Spatial-temporal patterns of fish trophic guilds in a freshwater river wetland ecosystem of northeastern China.

Muling River, situated amidst cultivated lands in Heilongjiang Province, northeastern China, has long been subjected to sand-digging activities, resulting in severe damage to its riverbed. However, little research has been conducted on the impact of this disturbance on the status of fish community structure and trophic guilds in this river. In this study, environmental factors, fish community structure, and fish trophic guild biomass distribution patterns from the Muling River basin were investigated among seasons (spring, summer, and autumn) and sections (upper, middle, and lower stream) in 2015 and 2017. During the six sampling times periods, 46 species of five orders and 12 families of fish were classified into seven trophic guilds. Fish species number and biomass were higher upper reaches of the watershed. The insectivores (16.26%), phytoplanktivores (10.09%), benthivores (40.17%), and omnivores (11.86%) were the dominant trophic guilds. We found that fish trophic guilds biomass and environmental factors such as transparency, water depth, pH value, total phosphorus, and chemical oxygen demand were highest in the upper section compared to other sections. Variation partitioning revealed that fish trophic guilds biomass was influenced more by environmental factors (61.2%), followed by section (0.7%) and season (0.1%). Partial RDA ordination showed that fish trophic guilds were positively correlated with water depth and transparency, while negative with turbidity. This study underscores the importance of considering trophic guilds of freshwater fishes to inform management strategies in regions experiencing significant environmental change.

Gradient Photonic Materials Based on One-Dimensional Polymer Photonic Crystals.

In nature, animals such as chameleons are well-known for the complex color patterns of their skin and the ability to adapt and change the color by manipulating sophisticated photonic crystal systems. Artificial gradient photonic materials are inspired by these color patterns. A concept for the preparation of such materials and their function as tunable mechanochromic materials is presented in this work. The system consists of a 1D polymer photonic crystal on a centimeter scale on top of an elastic poly(dimethylsiloxane) substrate with a gradient in stiffness. In the unstrained state, this system reveals a uniform red reflectance over the entire sample. Upon deformation, a gradient in local strain of the substrate is formed and transferred to the photonic crystal. Depending on the magnitude of this local strain, the thickness of the photonic crystal decreases continuously, resulting in a position-dependent blue shift of the reflectance peak and hence the color in a rainbow-like fashion. Using more sophisticated hard-soft-hard-soft-hard gradient elastomers enables the realization of stripe-like reflectance patterns. Thus, this approach allows for the tunable formation of reflectance gradients and complex reflectance patterns. Envisioned applications are in the field of mechanochromic sensors, telemedicine, smart materials, and metamaterials.

Gradients of Gluten Proteins and Free Amino Acids along the Longitudinal Axis of the Developing Caryopsis of Bread Wheat.

Gradients in the contents and compositions of gluten proteins and free amino acids and the expression levels of gluten protein genes in developing wheat caryopses were determined by dividing the caryopsis into three longitudinal sections, namely, proximal (En1), middle (En2), and distal (En3) to embryo. The total gluten protein content was lower in En1 than in En2 and En3, with decreasing proportions of HMW-GS, LMW GS, and α/ß- and γ-gliadins and increasing proportions of ω-gliadins. These differences were associated with the abundances of gluten protein transcripts. Gradients in the proportions of the gluten protein polymers which affect dough processing quality also occurred, but not in total free amino acids. Microscopy showed that the lower gluten protein content in En1 may have resulted, at least in part, from the presence of modified cells in the dorsal part of En1, but the reasons for the differences in composition are not known.

