Diverse River Research Articles

Effects associated by the change of cauce río San Lorenzo, Carmen de Viboral Antioquia

The research object of this project revolves around the changes in the riverbed during river diversion. For this purpose, sampling work was conducted in the San Lorenzo River basin of El Carmen de Viboral city in eastern Antioquia, taking into account physical and chemical variables and biological indicators such as benthic macroinvertebrates. It has been confirmed that the diversion and/or changes in the San Lorenzo riverbed have led to changes in its physical, chemical, and biological characteristics, manifested in a decrease in dissolved oxygen concentration and saturation, an increase in pH value (due to increased peripheral coverage and photosynthesis), and water temperature (with almost no water flow, resulting in an increase in its kinetic energy). Compared to normal river beds, the richness and diversity of aquatic macroinvertebrates have sharply decreased. It was also found that the community structure of large invertebrates with weaker resistance to other more tolerant pollution has changed, leading to a loss of aquatic biodiversity and an increase in phosphorus concentration in the water generated by trout waste.

Benthic macroinvertebrate assemblages in large river secondary channels: Contemporaneous and legacy effects of flow connectivity

AbstractIn large rivers, secondary channels occur where the main channel is divided by an instream island, forming one or multiple smaller channels outside the main channel. Secondary channels are highly variable in morphometry, flow characteristics, and degree of connectivity to the main channel. Engineered closing structures at the upstream end of most secondary channels restrict inflow from the main channel, resulting in gradients of flow connectivity among secondary channels that vary with river stage. We investigated the relationship of flow connectivity to benthic macroinvertebrate assemblage richness and structure among a series of secondary channels of the Lower Mississippi River. Samples were collected over 2 years at times of high and low river stages. We discovered (1) macroinvertebrate assemblage structure and taxonomic richness varied along the flow connectivity gradient, and (2) there was a legacy effect of prior connection on assemblage structure that lasted up to a year. We contend that for management and restoration planning aimed at conservation of large river biological diversity, an important consideration are the life history requirements of animals utilizing secondary channel habitats.

Effects of seining effort on estimates of fish diversity in a sand-bed river

Changes in species diversity can be an indicator of ecosystem disturbance, impairment, or recovery. Estimating sampling effort needed to adequately represent stream fish assemblages is necessary for informing conservation actions. Increased sampling intensity can increase species detection, affecting the accuracy and precision of biodiversity indices. Seining is commonly used in fish surveys in sand-bottomed streams of the western USA. Here, we sampled 20, 200-m long stream sites each with 40 consecutive seine hauls to determine how increased within-site effort affected measures of species diversity. An average of 10 seine hauls were required to collect 75% of species present at sites in 40 seine hauls, while 18 seine hauls were required to collect 100% of species observed at a site sampled with 40 hauls. Simpson’s diversity index was highly variable when fewer than 7 seine hauls were performed at each site but stabilized when effort was > 15 seine hauls per site. Total dissimilarity and β-diversity components were variable under low sampling effort and also stabilized when effort reached 15 seine hauls per site. However, sampling with more than 18–20 seine hauls per site yielded few additional species. In shallow, sand-bed streams, we suggest sampling with < 5 seine hauls per 200 m of stream can result in unreliable estimates of α-diversity and variation in β-diversity. Increased effort of 15–20 seine hauls per 200 m of stream captured nearly all species present in 40 hauls per 200 m and stabilized species evenness and β-diversity indices.

Anthropogenic land-use activities within watersheds reduce comammox activity and diversity in rivers

Nitrogen cycling plays a key role in maintaining river ecological functions which are threatened by anthropogenic activities. The newly discovered complete ammonia oxidation, comammox, provides novel insights into the ecological effects of nitrogen on that it oxidizes ammonia directly to nitrate without releasing nitrite as canonical ammonia oxidization conducted by AOA or AOB which is believed to play an important role in greenhouse gas generation. Theoretically, contribution of commamox, AOA and AOB to ammonia oxidization in rivers might be impacted by anthropogenic land-use activities through alterations in flow regime and nutrient input. While how land use pattern affects comammox and other canonical ammonia oxidizers remains elusive. In this study, we examined the ecological effects of land use practices on the activity and contribution of three distinctive groups of ammonia oxidizers (AOA, AOB, comammox) as well as the composition of comammox bacterial communities from 15 subbasins covering an area of 6166 km2 in North China. The results showed that comammox dominated nitrification (55.71%–81.21%) in less disturbed basins characterized by extensive forests and grassland, while AOB became the major player (53.83%–76.43%) in highly developed basins with drastic urban and agricultural development. In addition, increasing anthropogenic land use activities within the watershed lowered the alpha diversity of comammox communities and simplified the comammox network. Additionally, the alterations of NH4+-N, pH and C/N induced by land use change were found to be crucial drivers in determining the distribution and activity of AOB and comammox. Together, our findings cast a new light on aquatic-terrestrial linkages from the view of microorganism-mediated nitrogen cycling and can further be applied to target watershed land use management.

