L。各类群密度百分比例均以轮虫和桡足类无节幼体为主,甲壳动物以剑水蚤为主。经逐步回归分析表明,浮游动物群落密度(生物量)与河网水质因子(P0.01)之间相关性比水库(P0.05)更密切,总磷和氨氮分别入选了河网和水库所有有效的回归方程中。通径分析和决策系统分析表明,河网的总磷和叶绿素a含量对浮游动物群落变动具有正效应,溶解氧具有负效应;总磷含量是影响河网群落变动的最重要因子,叶绿素a含量则是影响群落增长最主要的限制因子。河网剑水蚤、无节幼体和轮虫群落的密度(生物量)与水体综合营养指数TLIc密度(TLIc生物量)之间有显著的线性回归关系(P0.001),无节幼体密度构成了TLIc密度变动的限制因子,轮虫生物量成为TLIc生物量变动的限制因子,而剑水蚤是一类最重要、稳定的水质指示群落,这对于筛选浮游动物群落的一些拓展性监测指标具有重要的参考作用。     

虾稻综合种养系统浮游动物群落结构及其与环境因子的关系

为探究虾稻综合种养(integrated crayfish-rice co-culture,ICRC)系统浮游动物的群落结构特征及其主要影响因素,对潜江市典型ICRC稻田渔沟和田面水体的浮游动物进行了季度研究,并分析了浮游动物和浮游植物、水体理化因子之间的相关性。结果显示:(1)共采集浮游动物60种,分别包含原生动物、轮虫、枝角类和桡足类12、28、10、10种(属),其中,优势类群为剑水蚤目无节幼体、桡足幼体以及蚤状溞(Daphnia pulex);Shannon-Wiener指数、Margalef指数和Pielou指数的年均值分别为1. 48、3. 42和0. 55;(2)浮游动物密度和生物量的变化范围分别为7. 65～1309. 50 ind./L、0. 08～50. 04 mg/L,年均值分别为360. 0 ind./L、17. 45 mg/L,桡足类和枝角类在密度和生物量上均占有绝对优势;(3)浮游动物物种数、多样性指数(田面除外)、密度和生物量均表现出明显的季节差异,其中密度和生物量在春季显著最高,相关性分析表明浮游动物物种数和资源量主要受总磷、浮游植物密度与生物量的影响;(4)浮游动物的物种数、多样性、密度和生物量在渔沟和田面两种生境间无明显差异。本研究表明ICRC系统中有丰富的大型浮游动物资源未得到利用,同时鉴于浮游动物可作为小龙虾早期生活史阶段的食物来源,需进一步研究秋冬季浮游动物变化,以及如何培育和合理利用此阶段的浮游动物以促进幼虾生长、提高存活率。     

The effects of a colony of the Armenian gull (<Emphasis Type="Italic">Larus armeniacus</Emphasis> Buturlin) on zooplankton in the Lake Sevan littoral zone (Armenia)

The zooplankton of the open and semi-protected parts of Lake Sevan littoral zones that have been affected by the products of vital activity of the colony of the Armenian gull (Larus armeniacus Buturlin) were studied. It was shown that in the open coastal area the number of species is higher as compared to a similar reference site. However, the impact of wave-driven mixing of the water resulted in the lack of significant changes in the number and biomass of invertebrates at the compared observation sites. At the semi-protected part, the number of species, as well as the number and biomass of zooplankton, are significantly higher compared to the reference site. At the nesting area at both types of shoals copepods compose the basis of the zooplankton number and biomass, with Calanoida being part of the dominant complex. At the reference sites of the open shoal Copepoda also prevail; at the semi-protected sites, it is Cladocera that prevail. The basic differences between the effect of the products of the birds’ vital activities and anthropogenic eutrophication on zooplankton were revealed.     

