Degradation succession of heterotrophic flagellate communities in microcosms

Degradation succession of heterotrophic flagellate communities was studied in samples of detritus and water from a small swamped lake in the environs of the settlement Borok, Yaroslavl province. Three stages of succession with different species composition of the heterotrophic flagellate community were clearly recognized. Cumulative properties of the community change with time. Maximum species richness, diversity, and abundance were observed on the fourth day of succession; their values gradually decreased later. The trophic and taxonomic community structure was most diverse at the earlier stages of succession. Primordial food (bacteria) concentration affects only the size of peak community properties, but has no influence on the pattern of succession changes. The influence of predators considerably reduced heterotrophic flagellate abundance and can shift the time of the stage with maximum species diversity in the course of succession.     

东昌湖浮游生物群落多样性季节变动与水质关系

报道了浮游生物物群落多样性指数与水质关系及初步分析了东昌湖的水质情况。2004年4月至2005年3月,采用PFU法及化学检测法对国内第二大人工湖——山东东昌湖的三个湖区9个采样点的浮游生物及水化学指标进行了初步调耷。共观察到浮游藻类76种,其中污染指示种为17种;原生动物92种,其中污染指示种为21种。浮游生物物种组成的多样性指数及化学水质分析显示,各湖区水质优劣程度依次为南湖区〉东南湖区〉西北湖区,调查结果表明东昌湖属于富营养化水体。     

极端水文干旱下鄱阳湖浮游动物群落结构特征及其影响因素

2022年鄱阳湖流域发生了特大干旱事件,对鄱阳湖生态环境产生了严重影响。为揭示极端水文干旱年的鄱阳湖浮游动物群落结构特征及其主要影响因素,于2022年1月(冬季)、4月(春季)、7月(夏季)和10月(秋季)对鄱阳湖浮游动物进行了综合调查。本次调查共鉴定出浮游动物70种(轮虫40种、桡足类17种和枝角类13种),丰度和生物量范围分别为0—152.67个/L和0—1.52 mg/L。浮游动物群落结构具有较大的时空差异：在季节上,物种数夏季最多,丰度和生物量呈现夏季最高、秋季最低的特征,干旱季节的Shannon-Wiener多样性指数和优势种组成明显不同于非干旱季节;在空间上,南部湖区的物种数、丰度、生物量高于北部湖区,多样性指数在中部湖区最高、北部湖区最低。极端水文干旱年的物种数、丰度和生物量均明显低于往年同期,但空间上的差异较小。相关性分析和冗余分析结果表明,浮游动物群落结构在干旱季节和非干旱季节的主要影响因素存在明显差异,其中干旱季节浮游动物群落结构主要受水温、水位、硝态氮、氨氮等的共同影响,非干旱季节受化学需氧量和水位的影响较大。总体上,极端水文干旱使得鄱阳湖浮游动物群落结构稳定性较...     

Detritus Quality Controls Macrophyte Decomposition under Different Nutrient Concentrations in a Eutrophic Shallow Lake, North China

Macrophyte decomposition is important for carbon and nutrient cycling in lake ecosystems. Currently, little is known about how this process responds to detritus quality and water nutrient conditions in eutrophic shallow lakes in which incomplete decomposition of detritus accelerates the lake terrestrialization process. In this study, we investigated the effects of detritus quality and water nutrient concentrations on macrophyte decomposition in Lake Baiyangdian, China, by analyzing the decomposition of three major aquatic plants at three sites with different pollution intensities (low, medium, and high pollution sites). Detritus quality refers to detritus nutrient contents as well as C∶N, C∶P, and N∶P mass ratios in this study. Effects of detritus mixtures were tested by combining pairs of representative macrophytes at ratios of 75∶25, 50∶50 and 25∶75 (mass basis). The results indicate that the influence of species types on decomposition was stronger than that of site conditions. Correlation analysis showed that mass losses at the end of the experimental period were significantly controlled by initial detritus chemistry, especially by the initial phosphorus (P) content, carbon to nitrogen (C∶N), and carbon to phosphorus (C∶P) mass ratios in the detritus. The decomposition processes were also influenced by water chemistry. The NO(3)-N and NH(4)-N concentrations in the lake water retarded detritus mass loss at the low and high pollution sites, respectively. Net P mineralization in detritus was observed at all sites and detritus P release at the high pollution site was slower than at the other two sites. Nonadditive effects of mixtures tended to be species specific due to the different nutrient contents in each species. Results suggest that the nonadditive effects varied significantly among different sites, indicating that interactions between the detritus quality in species mixtures and site water chemistry may be another driver controlling decomposition in eutrophic shallow lakes.     