Evaluation of physical and chemical parameters of two rivers crossed by PR 508 highway in Paranaguá/Brazil

Rivers are widely used by societies and have been degraded due to environmental impacts caused by human action over the years. This factor influences the extinction or decrease of the biological diversity of rivers and nearby regions. The anthropization on the rivers in the coastal region of Paraná causes impacts that can be evaluated through physical-chemical parameters of the local water resources. The objective of this work was to quantify the concentration of phosphate, ammonia and nitrate ions present in water samples from the Santa Cruz River and the Ribeirão River (Paranaguá - PR), which are crossed by PR 508 - Alexandra - Matinhos. The space-time sample collection took place in March and September of the year 2020. The values of turbidity, air and water temperature, concentration of phosphate, ammonia and nitrate ions were evaluated, in addition to the measurement of pH values, dissolved oxygen, electrical conductivity, total dissolved solids, in the four sampling points, being two points in each one of the evaluated water resources. The analytical investigation was carried out at the Laboratory of Environmental Impact Assessment of the Paranaguá Region (LAVIMA) using potentiometric, turbidimetric, conductometric and spectrophotometric methods. The results obtained in each of the parameters evaluated were compared to those established by National Council for the Environment (Conama) Resolution No. 357/2005. It was observed that the phosphate values obtained in the tests were higher than the maximum value recommended by the aforementioned normative resolution, and the other results presented results considered normal.

Assessment of Phytoplankton Diversity in Downstream Region of Meenachil River,kerala, During the Pre-monsoon and Monsoon Season

The present study aimed to assess the Phytoplankton diversity in the downstream of Meenachil River ,Kerala,during pre-monsoon and monsoon seasons. A total of 39 species belonging to five taxonomic divisions were identified, namely Chlorophyceae, Bacillariophyceae, Cyanophyceae, Euglenophyceae, and Xanthophyceae. The results revealed that Chlorophyceae was the dominant group, followed by Bacillariophyceae, Cyanophyceae, Euglenophyceae, and Xanthophyceae. The season-wise distribution of phytoplankton showed a higher abundance in the pre-monsoon season compared to the monsoon season. This study provides valuable insights into the phytoplankton diversity of Meenachil River, Kerala, and highlights the significance of monitoring seasonal changes in phytoplankton abundance for effective water resource management. The findings of this study can be useful for further research on water quality monitoring and management in rivers

Potentials and Constraints of Fairs and Festivals Tourism: A Study on Bangladesh

Bangladesh is a beautiful country. She is full of tourism resources that enable to attract tourists. Among these resources, natural and man-made attractions are notable. Natural scenic beauty, cultural diversity of ethnic minority people, rivers, lakes, hills, heritage and historical sites, various religious festivals, cultural festivals, fairs etc are core tourism resources. Many fairs and festivals are celebrated in every corner of the country throughout the year. These fairs and festivals create appeal for tourists. These fairs and festivals can significantly contribute to the development of tourism industry. This paper has highlighted the prospects of fairs and festivals in the country because it has the scopes of attracting domestic and foreign tourists in these occasions. However, there are some challenges for developing fairs and festivals tourism in the country as well. The researchers have focused on some constraints and provided suggestions to overcome the challenges in terms of developing fairs and festivals for tourism purposes. Journal of Business Studies, Vol. XLII, No. 1, April 2021 Page 107-132

Steps forward in biomonitoring 2.0: eDNA Metabarcoding and community-level modelling allow the assessment of complex drivers of Neotropical fish diversity.