Spatial and temporal variations in fish assemblage: testing the zonation concept in small reservoirs / Variações espaciais e temporais na assembleia de peixes: testando o conceito de zonação em pequenos reservatórios

Abstract Large reservoirs usually present spatial gradients in fish assemblage, distinguishing three strata (littoral, pelagic, and bathypelagic) along the vertical and horizontal axes, and three zones (fluvial, transitional, and lacustrine) along the longitudinal axis. The main objective of this study was to assess if small reservoirs also present the spatial gradients in fish assemblage attributes and structure as already observed in large reservoirs. Fish surveys were conducted quarterly, from 2003 to 2008, in the Mourão Reservoir (Mourão River, Paraná, Brazil), using gillnets with different mesh sizes, arranged in all strata of all three zones. Community attributes (species richness and evenness) were calculated for each sample, and differences were tested using three-way ANOVA (factors: zone, strata, year). Community composition was summarized using Correspondence Analysis (CA) and differences were tested with three-way ANOVA for each axis, controlling the same three factors. Because of the high variability in reservoir water level through time, all analyses were made considering temporal variations. Species richness presented a decreasing trend from fluvial to lacustrine zones, and higher values in littoral strata, possibly because upper reaches and littoral regions provide better conditions for fish to feed and to reproduce. Evenness was considerably low, presenting high variability, and no evident pattern. The expected longitudinal gradient was not found in this study indicating longitudinal similarity, contrary to observed in large reservoirs. Vertical and horizontal gradients were observed in all sampling stations, indicating that abiotic and biotic conditions are influencing fish distributions within the reservoir.

Resumo Grandes reservatórios, em geral, apresentam gradientes espaciais da assembleia de peixes, distinguindo três estratos (litoral, pelágico e batipelágico) ao longo dos eixos vertical e horizontal, e três zonas (fluvial, transição e lacustre) ao longo do eixo longitudinal. O principal objetivo deste estudo foi avaliar se pequenos reservatórios também apresentam tais gradientes espaciais, nos atributos e na estrutura da assembleia de peixes, como já observado em grandes reservatórios. As coletas dos peixes foram realizadas trimestralmente, de 2003 a 2008, no reservatório de Mourão (Rio Mourão, Paraná, Brasil), com redes de espera com diferentes tamanhos de malha, dispostas em todos os estratos de todas as três zonas. Atributos da assembleia (riqueza de espécies e equitabilidade) foram calculados para cada amostra, e as diferenças foram testadas utilizando ANOVA tri-fatorial (fatores: zona, estratos, anos). A estrutura da assembleia foi sumarizada usando uma Análise de Correspondência (CA) e as diferenças foram testadas com ANOVA tri-fatorial para cada eixo, controlando os mesmos três fatores. Devido à alta variabilidade no nível da água do reservatório ao longo do tempo, todas as análises foram feitas considerando as variações temporais. A riqueza de espécies apresentou tendência decrescente, da zona fluvial até a lacustre, com valores maiores no estrato litoral, possivelmente porque locais à montante e regiões litorâneas proporcionam melhores condições de alimentação e reprodução para os peixes. A equitabilidade foi consideravelmente baixa, apresentando alta variabilidade e nenhum padrão evidente. O gradiente longitudinal esperado não foi encontrado neste estudo, indicando similaridade longitudinal, ao contrário do observado em grandes reservatórios. Gradientes verticais e horizontais foram observadas em todas as áreas amostradas, sugerindo que as condições bióticas e abióticas estão influenciando a distribuição dos peixes ao longo do reservatório.

The Biogeographical Distribution of Soil Bacterial Communities in the Loess Plateau as Revealed by High-Throughput Sequencing.

The rigorous environmental stress of the severely eroded Loess Plateau may have promoted specific soil bacterial communities in comparison to other eco-environmental regions. In order to unmask the bacterial diversity and most influential environmental parameters, Illumina MiSeq high throughput sequencing of 16S rRNA from 24 representative soil samples collected across south-east to north-west transect of the Loess Plateau in northern Shaanxi, China was conducted. This high-throughput sequencing revealed a total of 1,411,001 high quality sequences that classified into 38 phyla, 127 classes, >240 orders, and over 650 genera, suggesting a high bacterial richness across the Loess Plateau soils. The seven dominant groups were: Proteobacteria, Actinobacteria, Acidobacteria, Planctomycetes, Gemmatimonadetes, Chloroflexi, and Verrucomicrobi (relative abundance of >5%). Increasing/decreasing soil pH and geographic longitudinal distance correlated significantly with increasing/decreasing bacterial richness and diversity indices. Pairwise correlation analysis showed higher bacterial diversity at longitudinal gradients across 107°39'-109°15' (south-east to north-west) in our studied Chinese loess zone. Variation partitioning analysis indicated significant influence of soil characteristics (~40.4%) than geographical distance (at a landscape scale of ~400 km) that was responsible for 13.6% of variation in bacterial community structure from these soils. Overall, contemporary soil characteristics structure the bacterial community in Loess Plateau soil to a greater extent than the spatial distances along the loess transect.

