Benthic meiofauna community composition at polluted and non-polluted sites in New Zealand intertidal environments

Meiofauna composition was investigated for six field sites, including polluted and non-polluted sites, within two regions (Auckland and Bay of Plenty) during winter (July-August 2004) in the North Island of New Zealand. Physico-chemical parameters were measured during the sampling period and meiofauna distribution and abundance were compared with these measured parameters. Analysis of meiofauna abundance indicated that foraminiferans, nematodes and ostracods were the taxa that contributed to the variability between field sites within the Auckland region. However, no clear taxa dominance was seen in the Bay of Plenty region. Comparison of meiofauna abundance and physico-chemical parameters was done using multivariate analysis (PRIMER). However, no clear relationships between the parameters were observed in any field site in either region. The Shannon-Weiner index of diversity did not show any clear differentiation between polluted and non-polluted field sites. Therefore, from the present study, the taxa or physico-chemical parameters used could not effectively characterise pollution at the investigated field sites.     

Land-use influence on the functional organization of Afrotropical macroinvertebrate assemblages

Studies investigating the effects of human activities on the functional organization of macroinvertebrate communities in tropical streams and rivers are very limited, despite these areas witnessing the greatest loss of natural forests globally. We investigated changes in taxon richness, numerical abundance and biomass of macroinvertebrate functional feeding groups (FFGs) in streams draining different land-use types in the Sosiani-Kipkaren River in western Kenya. Twenty-one sites in river reaches categorized as forested, mixed, urban or agricultural were sampled during the dry and wet seasons. Collected macroinvertebrates were identified to the lowest taxon possible (mainly genus) and classified into five major FFGs; collector-gatherers, collector-filterers, scrapers, predators and shredders. There were significant (p < 0.05) spatial variation in habitat quality, organic matter standing stocks, total suspended solids, electrical conductivity, dissolved oxygen, temperature and nutrient concentrations across land-uses, with forested sites recording lowest values in mean water temperature, electrical conductivity and nutrients while recording highest levels in dissolved oxygen concentrations. Responses in macroinvertebrates to changes in land-use varied with richness, abundance and biomass showing differences within FFGs. Biomass-based metrics responded more strongly to change in land-use while taxon richness was the least predictive, indicating replacement of taxa within FFGs across land-use types. Higher shredder abundance, biomass and richness were recorded in forested streams which were cooler with protected riparian areas and high biomass of coarse particulate organic matter. Collector-gatherers dominated agricultural and urban streams owing to an abundance of particulate organic matter and nutrients, while scrapers responded positively to increased nutrient levels and open canopy in mixed and agricultural streams where primary production and algal biomass was likely increased. Overall, this study provides further evidence of the effects of agricultural and urban land-uses on tropical streams and rivers and contributes to the use of macroinvertebrate FFGs as indicators of ecological health.     

Do installed stream logjams change benthic community structure?

Installed logjams constructed of wood are commonly used in stream restoration projects to provide habitat for lotic organisms. Macroinvertebrate densities are known to increase on logjam surfaces; however, less is known about the influence logjams have on benthic organisms inhabiting the surrounding streambed. To examine this, we conducted a before-after-control-impact (BACI) study in a stream in northern Minnesota, USA, to determine how an installed logjam affected the richness and abundance of three insect orders commonly used in biotic indices, the Ephemeroptera, Plecoptera, and Trichoptera (i.e., EPT taxa). A spanning logjam composed of three logs bound together was installed perpendicular to stream flow at the impact site. Initial sampling of the impact site and an upstream control found no differences among the ETP taxa. A year after installation, the logjam accumulated woody debris and altered flow so that near-bed current at the impact site was faster and more heterogeneous than at the control site. Although the richness and abundance of the macroinvertebrate community as a whole did not differ between sites after one year, it did for the Ephemeroptera and Plecoptera at the impact site. By contrast, Trichoptera richness and abundance did not change. Our results lend support to the hypothesis that installed logjams may enhance stream habitat not only by providing colonization surfaces for macroinverbrates, but also by altering the benthic environment of the surrounding habitat.     

