Presence Of Riparian Vegetation Research Articles

Riparian Vegetation Structure of the Jengok River, Kutaliman, Kedungabanteng District, Banyumas Regency

Jengok River has a high value for the Kutaliman community. The community utilizes the ecosystem services of the Jengok River and is inseparable from the presence of riparian vegetation, which controls water quality. This study aimed to determine riparian vegetation structure on the Jengok River, Kutaliman, Kedungbanteng district, and Banyumas Regency. The research was conducted in October-November 2022 in the Jengok riparian zone using a quadrat transect with sizes 20x20 m2 for trees dan 2x2 m2 for understoreys. Data were analyzed using the Shannon-Wiener Diversity Index (H'), the Modified Hill's Ratio Evenness Index (e'), the Margalef Richness Index (DMg), and the Important Value Index (IVI). The results show that the diversity of riparian vegetation based on the Shannon-Wiener Diversity Index (H') is a moderate category, and the Evenness Index (e') is the distribution of individuals per species evenly. Furthermore, the Margalef Richness Index (DMg) shows 4.51 for trees and 4.34 for understorey. The highest IVI in the tree stratum was Lansium domesticum Corrêa. In contrast, in the understorey stratum was Musa paradisiacal L. This indicates both species have an essential role in their community

Integrating presence-only and occupancy data to model habitat use for the northernmost population of jaguars.

Species distribution models (SDMs) have become an essential tool for the management and conservation of imperiled species. However, many at-risk species are rare and characterized by limited data on their spatial distribution and habitat relationships. This has led to the development of SDMs that integrate multiple types and sources of data to leverage more information and provide improved predictions of habitat associations. We developed a novel integrated species distribution model to predict habitat suitability for jaguars (Panthera onca) in the border region between northern Mexico and the southwestern USA. Our model combined presence-only and occupancy data to identify key environmental correlates, and we used model results to develop a probability of use map. We adopted a logistic regression modeling framework, which we found to be more straightforward and less computationally intensive to fit than Poisson point process-based models. Model results suggested that high terrain ruggedness and the presence of riparian vegetation were most strongly related to habitat use by jaguars in our study region. Our best model, on average, predicted that there is currently 25,463 km2 of usable habitat in our study region. The United States portion of the study region, which makes up 38.6% of the total area, contained 40.6% of the total usable habitat. Even though there have been few detections of jaguars in the southwestern USA in recent decades, our results suggest that protection of currently suitable habitats, along with increased conservation efforts, could significantly contribute to the recovery of jaguars in the USA.

Análise comparativa de elementos fí­sico-quí­micos e contaminantes em corpo d"™água do Riacho Grilo no estado de Sergipe

Este estudo objetivou analisar e comparar parâmetros fí­sico-quí­micos e bacteriológicos do Riacho Grilo, localizado em Sergipe, com os resultados da análise de 2009 pela SEMARH. A metodologia utilizou-se dos dados coletados em maio de 2015, para desenvolver um estudo comparativo com tal análise de 2009, acrescida do cobre total na água. A coleta das amostras foi in loco, com presença de mata ciliar e ausência de lixos na área. Notou-se sutil diferença entre os modelos devido í  forte chuva nos dias da coleta. No entanto, o fósforo, cloreto e coliformes apresentaram alterações significativas, sendo que, os dois primeiros indicam contaminação por produtos quí­micos, e os coliformes reduzidos podem ser derivados da chuva e dos valores para sólidos totais que podem levar a um acúmulo de bactérias. Como resultado, o ní­vel de cobre encontrado torna o uso da água imprópria.