A partial analysis of ecological segregation in the chironomid community of a bog lake

A small dystrophic lake was found to support 19 species of chironomid larvae, 13 of which are relatively abundant while the other six are classified as rare as they collectively constituted less than 0.25% of the total chironomid community. With the exception of one species pair, evidence of ecological segregation could be demonstrated for all abundant species that could be morphologically distinguished as larvae. Both members of the overlapping pair fed mainly upon coarse detritus, the most abundant food resource in the lake. Limited data on the six rare species failed to reveal ecological segregation from one or more of the abundant species.     

Effects of stream predator richness on the prey community and ecosystem attributes

It is important to understand the role that different predators can have to be able to predict how changes in the predator assemblage may affect the prey community and ecosystem attributes. We tested the effects of different stream predators on macroinvertebrates and ecosystem attributes, in terms of benthic algal biomass and accumulation of detritus, in artificial stream channels. Predator richness was manipulated from zero to three predators, using two fish and one crayfish species, while density was kept equal (n = 6) in all treatments with predators. Predators differed in their foraging strategies (benthic vs. drift feeding fish and omnivorous crayfish) but had overlapping food preferences. We found effects of both predator species richness and identity, but the direction of effects differed depending on the response variable. While there was no effect on macroinvertebrate biomass, diversity of predatory macroinvertebrates decreased with increasing predator species richness, which suggests complementarity between predators for this functional feeding group. Moreover, the accumulation of detritus was affected by both predator species richness and predator identity. Increasing predator species richness decreased detritus accumulation and presence of the benthic fish resulted in the lowest amounts of detritus. Predator identity (the benthic fish), but not predator species richness had a positive effect on benthic algal biomass. Furthermore, the results indicate indirect negative effects between the two ecosystem attributes, with a negative correlation between the amount of detritus and algal biomass. Hence, interactions between different predators directly affected stream community structure, while predator identity had the strongest impact on ecosystem attributes.     

Spatial patterns in aquatic vegetation composition and environmental covariates along chains of lakes in the Kokemäenjoki watershed (S. Finland)

The diversity and community structure of macrophyte vegetation was studied in 50 boreal lakes forming several upper reaches of lake chains around Lammi, southern Finland. Water chemical parameters and morphometry of the basins were included in a multivariate analysis. Floating-leaved vegetation was the dominant growth form, followed by emergent plants. In downstream lakes, the dominance of floating-leaved macrophytes declined, and emergent species increased in abundance. Species richness was highest in larger lakes, with a wider range of littoral habitats than smaller lakes. Electrical conductivity (range 18–151 mS cm⁻¹, 25 °C) of the water correlated well with patterns in diversity among lakes, but this was not the case for nutrient concentrations. As a whole, morphometrical characteristics of lake basins showed better correlations with vegetation structure than any of the measured chemical parameters. The macrophyte vegetation of neighbouring lake chains differed considerably, depending on the surrounding landscape properties, water quality of the lakes and immigration history of plant species.     

Dissecting spatiotemporal patterns of functional diversity through the lens of Darwin's naturalization conundrum

Darwin's naturalization conundrum describes the paradigm that community assembly is regulated by two opposing processes, environmental filtering and competitive interactions, which predict both similarity and distinctiveness of species to be important for establishment. Our goal is to use long‐term, large‐scale, and high‐resolution temporal data to examine diversity patterns over time and assess whether environmental filtering or competition plays a larger role in regulating community assembly processes. We evaluated Darwin's naturalization conundrum and how functional diversity has changed in the Laurentian Great Lakes fish community from 1870 to 2010, which has experienced frequent introductions of non‐native species and extirpations of native species. We analyzed how functional diversity has changed over time by decade from 1870 to 2010 at three spatial scales (regional, lake, and habitat) to account for potential noninteractions between species at the regional and lake level. We also determined which process, environmental filtering or competitive interactions, is more important in regulating community assembly and maintenance by comparing observed patterns to what we would expect in the absence of an ecological mechanism. With the exception of one community, all analyses show that functional diversity and species richness has increased over time and that environmental filtering regulates community assembly at the regional level. When examining functional diversity at the lake and habitat level, the regulating processes become more context dependent. This study is the first to examine diversity patterns and Darwin's conundrum by integrating long‐term, large‐scale, and high‐resolution temporal data at multiple spatial scales. Our results confirm that Darwin's conundrum is highly context dependent.     

