Characteristics Of Assemblages Research Articles

Alteration, uranium occurrence state, and enrichment mechanism of the Cretaceous Luohe Formation, southwestern Ordos Basin, western China

To ascertain the characteristics of mineral assemblages associated with uranium mineralization and enrichment mechanism of deep sandstone-type uranium deposits, drill-core logging, petrography and mineralogy, scanning electron microscopy (SEM), electronic probe micro analysis (EPMA), whole-rock analysis, X-ray diffraction (XRD) were used to identify the types, redox state of uranium minerals, and typical uranium-related mineral assemblages in the sandstone of the Cretaceous Luohe Formation, southwestern Ordos Basin. The results showed that the clastic grains in the gray and red uranium-bearing sandstone have undergone relatively strong alteration, while alteration of the clastic grains in the gray and red calcareous sandstone is relatively weak. The alteration minerals mainly include pyrite, anatase, kaolinite, chlorite, calcite, apatite, and feldspar. Uranium contents is highly consistent with S, P2O5, CaO, and FeO concentrations in the vertical direction and has a weak correlation with the total organic carbon. Uranium ores are mainly pitchblende and titanium-bearing uranium minerals. The Luohe Formation experienced transformation from a weak alkaline oxidation environment during the diagenetic stage to a weak acid reduction conditions in the early mineralization stage and then to a weak alkaline reduction environment in the middle–late mineralization stages. Typical alteration minerals associated with uranium ores include two types, which are formed in acid reduction and alkaline reduction redox stages, respectively. The alteration minerals related to acidic fluid process are pyrite, anatase, kaolinite, and apatite; those related to alkaline fluid mechanism consist of calcite and chlorite. Deep-seated uranium mineralization was formed by both acidic and alkaline reducing fluids, being dominated by acidic fluid conditions. In-depth investigation of the alteration and uranium ore minerals are of great scientific value to infer the fluid type of mineralization stage and reveal the enrichment mechanism of uranium deposits.

Spatial and seasonal variation in littoral fish assemblages of four estuarine lagoons on the Mexican Pacific coast

The shallowest zones of coastal lagoons are particularly appropriate nursery habitat for many fish species by providing refuge from predators and abundant food, among other benefits. However, little is known about the characteristics of fish assemblages and their relationship with environmental factors in these areas. The main objective of this study was to investigate the abundance and composition of the fish assemblages in the shallow zones (≤1 m) of four coastal lagoons in the Central Mexican Pacific and determine the correlation of their spatial and seasonal variations with selected abiotic variables. Fish samples were taken with a beach seine in the months of May and December during two consecutive years. Simultaneously, the physical and chemical variables of the water were measured, and the particle size of the sediment and content of organic matter were determined. A total of 26016 fish belonging to 60 species were collected, but only eight species (Poeciliopsis turrubarensis, Lile stolifera, Poecilia butleri, Eucinostomus currani, Anchoa sp, Gerres simillimus, Atherinella guatemalensis and Mugil setosus) accounted for more than 80% of the specimens. Significant differences in the composition of the fish assemblages between lagoons were found. The changes were principally related to the type of communication with the ocean, second to physical and chemical variables, primarily salinity, followed by size of the sediment particles (% of mud or sand). Observed seasonal changes could have been related to environmental and biological factors (e.g. recruitment) acting synergistically. No evidence was found that the state of eutrophication of the lagoons is severe and could be affecting the composition of the fish assemblages.

The holobiont self: understanding immunity in context.

Both concepts of the holobiont and the immune system are at the heart of an ongoing scientific and philosophical examination concerning questions of the organism’s individuality and identity as well as the relations between organisms and their environment. Examining the holobiont, the question of boundaries and individuality is challenging because it is both an assemblage of organisms with physiological cohesive aspects. I discuss the concept of immunity and the immune system function from the holobiont perspective. Because of the host-microbial close relations of codependence and interdependence, the holobiont is more often than not confused with the host, as the host is the domain in which this entity exists. I discuss the holobiont unique ecological characteristics of microbial assemblages connected to a host in a network of interactions in which the host is one of the organisms in the community but also its landscape. Therefore, I suggest viewing the holobiont as a host-ecosystem and discuss the implication of such a view on the concept of immunity and the meaning of protection. Furthermore, I show that viewing the holobiont as a host ecosystem opens the possibility of using the same ecological definition of boundaries and immunity dealing with an ecological system. Thus, the holobiont’s boundaries and immunity are defined by the persistence of its complex system of interactions integrating existing and new interactions. This way of thinking presents a notion of immunity that materializes as the result of the complex interdependence relations between the different organisms composing the holobiont similar to that of an ecosystem. Taking this view further, I discuss the notion of immunogenicity that is ontologically heterogeneous with various causal explanations of the processes of tolerance and targeted immune response. Finally, I discuss the possible conceptualization of already existing and new biomedical practices.