Morphodynamics of alternate bars in the presence of riparian vegetation

AbstractAlpine gravel‐bed rivers are dynamic systems that have been subjected to many anthropic alterations in the past centuries. Riparian vegetation development on previously bare sediment bedforms has been a common adjustment, raising important management issues in terms of flood risks and biodiversity. Many of these rivers are also channelized, and as a result present a pattern of alternate bars. Considering recent advances in numerical biomorphodynamic modeling, this study aims at exploring numerically the morphodynamics of alternate bars in the presence of riparian vegetation. To this end, a dynamic vegetation module has been implemented on top of an existing morphodynamic model, accounting for ecological processes of seed dispersal, seedling recruitment, growth, and mortality. Numerical simulations have been performed on a simplified reach of a gravel‐bed river with free migrating alternate bars at initial state. In this work 96 scenarios have been simulated, each representing 50 years of channel evolution, with different flood regimes characterized by various peak discharges and flood durations. Yearly peak discharge variability is explicitly modeled in 48 scenarios. Model outcomes present two possible equilibrium biomorphodynamic behaviors: stationary vegetated bars, or free migrating bars in the case of frequent vegetation removal during floods. This binary behavior holds true when the stochasticity of annual peak discharges is represented, and for a wide range of parameter values included in vegetation dynamic modeling. Transient mobility of vegetated bars is observed in specific configurations where large sediment deposits deflect the flow field, eroding bar heads. Modeled bar wavelengths are in the range of values predicted for free bars by linear bar theory, and remain far from the theoretical values of hybrid, steady bars. The shift from unvegetated migrating bars to steady vegetated bars seems to show that in these simulations vegetation constitutes a hydraulic forcing, leading to a shift from free bars to forced bars, with a final configuration largely inherited from the initial state. © 2019 John Wiley & Sons, Ltd.

Seasonal and longitudinal variation in fish assemblage structure along an unregulated stretch of the Middle Uruguay River

ABSTRACT Diversity patterns and their causes remain important questions, especially for ecosystems that preserve natural conditions. This is the case of fish diversity in large Neotropical rivers. In this context, we investigated fish diversity patterns along an extensive unregulated river section (ca. 450 km) in the Middle Uruguay River Basin. Sampling was conducted seasonally between May 2017 and March 2018, at six sites (patches) with contrasting environmental conditions. We collected 3,008 individuals belonging to 90 species. Nine were migratory, which summed relevant biomass in local assemblages (20 to 60%). We observed spatial variation in assemblage structure, but weak seasonal effects. Overall, biomass was similar among sites, but richness tended to increase downstream. Migratory fishes showed opposed trends, with higher richness and biomass upstream, particularly catfishes (Siluriformes). Ordination analyses separated sites in three groups based on variations in composition and abundance, and revealed associations between these groups and specific hydro-geomorphic conditions (i.e., flow, depth, channel width and the presence of riparian vegetation). Our study revealed that fish diversity distributes heterogeneously along the main channel, where hydro-geomorphic patches select for distinct assemblages along riverine gradients.

Land use modifies Odonata diversity in streams of the Brazilian Cerrado

The presence of riparian vegetation provides microclimatic regulation of stream conditions [e.g. luminosity (lux), air temperature (°C) and relative humidity (%)], which varies naturally throughout the day. These variables explain the diurnal behaviour patterns of ectotherms such as Odonata in natural areas. However, human land uses (e.g. pastures) modify the abiotic conditions of riparian environments, favouring the presence of disturbance-tolerant species. In this context, we assess relationships between riparian land use (control streams-natural areas and pasture), abiotic conditions habitat integrity index (in control and pastures streams), (air temperature, luminosity and humidity in control streams), and Odonata diversity (between pasture and control streams and throughout the time of day) in Brazilian savannah (Cerrado) streams. First, the control streams had higher habitat integrity index than pasture. Higher abundance and difference in composition of Odonata species were observed in streams surrounded by pasture relative to natural areas. The conversion of natural areas to pasture near streams was also accompanied by an increase in overall body size of Odonata species. Odonata species richness and abundance in natural areas varied throughout the day, but peaked around 12:00 h, coinciding with changes in air temperature and luminosity. Our study highlights that changes in the physical characteristics of streams through conversion of natural habitats to pasture will change environmental conditions and act as a filter on the distribution and persistence of Odonata species in Cerrado streams.

