Macrozoobenthic community of Poyang Lake,the largest freshwater lake of China,in the Yangtze floodplain

Poyang Lake (Poyang Hu) is located at the junction of the middle and lower reaches of the Yangtze (Changjiang) River, covering an area of 3283 km². As one of the few lakes that are still freely connected with the river, it plays an important role in the maintenance of the unique biota of the Yangtze floodplain ecosystem. To promote the conservation of Poyang Lake, an investigation of the macrobenthos in the lake itself and adjoining Yangtze mainstream was conducted in 1997–1999. Altogether 58 benthic taxa, including 22 annelids, 8 mollusks, 26 arthropods, and 2 miscellaneous animals, were identified from quantitative samples. The benthic fauna shows a high diversity and a marine affinity. The standing crops of benthos in the lake were much higher than those in the river, being 659 individuals/m² and 187.3 g/m² (wet mass) in the main lake, and 549 individuals/m² and 116.6 g/m² in the lake outlet, but only 129 individuals/m² and 0.4 g/m² in the river. The dominant group in the lake was Mollusca, comprising 63.4% of the total in density and 99.5% in biomass. An analysis of the functional feeding structure indicated that collector-filterers and scrapers were predominant in the lake, up to 42.2% and 24.7% in density and 70.2% and 29.2% in biomass, respectively, while shredders and collector-gatherers were relatively common in the river. The present study was restricted to the northern outlet and the northeast part of Poyang Lake. A scrutiny is required for the remaining areas.     

Sublittoral soft bottom communities and diversity of Mejillones Bay in northern Chile (Humboldt Current upwelling system)

The macrozoobenthos of Mejillones Bay (23°S; Humboldt Current) was quantitatively investigated over a 7-year period from austral summer 1995/1996 to winter 2002. About 78 van Veen grab samples taken at six stations (5, 10, 20 m depth) provided the basis for the analysis of the distribution of 60 species and 28 families of benthic invertebrates, as well as of their abundance and biomass. Mean abundance (2,119 individuals m^?2) was in the same order compared to a previous investigation; mean biomass (966 g formalin wet mass m^?2), however, exceeded prior estimations mainly due to the dominance of the bivalve Aulacomya ater. About 43% of the taxa inhabited the complete depth range. Mean taxonomic Shannon diversity (H′, Log e) was 1.54 ± 0.58 with a maximum at 20 m (1.95 ± 0.33); evenness increased with depth. The fauna was numerically dominated by carnivorous gastropods, polychaetes and crustaceans (48%). About 15% of the species were suspensivorous, 13% sedimentivorous, 11% detritivorous, 7% omnivorous and 6% herbivorous. Cluster analyses showed a significant difference between the shallow and the deeper stations. Gammarid amphipods and the polychaete family Nephtyidae characterized the 5-m-zone, the molluscs Aulacomya ater, Mitrella unifasciata and gammarids the intermediate zone, while the gastropod Nassarius gayi and the polychaete family Nereidae were most prominent at the deeper stations. The communities of the three depth zones did not appear to be limited by hypoxia during non-El Niño conditions. Therefore, no typical change in community structure occurred during El Niño 1997–1998, in contrast to what was observed for deeper faunal assemblages and hypoxic bays elsewhere in the coastal Humboldt Current system.     

黄河山东段河岸带春季大型底栖动物群落结构与多样性

河岸带是河流生态系统与陆地生态系统相互作用的生态交错带,具有明显的边缘效应和丰富的生物多样性。近年来,由于受人类活动(如水利工程、堤坝和农业生产等)的干扰,黄河下游河岸带生态系统受到严重破坏。为了解黄河下游河岸带大型底栖动物的群落结构现状和影响因素,于2015年5月对黄河山东段河岸带8个断面的底栖动物群落进行了系统调查,采用相对重要性指数、物种多样性指数和均匀度指数等方法分析该区域大型底栖动物的群落特征。调查期间共采集到37种底栖动物,其中,环节动物3种,软体动物7种,水生昆虫27种。底栖动物物种组成主要以水生昆虫为主,尤其是摇蚊幼虫。该段河岸带大型底栖动物的平均密度为(2 129±436)ind/m2,平均生物量为(2.20±0.75)g/m2。就空间分布而言,各断面底栖动物的种类数、优势种、现存量和多样性均呈现出明显的空间分布差异,且呈现出不规则波动,这表明河岸带受到严重的人为活动干扰。综合分析表明,各断面的河岸带形态(如宽度和生境类型)和水生昆虫的繁殖行为是影响黄河山东段河岸带底栖动物空间分布的主要因素。     

Factors influencing taxonomic composition and abundance of macrozoobenthos in extralittoral zone of shallow eutrophic lakes