Impacts of detritivore diversity loss on instream decomposition are greatest in the tropics

The relationship between detritivore diversity and decomposition can provide information on how biogeochemical cycles are affected by ongoing rates of extinction, but such evidence has come mostly from local studies and microcosm experiments. We conducted a globally distributed experiment (38 streams across 23 countries in 6 continents) using standardised methods to test the hypothesis that detritivore diversity enhances litter decomposition in streams, to establish the role of other characteristics of detritivore assemblages (abundance, biomass and body size), and to determine how patterns vary across realms, biomes and climates. We observed a positive relationship between diversity and decomposition, strongest in tropical areas, and a key role of abundance and biomass at higher latitudes. Our results suggest that litter decomposition might be altered by detritivore extinctions, particularly in tropical areas, where detritivore diversity is already relatively low and some environmental stressors particularly prevalent.

Relationships between characteristics of macrobenthic assemblages and environmental variables in the Heihe River Basin, China

Abstract To clarify the characteristics of macrobenthic assemblages and their response to the aquatic environment in the upper and middle reaches of the Heihe River, water quality, sediments and macrobenthos measurements were conducted in the summers of 2018 and 2019. The results showed that 50 species of macrobenthos were identified, belonging to 3 phyla, 7 classes, 15 orders and 32 families, mainly arthropods (37 species) and mollusks (11 species). Argyroneta aquatica, Chlaznius sp., dragonfly nymphs, Palaemon modestus, Radix auricularia, Cyraulus albus and Suecinea sp. were the dominant species in the whole study region; most of these are pollution-tolerant and moderately pollution-tolerant species. The macrobenthos density and biomass ranged from 10 to 577 ind./m2 and from 0.0907 to 50.0562 g/m2, respectively, showing high spatial heterogeneity. Predators were the main functional feeding group. One-way analysis of variance clarified that Margalef's index and the Shannon–Wiener index differed significantly among the spatial areas (P < 0.05). Canonical correspondence analysis showed that the spatial heterogeneity of the macrobenthos was affected by the water temperature and the total nitrogen and total phosphorus in sediments (P < 0.05).

Factors associated with distributions of six fishes of greatest conservation need in streams in midwestern USA

Abstract Many fish species of greatest conservation need (SGCN) in Iowa and Minnesota, USA, have been in decline for decades. A key reason for the decline is the alteration and degradation of naturally flowing streams owing to land use changes resulting from agricultural practices. Populations of several fishes have been adversely affected by widespread stream channelization that has resulted in more homogeneous stream habitats throughout Iowa and Minnesota. The goal of this study was to determine the abiotic and fish assemblage characteristics associated with the presence of these rare fishes. Electrofishing and seining were used to sample fish assemblages and 43 abiotic characteristics were measured at 111 sites in the North Raccoon and Boone River basins in central Iowa and the Rock River and Beaver Creek basins in north‐west Iowa and south‐west Minnesota during 2016 and 2017. Six SGCN, including the federally endangered Topeka shiner (Notropis topeka), were included in statistical modelling to determine habitat and fish assemblage characteristics associated with their presence. Species‐specific nonmetric multidimensional scaling ordinations indicated that abiotic characteristics and fish assemblages often differed between sites where SGCN were present and absent. Random forest and logistic regression models suggested that the presence of four of six SGCN were positively associated with species richness, whereas all other 10 important abiotic and fish assemblage variables were unique to only one or two of the six SGCN. Topeka shiners were present at 36% of sites and were positively associated with orangespotted sunfish (Lepomis humilis) catch per unit effort while being negatively associated with canopy cover and fantail darter (Etheostoma flabellare) catch per unit effort.