黑龙江省安兴湿地秋季浮游植物群落结构

于2010年10月(秋季)对黑龙江省安兴湿地浮游植物群落组成、丰度及优势种进行分析.共设置9个采样点,经鉴定共有浮游植物146个分类单位,包括128种17变种1变型,隶属于6门8纲12目25科45属,其中绿藻为优势门类,占浮游植物总数的39.7%,裸藻次之,占浮游植物总数的30.8%,硅藻居第三位,占浮游植物总数的21.9%,调查期间浮游植物的总丰度为181.4×106cells/L.优势度分析显示,安兴湿地秋季各采样点的浮游植物优势种都在3个以上,主要优势种有细粒囊裸藻(Trachelomonas granulosa Playf.)、梅尼小环藻(Cyclotella meneghiniana Kütz.)、细粒囊裸藻齿领变种(Trachelomonas granulosa var.crenulatocollis(Szab.)Hub.-Pest.)等.样点聚类和非度量多维标度分析表明,9个采样点浮游植物群落在相似度60%时可分为5组,各样点浮游植物种类在空间组成上相似性低,差异性较大,主要与其生境特点相关.典范对应分析显示优势种类变化与环境条件相一致,主要受温度、pH的影响.此外,在安兴湿地内还鉴定出大量的β-中污带指示种,结合多样性指数分析,本文初步推断安兴湿地水质可能受到了一定的污染.     

Effects of industrial outfalls on tropical macrobenthic sediment communities in Reunion Island (Southwest Indian Ocean)

Temporal changes in the composition of soft bottom macrobenthic assemblages at Reunion Island (Southwest Indian Ocean) were studied in the context of a long-term environmental monitoring programme studying the impacts of effluents of industrial sugar cane refineries that are transferred to shallow and deep coastal environments by different pathways: surface discharge and deep underground injection. Seven stations (between 20 and 160 m depth) were surveyed between 1994 and 2003 on the industrial zone. One additional station was surveyed on a reference site. Spatio-temporal changes in the composition of macrobenthic communities were assessed using several diversity indices, ABC curves, MDS and associated ANOSIM tests and biotic indices. Among the 171 taxa recorded, polychaetes were dominant (89 species), followed by crustaceans and molluscs. The analysis of spatial changes in the composition of macrobenthos showed the existence of distinct benthic communities along the depth gradient. Temporal changes in macrobenthos composition were most prominent at the shallowest station. They mainly corresponded to the decline of several initially dominant taxa and the increase of the Eunicid polychaete Diopatra cuprea. This station further showed increasing macrofaunal abundance, biomass and sediment organic content over time, concomitant with decreasing sediment grain sizes. In deeper environments, temporal changes were much smaller. Macrofaunal abundance and species richness increased progressively, suggesting a moderate impact on benthic ecosystems resulting from slight enrichments due to effluents rich in organic matter. Our results highlight an original response to disturbance pattern involving opportunistic Eunicidae species (D. cuprea) not previously described. Moreover, they allow for the comparison of the impact on macrofauna caused by industrial effluents exported by two distinct and different pathways in a tropical coastal high-energy marine environment.     

黑龙江呼兰河湿地藻类植物群落结构及分布特点

2009年5-10月期间对呼兰河湿地8个样点进行了5次藻类植物采样调查,经显微镜观察,共鉴定藻类植物158个分类单位,包括148种10变种,隶属于7门8纲14目23科50属.呼兰河湿地藻类群落组成以硅藻、绿藻为主,藻类植物的细胞密度变化范围在469.55×105-847.35×105 cells/L之间,不同采样点藻类...     

Limnology of four saline lakes in western Victoria, Australia: II. Biological parameters