Influence of riparian vegetation on flow resistance in mobile bed straight compound channels

Riparian vegetation is an important feature in rivers and essential in hydraulic engineering including flood management and river restoration. Deforestation activities have been pointed out as a contributing factor to the severity of flood damages. This shows that the importance of riparian vegetation in river restoration schemes in order to lessen the issues of flood risk and flood protection. The riparian vegetation creates additional resistance to flood flow which resulted in velocity reduction, increasing of flow depth and transportation of sediment in rivers. The hydraulics of flood flows in vegetated floodplain of mobile bed straight channel was experimented in the Hydraulics Laboratory, Faculty of Civil Engineering, Universiti Teknologi Malaysia. Two-lined steel rods with tandem and staggered arrays to simulate as rigid emergent vegetation were placed along the riparian zone of an asymmetrical channel. The flow resistance including Manning’s n, Darcy’s f and drag force, FD were studied. The findings showed that the riparian vegetation had increased the Manning’s n by 20%. Meanwhile, staggered arrangement of vegetation was found to generate the highest Darcy’s f of about 16% as compared to tandem arrangement. The presence of riparian vegetation also found to induce 20% more drag force compared to the main channel roughness effect. The dramatically changes of bed morphology also led to the increase of the flow resistance in the channel.

Structure of the ichthyofauna of adventitious streams in the South Pantanal

ABSTRACT: The ichthyofauna of the Taquari River, one of the main tributaries of the South Pantanal, has been studied since the 1970s; however, there is a gap on the studies about the ichthyofauna present on the small adventitious streams of this highly dendritic system. These streams are small tributaries that flow directly into large rivers (mainstem), at least three orders greater in magnitude. The aim of this study was to analyze the structure of the ichthyofauna of five adventitious streams of the Upper Taquari River, South Pantanal, evaluating its temporal variation (dry and wet season) and the relation to the habitat characteristics and the conservation of the streams. Thirty-seven species were collected, from which 14 are exclusive to the Paraguay River basin, one species [Apteronotus albifrons (Linnaeus, 1766)] could represent a new record for this basin, and six species need taxonomic confirmation. The analysis indicated only the existence of spatial variation in the ichthyofauna structure of the streams sampled, with the similarity patterns related to the distance between the streams and to their conditions of conservation. The stream with greater size and preserved riparian forest was the one with the highest values of fish diversity and evenness. On the other hand, the stream with the smallest percentage of riparian forest and highest proximity to urban area presented the lowest diversity. The small size of these adventitious systems should serve as protection against large predators, which have their access to those areas hampered by their own size. Otherwise, the mainstem may also act as source of dispersal of small-bodied schooling fishes to the adventitious streams, where the greater heterogeneity of habitats and the presence of riparian vegetation should offer shelter and food supply for small species.

Habitat and abundance of the Neotropical otter (Lontra longicaudis annectens) in Pueblo Nuevo, Durango, Mexico