DNA Barcoding Identifies Unknown Females and Larvae of Fannia R.-D. (Diptera: Fanniidae) from Carrion Succession Experiment and Case Report.

Simple SummaryInsects are frequently attracted to animal and human cadavers, usually in large numbers. The practice of forensic entomology can utilize information regarding the identity and characteristics of insect assemblages on dead organisms to determine the time elapsed since death occurred. However, for insects to be used for forensic applications it is essential that species are identified correctly. Imprecise identification not only affects the forensic utility of insects but also results in an incomplete image of necrophagous entomofauna in general. The present state of knowledge on morphological diversity and taxonomy of necrophagous insects is still incomplete and identification of immature and female forms can be extremely difficult. In this study, we utilized molecular identification methods to link conspecific sexes and developmental stages of forensically important flies. We identified larvae and females of flies collected from animal and human cadavers which otherwise were morphologically unidentifiable. The present study fills a gap in taxonomy of flies and provides data facilitating application of new species as forensic indicators.Application of available keys to European Fanniidae did not facilitate unequivocal species identification for third instar larvae and females of Fannia Robineau-Desvoidy, 1830 collected during a study of arthropod succession on pig carrion. To link these samples to known species, we took the advantage of molecular identification methods and compared newly obtained cytochrome oxidase subunit I (COI) barcode sequences against sequences deposited in reference databases. As an outcome of the results obtained, we describe for the first time a third instar larva of Fannia nigra Malloch, 1910 and Fannia pallitibia (Rondani, 1866) and a female of Fannia collini d’Assis-Fonseca, 1966. We provide combinations of characters allowing for discrimination of described insects from other Fanniidae. We provide an update for the key by Rozkošný et al. 1997, which allows differentiation between females of F. collini and other species of Fanniidae. Additionally, we provide a case of a human cadaver discovered in Southern Poland and insect fauna associated with it as the first report of F. nigra larvae developing on a human body.

Characteristics of macrofaunal assemblages and their relationships with environmental factors in a semi-enclosed bay

Characteristics of macrofaunal assemblages and their relationships with environmental factors in a semi-enclosed bay were studied seasonally in China. A total of 251 species were identified, including polychaetes (104 species), crustaceans (73 species), mollusks (51 species), and other phyla (23 species). Mean values of macrofaunal abundance were 1210, 2483, 3209, 3600 ind./m2 while those of biomass were 56.88, 176.15, 136.28, 265.55 g/m2, respectively. Ranges of species richness index, evenness index, Shannon-Wiener index were 1.54–8.16, 0.17–0.90, 0.69–4.78, respectively. The diversity indices were affected by bottom water salinity and pH. BIOENV analysis showed that water depth, phaeophorbide, and silt-clay proportion had important impacts on macrofaunal assemblages while abundance and biomass were affected by bottom water temperature, salinity, and water depth. Compared with historical data, macrofaunal species number, abundance and biomass showed a slight increasing trend, which may be due to the water quality improvement of this bay.

New insights from geostatistics on the genetic relationship between shales, mudstones, and sandstones within a parasequence in the lower Chang7 Member of the Upper Triassic Yanchang Formation, Ordos Basin, Northern China

Abstract The Chang7 Member of the Upper Triassic Yanchang Formation in the Ordos Basin, North China, has received much attention in recent years due to its huge shale oil potential. However, few studies of the relationship between black shale and other lithofacies are available, and the origin of black shales in the parasequence is poorly understood. In this paper, we describe the detailed petrography of the Chang7 Member sampled by 578 drill holes in the southern Ordos Basin and present geochemical data to reveal the relationships between black shales, mudstones, and sandstones, aiming to understand the factors that controlled the formation of the black shales. Four sedimentary assemblages were identified within the Chang7_3 parasequence, using geostatistic cluster and correlation analyses. High total organic carbon (TOC) shale (HTS), HTS + medium-TOC shale (MTS), low-TOC mudstone (LTM), and fine sandstone (FS) facies were predominant in Assemblage 1, Assemblage 2, Assemblage 3, and Assemblage 4, respectively. The FS facies had almost no effect on the formation and preservation of organic carbon. The number of mudstone interbeds is sufficiently large to cause marked negative changes in the thickness and organic-carbon abundance of black shale. The sedimentary assemblage characteristics in a parasequence provide important insights into the link between black shale and other facies. This study has profound implications for understanding the formation mechanisms of black shale in lacustrine systems.