Community characteristics and of zooplankton in Qinzhou Bay

Qinzhou Bay, the biggest bay in Guangxi Province, is very species-rich and is developing a robust marine economy. In recent years, as human impact has increased, problems associated with the environment have become more complicated. Measuring zooplankton diversity and abundance is a way to monitor environmental conditions. According to the data from four ecological surveys of the zooplankton in Qinzhou Bay during 2008 and 2009, a total of 134 species of zooplankton were identified, including 52 Copepoda species, 27 Medusa species, 14 Planktonic larvae, 9 Chaetognatha species, 8 Pteropoda species, 5 Amphipoda species, 4 Cladocera species, 4 Ostracoda species, 3 Thaliacea species, 2 Appendiculata species, 2 Sergestdae species, 2 Protlsta species, 1 Rotiera species and 1 Cumacea species. The fauna was clearly characterized as tropical population. The total species number was highest in autumn, followed by spring, winter and summer. Zooplankton species diversity in Qinzhou Bay has increased compared with the results obtained in 1983–1985 (83 species). However, compared with other bays, the number of zooplankton species in Qinzhou Bay is close to Daya Bay (128), higher than in Zhilin Bay (60), Jiaozhou Bay (81) and Luoyuan Bay (70), and far lower than in the north South Sea (709). We adopted the dominant index Y > 0.02 as the distinguishing standard of dominant species. The number of dominant species in spring, summer, autumn and winter were six, nine, eight and five. There was only one common dominant species (Penilia avirostris) appeared in different seasons, For summer and autumn, the shared dominant species numbered about four. Between other seasons, the shared dominant species varied between two and three. The number of uniquely dominant species was four in summer, three in autumn and one in both spring and winter. The dominant species in different seasons have some overlaps and some differences. The average biomass of zooplankton was 378 mg/m³ at all times of year. The average biomass was largest in autumn, followed by winter, and was the least in spring and summer. The average density of zooplankton for the entire year was 805.11 ind/m³. The average density was largest in summer, followed by winter, and was least in autumn and spring. Copepoda and Planktonic larvae were the major components of zooplankton in spring and summer at Qinzhou Bay, with the other species’ densities under 10%. In autumn, Copepoda, Planktonic larvae and Chaetognatha were the major components of the biomass, and in winter, the major species were Copepoda and Cladocera, with the others species’ density under 10%. The average value of the Shannon–Wiener diversity index (H′) was 3.84 and the evenness index (J′) was 0.77. The zooplankton diversity index and community evenness overall were good and the community organization had a complete and stable state, but the status of the community was relatively weak. The relationship between biomass/density of zooplankton and environmental factors is remarkable. Biomass and density are positively correlated with temperature and nutrient concentration, and are negatively correlated with salinity.     

Copepod feeding in a tuna fishery area of the tropical Atlantic Ocean

Biomass, feeding and metabolic rates of planktonic copepods were studied in an oligotrophic area of the tropical Atlantic Ocean during an instability wave period (boreal summer) and a stratified period (boreal winter). In summer, zooplankton biomass was higher than in winter, showing a positive effect of the instability wave. Moreover, feeding equilibrated metabolic expenditures of copepods in most cases during the instability. In contrast, in stratified conditions copepods did not equilibrate their metabolic budget. Our results suggest that the microbial loop was the dominant trophic pathway during both periods but with a quicker cycling during the instability.     

Composition, abundance and distribution of macrozooplankton in Culebra Bay, Gulf of Papagayo, Pacific coast of Costa Rica and its value as bioindicator of pollution

The abundance, distribution and composition of the macrozooplankton of Culebra Bay, Costa Rica (10 degrees 38' N - 85 degrees 40' W) were studied at four stations throughout the dry (February-May) and rainy (September-November) seasons of 2000. The samples were collected at two-week intervals using a 500 microm mesh net with a 0.5 m diameter opening. Copepods (23-31%) and ostracods (20-34%) were predominant throughout the year, followed by cladocerans (2.5-14%), zoea (6.6-9.5%), and siphonophores (2.5-7.2%). High densities of zooplankton were obtained in February and March with peak abundance on March 18. The lowest densities were observed on September 3 and November 5. Significant differences in abundances at each station were observed for the groups Acartia tonsa (Copepoda), Ctenophora, Medusae, Ostracoda, Zoea, and Amphipoda. Comparison of the dry and rainy seasons revealed significantly higher zooplankton abundance in the dry season and copepod domination of all stations; during the rainy season ostracods dominated the off-shore areas. Zooplankton abundance and distribution are influenced by upwelling, which occurs during the dry season in Culebra Bay.     

Why do symbiotic copepods matter?

Currently, less than 10% of the members of the World Association of Copepodologists are working actively on symbiotic copepods. This surprisingly small guild of workers is thought to result from a general lack of understanding of the importance of symbiotic copepods. Symbiotic copepods as a whole comprise more than one-third (4224/11956 or 35.33%) of known copepods. They are found not only in the five major orders of Copepoda (Calanoida, Harpacticoida, Cyclopoida, Poecilostomatoida and Siphonostomatoida), but also in association with all major phyla of marine animals, ranging from sponges up to mammals (cetaceans). Discussion on these subjects is augmented with information on the impact of symbiotic copepods on aquaculture, and their exhibition of unusual biological phenomena. It is concluded that copepodologists today need to pay more attention to the symbiotic copepods, if copepodology is to become a major subject of modern biological sciences.     