Major biological parameters of four permanent (Lake Colac, Modewarre, Bolac and Tooliorook), shallow and slightly saline lakes in the volcanic plains of western Victoria, Australia recorded bi-monthly between November 1999–September 2001 are described. Chlorophyll a concentration ranged from 3–29 μg l⁻¹ with peaks in autumn. Phytoplankton taxa recorded were diverse, with Chlorophyta and Bacillariophyta being common. Cyanobacterial blooms were recorded mostly in summer. Zooplankton abundance in the lakes ranged from 12–368 individuals per litre. Rotifera dominated Lake Bolac, Copepoda dominated Lake Modewarre and they co-dominated Lake Colac and Tooliorook. Zooplankton interactions with phytoplankton suggest that simple predator-prey relationships cannot fully explain the trends exhibited and that a more complex model was acting to regulate algal biomass. A decline in the abundance of zooplankton in summer in Lake Modewarre was attributed to predation by high number of exotic larval carp at that time of the year. A total of 25 benthic macroinvertebrate taxa were recorded from Lake Colac, 30 from Modewarre, 22 from Bolac and 35 from Tooliorook. Twenty-one of the 45 taxa identified occurred in at least three lakes. Nine of the 12 taxa that occurred in only one lake were from Lake Tooliorook. Simpson's diversity index was low in Lake Bolac when compared to other three lakes. Lake Modewarre had more benthic individuals (3246 Ind m⁻²) than other three lakes (range 624–1397 Ind m⁻²). The combined contribution of Ostracoda, Amphipoda and Gastropoda dominated the benthos in all the lakes throughout the study period. Macroinvertebrate taxa richness was higher in the present study lakes than recorded from the lakes in the region. Frequency of sampling and number of sampling sites seemed more important in determining species richness than the size and shallowness of the lakes.     

Studies of a contaminated brackish marsh in the Hackensack Meadowlands of Northeastern New Jersey: benthic communities and metal contamination

Cores taken from 16 stations within Eight Day Swamp, a highly contaminated marsh in the Hackensack Meadowlands, were analyzed for metal concentrations and for benthic community structure. Metal levels were compared with the benchmark ERM values, and expressed in terms of toxic units. Mercury was the most important metal in all the samples in terms of its contribution to the total toxic units. The overall abundance and taxa richness in the benthic community were associated with the height of the location relative to the tidal cycle, but were generally not significantly correlated with metal concentrations at the sites. Ordination of the communities showed that the communities that were low-lying (on the mudflat) were most similar to one another, and those that were higher up on the marsh were most similar to one another. However, diversity indices (Shannon-Wiener H' and Simpson's) were significantly associated with concentrations of the metals (except As) and with the sum of the toxic units at a station.     

The influence of biotope on invertebrate assemblages in lentic environments: A study of two perennial alkaline wetlands in the Western Cape,South Africa

As a step towards the biological assessment of wetlands in South Africa, this study investigates the influence of biotope characteristics on the spatial distribution of aquatic invertebrates. The aim was to assess whether different wetland biotopes support significantly different invertebrate assemblages in terms of the composition and abundance of microcrustaceans and macroinvertebrate taxa. During October 2006, three different biotopes were sampled within Verlorenvlei and Wave's Edge wetlands (Western Cape, South Africa) using a long-handled sweep net. Composition and abundance of invertebrate assemblages were compared between and within sites for each of the wetlands. Assemblage composition generally differed among biotopes within each wetland, as revealed by cluster analysis and MDS plots. At Verlorenvlei, biotopes formed distinctive clusters with low site-specific variability. Assemblage composition at Wave's Edge revealed coarser groupings with clusters distinguishing between vegetated and non-vegetated biotopes only. Biotopes within each wetland differed significantly in terms of taxon richness, Shannon diversity and mean total invertebrate biomass (g m⁻³), whilst mean total density (ind m⁻³) differed only between biotopes in Verlorenvlei. Considerable shifts in invertebrate assemblage structure corresponded to differences in electrical conductivity among sites at Verlorenvlei. For large physico-chemically heterogeneous wetlands such as Verlorenvlei, it is suggested that smaller physico-chemically homogenous zones should be identified a priori and within these areas vegetated biotopes should be sampled over the broadest possible spatial scale, whilst open-water biotopes can be sampled more narrowly. For small, reasonably homogenous wetlands such as Wave's Edge, we suggest a less broad spatial representation of biotopes and instead one should concentrate on increasing the number of sample repetitions per site.     

Do hydraulic units define macroinvertebrate assemblages in mountain streams of central Argentina?