Palynological evidence of Middle Pleistocene palaeoenvironmental changes from the ‘Buca dell’Onice’ flowstone (Alpi Apuane, Central Italy)

AbstractBuca dell’Onice di Monte Girello is a small cave located in the Alpi Apuane (central Italy). It preserves an exceptionally thick flowstone deposited intermittently during the Middle Pleistocene. Two main depositional cycles, separated by a physical discontinuity, have been recognised and described. This discontinuity and the top surface of the flowstone attest to two main phases of interrupted growth related to palaeoenvironmental and palaeoclimate changes. Pilot palynological investigations support the existence of such changes. Despite the high number of barren pollen samples and the overall very low concentration of pollen grains per gram of sediment, palynology furnishes some interesting insights especially regarding floral composition, vegetation cover and local to regional climate. The pollen record also contributes to the definition of the stratigraphic distribution of taxa no longer growing in this area (i.e. Carya and Picea). According to the pollen assemblage characteristic of arboreal vegetation cover, the flowstone was deposited predominantly during humid phases under both warm and cool climate conditions (interglacials/interstadials and at the end of interglacials). The warm and cool phases correspond, respectively, to increases of mixed thermophilous forest taxa and montane arboreal taxa. On the other hand, the pollen record does not show the major expansion of open vegetation associated with the coldest and driest conditions, which apparently fall at the main middle discontinuity and at the top interruption of the flowstone. Previous data permit changes in precipitation to be identified as one of the major limiting factors for the growth of this flowstone, probably in a period including MISs 13‐10. The more significant lithological features of the flowstone as well as the vegetal and climate signatures suggest that its development principally represents a response to global events including teleconnections active between the Mediterranean and the Atlantic circulation, with minor contribution from local factors.

Every hunter needs a knife: Hafted butchering knives from Maisières-Canal and their effect on lithic assemblage characteristics

Despite the central role butchering tools have had in the origins and development of human technologies, they have been overlooked in technological and functional studies with few exceptions. We use new results on the Gravettian assemblage from Maisières-Canal (Belgium) to illustrate how butchering knives were integrated in lithic production sequences and how the hafting, use and maintenance of these tools have affected the characteristics of the resulting lithic assemblage. The detailed low and high magnification analysis of a sample of knives, previously characterised as “tanged points”, “Maisières points”, and “tanged scrapers”, shows that these hunting knives were nearly always used hafted and had extensive use-lives. They were therefore an important component in the toolkits of the Gravettian hunter-gatherers occupying the site and are partly responsible for some of the most idiosyncratic traits of the lithic assemblage. These results underline the importance of maintaining a broad view of different tasks and needs to which toolkits responded, and encourage future studies to approach lithic assemblages from this perspective instead of prioritising projectile armatures.

Fluid-rock reactions of the Triassic Taiyangshan porphyry Cu-Mo deposit (West Qinling, China) constrained by QEMSCAN and iron isotope