The way we inventory and monitor biodiversity globally has been revolutionized by new molecular and ecological methods (Pawlowski et al 2021). Nonetheless, the Neotropical realm still represents a great challenge to our understanding of species distribution patterns and the role played by different drivers of biodiversity. The paper by Coutant et al. (2022) is a great advance towards a holistic approach to quantifying the contribution of environmental and anthropogenic factors that drive community assembly in the Amazon, and how we can apply such knowledge to guide future monitoring programmes. Disentangling the relative roles played by multiple drivers of biodiversity allowed them to also highlight hotspot areas hosting unique freshwater fish diversity and to pinpoint conservation priorities. Toward this end, the authors applied an innovative framework that included the use of environmental DNA (eDNA) to conduct fish inventories combined with community-level modelling. Their multifaceted approach accounting for taxonomic and functional measures of biodiversity allowed a thorough evaluation of ecological patterns. They reported a mismatch between functional and taxonomic biodiversity in their responses to geographical, environmental, and anthropogenic factors. Functional diversity was influenced by environmental and anthropogenic factors, while fish taxonomic diversity was determined by dispersal restrictions at both intra and inter-basin scales in the Guiana Shield. The role played by dispersal limitation and human activities in shaping fish diversity in large rivers is very relevant considering that Amazonian freshwater ecosystems are facing large-scale degradation due to human activities greatly impairing river connectivity (Castello & Macedo, 2016).

Bacterial Community and Diversity of River Ecosystems on the Qinghai-Tibet Plateau Based on 16S rRNA Gene Sequencing

In recent years, the ecosystems on the Qinghai-Tibet Plateau (QTP) have been facing a high risk of degradation due to the impacts of climate change and human activities. As one of the important components in river ecosystems, microbial communities can reflect the overall changes in the watershed and are regarded as indicators of the health of river ecosystems. In order to investigate the diversity and composition characteristics of bacterial communities in river ecosystems on the QTP, 65 samples were collected from the Yellow River, Yangtze River, Lancang River, Nujiang River, Yarlung Tsangpo River, and Qaidam Basin on the QTP in July 2021 and were analyzed using 16S rRNA high-throughput sequencing. The results showed that the detected bacterial communities covered 65 phyla and 1311 genera in total. Bacterial communities had high α-diversity indexes across the rivers, indicating that the bacterial richness and diversity in rivers on the QTP were at a high level. Among them, Chao and observed OTUs had significantly negative relationships with SRP/TP. The dominant phyla were Proteobacteria, Bacteroidota, Actinobacteriota, and Cyanobacteria. The dominant classes were γ-proteobacteria, Bacteroidia, and α-proteobacteria. The dominant genera were Flavobacterium and Limnohabitans. The results of principal coordinate analysis and permutational MANOVA suggested significant differences in bacterial community structure among the rivers on the QTP. Canonical correspondence analysis showed that the significant environmental variables associated with the variation in the bacterial communities were physicochemical properties of the river water, including conductivity, pH, dissolved silicon, and dissolved organic carbon, as well as watershed characteristics, including the average normalized differential vegetation index, average slope, cumulative water channel distance, catchment size, proportion of shrub area, and average elevation. Among them, conductivity had the strongest influence on bacteria distribution on the QTP. These results provide a database and information for understanding the composition characteristics of microbial communities on the QTP and identifying environmental factors influencing the diversity of bacteria communities.

Fish Diversity of Pahumara River of Barpeta District, Assam

A study was undertaken in the Pahumara River of Barpeta District , Assam during the year 2022 to document the fish fauna and its conservation status. The result reveals the presence of 51 species belonging to 7 orders and 17 families from four sampling station. The most dominant order is Cypriniformes from station-1 followed by Perciformes from station-2 . The IUCN status of the fishes were also evaluated as lower risk near threatened, vulnerable, lower risk least concern, endangered , not evaluated and critically endangered. The total number lower risk near threatened was found to be 20 followed by vulnerable which is found to be 13 , not evaluated 13,lower risk least concern 2, and endangered 3 . The study on the Pahumara river calls an urgent need for conservation of the species in the river of the Barpeta District.