淡水排放对杭州湾湿地浮游动物群落分布的影响

于2010年4月至2011年1月对杭州湾南岸滩涂湿地5个断面(S1-S3为排水区, S4-S5为非排水区)的高潮位和中潮位分别进行浮游动物群落结构的周年调查, 共发现浮游动物38种(轮虫15种, 枝角类4种, 桡足类19种)。排水区浮游动物年平均密度88.89 ind./L, 生物量0.41 mg/L, 非排水区平均密度仅4.21 ind./L, 生物量0.10 mg/L。排水区轮虫和桡足类的第一优势种分别为萼花臂尾轮虫(Brachionus calyciflorus)和汤匙华哲水蚤(Sinocalanus dorrii), 而非排水区第一优势种为中华哲水蚤(Calanus sinicus)。S2-S3断面中潮位的水体营养盐浓度、浮游动物密度和生物量均明显大于高潮位。淡水排放、潮沟径流和潮汐决定了滩涂湿地群落的时空格局, 后两者还解释了排水区中、高潮位间群落结构组成的差异。       

Complementary impact of copepods and cladocerans on phytoplankton

The differences in the impact of two major groups of herbivorous zooplankton (Cladocera and Copepoda) on summer phytoplankton in a mesotrophic lake were studied. Field experiments were performed in which phytoplankton were exposed to different densities of two major types of herbivorous zooplankton, cladocerans and copepods. Contrary to expectation, neither of the two zooplankton groups significantly reduced phytoplankton biomass. However, there were strong and contrasting impacts on phytoplankton size structure and on individual taxa. Cladocerans suppressed small phytoplankton, while copepods suppressed large phytoplankton. The unaffected size classes compensated for the loss of those affected by enhanced growth. After contamination of the copepod mesocosms with the cladoceran Daphnia , the combined impact of both zooplankton groups caused a decline in total phytoplankton biomass.     

Summer feeding activities of zooplankton in Prydz Bay, Antarctica

Grazing of dominant zooplankton copepods (Calanoides acutus, and Metridia gerlachei), salps (Salpa thompsoni) and microzooplankton was determined during the austral summer of 1998/1999 at the seasonal ice zone of the Prydz Bay region. The objective was to measure the ingestion rates of zooplankton at the seasonal ice zone, so as to evaluate the importance of different groups of zooplankton in their grazing impact on phytoplankton standing stock and primary production. Grazing by copepods was low, and accounted for <1% of phytoplankton standing stocks and 3.8-12.5% of primary production for both species during this study; even the ingestion rates of individuals were at a high level compared with previous reports. S. thompsoni exhibited a relatively high grazing impact on primary production (72%) in the north of our investigation area. The highest grazing impact on phytoplankton was exerted by microzooplankton during this investigation, and accounted for 10-65% of the standing stock of phytoplankton and 34-100% of potential daily primary production. We concluded that microzooplankton was the dominant phytoplankton consumer in this study area. Salps also played an important role in control of phytoplankton where swarming occurred. The grazing of copepods had a relatively small effect on phytoplankton biomass development.     

Zooplankton abundance, community structure and dynamics in relation to inorganic turbidity, and their implications for a potential fishery in subtropical Lake le Roux, South Africa

SUMMARY. 1. The abundance and composition of entomostracan zooplankton were studied between 1977 and 1984 in relation to abiotic and biotic conditions in Lake le Roux (LLR), a large silt-laden reservoir on the Orange River formed in 1976. The community consisted of Metadiaptomus meridianus, Lovenula excellens (Calanoida), Daphnia gibba, D. barbata, D. longispina and Moina brachiata (Cladocera), and various Cyclopoida. 2. Zooplankton biomass varied seasonally from winter lows below 50 mg m^?2 dry wt at temperatures of 9–10°C to summer peaks generally above 1000 mg m^?2 at 21–23°C. It correlated strongly and positively with prevailing water temperature and transparency but only weakly with chlorophyll concentration. 3. Mean annual zooplankton biomass, which varied four-fold (97–408 mg m^?2) in 7 years, increased with annual mean transparency (23–75 cm Secchi depth) and especially with summer heat content (33–230 degree-days above 20°C) which was itself positively correlated with transparency. 4. Daphnid species showed most annual variation in abundance. Large forms(D. gibba and D. barbata) were scarce or absent in two years of very low transparency and low planktivore abundance. The smaller D. longispina developed once during clearer conditions when more fish were present. Copepod biomass also varied inversely with turbidity, but was not as severely reduced at high turbidities. 5. Smallmouth yellowfish(Barbus aeneus: Cyprinidae) is the principal planktivore and candidate fishery species in LLR. It feeds selectively on Lovenula and large daphnids. Catches and growth rates of yellowfish varied directly with the abundance of zooplankton, particularly large food forms, and with water transparency. High turbidity and associated food limitation seems to reduce standing stocks especially of the daphnid zooplankton more than the effects of fish predation. 6. Spawning of yellowfish depends upon the release of water from an upstream reservoir which concurrently reduces transparency and thus zooplankton availability in LLR. Transparency values above 30–35cm SD appear necessary for the development of sufficient and suitable zooplankton to benefit the fishery.     