Zoobenthos is an essential part of shallow lake ecosystems, exerting a considerable impact upon their functioning. We studied 13 eutrophic, shallow, polymictic lakes from Northern Poland to find out which environmental factors influence taxonomic composition, abundance and biodiversity of their zoobenthos. The Canonical Correspondence Analysis allowed to distinguish three lake types: (1) macrophyte-dominated lakes, with high plant cover and well illuminated bottom, inhabited by abundant, diverse benthic taxa; (2) deeper phytoplankton-dominated lakes, with shaded bottom, high sediment oxygen demand (SOD) and rather sparse zobenthos community, dominated by Chironomus and Chaoborus larvae; (3) shallower phytoplankton-dominated lakes, with intermediate amount of light at the bottom and lower SOD values and comparatively diverse zoobenthos, but with lower number of taxa than in the first group. Apart from plant presence, distinguishing between macrophyte-dominated lakes and the other types, the most important variable in the CCA was amount of light reaching the bottom. Probably the impact of light on the bottom fauna was indirect: light stimulated development of macrophytes or phytobenthos (depending on its intensity) and thus improved food and oxygen conditions. Zoobenthos was also affected by oxygen conditions (mainly SOD), presumably by short-time oxygen depletions occurring in the deep phytoplankton-dominated lakes and preventing survival of some benthic taxa.     

Finding appropriate reference sites in large-scale aquatic field experiments

Defining the reference condition is one of the most critical aspects of ecosystem investigations since it describes the baseline against which the experimental sites will be evaluated and compared. In large-scale ecosystem experiments, this reference is ideally another ecosystem which is similar to the experimental system. We investigated two streams for their potential as experimental sites for a full-size pairwise ecosystem experiment. Temporal (2 years) and spatial (pool, riffle) variabilities of abiotic factors and as biotic element the structure of the macroinvertebrate communities were investigated. Criteria of similarity that we applied at the two streams were: (1) high similarity in abiotic factors, (2) only small differences in the faunal assemblages (abundance structures, composition, feeding types), and (3) that the differences between the two systems should not exceed the temporal and spatial differences within each system. Among the abiotic factors investigated, only the inorganic nutrients (nitrate and soluble reactive phosphorus), major ions (magnesium, calcium), electric conductivity, and pH showed significant differences between the two streams. Discharge rate, current velocity, temperature, and oxygen concentrations did not significantly differ between the streams. Also, the community structure did not differ in species richness, abundance, and biomass; and only small differences in dominance structure and feeding-type composition were observed. The differences between habitats within each stream were always higher than those between the streams. Thus, both the streams are characterized by a similar structure of the macroinvertebrate community, a main component of the stream food-web, which make them suitable for a full size pairwise ecosystem experiment. The present case study can form a basis for other full-size field experiments.     

淮北煤矿区塌陷湖大型底栖动物群落结构及水质生物学评价

2013年对淮北采煤塌陷湖(乾隆湖和临涣湖)大型底栖动物群落结构进行了季节性调查。共采集到大型底栖动物26种, 隶属于3门5纲17科. 乾隆湖和临涣湖年平均密度分别为230.85和215.80 ind./m2, 年平均生物量分别为56.11和36.38 g/m2。两湖大型底栖动物以摇蚊幼虫、霍甫水丝蚓和苏氏尾鳃蚓为优势类群, 底栖动物最高密度均出现在夏季(乾隆湖为 278.0 ind./m2, 临涣湖为288.2 ind./m2); 生物量则主要以软体动物和水生昆虫为主, 夏季和秋季大型底栖动物生物量明显高于春季和冬季。运用Shannon多样性指数(H')、Margalef多样性指数(D)和Biotic Index生物学指数(BI)对乾隆湖和临涣湖进行水质生物评价研究, 结果显示Shannon多样性指数不适宜于该两湖的水质生物评价, BI的评价结果与水质状况基本相符。综合 Margalef多样性指数和BI生物指数评价的结果表明: 乾隆湖和临涣湖春季和冬季处于轻度污染状态, 夏季和秋季处于中度污染状态。     