The Neotropical otter is a predator located in the upper trophic level; its geographical distribution stretches from northern Mexico to central Argentina. It lives in river banks, where it rests, plays, marks its territory, cleans its fur and breeds its offspring. Lontra longicaudis is sensitive to alterations in the habitat, either by the degradation of river bank environments and by pollution of water bodies; hence, it is considered as an indicator of the degradation of aquatic ecosystems. This species is currently included in the threatened species category according to NOM-059-SEMARNAT-2010. The aim of this work is to characterize the habitat and determine the abundance of the Neotropical otter in the upper part of San Diego River, to assess whether the sea otter population abundance is directly related on the characteristics of the habitat and the seasonal dynamics. The monitoring was carried out over two years (2012-2013). Eight kilometers along the river were sampled considering 3 segments of equal length, since preliminary visits revealed that these had distinctive physical and environmental characteristics. The physicochemical parameters of water were measured, plant species growing along the river bank were identified, 266 samples of feces were collected, and otter relative abundance was estimated. Segment 1 showed an acid water pH, with low temperatures and plant species of the genera Pinus, Quercus and Juniperus along the river banks; the second segment showed a neutral pH, with higher temperatures, and scarce riparian vegetation; the third segment again displayed riparian vegetation, with warm water and near-neutral pH. The relative abundance determined for the otter population averaged 0.46 otters/km. A model for predicting otter abundance was obtained, which yielded a prediction error of ± 0.27 otters/km. The characteristics of the habitat associated with otters in this area were similar to those described by other authors for other parts of the country, namely a neutral pH, clean oxygen-rich waters, low water temperature in the upper portions of the river, presence of riparian vegetation, with stretches of rapids and shallow areas with pools of slow-flowing, deep water. Separately, the abundance of otters found in this case lied within a range that differed from the one reported by other authors, which varies between 0.21 and 1.22 otters/km; again, this was not a fixed value, but varied over the sampling period: it decreased in the rainy season and rose in the dry season. The abundance-habitat relationship model showed an acceptable fit; however, the most significant variables were total dissolved solids, pH, flow zone and depth. This study made possible to determine the current status of the otter and the conditions of its habitat in this area; however, further studies are needed to gain a detailed understanding on the species to support decision-making and implement conservation actions.

Impacts of oil palm plantations on changes in environmental heterogeneity and Heteroptera (Gerromorpha and Nepomorpha) diversity

This study evaluates the effects of oil palm plantations on environmental heterogeneity and diversity (α and β) of aquatic Heteroptera (semi-aquatic and aquatic species) in Amazon streams. We assessed eight streams located in forested areas and 12 in oil palm plantations. As expected, oil palm areas had lower environmental heterogeneity, despite the presence of riparian vegetation. Heteropteran communities differed in forest and oil palm areas, however, only semi-aquatic bugs were affected by environmental variables. Streams in oil palm plantations had lower α-diversity and distinct community structures when compared to forest sites. Oil palm plantation did not affect the β-diversity of semi-aquatic bugs, however, there was increased β-diversity of aquatic bugs in these areas. These results reflect the impacts of environmental heterogeneity generated by plantations next to riparian vegetation, inducing local diversity loss. Effects on β-diversity differed among groups of Heteroptera, mainly due to the differences in the life histories of each group. Semi-aquatic bugs seem to undergo environmental filtering, while aquatic bugs can be structured by limiting similarity. Thus, the management and land conservation strategies adopted to preserve ecosystems within oil palm plantations were insufficient for the protection of aquatic heteropteran communities. In summary, such conservation policies should account for the particularities of different groups of the aquatic ecosystem; especially for aquatic fauna, which are usually overlooked in conservation policies for the Brazilian Amazon.

Avaliação de bacia hidrográfica por alunos do Ensino Fundamental: contribuição ao ensino dos recursos hídricos

This work developed and tested a rapid assessment protocol (RAP) in a watershed of the Paraíba do Sul River Basin, to be applied by elementary school students. The study was conducted in a public school of São José dos Campos (SP), with 60 students of the 6th grade (n = 30) and 7th grade (n = 30). The protocol developed includes 12 parameters with text consistent with student levels and with illustrations of the variables of each parameter. The parameters are the type of usage of the stream margins, erosion and siltation, presence of sewage, presence of aquatic plants, water odor, water oiliness, water transparency, type of bottom, rapids and water flow, garbage presence, the presence of animals, and the presence of riparian vegetation. The results showed that 65% of the students understood all parameters and showed great interest in the proposed protocol; the others needed to better understand the parameters of erosion and siltation, presence of aquatic plants, rapids, water flow and presence of riparian vegetation. It was found that the developed RAP was appropriate and can contribute as an educational tool for the study of water quality.

