River Islands Research Articles

Hydrological-driven changes in the phytoplankton community structure under nutrient stress in island river ecosystems

While the spatiotemporal dynamics of phytoplankton community structures in river ecosystems have been extensively studied, their primary driving factors remain elusive, particularly at the watershed scale. This research examined the phytoplankton community structure across three watersheds of an island and concurrently analyzed its response to water level fluctuations (WLFs). The phytoplankton density was notably higher at elevated water levels, registering an increase of 1.29 times in Nandu River, 1.34 times in Changhua River, and 1.28 times in Wanquan River. Notably, the middle reaches of the Changhua River recorded the highest phytoplankton density (4.46 × 108 cells/L). Broadly speaking, Cyanophyta, Chlorophyta, and Bacillariophyta remained the predominant phytoplankton across varied water levels. Dominant phytoplankton species varied with water levels; however, the most prevalent species consistently belonged to the Cyanophyta group, primarily Microcystis or Merismopedia, with dominance ranging between 0.17 to 0.38 (low water level) and 0.18 to 0.32 (high water level). Enhanced phytoplankton diversity and richness were observed at higher water levels, correlating with increased concentrations of NH4+-N, NO3−-N, and PO43− in the river water. Consequently, nutrient fluctuations driven by hydrodynamics significantly influence the phytoplankton community structure in island river ecosystems.

Ephemeral river islands serve as roosting and foraging habitat for boreal and austral migratory songbirds.

Ephemeral river islands serve as roosting and foraging habitat for boreal and austral migratory songbirds.

Experimental study on thermal–hydraulic performance of a nature-inspired mini-channel heat exchanger manufactured by 3D printing

Zigzag-channel printed circuit heat exchangers (PCHEs) are widely used in nuclear energy, solar energy, and aerospace due to their good heat transfer performance. However, the high flow resistance of zigzag channels leads to large pumping power consumption and thus limits the overall performance. Although previous modified channels could reduce the flow resistance of PCHEs, they also bring a decrease in the heat transfer efficiency. Inspired by river islands, this study proposes a novel nature-inspired channel. The nature-inspired channel heat exchanger, along with a traditional zigzag-channel heat exchanger, were manufactured by 3D printing. The high-temperature air-air flow and heat transfer experiments show that the nature-inspired channel heat exchanger increases the average heat transfer rate by 1.5% and significantly reduces the pressure drop by 34.85%. The addition of airfoil fins at the corners effectively alleviates the flow resistance caused by flow separation, reattachment, and collision, leading to a higher Nusselt number and a lower Fanning friction factor. The Nusselt number of nature-inspired channel is 59% higher than that of the zigzag channel with a 15° inclined angle. This work demonstrates that the nature-inspired channel could significantly reduce the flow resistance while maintaining high heat transfer efficiency compared with the traditional zigzag channel.

Indigenous Knowledge in Tourism Development: The Case of Hô River Island, Tra Vinh Province, Vietnam

Abstract Climate change is affecting various aspects people’s lives in the Mekong Delta, Vietnam, especially those who are living in the low-elevation terrain such as small river islands. Some studies revealed that indigenous knowledge can assist local people in mitigating the damage to agricultural production caused by climate change. Thus, this paper analyzes the application of indigenous knowledge of the people in Hô Island, Tra Vinh province in tourism development in the context of climate change. The qualitative approach was utilized in this paper including 35 semi-in-depth interviews and participant observations in 13 events. The results showed that indigenous knowledge not only greatly contributed to creating impressive tourism products and services but also formed secondary livelihoods aside from agriculture, which improved the living standards for the people in Hô Island. This research implies that there is a need for policies and training courses to raise general awareness of the adaptation of indigenous knowledge in economic development, and particularly, tourism development in vulnerable geographic areas (such as small river islands) in the context of climate change observed in the Mekong Delta.

Numerical simulation of morphological evolution in a gravel-bed meandering river during floods: a case study on the Sai-Jiang river

ABSTRACT The water velocity undergoes a significant increase during the initial stage of floods. The present study focuses on investigating the scours and silting occurring in an S-shaped gravel-bed river. The primary objective is to analyze the impact of 10-year flood events on both the riverbed and bank stability. This river is located in the Sai-jiang River reach, Fujian Province, China. A numerical model of riverbed scours and silting is herein tested. The research results indicate that the morphological evolution of the whole river section is affected in the early stage of flood evolution; however, in the later stage, some key places such as the bridge and the river land are still greatly affected. The apex of the river bend is in close proximity to the downstream river island, resulting in scour at the head of the river island that deviates from conventional patterns of head scour and tail siting. Furthermore, the presence of artificial structures like bridges exacerbates the scour and silting processes in river beds during flood events. For this case, the riverbed adjacent to the Banzhong Bridge pier experienced a widening of approximately 50 m and downstream extension of around 300 m, with a maximum vertical scouring depth of 2.87 m.