MACRO-PATTERNS OF SPECIES DIVERSITY AND STANDING CROPS OF MACROZOOBENTHOS IN THE YANGTZE RIVER BASIN北大核心CSCD

We summarize macro-patterns of macrozoobenthos in the Yangtze River basin in this paper. A total of 1033 taxa (species/genus) belonging to 3 phyla, 7 classes, 162 families and 513 genera have been recorded from the Yangtze River Basin, including 121 annelids, 318 molluscs and 594 arthropods. In terms of taxa distributions, the species/genus number of annelids and of molluscs in the middle reaches were the highest, while that of arthropods in the upper reaches was the highest; the species/genus number of annelids and of molluscs in the lakes were the highest, while that of arthropods in the tributaries was the highest; the species/genus number of macrozoobenthos in the middle mainstem sub-basin ranked first, and that of the upper mainstem sub-basin, of the Jinshajinag sub-basin, of the Lake Dongting sub-basin and of the Lake Poyang sub-basin second. The total density of macrozoobenthos in the Yangtze River basin was 672 ind./m2, and insects were predominant; the total biomass was 34.22 g/m2, and molluscs were predominant. In terms of standing crops distribution, the total density of macrozoobenthos in the middle reaches was the highest, the total biomass in the lower reaches the highest, while the total standing crop in the upper reaches was the lowest; the total density and biomass of macrozoobenthos in the lakes ranked first, those in the tributaries second, and those in the mainstem last; the total density of macrozoobenthos in the Lake Taihu sub-basin was the highest, and the total biomass in the Lake Poyang sub-basin was the highest. Our study indicates that the upper and middle mainstem sub-basins, the Jinshajiang sub-basin, the Lake Dongting sub-basin and the Lake Poyang sub-basin are important distribution regions for macrozoobenthos. By integrating more information of aquatic organisms, we should make comprehensive and systematic conservation planing of the Yangtze River system and implement them as soon as possible. © 2019, Institute of Hydrobiology, Chinese Academy of Sciences. All rights reserved.     

Population fluctuations of chironomid and simuliid Diptera at Myvatn in 1977–1996

Aquatic dipterans dominate the macrozoobenthos of Lake Myvatn and the River Laxá and are important in the food web. As benthic sampling is time-consuming and expensive, a window trap was developed in order to facilitate the monitoring of the zoobenthos resource. Four window traps were operated at Myvatn and Laxá during 1977–1996. The results yielded population indices for about 20 species of chironomids and one simuliid. Numbers of the most abundant midge species showed close correlations between 2 trap sites on the lake shore, 5 km apart; Cricotopus tibialis did not show such synchrony. At the River Laxá, the dominant blackfly (Simulium vittatum) showed correlation between 2 trap sites, at the outlet and 3 km downstream; while the chironomids, apart from Micropsectra atrofasciata, did not. The dominant midge of Lake Myvatn, Tanytarsus gracilentus showed 3 cyclic oscillations during the 20-year period. The fluctuations were tracked by Micropsectra lindrothi, Procladius islandicus, Orthocladius consobrinus, Psectrocladius barbimanus and Chironomus islandicus. A group of non-cyclic species included Cricotopus sylvestris and Orthocladius oblidens.     

西江大型底栖动物群落特征研究

河流担负着水源供给、食物生产、旅游、航运等功能。近年来, 人类活动的加剧导致河流生态系统受到威胁。底栖动物常被作为环境指示生物, 研究其群落特征为河流保护及管理有着重要意义。为了航运需求,西江开展了航道整治工程, 由此引起河道生物栖息生境条件的改变, 从而影响河流的生态健康。为了西江的保护和管理, 研究于2009 年枯水期和2010 年丰水期对西江的底栖动物开展了系统调查。调查期间共鉴定底栖动物70 种, 隶属于30 科59 属。其中环节动物7 科12 属16 种, 软体动物11 科14 属21 种, 节肢动物11科32 属32 种, 其他动物1 科1 属1 种。底栖动物的密度和生物量分别为140 ind/m2、0.23 g dry weight/m2。统计分析表明河床底质在底栖动物丰度和分布上起着尤为重要的作用。稳定性越高的底质越有利于底栖动物生存。软泥底质以直接收集者(主要包括颤蚓科寡毛类和摇蚊亚科昆虫)占优, 而各类石质底质则以刮食者(主要是短沟蜷Semisulcospira spp.)或过滤收集者(主要是淡水壳菜Limnoperna lacustris)占优。西江航道整治工程的开展降低了生境条件质量甚至使得原有生物栖息地丧失, 由此会对底栖动物的生存产生不利影响。       

黑竹冲河蚋的周年生产量及其营养基础分析

大型底栖动物在河流生态系统中发挥着重要作用,2003年6月至2004年6月间对汉江流域2级河流--黑竹冲河大型底栖动物群落优势种类的生产力进行为期一周年的调查研究,并对其生产量的营养基础进行了初步分析,结果表明,主要优势种蚋(Simuliumsp.)的生活史为一年一代,成虫羽化主要发生在冬季;种群生物量和多度在12月到峰值,分别为115ind·m^-2,250.9mg·m^-2;采用龄期频率分布法(size-frequencymethod)测算的周年生产量为3.9216g·m^-2·a^-1,P/B为4.6.在其前肠内含物中,无形态碎屑、真菌和硅藻所占比例分别为60.40%、3.91%和35.96%,对生产量的贡献率分别为:32.2%、10.4%和57.4%.