Ichthyofaunal diversity in the lower Narayani River, Chitwan, Nepal

Narayani River in Nepal is an excellent habitat for diverse groups of aquatic organisms. A stretch of 70 km of lower Narayani River was studied for fish diversity and composition. A total species richness of 40 representing 14 families and 7 orders was reported. Order cypriniformes had high taxa dominance of 67% whereas least taxa richness of only 2 % with single species were recorded from orders Beloniformes, Clupeiforms, Gobiiformes and Osteoglossiformes. Simpson diversity index ranged from 0.1 to 0.8 whereas Shannon diversity and Pielou’s evenness ranged from 0.2 to 2.1 and 0.3 to 0.8, respectively. Minimum taxa richness and abundance were recorded in river stretches with industrial effluents situated along the bank of the river. High conservation species such as Wallago attu, Chitala chitala, Tor tor and Neolissochilus hexagonolepis were documented in the most downstream section, i.e., Tribeni of the river. Non-metric multidimensional scaling (NMDS) analysis distinguished three clusters of sites for the river where fish community composition was found to be significantly different (p &lt;0.05). The outcomes of the study help identifying critical river stretches that need high conservation efforts for conserving fish diversity in the lower Narayani River.

Hydromorphological discontinuities deeply modify the benthic multi-species assemblage diversity in a Mediterranean running river

The aim of the study was to investigate the modifications of the macroinvertebrate multi-species assemblage in relation to hydromorphological discontinues, since macroinvertebrates are traditionally exploited in water quality assessment activities. Three sampling sites characterized by different hydrological characteristics were selected in five stations along the River Aniene in Central Italy. We evaluated the macroinvertebrate structure, traits, biotic and diversity indices in relation to the erosive power. Among macroinvertebrate taxa, Elminthidae and Chironomidae families showed a particular occurrence pattern associated with the site at the base of vertical drop, characterized by the stronger hydrodynamic. However, the water quality status was high, not showing differences between the three sites. Our finding has a novelty value as similar studies on the investigation of the hydromorphological discontinuities on macroinvertebrate structure and ecological traits are very scarce in the literature.Graphical abstract

Geomorphic diversity of the middle Araguaia River, Brazil: A segment-scale classification to support river management

The complex mosaic of geomorphic units that characterizes the fluvial corridor of large rivers poses challenges to effectively describe and discriminate the landforms diversity, and is relationships with the hydrosedimentological dynamics and state of the system. Consequently, the classification of the diverse array of fluvial features into discrete segments can be a systematic and organized approach useful to sustain geomorphically-informed management strategies. Here we propose a methodological approach and characterize the geomorphic diversity of the middle Araguaia River by applying a classification of reaches into segments with a certain consistent level of morphological variability. A GIS framework developed for this purpose relied on the survey, analysis, and statistical treatment of morphological variables derived from remote sensing data. It allowed to differentiate 19 distinct reaches (R1-R19) that were further clustered into five major segments (SI-SV). We investigated the first-order controls of the fluvial style in each of the identified segments and found that changes in valley gradient influence in a major way the segments I, III, and IV, while the entrance of important tributaries and the nature of the valley floor are natural governing factors in segments II and V, respectively. The system exhibits a significant morphological diversity among segments, and it is strongly influenced by the late Holocene avulsion history of the river. Given the increasing pressure of human activities on the hydrological system, the present study can be of use to subsidize sustainable management plans aiming to safeguard the last large free-flowing river of the Cerrado biome, and our methodological proposal is valid for use in other large rivers worldwide.

IMPACTS OF CLIMATE CHANGE ON PHYTOPLANKTON COMPOSITION AND VARIABILITY IN IKO RIVER, COASTAL WATER OF EASTERN OBOLO, NIGERIA

This study investigated the effects of climate change on phytoplankton composition and diversity in Iko River, coastal water of Eastern Obolo, Akwa Ibom State, South Eastern Nigeria. The study area was greatly influenced by tidal flush from the Atlantic Ocean. Phytoplankton samples were collected monthly from October 2021 to March 2022 at high tide and low tide from 3 stations. Phytoplankton was identified and diversity was calculated using standard indices. Dissolved oxygen (3.3–6.0 mg/L) was above WHO guidelines of &lt;5.0mg/L and BOD (2.40-5.30 mg/L) in this study was above the (4.0 mg/L) limit recommended as suitable for aquatic life by the National Environmental Standards and Regulation Enforcement Agency (NESREA), which could pose a threat to aquatic life. A total number of 65 species of phytoplankton were identified in the study area. Bacillariophyta was the dominant group (69%) throughout the study in species number, occurrence and abundance. The increasing order of dominance values was; Bacillariophyta &gt; Cyanophyta &gt; Chlorophyta &gt; Dinophyta &gt; Euglenophyta . Diversity indices (Margalef, Shanon, Dominance, Simpson Evenness and Equitability) showed spatial variations significant at (P&gt;0.05). Pollution-indicator species such as; Tabellaria fenestrata, Nitzschia. paradoxa, N. filiformis, N. longissima, Cymbella cuspidata, Melosira distans and Anabaena constrica were recorded at either high tide, low tide or at both tides. Concerted efforts have been recommended to Government agencies and individuals to help reduce natural and anthropogenic pollution of the coastal water bodies.