Larger zooplankton in Danish lakes after cold winters: are winter fish kills of importance?

Winter fish kills can be intense under ice in shallow lakes, and have cascading effects on the food web and ultimately on lake water clarity. In maritime Western Europe, winters are usually mild, but occasional colder periods may also have strong effects on lake fish communities. Global warming may have disproportionate effects by delaying freezing and shortening the period of ice coverage. We studied differences in zooplankton (cladocerans, copepods, and rotifers): phytoplankton biomass, zooplankton community structure, and individual body size among 37 Danish lakes of various depths, chemical characteristics, and trophy, by comparing four winters of different severity (mean winter temperatures ranging from −1.19°C in 1996 to +2.9°C in 1995). We found that crustacean mean body sizes were significantly larger in the summer following a severely cold winter. The zooplankton communities in the summer after a cold winter had a significantly larger proportion of larger-bodied species and taxa. Phytoplankton biomass, expressed as chlorophyll-a (chl-a), was lower and zooplankton herbivory (chl-a:TP index), higher, in the summer after the severely cold winter of 1995/1996. All these effects were stronger in shallow lakes than in deep lakes. Changes in zooplankton during summer 1996, compared with other years, were likely caused by fish kills under ice during the preceding severe winter of 1995–1996. Fish kills due to under ice oxygen depletion would be expected to occur earlier and be more complete in the shorter water columns of shallow lakes. With climate change, severe winters are predicted to become less frequent and the winters to be milder and shorter. In general, this is likely to lead to higher winter survival of fish, lower zooplankton grazing of phytoplankton the following summer and more turbid waters, particularly in shallow eutrophic lakes.     

浙江两类饮用水源地浮游动物种类组成及其类群相关性分析

于2009年7月至2010年4月,在浙江省选取了10个水库和10个河网饮用水源地,进行4个季节的浮游动物采样调查。记录浮游动物101种(轮虫60,枝角类24和桡足类17种)。水库和河网轮虫的优势种分别为角突臂尾轮虫(Brachionus angularis)和针簇多肢轮虫(Polyarthratrigla),枝角类分别为颈沟基合溞(Bosminopsis deitersi)和长额象鼻溞(Bosmina longirostris),桡足类均为温剑水蚤(Thermocyclops)。水库中有一些能指示良好生态或水质的指示性种类。水库枝角类与桡足类群落之间周年在丰度和生物量上均有极显著的正相关关系(P<0.01),轮虫与桡足类类群之间的相关性最弱;河网枝角类与桡足类在夏、秋、冬季有显著的正相关性(P<0.05)。浮游动物类群之间的相关性程度,以水库的秋季与河网的夏季为最高。轮虫与浮游甲壳动物的种类丰富度随着饮用水源水体透明度的变化呈现相反的变化趋势。     

Short-term changes in the Barra Bonita reservoir (São Paulo, Brazil): emphasis on the phytoplankton communities

We investigated the biomass, primary productivity, species diversity and their controlling factors in the deeper region of the Barra Bonita reservoir (22°29S and 48°34W) in the State of São Paulo, Brazil. To accomplish this, short term changes (days and month) were measured during two periods of the year, winter 1993 and summer 1994. The response of the phytoplankton communities to the variability of the system, taking into account the Intermediate Disturbance Hypothesis (IDH), indicated that the frequency and intensity of the disturbances have a critical influence on the establishment of the communities. In Barra Bonita Reservoir the conditions for mixing in the winter were probably important for maintaining high diversity. On the other hand, in summer, the concentrations of suspended material, the high temperatures, and the greater stability of the water column, were probably responsible for permitting the establishment of Microcystis aeruginosa.     

Seasonal fluctuations of zooplankton biomass in Lake Xolotlán (Managua)

Seasonal fluctuations of zooplankton biomass (dry weight) were determined during a year in two localities of Lake Xolotlán (Managua). Biomass estimations of the most common species of rotifers, cladocerans and copepods were made. The maximal zooplankton biomass was observed in February–April (dry season) in coincidence with the period of highest phytoplankton abundance. Copepods contributed with 78% and 84% to the mean zooplankton biomass at points 1 and 7, respectively. Cladocera biomass was lowest during most of the year, and it was probably controlled by fish predation. Development of rotifer biomass was more intense during the rainy season, when detritus particles were more abundant. Daily fluctuations of zooplankton biomass were not pronounced.     