Methods to assess the physical habitat provide important tools for many aspects of river management. Hydraulic units (defined as a homogeneous patch of flow type and substrate) were described in mountain streams of Central Argentina and the distribution of macrozoobenthos in these habitat units was analyzed. Four streams from the upper Carcarañá River Basin (Córdoba, Argentina) were sampled in two hydrological periods. Hydraulic units (as substrate and flow type), current velocity, depth, macrophytes and macroalgae were assessed. Three benthic samples were taken in each hydraulic unit. A total of 12 hydraulic units were registered, which varied seasonally in their proportional abundance. The highest values of taxonomic richness, total abundance, diversity and evenness were found in the low-water period. The most heterogeneous hydraulic units (characterized by substrate of diverse grain size) presented the highest richness, diversity and evenness, whereas the highest total abundance was observed in hydraulic units with homogeneous substrate, such as bedrock or gravel sand. Canonical correspondence analysis grouped samples and taxa mainly in relation to the hydraulic units, and temporal variation in macroinvertebrate assemblages was observed. We found that the interaction between hydrological and geomorphological conditions affected benthic assemblages and that their organization is important at a mesoscale. Therefore, hydraulic units may be considered important tools in assessing stream integrity in lotic systems of central Argentina.     

Latitudinal changes in larger benthic foraminiferal assemblages in shallow-water reef sediments along the Ryukyu Islands, Japan

Abstract The taxonomic diversity of hermatypic corals decreases with increasing latitude, which correlates with sea‐surface temperatures. However, little is known about latitudinal changes in the taxonomic diversity and biogeographic patterns of larger benthic foraminifera, although their physiological requirements are similar to those of hermatypic corals because of their symbiotic relationships with microalgae. The present study examined how the abundance and taxonomic composition of larger foraminiferal assemblages in shallow‐water reef sediments change with latitude along the Ryukyu Islands (Ryukyus), which are located near the northern limit of coral‐reef distributions in the western Pacific Ocean. Three islands from different latitudes in the Ryukyus were selected to investigate latitudinal changes in larger foraminiferal assemblages: Ishigaki Island (24°20′N, 124°10′E), Kudaka Island (26°09′N, 127°54′E) and Tane‐ga‐shima Island (30°20′N, 131°E). Four sediment samples were taken at each of three topographic sites (beach, shallow lagoon and reef crest) on the reef flat of each island. Foraminiferal tests of a 2.0‐ to 0.5‐mm size fraction were selected, identified and counted. The variations in foraminiferal abundance in reef sediments from three latitudinally different islands exhibit two contrasting trends along reef flats: a shoreward decrease on Ishigaki and Tane‐ga‐shima Islands and a shoreward increase on Kudaka Island. A total of 25, 24 and 13 foraminiferal taxa were identified in Ishigaki, Kudaka and Tane‐ga‐shima Islands, respectively. Baculogypsina sphaerulata, Neorotalia calcar and Amphistegina spp. were dominant (i.e. >3% of foraminiferal assemblages) in the three islands. Calcarina gaudichaudii and Calcarina hispida were common on Ishigaki and Kudaka Islands but were absent on Tane‐ga‐shima Island. Larger foraminiferal assemblages from three different reef‐flat environments on Ishigaki Island can be distinguished, whereas those from the three environments on Kudaka and Tane‐ga‐shima Islands are similar in composition. These latitudinal changes in larger foraminiferal assemblages in reef sediments may possibly be caused by variations in the topography of reef flats, distributions and standing crops of living foraminifers on reef flats, and the northern limit of some calcarinid species in the northern Ryukyus.     

Potential responses of oligochaetes (Annelida, Clitellata) to global changes: Experimental fertilization in a lowland stream of Argentina (South America)

One of the possible consequences of climatic change for streams and rivers in the pampean region of South America is an increment in nutrient loads. To analyze this possible perturbation on a biological scale, the response of oligochaetes to an experimental eutrophication of the La Choza Stream, Argentina was studied. We proposed that the addition of nutrients could increase the abundance, biomass, and species composition of the stream. Two stretches (Control and Treatment sites) were selected, with bimonthly samples being taken (March 2007 through February 2009) in two habitat types: the sediments and the aquatic vegetation. On each sampling occasion the environmental variables were measured. The nutrient addition consisted in the continuous dissolution of a commercial fertilizer. The oligochaete mean density and total biomass, the taxonomic richness, the Shannon diversity (H′), and the evenness (E) were calculated and the BACI ANOVA design used to compare the differences between the sites. Thirty-three species of the families Naididae (Naidinae, Pristininae, Tubificinae, and Rhyacodrilinae), Opistocystidae, Enchytraeidae plus Aphanoneura Aeolosomatidae were collected. The oligochaete abundance and biomass increased significantly in the sediments and on the aquatic vegetation, especially among the Naidinae and Pristininae during their asexual reproductive phase. The diversity and evenness varied significantly in the sediments with the nutrient addition. Significant differences in the species richness and diversity were found on the aquatic vegetation, with both increasing at the treatment site after the fertilization. A significant correlation (Spearman) was observed between the oligochaete density in the sediments and the NO₃-N and NH₄-N concentration in the water. The increment in the naidines resistant to the fertilizer throughout the experiment could be explained by the greater nutrient availability, their mode of reproduction, and their short life cycles. The results of our study suggested that the incorporation of nutrients modified the composition of the oligochaete assemblage in favor of herbivores and detrivores. The usefulness of these indicator organisms in monitoring freshwater systems is subsequently discussed.     