Plankton Diversity in Aek Rao River Gunung Tua

The purpose of this study was to determine the index of plankton diversity in the Aek Rao River, Gunung Tua. The research was carried out from April to May 2022 in the Aek Rao River, Gunung Tua. The sampling method used purposive random sampling which consisted of 3 observation stations, namely station 1 upstream, station 2 for residential areas and station 3 for densely populated areas. The results showed that the composition of plankton in the Aek Rao River, Gunung Tua consisted of 3 classes of phytoplankton, namely Bacillariophyceae, Chlorophyceae and Cyanophyceae, while the zooplankton class consisted of 4 classes, namely Mastigophora, Monogononta, Crustacea and Ciliophora. The highest diversity index in phytoplankton was obtained at station 1 of the sand mining area with a value of 1, 39 which indicates that the level of diversity is in the medium category. In zooplankton the highest diversity index was found at station 3 with a value of 0.33 which indicated that the level of diversity was included in the low category. While the highest dominance index for phytoplankton was found at station 3 in densely populated areas with a value of 0.43 while zooplankton was found at station 1 in a sand mining area with a value of 0.00563, both values ​​indicated that there was no dominant plankton genus in that area.

Study on the fish species diversity and macro invertebrates of the river Narmada in Nimar Region of M.P.

The fishes are one of the most important vertebrate, provided rich protein sources for human and several animals and important elements in the economy of many countries. Fish diversity of river essentially represents the fish faunal diversity. Rivers conserve a rich variety of fish species which supports the from the period August 2009 to July 2010. The aim of the study was to explore the fish fauna of Narmada River. In the course of investigation, four sampling spots were selected Viz. Omkareshwar, Mandleshwar, Maheshwar and Barwani of Narmada River. The total 43 fish species were recorded under four orders, nine families and 16 genera. 21 species of commercial fisheries. The country is rich in diversity of such important group of animals keeping in the view, the diversity of fish fauna of the Narmada River in Omkareshwar to Barwani, Madhya Pradesh, Central India has been studied Cypriniformes, three species of Ophiocephaliformes, two species. The Cyprinidae family is dominant and sub dominant family is of Perciformes and one species of Mastacembeliformes have been recorded Ophiocephalidae. Recently, the Tor fish species commonly called ‘Mahasheer” has been declared state Fish of Madhya Pradesh. The over fishing and pollution are the major threat for fish diversity of the Narmada River.

Floristic diversity and scientific monitoring of landscapes lower Sula river (border areas of Nyzhnosulskyi National Nature Park)

The paper analyzes the floristic diversity of certain adjacent areas of the border zone of the Nyzhnosulskyi National Nature Park. The obtained new data made it possible to determine the ecological state of the meadow-steppe landscape, as well as the possible use of disturbed lands bordering the buffer zone. The necessity of introducing a protective zone of the National Nature Park has been proven. This will allow to timely assess the ecological state of landscapes; to prevent negative consequences for the protected areas, and in the future to include them in the composition of the protected territory. The conducted studies of floristic diversity and monitoring of disturbed lands in the southern border zones of the Nyzhnosulskyi National Park made it possible to state that there are threats of salinization, impoverishment of floristic diversity, and soil degradation for the southern border area under conditions of increased anthropogenic load or resumption of agricultural operations. It has been established that rare and red-listed plants within the landscape complex “Ivanivski Ozera”, which are also known within the National Nature Park “Nyzhnosulskyi”, have disappeared under the influence of mechanical and chemical intervention by farmers. Some halophytes and other steppe plants with deep or branched root systems remained. Taking into account the peculiarities of the relief of the territory of the Ivanivskі Lakes, the aridization of the climate and the speed of soil salinization processes in the lower Sula within the Obolon depression and under the conditions of further ploughing of the land, the territory will turn into salt marshes. The area of soil salinization will extend to the territory of the Park, which will lead to irreversible changes in the phytocoenosis and the appearance of salt marshes and an even greater number of halophytes. Scientific monitoring of the disturbed lands of the border zone of the nature reserve confirms that for the preservation and protection of floodplain complexes of the Sula River and meadow-swamp ecosystems, it is necessary to provide systematic research and a timely forecast of ecological changes in landscapes; prevention and elimination of negative consequences for protected floristic areas. In addition, it is advisable to include the lands of the buffer zone as part of the protected area of the National Nature Park and determine the degree of effectiveness of measures aimed at the preservation and restoration of land resources.