The multiphase hydrothermal superposition phenomena on porphyry deposits, the mineral complexity and characteristics of the alteration-associated assemblages limit a further determination for the magmatic-hydrothermal evolution in porphyry deposits. The Taiyangshan porphyry Cu-Mo deposit in the northern margin of the Triassic West Qinling Orogenic Belt exhibits a multi-stage, alteration-related quartz sulfide veins that recorded element migration processes during fluid-rock reactions. In this study, we investigated hydrothermal veins in the Taiyangshan deposit focusing on vein compositions and structures as well as the evolution of ore formation, using quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) and iron isotope analyses. The formation of the early K-feldspar-biotite-quartz-magnetite-apatite veins is closely associated with the early potassic alteration, and during the fluid-rock reactions, Si, S, Fe, and K migrated in, while Mg, Ca and Na migrated out. K-feldspar-chlorite-pyrite-chalcopyrite-quartz veins correlated to the propylitic alteration, dominantly caused the migration of Si, Fe, S, Ca Mg, Al and K. Quartz-sericite-pyrite veins corresponding to the phyllic alteration processes that occurred in a relatively late stage, during the fluid-rock reactions of which, Si, Fe, S, and K migrated into the system. The δ56Fe whole-rock values of altered porphyries range from 0.08‰ to 0.31‰, and δ56Fe values of pyrite from quartz veins range from 0.30‰ to 0.57‰. Iron isotope compositions of both pyrites of the ore-bearing wall rocks and the quartz-sulfide veins of the Taiyangshan Cu-Mo deposit are generally uniform, which indicate the same source origin between the ore-bearing porphyry and the iron isotope compositions of the metal sulfide in the quartz veins, and additionally highlight that the ore-forming source is closely related to the ore-bearing porphyry. Magnetite precipitated in the early stage of potassic alteration, resulting in the enrichment of the light Fe isotope in the early fluids. Crystallization and precipitation of pyrite mainly occurred during processes of propylitic and phyllic alteration, leading to an absorption of the light Fe isotope, and elsewhere, an enrichment of the heavy Fe isotope in the fluids. During the fluid-rock reactions of propylitic and phyllic alteration, a large amount of S migrated into the veins, thereby promoting the fractionation of Fe isotope. Moreover, the development of the ore-forming fluids enriched with heavy Fe isotope from early potassic- to late phyllic alteration, are indicative of isotopic progressions from the early lithostatic pressure to the late hydrostatic pressure. Our research on the Taiyangshan Cu-Mo porphyry deposit helps to explain the evolutionary processes of the magmatic–hydrothermal system, and improves our understanding of the porphyry metallogenic evolution model.

Surface pollen assemblages from different sedimentary environments in the Yinchuan Basin, North China, and their significance for stratigraphic pollen records

Understanding the sources areas and transport mechanisms of pollen grains is important for reconstructing vegetation and climate from fossil pollen data. We studied the modern pollen assemblages of 28 surface samples from different geomorphic units (mountains, the central basin, and the riverine zone) in the Yinchuan Basin in China. Our aim was to compare the characteristics of the pollen assemblages from the different sedimentary environments and to determine the differences in pollen source areas and transport mechanisms. The results show that: (1) The pollen assemblages from the mountain and piedmont alluvial fan environments were dominated by trees, with the tree pollen content decreasing with decreasing altitude. The pollen in the piedmont alluvial fan environment was mainly transported by surface runoff, and assemblage combines the characteristics of both the mountain and the local vegetation. (2) The pollen assemblages from the central basin were dominated by pollen produced by the zonal desert-steppe vegetation. (3) The pollen assemblages from the riverine zone were dominated by a long-distance component from within the upper part of the drainage area. The results suggest that in sedimentary pollen records from the Yinchuan Basin, the arboreal pollen component primarily reflects vegetation changes within the surrounding mountains; the herbaceous pollen component is an indicator of changes in desert-steppe vegetation; and the long-distance fluvially-transported pollen component reflects vegetation changes in the upstream drainage area.

Responses of phytoliths in topsoil samples to temperature variation in temperate region.

Modern phytolith research is the premise to accurately reconstruct the regional paleovegetation and paleoclimate. It is thus particularly important to study the spatial distribution characteristics of the phytolith assemblages and the response of the phytolith to environmental factors. In this study, we collected 54 topsoil samples along the isohyet of 600 mm in Northeast China to examine the distribution patterns of phytolith along the gradient of single environmental factor. With this special sampling method, we targeted to reveal the responses of phytolith assemblages in the topsoil to the variation of temperature. The results showed that there were a large number of phytoliths with various morphotypes in the 54 topsoil samples in Northeast China. The phytolith morphotypes were the same, including elongate, lanceolate, blocky, cuneiform, tabular, saddle, rondel, bilobate, trapeziform polylobate, prism, silicified stomata, conduit, papillae, sclereid and carinate. In gene-ral, the contributions of elongate and lanceolate were high; the contributions of short cell phytoliths, blocky, tabular and cuneiform were small relatively; the contributions of the other types of phytoliths were less than 1.0% and appeared sporadically in the topsoil samples. Besides, the phytolith assemblages of the topsoil samples were different among Xiaoxing'an Mountains, Songliao Plain and Liaoxi hills. Combined with the discriminant analysis, the samples from the three regions could be effectively separated based on the phytoliths assemblages, with a total accuracy of 94.4%. Specifi-cally, the average percentage of elongate, lanceolate, prism was the largest in Xiaoxing'an Mountains, and was the smallest in Liaoxi hills; the percentage of saddle, bilobate, papillae was the largest in Liaoxi hills and the smallest in Xiaoxing'an Mountains; the percentage of blocky, tabular, cuneiform was the largest in Songliao Plain. Meanwhile, the percentages of the elongate, lanceolate, prism, saddle, bilobate, papillae, blocky, tabular, cuneiform were significant diffe-rences among the three regions. There were significant negative correlations between the percentages of elongate, lanceolate, prism and the annual average temperature, and positive relationships between the percentages of the blocky, tabular, cuneiform, bilobate, papillae and the annual average temperature. However, the percentage of saddle, rondel and trapeziform polylobate did not change with increasing annual average temperature.