Impact of reservoirs and channelization on lowland river macroinvertebrates: A case study from Central Europe

In order to assess and compare the ecological impacts of channelization and shallow lowland reservoirs, macroinvertebrate communities of a lowland metapotamal river below reservoirs with epilimnial release were studied. The study was carried out in the Dyje River (Czech Republic) at five sites located from 1.5 to 22.5 km downstream of the reservoir outfall. The five sites differed in the degree of channel modification from natural muddy banks to riprap regulation. Seven samples were collected during the years 1998 and 1999 at each site using a semiquantitative method. The data were processed using multivariate analyses and methods for assessing the ecological and functional structure of communities. Altogether, 261 species of benthic macroinvertebrates were recorded including several rare and threatened taxa. Based on the results of principal component analysis (PCA), most of the variability within the species data (the first PCA axis) was explained by the degree of channel modification, from natural muddy banks with aquatic vegetation to a man-made riprap. The second axis was strongly correlated with current velocity. The sites differed in species richness, total abundances, proportion of individual functional feeding groups, pattern of the distribution of the current preference groups, and values of several biotic indexes, all of which also corresponded to the degree of channel modification. Thus, the morphological man-made modifications of the river channel were found to be the main factor affecting lowland river macroinvertebrates and their biodiversity. Our results suggest that the biggest threat to benthic macroinvertebrate diversity of lowland rivers comes from channelization. The impact of reservoirs can be completely overwhelmed by the impact of channelization, especially when muddy banks with aquatic vegetation present a substantial part of habitat diversity and significantly contribute to the total species pool.     

Stream macroinvertebrate communities change with grassland afforestation in central Argentina

Lotic ecosystems are highly affected by land use changes such as afforestation of natural areas for management or commercial purposes. The aim of this study was to analyze the effect of pine plantations on benthic invertebrate communities in mountain grassland streams. Additionally, we assessed if the hydrological period modifies the effect of afforestation on stream invertebrates. Three headwater streams draining grasslands (reference streams) and three draining plantations of Pinus elliottii were selected in a mountain watershed of Córdoba province (Argentina). Hydrologic and physicochemical variables were registered and benthic invertebrate samples were collected in each stream at two different hydrological periods. Total invertebrate abundance, richness and diversity were reduced in afforested streams as well as the number of indicator taxa. In addition, invertebrate functional structure (i.e. taxonomic richness and total and relative abundance of functional feeding groups, FFG) showed differences between streams with different riparian vegetation and between hydrological periods. Total abundance of all FFGs was lower in afforested streams and scrapers’ relative abundance was higher in grassland streams at the low water period. In addition, in most FFGs richness was diminished in afforested streams. Changes in light intensity, hydrology and coarse organic matter inputs produced by afforestation alter fluvial habitats and consequently the composition and trophic structure of invertebrate communities in grassland streams of Córdoba mountains.     

The effects of sewage discharge on shallow hard substrate sessile assemblages

On rocky shores, sewage discharges can modify natural distribution patterns of sessile organisms. The impact of sewage on shallow hard substrate assemblages has been assessed along SW Apulian coast (Ionian Sea, Italy), providing a framework to evaluate the benefits of future sewage displacement to deeper waters. Four locations (three controls and one putatively impacted) were selected and three sites were chosen at each location. Each site was sampled by 10 replicate photographic records. Univariate analyses revealed that the outfall did not affect the spatial distribution of number of taxa, total cover and abundance of some dominant taxa (mostly algae, sponges and bryozoans). The outfall negatively influenced the natural distribution pattern of filamentous green algae, whilst some algae (i.e. Gelidiales and Colpomenia sinuosa) were exclusively present at the impacted location. Multivariate analyses revealed that the outfall heavily modified the natural pattern of variability in the structure of the assemblage.     