Disturbance legacy of a 100-year flood event: large wood accelerates plant diversity resilience on gravel-bed rivers.

Understanding biodiversity resilience after a major disturbance is a key issue in basic and applied science. Plant diversity in gravel-bed rivers is affected by flood events, which are one of the most effective disturbance agents in the flow regime, affecting species distribution, and ecosystem dynamics. Although disturbance plays a critical role in community assembly mechanisms, how plant diversity recovers after a severe disturbance, such as a 100-year flood event remains unknown. The present study examined how the disturbance legacy of large wood in gravel-bed river ecosystems contributes to the resilience of plant diversity. The present study demonstrated that the resilience of plant species in disturbance legacy sites, namely deposited large wood sites, was higher than that in open habitat sites. Indicator species analysis revealed that perennial plants were the most important indicator species of disturbance legacy sites. These results suggest that perennial species richness contributes to the resilience of high plant diversity across the disturbance legacy sites in this region. After major flood events, land managers often remove large wood and debris jams to avoid secondary disasters, such as embankment collapse. However, we suggest that large wood should be retained on the gravel beds to aid the recovery of biodiversity and ecosystems. Furthermore, understanding the relationships between disturbance legacies and ecosystem resilience can contribute to the formulation of strategies for sustainable ecosystem management and biodiversity conservation in the future.

Keragaman Plankton di Sungai

This study aims to determine plankton diversity in the Aek Pala River, Labuhanbatu Regency. The method used is descriptive observative. Sampling was done by filtering 10 L of water using a plankton net. The results showed that there were 15 genera of plankton in Aek Pala waters, including 10 types of phytoplankton and 5 types of zooplankton. The most abundant diversity of phytoplankton species found was in the class Chlorophyceae, which was 75% (7 species). In contrast, the highest diversity of zooplankton species is from the class Crustacea (3 species). In addition, the physical and chemical parameters of the waters show that Aek Pala waters are very good for supporting plankton life. In conclusion, the diversity of plankton species obtained included phytoplankton (classes Chlorophyceae, Bacillariophyceae and Dinophyceae) and zooplankton (classes Crustacea and Rotifera). The abundance of plankton found categorizes that the river waters have moderate fertility. &#x0D; Keywords: Diversity, Plankton, Zooplankton, Phytoplankton and Aek Pala River

Fish Diversity along the Mekong River and Delta Inferred by Environmental-DNA in a Period of Dam Building and Downstream Salinization

The Mekong River is one of the largest rivers in the world and hosts the second greatest fish diversity in the world after the Amazon. However, despite the importance of this diversity and its associated biomass for human food security and the economy, different anthropogenic pressures threaten the sustainability of the Mekong River and fish diversity, including the intense damming of the main river. Both the increase in salt-water penetration into the Mekong Delta and the disrupted connectivity of the river may have serious impacts on the numerous freshwater and migratory species. To evaluate the potential of an eDNA approach for monitoring fish diversity, water was sampled at 15 sites along the salinity gradient in the Mekong Delta and along 1500 km of the main stream, from Vietnam to Thailand and Laos. A total of 287 OTUs were recovered, of which 158 were identified to the species level using both reference sequences available in GenBank and references obtained locally. Agglomerative hierarchical clustering and PCA identified up to three main species assemblages in our samples. If the transition from brackish to freshwater conditions represents the main barrier between two of these assemblages, more surprisingly, the two other assemblages were observed in the freshwater Mekong, with a spatial disjunction that did not match any biogeographic ecoregion or the Khone falls, the latter thought to be an important fish dispersion barrier. Between 60% and 95% of the freshwater species were potamodromous. This pioneer eDNA study in the Mekong River at this geographical and ecological scale clearly confirmed the potential of this approach for ecological and diversity monitoring. It also demonstrated the need to rapidly build an exhaustive Mekong fish barcode library to enable more accurate species’ assignment. More eDNA surveys can now be expected to better describe the ecological niche of different species, which is crucial for any models aimed at predicting the impact of future damming of the Mekong.