Distinct drivers of bacterial community assembly processes in riverine islands in the middle and lower reaches of the Yangtze River.

Riverine islands are widespread alluvium wetlands developed in large rivers, and bacterial communities are crucial to their ecological function, yet their assembly processes are rarely addressed. The ecosystem services provided by the middle and the lower Yangtze are primarily threatened by pollution discharge from agricultural land use, and resource overutilization (e.g., embankments), respectively. Here, we assessed bacterial community assembly processes and their drivers within riverine islands in the middle Yangtze River (MR islands) and those in the lower reach (LR islands). A significant distance-decay relationship was observed, although the turnover rate was lower than that of the terrestrial ecosystem with less connectivity. Deterministic and stochastic processes jointly shaped community patterns, and the influence of stochastic increased from 26% in MR islands to 59% for those in LR islands. Meanwhile, the bacterial community in MR islands was controlled more by inorganic nitrogen availability, whereas those in LR islands were governed by pH and EC, although those factors explained a limited fraction of variation in the bacterial community. Potential indicator taxa (affiliated with Nocardioides and Lysobacter) characterized the waterway transport pollution. Overall, our study demonstrated that bacterial community dissimilarity and the importance of dispersal limitation increased concurrently along the flow direction, while distinct local factors further determined bacterial community compositions by selecting habitat-specificity taxa and particularly metabolism function. These findings enhanced our understanding of the mechanisms driving changes in bacterial communities of riverine islands subject to increased anthropogenic impacts.IMPORTANCERivers are among the most threatened ecosystems globally and face multiple stressors related to human activity. However, linkages between microbial diversity patterns and assembly processes in rivers remain unclear, especially in riverine islands developed in large rivers. Our findings reveal that distinct factors result in divergent bacterial community compositions and functional profiles in the riverine islands in the middle Yangtze and those in the lower Yangtze, with substantial differentiation in deterministic and stochastic processes that jointly contribute to bacterial community assemblages. Additionally, keystone species may play important metabolic roles in coping with human-related disturbances. This study provides an improved understanding of relationships between microbial diversity patterns and ecosystem functions under environmental changes in large river ecosystems.

Evaluation of Nonpoint Source Microbiological Pollution Loads on Eagle Island River

Evaluation of Nonpoint Source Microbiological Pollution Loads on Eagle Island River

Spatiotemporal response of the optical characteristics of dissolved organic matter to seasonality and land use in tropical island rivers.

Dissolved organic matter (DOM), a pivotal component in the global carbon cycle, plays a crucial role in maintaining the productivity and functionality of aquatic ecosystems. However, the driving factors of variations in the properties of riverine DOM in tropical islands still remain unclear. In this study, the spatiotemporal response of the optical characteristics of riverine DOM to seasonality and land use on Hainan Island in southern China was investigated. Our results revealed that DOM in the rivers of Hainan Island exhibited a relatively high proportion of fulvic acid and demonstrated strong terrestrial sources. The optical properties of DOM exhibited significant variations both seasonally and spatially. Land use exerted a dominant influence on riverine DOM. Specifically, during the wet season, riverine DOM exhibited larger molecular weight, increased chromophoric DOM (CDOM) abundance, and higher Fmax compared to the dry season. Furthermore, riverine DOM influenced by grassland and farmland showed higher CDOM abundance, Fmax, and humification degree in contrast to those impacted by forest and urban. Random forest and correlation analysis results indicated that grassland and farmland enhanced the Fmax of DOM by increasing levels of TP, NO3--N, Chl a, and NH4+-N in the dry season. However, during the wet season, the increased Fmax of DOM induced by grassland and farmland relied on the increments of Chl a and TP concentrations. This study improves our understanding of the spatiotemporal fluctuations of DOM in the rivers of Hainan Island, highlighting the effects of season and land use on DOM. It offers valuable support for improving water quality and contributes to enhancing human comprehension of the global carbon cycle.

Assessing Multi-Decadal Landmass Changes and River Bank Erosion in the Char Areas of Majuli River Island of Assam, India

Majuli, the biggest populated river island, which is bordered to the north by the Subansiri River and to the south by the powerful Brahmaputra River. Since ancient times, the island has been continuously eroding, which is cause for serious concern. The current method uses Remote Sensing (RS) satellite imagery covering the years 1976 to 2024 and Survey of India (SOI) toposheets to study the erosion–deposition processes in a Geographic Information System (GIS) environment. The observation has revealed a dramatic change in reduction of land area of the Majuli Island. This paper provides a comprehensive analysis of the long-term changes in landmass and erosion patterns in the char areas of Majuli Island, highlighting both the environmental challenges and the socio-economic implications for local communities. It is evident that the erosion rate on the island mass was significantly higher than that of the depositional processes.