南洞庭湖区软体动物物种多样性评估及保护对策

洞庭湖孕育和维持了较高和独特的软体动物多样性。尽管有关该湖软体动物的调查较多, 但多分散于各文献中。本文结合文献调研和现场调查(2013-2018年), 系统评估了南洞庭湖区软体动物物种多样性, 解析驱动群落格局演变的关键因子, 并提出合理的保护对策。共记录2纲5目14科33属87种(腹足纲41种, 双壳纲46种), 其中本调查记录54种, 隶属于2纲5目12科31属, 包括腹足纲22种, 双壳纲32种。评估结果显示处于近危和受威胁等级物种21种, 包括腹足纲4种和双壳纲17种。调查区域软体动物平均密度和生物量分别为173.1 ind./m ²和279.3 g/m ²。优势种为河蚬(Corbicula fluminea)、大沼螺(Parafossarulus eximius)、铜锈环棱螺(Bellamya aeruginosa)、卵河螺(Rivularia ovum)。基于距离的冗余分析(distance-based redundancy analysis, dbRDA)结果显示, 局域环境因子(底质类型、水深、pH、总溶解固体和总磷)制约软体动物的群落变异。另外, 区域内的人类活动(如商业采砂、建坝和沿岸土地利用、过度捕捞和非法电捕等)亦深刻影响软体动物的生存。这些人类干扰已导致软体动物物种多样性显著下降, 可能造成一些特有物种的局域性灭绝。为了恢复和保护软体动物物种多样性和资源, 应采取一系列对策, 包括管控合法的挖沙业和取缔非法挖沙业、禁止过度捕捞和非法电捕、维持水文的自然节律、恢复沿岸自然湖滨带和控制点源和面源污染物排入等。我们呼吁尽快在南洞庭湖区建立软体动物国家级自然保护区, 以保护该湖区(可能是整个洞庭湖)残存的软体动物物种多样性和特有性。     

Responses of epilimnetic phytoplankton to experimental nutrient enrichment in three small seepage lakes

This paper describes the responses of three epilimnetic phytoplanktoncommunities to experimental nitrogen and phosphorus enrichmentas compared to the phytoplankton community in a fourth, unmanipulated,lake. Increased nutrient inputs increased total phytoplanktonbiomass, primary productivity, chlorophytes, cryptomonads andspecies turnover rates in all three enriched lakes; cyanobacteriaincreased in two of the three enriched lakes. However, nutrientaddition also led to declines in previously dominant dinoflagellatesand chrysophytes, and in species diversity. At the species level,there were large changes in community composition from yearto year in both enriched and reference lakes, suggesting thatphytoplankton community composition is highly dynamic even inthe absence of enrichment. Overall, changes in total biomass,productivity and species diversity were consistent among theenriched lakes, while changes in species composition differeddue to variation in the physical, chemical and biotic environmentof each lake. This suggests that aggregated variates are moreuseful for quantitative prediction of nutrient effects, whilespecies responses can be used to signal qualitative differencesin environmental conditions among lakes. ³Present address: Department of Biological Sciences, DartmouthCollege, 6044 Gilman Laboratory, Hanover, NH 03755-3576, USA     

Factors Affecting the Benthic Community Structure of a Discontinuous Stream in Guadelupe Mountains National Park,Texas

McKittrick Creek, a discontinuous mountain-desert stream in Guadelupe Mountains National Park, Texas, was sampled at discrete locations (pools) to test for differences in biomass, density, species diversity, equitability, and species richness in the benthic macroinvertebrate community. Significant differences occurred among pools for these biotic characteristics of the benthic community along the downstream gradient. Pools connected by flow were more similar to each other than pools separated by dry reaches. Variation in the quantity of coarse detritus and periphyton best explained differences among pools.     

Environmental determinants of macroinvertebrate diversity in small water bodies: insights from tank-bromeliads

The interlocking leaves of tank-forming bromeliads (Bromeliaceae) collect rainwater and detritus, thus creating a freshwater habitat for specialized organisms. Their abundance and the possibility of quantifying communities with accuracy give us unparalleled insight into how changes in local to regional environments influence community diversity in small water bodies. We sampled 365 bromeliads (365 invertebrate communities) along a southeastern to northwestern range in French Guiana. Geographic locality determined the species pool for bromeliad invertebrates, and local environments determined the abundance patterns through the selection of traits that are best adapted to the bromeliad habitats. Patterns in community structure mostly emerged from patterns of predator species occurrence and abundance across local–regional environments, while the set of detritivores remained constant. Water volume had a strong positive correlation with invertebrate diversity, making it a biologically relevant measure of the pools’ carrying capacity. The significant effects of incoming detritus and incident light show that changes in local environments (e.g., the conversion of forest to cropping systems) strongly influence freshwater communities. Because changes in local environments do not affect detritivores and predators equally, one may expect functional shifts as sets of invertebrates with particular traits are replaced or complemented by other sets with different traits.     