Pollen distribution and transportation patterns in surface sediments of Liaodong Bay, China

Understanding pollen transport pathways and dispersal mechanism from the land to sea is a prerequisite for marine palynological study. Palynological analysis of 164 surface sediment samples in Liaodong Bay, and 39 analogous surface alluvium samples from its five inflowing rivers, identifies the distribution patterns, pathways and possible sources of pollen and spores. The results show that pollen and spore assemblages in surface sediments are well correlated to regional vegetation distribution, and the variations of pollen assemblage in different parts of Liaodong Bay reflected local vegetation changes along the coast. High pollen concentrations are mainly distributed in the estuaries of inflowing rivers, coastal waters and sea muddy areas. The pollen assemblage characteristics of alluvial samples are similar to those from coastal waters with water depths <8.5 m. Samples from the alluvium and surface sediments of coastal waters were dominated by herbaceous pollen taxa including Artemisia, Amaranthaceae, Poaceae, Cyperaceae and Typha. Herbaceous pollen percentages and concentrations decreased as the water depth increased, indicating that pollen and spores in the coastal waters of Liaodong Bay are mainly carried by the inflowing rivers. However, pollen assemblages for samples with water depth >8.5 m are significantly different from those of the alluvium. In samples taken below a depth of 8.5 m, the arboreal pollen is dominated by airborne Pinus, and there is a high number of the waterborne Selaginella fern spores, both of which are sourced from a wider region. In the Liaodong Bay, both wind and ocean current transportation determines the pollen distribution patterns in deeper waters, while fluvial and longshore current transportation determines the pollen assemblages found in shallow waters. The dispersal characteristics of pollen assemblages between the land and the sea in Liaodong Bay provide a theoretical basis for the interpretation of fossil pollen assemblages and past sea level changes.

Impact of multiple stressors on the fish community pattern along a highly degraded Central European river – a case study

In this study, we provide a descriptive assessment of how chemical and hydro-morphological stressors have affected the fish community along one of the most impacted rivers in Central Europe. In addition to the toxicity of combined pollutants (expressed in toxic units), a range of hydro-morphological characteristics were measured to assess which stressors have had an impact. No longitudinal spatial trend was observed in fish assemblage characteristics as individual sites were affected by different stressors. Instead, five largely artificial assemblage “zones” were identified corresponding to different combinations of stressors. Water quality (principally dissolved O2) and hydromorphology were the main drivers affecting fish presence and density, with self-purification processes, restocking from tributaries and geomorphology promoting fish survival and/or recovery, despite increasing toxic pressure downstream. Our results suggest that a) toxic units alone are insufficient to establish causative factors in fish community loss as they do not take account of hydro-morphological stressors, many of which interact with and/or mask each other, and b) that a single WFD monitoring site in such heavily impacted rivers is insufficient to assess ecological status; rather, the ecological status of specific “zones” (identified based on fish assemblage structure, habitat and water quality) should be assessed, with the ultimate aim of merging the zones and returning the river to a single functioning longitudinal ecosystem, accepting that this is unlikely to resemble the natural pre-industrial status of the river.