Macroinvertebrate communities along the main stem and tributaries of a pre-Alpine river: composition responds to altitude,richness does not

We collected quantitative macroinvertebrate samples and measured environmental and geographical parameters at 13 sites: six along the main stem and seven in tributaries close to the main channel over a 700 m gradient in altitude and 22 km longitudinal distance along the River Kokra in the Slovenian Alps. Our objectives were 1) to compare longitudinal patterns in richness and community composition between main stem and tributary sites, and 2) to determine the relative importance of the replacement and richness difference component for overall beta diversity and of environmental versus spatial distance on beta diversity among main stem and tributary sites.In total 138 taxa were identified. There were no differences between main stem and tributary sites in mean abundance or taxon richness (67 and 58, respectively). A nMDS and ANOSIM based on Bray-Curtis similarities found no separation of main stem and tributary sites, but that upper (≥880 m a.s.l) and lower sites (≤680 m a.s.l.) formed two different groups. In both main stem and tributaries taxon richness increased only slightly going downstream while the community composition (DCA1) was much better explained by altitude and distance from source.Overall, beta diversity (Sørensen and Bray-Curtis dissimilarity) was similar for the two groups, and total Sørensen dissimilarity was driven mainly by replacement in main stem (78 %) and tributary sites (77 %). Mantel tests showed that main stem dissimilarities were significantly correlated to environmental PCA distance, watercourse distance, overland distance and altitudinal differences. Tributary dissimilarities were not correlated to any of these four factors. GLMs showed that dissimilarity among main stem sites was explained only by altitude difference, while no factors were significant among tributary sites, even though nearly so for environmental PCA distance.The study illustrates the importance of measuring beta diversity along ecological gradients, such as river continua and/or altitudinal gradients, where alpha diversity may fail to detect relatively minor changes in assemblage composition. Such changes are likely to occur due to present and future climate warming.     

1988-2016年洞庭湖大型底栖动物群落变化及驱动因素分析

洞庭湖是我国第二大淡水湖泊,其水文条件对湖泊湿地生态系统健康的维系发挥着不可替代的作用.近年来,水环境恶化日益威胁湖区水生态系统健康.然而,有关底栖动物水生态健康评价的研究仍然停留在物种群落结构方面,缺乏底栖动物群落功能对水污染响应的研究,尤其在较长时间尺度上.因而,本研究分析了19882016年近30 a来洞庭湖的水质和底栖动物群落数据,探寻底栖动物群落功能对水环境恶化的响应规律.结果表明,洞庭湖水体总氮浓度是威胁底栖动物物种和功能群落变动的主要因素.此外,不断恶化的水环境驱动底栖动物物种和功能群落结构改变,表现为敏感水生昆虫的比例下降,寡毛类、小型软体动物比例的上升,并伴随着体长为1.00~1.99 cm、背扁型、侧扁型、不移动等功能性状类别比例的下降.同时,水环境恶化降低物种丰富度、功能丰富度和劳氏二次熵多样性.基于距离的冗余分析结果显示,水体氮营养盐、重金属离子和有机污染物共同驱动底栖动物物种群落结构的变异,而营养盐类与无/有机污染物决定着其功能群落结构的变异.鉴于洞庭湖水质不断恶化的状况,本研究建议采取一系列措施,包括合理管控湖区周边废水直排入湖、取缔湖区内的非法采砂以及调控枯水季洞庭湖水位等.生物监测和评价方面,建议将底栖动物物种和功能群落一并纳入评价体系,且优先选用物种丰富度、功能丰富度和劳氏二次熵指数评估换水周期较短的大型浅水湖泊水质变化对底栖动物物种和功能多样性的影响.     