Microbial Biodiversity in the Water of Lake Baikal

An investigation of the microbial community of Lake Baikal by the methods of general and molecular microbiology showed that culturable bacterial strains are represented by various known genera. The lake water contains a great number of bacterial morphotypes, as revealed by electron microscopy, and a great diversity of nonculturable microorganisms belonging to different phylogenetic groups, as revealed by 16S rRNA gene fragment sequencing. The inference is made that the microbial community of Lake Baikal contains not only known species but also new bacterial species that are possibly endemic to the lake.     

基于高通量测序研究青藏高原茶卡盐湖微生物多样性

【目的】茶卡盐湖(Chaka Salt Lake,CSL)是青藏高原有名的天然结晶盐湖,具有独特的石盐盐湖矿床,盛产青盐。盐湖卤水环境中存在丰富的嗜盐菌资源和潜在的新种,细菌和古菌的群落结构特征和物种多样性尚不明确。【方法】采用Illumina高通量测序平台对茶卡盐湖水样和底泥混合物中的细菌和古菌群落进行16S r RNA基因(V3-V5区)高通量测序,检测4个样本的群落结构差异和微生物多样性。【结果】获得细菌和古菌总有效序列分别为117 192和110 571条。结果分析表明细菌和古菌的物种注释(Operational taxonomic unit,OTU)数目分别为421和317,获得分类地位明确的细菌种类为14门28纲170属,古菌为5门4纲34属。细菌的优势类群是厚壁菌门(Firmicutes),所占比例为68.37%,其次为变形菌门Proteobacteria(20.49%);优势种属依次为芽孢杆菌属Bacillus(41.94%)、海洋芽孢杆菌属Oceanobacillus(8.03%)、假单胞菌属Pseudomonas(7.67%)、盐厌氧菌属Halanaerobium(7.42%)和乳球菌属Lactococcus(7.38%);古菌的优势类群以广古菌门(Euryarchaeota)盐杆菌纲(Halobacteria)为主,优势菌是Halonotius(17.21%)和盐红菌属Halorubrum(16.23%)。【结论】揭示了茶卡盐湖中细菌和古菌的群落结构及物种多样性,为嗜盐菌的开发及后续微生物资源的挖掘提供了理论依据。     

Species diversity in spatial and temporal dimensions of fruit-feeding butterflies from two Ecuadorian rainforests

To test the hypotheses that butterflies in an intact lowland rainforest are randomly distributed in space and time, a guild of nymphalid butterflies was sampled at monthly intervals for one year by trapping 883 individuals of 91 species in the canopy and understory of four contiguous, intact forest plots and one naturally occurring lake edge. The overall species abundance distribution was well described by a log-normal distribution. Total species diversity (γ-diversity) was partitioned into additive components within and among community subdivisions (α-diversity and β-diversity) in vertical, horizontal and temporal dimensions. Although community subdivisions showed high similarity (l-β-diversity/γ-diversity), significant β-diversity existed in each dimension. Individual abundance and observed species richness were lower in the canopy man in the understory, but rarefaction analysis suggested that the underlying species richness was similar in both canopy and understory. Observed species richness varied among four contiguous forest plots, and was lowest in the lake edge plot. Rarefaction and species accumulation curves showed that one forest plot and the lake edge had significantly lower species richness than other forest plots. Within any given month, only a small fraction of total sample species richness was represented by a single plot and height (canopy or understory). Comparison of this study to a similar one done in disturbed forest showed diat butterfly diversity at a naturally occurring lake edge differed strongly from a pasture-forest edge. Further comparison showed that species abundance distributions from intact and disturbed forest areas had variances that differed significandy, suggesting mat in addition to extrapolation, rarefaction and species accumulation techniques, the shapes of species abundance distributions are fundamental to assessing diversity among sites. This study shows the necessity for long-term sampling of diverse communities in space and time to assess tropical insect diversity among different areas, and the need of such studies is discussed in relation to tropical ecology and quick surveys in conservation biology.     