Spatial variation in macrobenthic assemblages and their relationship with environmental factors in the upstream and midstream regions of the Heihe River Basin, China

The Heihe River is a typical inland river under increasing anthropogenic pressure. To explore the characteristics of the macrobenthic assemblages and their relationships with environmental factors in the upstream and midstream regions of this basin, abiotic conditions and macrobenthic assemblages were investigated in the summers of 2018 and 2019. A total of 50 species were collected, and Arthropoda and mollusks were the dominant groups. A significant increase in standing stock was observed from the upstream to midstream, and predators (PR) were the main functional feeding group. A one-way analysis of variance (ANOVA) revealed that the Shannon-Wiener index and Margalef’s index values significantly differed at the spatial scale (P < 0.05). A redundancy analysis (RDA) and Pearson correlation analysis showed that the spatial heterogeneity of the macrobenthos was influenced by the biochemical oxygen demand (BOD5), water temperature (WT), total nitrogen (TN), salinity, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), and potassium permanganate index (CODMn) (P < 0.05). The spatial variation of macrobenthos was mainly governed by natural conditions and human disturbances.

Fish Response to Multiple Anthropogenic Stressors in Mediterranean Coastal Lagoons: A Comparative Study of the Role of Different Management Strategies

Transitional waters are among the most productive ecosystems of the world and their biotic communities show high diversity and complex mechanisms of self-regulation that provide valuable ecosystem services and societal goods and benefits. In this work a comparison of the fish assemblages of three non-tidal Mediterranean coastal lagoons is carried out in order to evaluate the impacts of alternative management strategies. The anthropogenic pressures acting on the lagoons were quantified by means of categorical indicators, while the characteristics of the fish assemblages were summarized in multi-metric indices (MMIs). Two MMIs were developed using data collected with a beach seine net and with fyke nets, following an empirical approach that selects, from a pool of 73 metrics, the combination that maximizes the MMI/pressure relationship. The two MMIs include four metrics each, most of which are based on feeding mode functional guilds and habitat use functional guilds, and they are sensitive to anthropogenic pressures. The human activities directly or indirectly affecting water quality are the ones that most influence the fish assemblage, while the presence of artisanal fisheries, a typical and relevant resource use in these lagoons, seems to play a beneficial role. Lagoon fisheries management relies on the maintenance of infrastructures that guarantee the hydraulic functioning of the lagoon, thus ensuring exchanges with the adjacent coastal sea, and therefore indirectly contributing to the habitat quality.