Spatial and temporal variations in fish assemblage: testing the zonation concept in small reservoirs

Abstract Large reservoirs usually present spatial gradients in fish assemblage, distinguishing three strata (littoral, pelagic, and bathypelagic) along the vertical and horizontal axes, and three zones (fluvial, transitional, and lacustrine) along the longitudinal axis. The main objective of this study was to assess if small reservoirs also present the spatial gradients in fish assemblage attributes and structure as already observed in large reservoirs. Fish surveys were conducted quarterly, from 2003 to 2008, in the Mourão Reservoir (Mourão River, Paraná, Brazil), using gillnets with different mesh sizes, arranged in all strata of all three zones. Community attributes (species richness and evenness) were calculated for each sample, and differences were tested using three-way ANOVA (factors: zone, strata, year). Community composition was summarized using Correspondence Analysis (CA) and differences were tested with three-way ANOVA for each axis, controlling the same three factors. Because of the high variability in reservoir water level through time, all analyses were made considering temporal variations. Species richness presented a decreasing trend from fluvial to lacustrine zones, and higher values in littoral strata, possibly because upper reaches and littoral regions provide better conditions for fish to feed and to reproduce. Evenness was considerably low, presenting high variability, and no evident pattern. The expected longitudinal gradient was not found in this study indicating longitudinal similarity, contrary to observed in large reservoirs. Vertical and horizontal gradients were observed in all sampling stations, indicating that abiotic and biotic conditions are influencing fish distributions within the reservoir.

Resumo Grandes reservatórios, em geral, apresentam gradientes espaciais da assembleia de peixes, distinguindo três estratos (litoral, pelágico e batipelágico) ao longo dos eixos vertical e horizontal, e três zonas (fluvial, transição e lacustre) ao longo do eixo longitudinal. O principal objetivo deste estudo foi avaliar se pequenos reservatórios também apresentam tais gradientes espaciais, nos atributos e na estrutura da assembleia de peixes, como já observado em grandes reservatórios. As coletas dos peixes foram realizadas trimestralmente, de 2003 a 2008, no reservatório de Mourão (Rio Mourão, Paraná, Brasil), com redes de espera com diferentes tamanhos de malha, dispostas em todos os estratos de todas as três zonas. Atributos da assembleia (riqueza de espécies e equitabilidade) foram calculados para cada amostra, e as diferenças foram testadas utilizando ANOVA tri-fatorial (fatores: zona, estratos, anos). A estrutura da assembleia foi sumarizada usando uma Análise de Correspondência (CA) e as diferenças foram testadas com ANOVA tri-fatorial para cada eixo, controlando os mesmos três fatores. Devido à alta variabilidade no nível da água do reservatório ao longo do tempo, todas as análises foram feitas considerando as variações temporais. A riqueza de espécies apresentou tendência decrescente, da zona fluvial até a lacustre, com valores maiores no estrato litoral, possivelmente porque locais à montante e regiões litorâneas proporcionam melhores condições de alimentação e reprodução para os peixes. A equitabilidade foi consideravelmente baixa, apresentando alta variabilidade e nenhum padrão evidente. O gradiente longitudinal esperado não foi encontrado neste estudo, indicando similaridade longitudinal, ao contrário do observado em grandes reservatórios. Gradientes verticais e horizontais foram observadas em todas as áreas amostradas, sugerindo que as condições bióticas e abióticas estão influenciando a distribuição dos peixes ao longo do reservatório.