Diversity and distribution of molluscan fauna of Asthamudi estuary,Kerala, India

The survey of molluscan fauna of Ashtamudi estuary of the southwest coast of India recorded the presence of 119 species classified under 3 classes (Polyplacophora, Gastropoda and Bivalvia), 57 families and 96 genera. The species diversity was dominated by the Gastropoda (69 species), followed by the Bivalvia (49 species) and the Polyplacophora (1 species). The report includes four species recorded for the first time from India: Desmaulus edgarianus (Melvill, 1898), Pilosabia trigona (Gmelin, 1791), Nassarius javanus (Schepman, 1891) and Jorunna labialis (Eliot, 1908). The true diversity of the mangrove region was as good as that of a community with 31.380 (=?31) equally common species; the respective values for the bar mouth and lake regions were 15.516 and 8.997, respectively, indicating that the molluscan species assemblage of the mangrove was the most diverse and of the lake, the least. True β-diversity across this gradient registered 1.792, which means that though there were three communities, they were equivalent to only 1.792 (=?2) effective communities, i.e., the three actual communities were as different from each other as 2 with equal weights and no species in common.

     

湖泊富营养化对轮虫群落结构及物种多样性的影响

2005年7月至2006年6月, 我们对安徽省芜湖市境内5个湖泊中轮虫的群落结构及部分水质特征参数进行了调查, 用相关加权综合营养状态指数(TLIc)评价了各湖泊的营养水平, 分析了其中的轮虫群落结构、多样性指数及其与TLI_C之间的关系。经鉴定, 5个湖泊中共采集到轮虫79种, 隶属18科31属; 不同营养水平湖泊中出现的轮虫种类数有明显的差异(P<0.01)。除龙窝湖外, 其余4个湖泊中的轮虫种类数与TLI_C均呈显著负相关关系(r＝–0.984, P<0.05)。湖泊水体的富营养化进程显著地提高了轮虫总密度和第一优势种的优势度, 降低了轮虫群落的均匀度和物种多样性指数。     

Detritus-dependent development of the microbial community in an experimental system: qualitative analysis by denaturing gradient gel electrophoresis.

Correlations between the biomass of phytoplankton and the biomass of bacteria and between the biomass of bacteria and the biomass of protozoans suggest that there is coupling between these compartments of the "microbial loop." To investigate this coupling on the species level, bacteria and protozoans from untreated lake water inocula were allowed to grow on detritus of the green alga Ankistrodesmus falcatus or the cyanobacterium Oscillatoria limnetica in continuous-flow systems for 1 month. Denaturing gradient gel electrophoresis (DGGE) of the 16S and 18S rRNA genes was used to monitor the development of the bacterial community structure and the eukaryotic community structure, respectively. Nonmetric multidimensional scaling of the DGGE profiles revealed the changes in the microbial community structure. This analysis showed that significantly different bacterial communities developed on the green algal detritus and on the cyanobacterial detritus. Although similar results were obtained for the eukaryotic communities, the differences were not significant. Hence, our findings indicate that the origin of detritus can affect the structure of at least the bacterial community. A phylogenetic analysis of 20 18S ribosomal DNA clones that were isolated from the continuous cultures revealed that many sequences were related to the sequences of bacterivorous protozoans (members of the Ciliophora, Rhizopoda, Amoeba, and Kinetoplastida). One clone grouped in a recently established clade whose previously described members are all parasites. The affiliations of about 20% of the clones could not be determined.     

苏州工业园区湖泊后生浮游动物群落结构及影响因子

苏州工业园区地处长江流域下游,随着城市化进程的不断推进,园区水生态系统结构与功能的稳定面临严峻考验。浮游动物作为水生态系统的重要组成部分,探究其群落结构的形成机制对生物多样性保护及生态系统健康发展具有重要意义。为深入了解苏州工业园区五个主要湖泊后生浮游动物群落结构的动态变化及影响因子,于2018年7月至2019年6月进行4次调查。研究共检出后生浮游动物112种（轮虫65种、枝角类29种、桡足类18种）,其中优势种12种（轮虫10种、枝角类和桡足类各1种）。Jaccard相似性分析表明,湖泊间后生浮游动物物种组成整体处于中等相似水平。后生浮游动物密度呈现出显著的季节和湖泊差异,而生物量、Shannon-Wiener多样性指数、Pielou均匀度指数以及Margalef丰富度指数仅存在显著的季节差异。聚类分析结果表明,夏季和秋季后生浮游动物群落结构最为相似。RDA分析表明,水温、溶解氧和pH是影响园区湖泊后生浮游动物群落结构的主要环境因子。Pearson相关性分析表明,湖泊面积与后生浮游动物群落结构无显著相关关系,样点近岸距离与生物量具有显著的正相关关系。基于水质评价标准和物种多样性指数可知,园区湖泊水质整体处于轻-中度污染水平。研究表明苏州工业园区五大湖泊后生浮游动物群落结构表现出同质化趋势;季节变化、环境因子以及样点近岸距离是调控群落结构形成的主要因素。