崇明岛内河夏季鱼类群落组成及分布特征

PDF HTML阅读 XML下载 导出引用 引用提醒 崇明岛内河夏季鱼类群落组成及分布特征 DOI: 10.5846/stxb202002240321 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 上海市科委项目（19DZ1203801）；国家自然科学基金（41977344，41761144062） Community composition and distribution characteristics of the fish assemblages in the rivers of Chongming Island in summer Author: Affiliation: Fund Project: Science and Technology Committee of Shanghai Municipality, The National Natural Science Foundation of China 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:崇明岛为世界最大的河口冲积沙岛，岛内河网水系发达。2018年6月，选择崇明岛内主要代表性河道包括北横引河、南横引河和竖河（庙港、堡镇港、八滧港），设置16个固定站点，对内河鱼类开展了拖网调查，分析了崇明岛内河夏季鱼类群落组成及分布特征。调查期间共采集到鱼类4417尾，分属6目9科30种，主要为鲤形目鲤科鱼类；其中，淡水鱼类27种，洄游鱼类2种，近海鱼类1种。从空间分布来看，北横引河记录鱼类20种，南横引河记录鱼类17种，竖河记录鱼类18种，不同河道鱼类种类组成及优势种特征存在明显差异，其共有优势种为鲫Carassius auratus、似鳊Pseudobrama simoni和翘嘴红鲌Erythroculter ilishaeformis，部分种类只在特定的河段有记录。北横引河各站点平均物种数、丰度和生物量均高于南横引河和竖河，但3类河道间不存在显著差异（P>0.05）；主要优势种鲫、翘嘴红鲌和似鳊平均体长均以北横引河为最大，且在南横引河与北横引河中的个体体长均存在极显著差异（P<0.01）。聚类和排序分析结果表明，北横引河和南横引河鱼类组成差异较大，而竖河介于两者之间。相似性分析的结果也表明，南、北横引河鱼类群落结构差异极显著（R=0.524，P=0.008），且这两组间鱼类种类组成的平均相异性最高，为43.92%，造成两组间差异的主要物种有10种（贡献率均大于5%）。综合来看，崇明岛内河鱼类群落组成与分布特征不同于一般的内陆河流，而具有河口型岛屿的特点。未来需要在长期监测基础上，综合多种因素，对崇明岛内河鱼类组成、分布、变化趋势及内在机理开展系统研究。 Abstract:Chongming Island is the largest estuarine alluvial island in the world. It has a well-developed river network. In June 2018, trawl surveys on the fish were carried out in 16 fixed sampling sites in the representative rivers of Chongming Island, including the Nanheng Canal, Beiheng Canal and also the vertical canals Miaogang, Baozhengang, and Bayaogang. The composition and distribution characteristics of the fish communities in summer were analyzed based on these surveys. A total of 4417 specimens belonging to 6 orders, 9 families and 30 species of the fishes were collected in the surveys. Among them, 27 species were freshwater fish, 2 species were migratory fish and 1 species was coastal marine fish. And 20, 17 and 18 fish species were recorded in the Beiheng Canal, Nanheng Canal, and the vertical canals respectively. The characteristics of the fish assemblages, including the dominant species, varied among the rivers. The common dominant species of all the rivers were Carassius auratus, Pseudogramma simoni and Erythroculter ilishaeformis. Some species were only recorded in some specific reaches. The average species number, abundance and biomass of the fish in the Beiheng Canal were much higher than those in the Nanheng Canal and also the vertical canals, but there was no significant difference among the rivers (P>0.05). The average body length of major dominant species, Carassius auratus, Pseudogramma simoni and Erythroculter ilishaeformis in the Beiheng Canal were also the largest, and there was a very significant difference in individual body length between the Nanheng Canal and the Beiheng Canal (P<0.01). Cluster and nMDS analysis showed the greater difference between the fish assemblages in the Beiheng Canal and the Nanheng Canal, while those in the vertical canals were between these two. The results of ANOSIM also showed that the difference of the fish community structure between the Beiheng Canal and the Nanheng Canal was extremely significant (R=0.524, P=0.008), the average dissimilarity between these two groups appeared to be the highest at 43.92%, and there were 10 main species causing such difference (contribution rate was greater than 5%).In general, we found out that the community composition and distribution characteristics of the fish assemblages in the rivers of Chongming Island were different from those of general inland rivers, while had some characteristics of the estuarine islands. In the future, comprehensive studies on the community composition, distribution characteristics, developing trends and the corresponding mechanisms of the fishes in the rivers of Chongming Island should be carried out based on the long term monitoring. 参考文献 相似文献 引证文献

Chironomid riverine assemblages at the regional temperate scale – compositional distance and species diversity

Chironomids are the most common and abundant benthic invertebrate family in freshwater environments worldwide, but most studies on chironomid assemblages focus on presence/absence of species rather than abundance and community composition. This makes the assessment of chironomid assemblage composition and diversity limited in any physiographic zone and at any scale. This study enhances knowledge of chironomid abundance in rivers in Central Europe, which is typical part of the temperate climatic zone, and investigates chironomid (inter-)assemblage characteristics. Benthic assemblages of seven lowland rivers were sampled monthly over annual cycles with a total of 61 chironomid species detected. PCA was used to determine the environmental profile of the rivers at study sites, while cluster and ANOSIM analysis and univariate diversity indices were applied to the chironomid samples of the assemblages grouped at the river level to identify their similarities and differences. The environmental profile explained much of the cluster and ANOSIM-based patterns of the rivers’ compositional distances, and also some values of given univariate diversity indices. SIMPER analysis distinguished a group of 14 species that explained almost 60% of differences between the assemblages. The contribution of each species of the group was similar, ranging between 6.13% and 2.87%, yet on average several times greater than that of each of the remaining 47 species. Univariate diversity values differed from index to index and from river to river, and indicated that the application of few such indices, particularly one, may be misleading. The N 1 gamma diversity of the whole region (calculated from 82 samples) was 18.31 species, which was multiplicatively decomposed into the average alpha component of 4.04 species, and beta component of 4.53 assemblages.