Presence of riparian vegetation increases biotic condition of fish assemblages in two Brazilian reservoirs

Abstract The riparian vegetation in lakes and reservoirs is source of course wood structures such as trunks and branches and is used as sheltering, spawning and foraging habitats for fishes. The reduction of these submerged structures can thus, affect the composition and structure of fish assemblages in reservoirs. Aim To evaluate the influence of riparian vegetation on the biotic condition of fish assemblage by adapting the Reservoir Fish Assemblage Index (RFAI) to two reservoirs in the Upper Paranapanema river basin, São Paulo State, Brazil. Methods The RFAI was adapted from metrics related to the functional characteristics and composition of fish assemblages through a protocol of metric selection and validation, and to its response to the presence of riparian vegetation. Results The final RFAI was composed by nine metrics, been lower in sites without riparian vegetation as consequence of the predominance of larger individuals and the percent of piscivorous and detritivorous fishes. Conclusions These results suggest that increasing shore habitat complexity in reservoirs by maintaining riparian vegetation increases fish biotic integrity.

Avaliação qualitativa de nascentes com diferentes coberturas do solo e conservação da vegetação em seu entorno no córrego Pimenta

The sources lose their qualitative and quantitative capacity of water, when it is changed by human actions. The objective of this research was to qualitative evaluation of four sources, to evaluate the positive and negative impacts on their surroundings in creek Pepper as well as the framing of each source in CONAMA Resolution 357/05. For the physical characterization of the sources and their surroundings were classified as preserved, disturbed or degraded, beyond the positive and negative environmental impacts. Sampling of surface water were made ​​in the period of one year , with ten physicochemical parameters monitored. The first source (N1) it is preserved and presents coverage of riparian forest. The source two (N2) has coverage of riparian forest and is in a state of disturbance. The source three (N3) has coverage of bamboo forest and natural forest and it is degraded. The source four (N4) has pasture cover and is in degradation. The adjust of physico-chemical parameters had the N1 within the standards for Class II, the N2 is adjusting for Class III , N3 and N4 did not show the values allowed in class II and III. The sources preserved and disturbed with riparian vegetation had all positive impacts, while degraded sources have the most negative impacts. The presence of riparian vegetation in disturbed and preserved sources auxiliary in qualitative protection of water resources compared the degraded sources.

<b>Does a small forested area contribute to enhance species richness and diversity of fish assemblage at an urban stream?</b> - doi: 10.4025/actascibiolsci.v35i4.16592

Conservation Units (CU) aim to contribute to the balance between human and environmental demand, by protecting natural resources and biological communities. In this study we examined the differences in the attributes of the fish community in four stretches of an urban stream, two inside and two outside the CU, without vegetation cover, and tested the hypothesis that the presence of riparian vegetation is positively reflected in the attributes of fish fauna. Five species were caught, distributed into four orders and five families. Attributes like richness, abundance, dominance, Shannon-Wiener diversity, and evenness were estimated and significant differences were detected for continuous stretches considering stream flow direction. The first stretches (URBI and UCI) presented a lower diversity that increased gradually until the last stretch, and an inverse result was found for dominance. These changes occurred regardless the location of the stretch, in- or outside the CU. The importance of Conservation Units within urban areas is severely affected by the lack of continuity of forested areas, especially riparian vegetation. Therefore, we suggest the effective recovery of permanent preservation areas and of riparian vegetation in order to mitigate the impacts of human activities.

Can landscape metrics help determine the Culicoides imicola distribution in Italy?

Culicoides imicola is considered to be one of the main vectors of bluetongue disease in the Mediterranean Basin. However, local variations occur. For example, in Italy, C. imicola is a stable and abundant population in Sardinia and is widely distributed across the island, whilst in Tuscany on the Italian mainland, it ranges from low abundance in the west and coastal areas to absence in the eastern part of the region. Entomological surveillance data collected over 10 years were used to classify 52 sites as low to medium or high C. imicola abundance in Sardinia, and 59 sites as either positive or negative in Tuscany. The land cover was mapped from high-resolution remote sensing images using an object-based image analysis approach and a set of landscape metrics with 500 m buffers around each site. Multivariate analysis was used to test the statistical association of landscape metrics to C. imicola presence and abundance together with other eco-climatic and topographic variables. In Sardinia, 75% of the sites were correctly classified based on altitude alone and the inclusion of landscape- related variables did not improve the classification. In Tuscany, the mean annual temperature allowed classifying 70% of the positive/negative sites correctly. When landscape metrics was included in the multivariate model, an improvement up to 80% was obtained. The presence of riparian vegetation and water was found to be positively correlated with C. imicola presence, whilst forest (including the edge between the forest and cultivated areas) was found to be negatively related to the presence of C. imicola.