西藏尼洋河水生生物群落时空动态及与环境因子关系:4.浮游动物

于2008-2009年按照季节调查西藏地区尼洋河浮游动物群落的组成、丰度和多样性,并运用多元统计方法定量分析浮游动物的空间和季节变化特征及其与主要环境因子之间的关系.结果显示,尼洋河浮游动物包括原生动物、轮虫、枝角类和桡足类,其中原生动物9目13科14属,轮虫1目7科17属,枝角类仅1目1科1属,桡足类2目2科2属.原生动物以砂壳虫和瞬目虫属为主,轮虫则以橘轮虫属和单趾轮虫属为主.尼洋河浮游动物的物种丰富度和生物量随尼洋河海拔高度不断提升呈现递减的趋势,夏季浮游动物生物量、物种丰富度、总丰度较低,其中夏季浮游动物物种丰富度最低,而浮游动物生物量和总丰度则仅高于冬季.受到水体稳定性的影响,尼洋河浮游动物Shannon-Wiener多样性指数和均匀度指数在交汇处较低;季节方面,夏季最低,冬季次之.尼洋河原生动物和轮虫总丰度在季节方面存在相似的演替规律,即出现2次高峰和2次低谷,2次高峰分别出现在春季和秋季,2次低谷分别出现在夏季和冬季.尼洋河浮游动物沿程变化方面,浮游动物群落4个指标不存在显著差异.尼洋河浮游动物季节变化方面,仅总丰度秋季和冬季之间存在显著差异,其他3个指标在各个季节之间均不存在显著差异.典范对应分析表明,原生动物类群里,砂壳虫属丰度受水体溶解氧浓度的影响较大,前管虫、袋座虫、肾形虫、瞬目虫和斜口虫属丰度受水体矿化度的影响较大,鳞壳虫属丰度则主要与水体中氨氮浓度关联较大;轮虫类群里,单趾轮虫、无柄轮虫、枝胃轮虫、囊足轮虫属丰度与水体的矿化度关联较大,龟甲轮虫属丰度则与总磷浓度有着较大的关联.分类回归树模型预测了尼洋河浮游动物时空分布与主要环境因子之间的定量关系,结果表明尼洋河浮游动物总丰度受到硬度、季节、海拔以及河道底质等因素的影响,Shannon-Wiener多样性指数受到总碱度、季节、硬度和水温的影响,均匀度指数受到总碱度、总磷浓度和水温的影响.这些关键环境因子对尼洋河水域浮游动物的时空变化有着重要的指示作用,建议加强对浮游动物及这些环境因子的关注,推动尼洋河水域生态环境的可持续发展.     

云贵高原湖泊夏季浮游植物组成及多样性

浮游植物是水生生态系统中重要的初级生产者,对维持水生态系统的平衡起着十分重要的作用.根据2008年云贵高原湖泊丰水期浮游植物调查数据,系统地分析了云贵高原13个湖泊中浮游植物的种群密度、生物量、组成及其多样性.云贵高原13个湖泊中共鉴定出浮游植物7门109种(绿藻52种、蓝藻23种、硅藻20种、其他14种).13个湖泊浮游植物Shannon-Wiener指数在0.5-2.2之间,其值大小与单个环境因子无显著相关.相关分析发现浮游植物总量与总氮、总磷、CODMn、硝态氮含量显著正相关,物种丰富度与总氮、总磷(0.1mg/L范围内)、CODMn含量亦显著正相关.另外,研究也发现各湖泊间浮游植物组成的相似性与各湖泊间营养状态差异显著负相关.由此可见,湖泊的营养状态不仅影响浮游植物的总量、组成以及物种丰富度,而且也影响各湖泊物种组成的相似性.     

Occurrence of brackish water phytoplankton species at a closed coral reef in Nansha Islands, South China Sea

The phytoplankton assemblage of Zhubi Reef, a closed coral reef in Nansha Islands (South China Sea, SCS) was studied in June 2007. A total of 92 species belonging to 53 genera and four phyla have been identified. The dominant taxa in the lagoon were the diatom Chaetoceros and cyanobacteria Nostoc and Microcystis, while in reef flats were cyanobacteria Trichodesmium erythraeum, dinoflagellates Gymnodinium and Prorocentrum. The species richness and diversity were consistently lower in the lagoon than in reef flats. Classification and nMDS ordination also revealed significant dissimilarity in phytoplankton community structure between the reef flat and lagoon, with statistical difference in species composition and abundance between them (ANOSIM, p = 0.025). Nutrient concentrations also spatially varied, with ammonium-enrichment in the lagoon, while high Si-concentration existed in reef flat areas. Both nutrient levels and currents in SCS may play important roles in determining the composition and distribution of microalgae in Zhubi Reef and SCS.