Patterns of energy storage in Pseudoboeckella poppei (Crustacea,copepoda) from two contrasting lakes on Signy Island,Antarctica

The copepod Pseudoboeckella poppei (Daday) (Calanoida, Centropagidae) was sampled from Sombre and Heywood Lakes on Signy Island, Antarctica (60° S, 45° W) between January 1984 and March 1985. Sombre Lake is clear and oligotrophic with little phytoplankton and a bottom sediment low in organic content. By contrast Heywood Lake is turbid and mesotrophic; a substantial phytoplankton develops in summer and the bottom sediments are comparatively rich in organics. Both lakes freeze over for much of the year, forcing the copepods to adopt a benthic feeding strategy over winter. Adult Pseudoboeckella feed on phytoplankton when this is available, but also on detritus, diatoms and short algal filaments stirred up from the sediment. In Heywood Lake, male copepods show a smooth seasonal trend in lipid content with lipid being synthesised in early summer and utilised in late summer and winter. The summer increase in lipid content is associated with an increase in dry weight. Female lipid contents show evidence of two peaks of egg production. In Sombre Lake both male and female copepods increase in size during summer and show a wider range of lipid contents than in Heywood Lake; it is likely that this is due to the poorer winter feeding conditions which necessitate the synthesis of a much larger store of reserves during the summer. In contrast to marine calanoid copepods, lipid stores are exclusively triacylglycerol with no trace of wax ester.     

Physico-chemical limnology and plankton dynamics of Mazvikadei,a tropical reservoir in Zimbabwe

The limnology of Mazvikadei Reservoir, northern Zimbabwe, was investigated in 2015 to determine whether it had changed since filling in 1990. The reservoir is characterised by low algal biomass, low nutrients (i.e. N and P) and high water clarity/transparency. Fifty-four species of phytoplankton were recorded, comprising Bacillariophyta, Chlorophyta, Cyanophyta, Desmids, Dinophyta and Euglenophyta. Chlorophyta numerically dominated in the hot dry season, whereas Bacillariophyta, Desmids, Dinophyta and Euglenophyta dominated in the cool dry season. Species richness was highest at the onset of the cool dry season, in response to high nutrient concentrations. Phytoplankton abundance and composition were significantly correlated with temperature, nitrates and total nitrogen. Nineteen zooplankton species were recorded, including Copepoda, Cladocera and Rotifera. Overall, Cladocera were numerically dominant and became most abundant during the cool dry season. Rotifers and copepods dominated during the hot dry season. The zooplankton abundance was correlated with reactive phosphorus and phytoplankton abundance. The trophic state of Mazvikadei Reservoir seems to have stabilised and to have assumed the physico-chemical characteristics and plankton community typical of an oligotrophic lake.     

安庆西江浮游动物群落结构及江豚生存状况评估

为了解安庆西江浮游动物群落结构, 进而评价江豚(Neophocaena asiaeorientalis asiaeorientalis)的生存状况, 于2015年4月至2016年1月对西江浮游动物和环境因子进行了季节性调查。研究结果表明: (1)共采集浮游动物55种, 其中原生动物13种、轮虫27种、枝角类9种、桡足类6种。4个季节间浮游动物种类数差异较大, 夏季种类数最多, 为39种; 冬季种类数最少, 仅为16种。(2)全年浮游动物平均密度和生物量分别为4115 ind./L和1.735 mg/L, 且均以原生动物和轮虫为主。方差分析结果表明, 不同季节间浮游动物密度和生物量均存在显著差异, 且夏季浮游动物密度和生物量均显著高于其他3个季节。(3)全年共记录优势种12种, 其中原生动物4种、轮虫6种、桡足类2种; 不同季节间浮游动物优势种的组成差异明显。(4)采用浮游动物生物量对水质的评价结果显示西江水体处于中营养状态; 运用Shannon多样性指数和Margalef多样性指数对水质的评价结果显示西江水体处于α-中污状态, 表明西江水质基本上满足江豚生存需求。(5)依据浮游动物的现存量, 估算出西江食浮游动物鱼类的渔产力为54340.2 kg, 相应地可满足36头江豚的营养需求。研究结果不仅有助于了解长江故道这种特殊水体浮游动物的群落特征, 还对迁地保护区江豚的保护有重要意义。