Longitudinal processes in Salto Grande reservoir (Americana, SP, Brazil) and its influence in the formation of compartment system

Studies on the longitudinal processes in reservoirs, involving physical, chemical and biological processes have been thoroughly appraised, suggesting the existence of a longitudinal organization controlled by the entrance and circulation of water which inserts modifications in the structuring of the system. To evaluate this effect, the Salto Grande reservoir (Americana, SP) was analyzed in 11 sampling stations in its longitudinal axis, in the rainy and dry seasons of 1997 considering the physical chemical and biological variables. Analyzing the results in agreement with the declining concentration degree of the river--barrage direction, a more significant correlation was verified in the dry period for total phosphorus (r² = 0.86), dissolved total phosphate (r² = 0.83), nitrite (r² = 0.93), inorganic phosphate (r² = 0.89), ammonium (r² = 0.84) and suspended material (r² = 0.85). In the rainy period, only nitrite (r² = 0.90) and conductivity (r² = 0.89) presented correlation with the distance of the dam, which demonstrates the effects of precipitation and the operational mechanism of the dam, as well as the distinction among the physical (sedimentation), chemical (oxidation) and biological (decomposition) processes in spatial heterogeneity of the system. These factors were decisive in the organization of these communities, with higher occurrence of rotifers and copepods in relation to cladocerans, the first ones being more abundant in the entrance of the Atibaia river, decreasing towards the dam direction, while copepods presented an inverse pattern. A distribution pattern similar to Copepoda was also verified for the Cladocera, evidencing a tendency to increase the density of organisms in the stations distant to the entrance of the Atibaia river, not being registered, however, a distribution gradient in the longitudinal axis, as observed for rotifers and copepods. In relation to the trophic degree a longitudinal gradient was also verified from eutrophic to oligotrophic depending on the location of the sampling station in relation to the longitudinal axis and period of analysis. The differences obtained, relating to the distribution of the environmental variables, demonstrate a characteristic pattern for reservoirs, with a longitudinal gradient in the sense river--barrage that inserts changes in the physical and chemical composition of the water, contributing to the differentiated establishing of biological communities.

Estudos sobre os processos longitudinais em reservatórios, envolvendo os processos físicos, químicos e biológicos, têm sido amplamente avaliados, sugerindo a existência de uma organização longitudinal controlada pela entrada e circulação da água, a qual insere modificações na estruturação do sistema. Para avaliar esse efeito, o reservatório de Salto Grande (Americana, SP) foi analisado em 11 estações de amostragem de seu eixo longitudinal, nos períodos seco e chuvoso de 1997, considerando-se variáveis físicas, químicas e biológicas. Analisando-se os resultados de acordo com o grau de decaimento das concentrações no sentido rio--barragem, verificou-se correlação mais significativa no período seco do que no chuvoso para fósforo total (r² = 0,86), fosfato total dissolvido (r² = 0,83), nitrito (r² = 0,93), fosfato inorgânico (r² = 0,89), amônio (r² = 0,84) e material em suspensão (r² = 0,85). No período chuvoso, apenas nitrito (r² = 0,90) e condutividade (r² = 0,89) apresentaram correlação com a distância da barragem, o que demonstra o efeito da precipitação e do mecanismo operacional da barragem, bem como a distinção entre os processos físicos (sedimentação), químicos (oxidação) e biológicos (decomposição) na heterogeneidade espacial do sistema. Esses fatores foram determinantes na organização das comunidades, com maior abundância de rotíferos e copépodos em relação aos cladóceros, sendo os primeiros mais abundantes na entrada do rio Atibaia, decrescendo em direção à barragem, enquanto copépodos apresentaram padrão inverso. Padrão de distribuição semelhante aos copépodos também foi verificado para os cladóceros, evidenciando tendência ao aumento da densidade de organismos nas estações distantes da entrada do rio Atibaia, não sendo registrado, porém, gradiente de distribuição no eixo longitudinal, como observado para rotíferos e copépodos. Em relação ao grau de trofia também se verificou gradiente longitudinal de eutrófico a oligotrófico, dependendo da localização da estação de amostragem em relação ao eixo longitudinal e período analisado. As diferenças obtidas quanto à distribuição das variáveis ambientais demonstram um padrão característico para reservatórios, com gradiente longitudinal no sentido rio--barragem que insere modificações na composição física e química da água, contribuindo para o estabelecimento diferenciado das comunidades biológicas.