Blackfly (Diptera, Simuliidae) communities and species richness estimation in Carpathian montane streams

Abstract The present work gives the result of blackfly fauna research of the Slovenský raj (West Carpathians, Slovakia). Our aim was to describe the composition of blackfly communities, find indicator species for communities, describe environmental factors affecting communities and determine the potential changes in species richness. Research was carried out in 2007 and 2008. The presence of 22 species of blackflies was confirmed at 20 sites in the area of Slovenský raj. 12 species were recorded for the first time in this area. The potential for further increase in diversity was calculated by a nonparametric estimation of species richness. Two main groups of sites with their typical blackflies communities were indentified using a TWINSPAN analysis. The presence of Simulium ornatum, S. variegatum and S. argyreatum was typical in larger streams in broad valleys. The absence or low abundance of these species was typical for smaller streams in canyons. Based on the species composition of blackflies communities, we identified 6 groups of sites: 1. anthropogenically disturbed submountain rivers (typical species: Simulium ornatum, S. reptans, S. equinum), 2. undisturbed metarhithral (typical species: Simulium bertrandi, S. codreanui, S. costatum, S. vernum, S. argenteostriatum, S. degrangei, S. argyreatum, S. variegatum), 3. undisturbed hyporhithral (typical species: Simulium trifasciatum, S. tuberosum), 4. undisturbed epirhithral (typical species: Prosimulium hirtipes, P. rufipes), 5. hypocrenal (typical species: Simulium cryophilum, S. monticola) and 6. anthropogenically disturbed epirhithral (typical species: Simulium brevidens, S. maximum). The most important environmental factors explaining differences in species composition like altitude, flow speed, pH, conductivity, oxygen saturation, sulphates concentration and presence of riparian vegetation were identified by the CCA analysis.

The colonization success of an exotic Poaceae is related to native macrophyte richness, wind disturbance and riparian vegetation

Biotic and abiotic factors are filters that prevent invasions in aquatic and terrestrial ecosystems. In this investigation we tested the hypothesis that the success of a non-native Poaceae (Urochloa subquadripara) is positively correlated with the richness of native macrophytes and negatively correlated with wind disturbance (fetch) and presence of riparian vegetation on coarse spatial scales. Our samplings were carried out in a tropical reservoir (Rosana Reservoir, Brazil). We first compared competing models using the Akaike criterion to find the main combinations of explanatory variables (native macrophyte richness, fetch, and presence of riparian vegetation) associated with the success of U. subquadripara. Then, we applied multiple regressions to assess the coefficient of determination of the best models selected according to the Akaike criterion. The probability of occurrence of U. subquadripara increased significantly with increases in the number of native macrophyte species, but decreased with fetch and the presence of riparian vegetation. Stand width and maximum depth of occurrence (indicators of the success of this Poaceae) were also positively related with native richness and negatively with fetch and riparian vegetation. Our results supported our expectation that wave disturbance is an important variable explaining U. subquadripara success. Because the less exposed sites are also more favorable for colonization by natives, positive relationships between the success of non-native species and native diversity emerge at the coarse scale. Taken together, our results support the theory of “biotic acceptance”; that is, favorable sites are more prone to colonization by both native and non-native species.

Influence of landscape on assemblages of Chironomidae in Neotropical streams

Landscape is important in determining the composition of aquatic assemblage, and benthic in- vertebrates, particularly Chironomidae, are often used as bioindicators of environmental quality because their occurrence and distribution are influenced by different land uses. The objective of this study was to evaluate the influence of different land uses, considering three landscape scales (drainage basins, riparian buffer and streams), on chironomid assemblage. We sampled streams located in an agricultural matrix by collecting chir- onomid larvae and water samples and performed a landscape analysis using Geographical Information System techniques. The drainage basins had a high percentage of agricultural land use; in all of the drainage basins studied, 79% of the riparian buffer was not in accordance with Brazilian law. Cricotopus proved to be a good indicator of the agricultural conditions, whereas Thienemanniella and Rheotanytarsus proved to be indicators of exposed soil. Lopescladius was more sensitive to disturbance and was positively correlated with the presence of riparian vegetation. Although the variables at the local scale (stream) were responsible for a major change in the assemblage, the landscape attributes at large scales (drainage basin and riparian buffer) generated significant effects on Chironomidae fauna. Our results suggest the importance of the conservation of two larger landscape scales to support the equilibrium and maintenance of aquatic assemblage.

Trophic structure of a fish community in Bananal stream subbasin in Brasília National Park, Cerrado biome (Brazilian Savanna), DF

The aim of this study was to determine the trophic structure of the fish community in the Bananal stream subbasin, which belongs to a well-preserved Cerrado area (Brazilian Savanna) in Brasília National Park, Brazil. We also evaluated the influence of environmental variations in the diet of fish species. Four samples were taken in each 30 m long established transect, two in the rainy season and two in the dry season. A total of 1,050 stomachs of the 13 most abundant species were analyzed. A total of 36 food items were consumed, where 24 were autochthonous, 8 allochthonous, and 4 of undetermined origin. Non-metric multidimensional scaling (NMDS) analysis, in addition to the results of frequency of occurrence and abundance charts, was used to determine four groups of feeding guilds: detritivores, omnivores (tending toward herbivory and invertivory), invertivores and piscivores. Around 69% of the volume of resources consumed was allochthonous, which proves the importance of the resources provided by riparian vegetation. The contribution of autochthonous and allochthonous items in the diet differed due to seasonality for Aspidoras fuscoguttatus, Astyanax sp., Characidium xanthopterum, Hyphessobrycon balbus, Kolpotocheirodon theloura, Moenkhausia sp., Phalloceros harpagos, and Rivulus pictus. Despite the Cerrado climate characteristics, there was no significant influence of season on the fish diet. The absence of seasonal variation and the predominance of allochthonous items in the fish diet are probably associated with the presence of riparian vegetation, which acts as a transition area in the Cerrado biome and provides resources for the aquatic fauna. This work shows the importance of studies in non-disturbed areas considered here as a source of information concerning the biology of fish species and as a guide for direct conservation policies on the management of aquatic resources, recovery of damaged areas and determination of priority areas for conservation.

Caesium-137 in sandy sediments of the River Loire (France): Assessment of an alluvial island evolving over the last 50 years

Recent sedimentological and morphological evolution of an island in the River Loire (France) was investigated using the 137Cs method. This study describes the morphological adjustment of the island in the last 50 years, which corresponds to the increased bed incision of this sandy, multiple-channel environment because of, among other things, the increase in sediment extraction up to 1995. The results show that some 137Cs can be retained by sandy particles, potentially in clay minerals forming weathering features included in detrital sand grains. From a morphological perspective, significant lateral erosion can be observed in the upstream part of the island, while a weak lateral accretion occurs in its downstream section. Data about 137Cs and aerial photographs show that the morphology of the island margins has undergone significant changes leading to a lateral migration, while the centre of the island has remained relatively stable or is slowly eroding. The migration of the island depends on: (1) the withdrawal of inherited preincision morphological units, such as levees, or the development of new units, such as a channel shelf; (2) water and sediment supply from surrounding channels during flood events; (3) preferential sediment trapping (20 mm year − 1 ) from the presence of riparian vegetation on the bank of the secondary channel that is subject to narrowing. The sedimentological and morphological response of the island in the context of incision of the Loire river bed is expressed mainly by lateral migration and secondarily by a low vertical adjustment.