MAJULI RAAS MAHOTSAV AND ITS PRESENT-DAY RELEVANCE WITH RESPECT TO SOCIO-ECONOMIC DEVELOPMENT OF MAJULI

Majuli, the world's largest river island (Guinness World Records) situated in the Brahmaputra River in Assam, India, hosts an annual cultural extravaganza in the month of November known as the Raas Mahotsav. This research article explores the historical and cultural significance of the Majuli Raas Mahotsav and analyses its present-day relevance in contributing to the socio-economic development of Majuli. For this study secondary data is collected through review of academic literature, from government reports, government websites and media articles. The study provides a comprehensive analysis of how the festival contributes to local economic growth, cultural preservation, and community cohesion. By examining the impact of the festival on tourism, local businesses, and community engagement, this study aims to shed light on the potential of cultural events like Majuli Raas Mahotsav as catalysts for regional development. This research contributes to the ongoing discourse on leveraging cultural heritage for sustainable development and offers valuable insights for policymakers, researchers, and cultural enthusiasts alike.

An Investigation on the Present Status of Wetlands in Majuli River Island; The World Largest River Island and Its Fishery Resources

An Investigation on the Present Status of Wetlands in Majuli River Island; The World Largest River Island and Its Fishery Resources

Sacred Isles: Islands as Sites of Religious, Spiritual or Supernatural Exception

The articles in this inaugural publication of the periodic section on ‘Sacred isles: Islands as sites of religious, spiritual or supernatural exception’ in Folk, Knowledge, Place examines the complex interplay between sacred isles, geography and human experience. Through empirical research, theoretical analysis and comparative studies, the papers contribute to island studies by revealing the layers of meaning embedded in island landscapes and their roles in spiritual and cultural life. The three articles in the present issue discuss diverse locations, covering distinct small island settings with sacred connections in England (St Michael’s Mount), Guernsey (Lihou) and the river islands of Guangzhou in China. Drawing from a rich body of scholarly work across island studies, folklore studies, religious studies and geography, this periodic section foregrounds how the inherent spatial characteristics of islands—such as isolation, defined coastlines and unique environmental conditions—imbue them with mystique and sanctity. Such attributes foster a heightened sense of space and intimacy with the environment and enhance their appeal as sacred sites. While highlighting how islands can embody cultural heritage and religious devotion, the articles also explain some of the ways sacred isles can transcend island space, moving between and across islands and related revered settings where a consideration of sacred interconnections becomes necessary for comprehending islands on their own terms.

Effect of dumpsite on groundwater quality: A case study of bonny island rivers state

This study investigates the effect of dumpsite activities on groundwater quality in Bonny Island, Rivers State, Nigeria. Bonny Island, an ancient coastal city with significant economic importance due to its oil and gas industries, faces potential environmental threats from dumpsite activities. The research utilized vertical electrical sounding (VES) and 2D resistivity profiling (ERT) to assess subsurface contamination. Measurements were taken to determine the lateral and vertical spread of contaminants at the dumpsite. Complemented by laboratory analysis of groundwater samples from the two dumpsites, groundwater samples were analyzed for a range of physical, chemical, and biological parameters, such as pH, TDS, TSS, DO, Nitrates, Sulphates, Chlorides, heavy metals, and other pollutants. Results obtained indicate that the groundwater near the dumpsites exhibits varying levels of contamination. The VES and ERT profiles revealed low resistivity zones at shallow depths, indicating possible clay-rich soil or topsoil contamination from leachate. High resistivity areas in the middle depths suggest cleaner zones, but low resistivity at both ends of the profiles indicates further spread of the leachate. Laboratory analyses of groundwater sample showed that most parameters were within acceptable limits set by WHO and NSDWQ, except iron, which exceeded the permissible limit, suggesting contamination of iron at the site. These findings highlight the need for continuous monitoring and remediation efforts to prevent further deterioration of groundwater quality. This study underscores the critical importance of protecting groundwater in economically vital and ecologically sensitive regions like Bonny Island.

Environmental DNA metabarcoding reveals the effect of river slope on diadromous fish communities in island rivers

Understanding the natural factors that influence diadromous fish communities in river ecosystems is crucial for effective biodiversity management. However, this remains an unexplored and challenging task. Here, the relationship between river morphology and diadromous fish communities within rivers was explored. We focused on river slope and estuary size, as these may constrain their upstream migration and affect the availability of important nursery grounds for some species. Using environmental DNA metabarcoding, we investigated the diadromous fish communities within 12 rivers of subtropical Yakushima Island, southern Japan, and compared the community differences among rivers with different river slopes and estuary sizes. Fewer diadromous fish species were detected in rivers with steeper slopes and smaller estuaries. Additionally, the community similarity was greater among rivers with analogous gradients and estuary sizes. These results indicate that river slopes exert a species-selective effect on diadromous fish communities by affecting their upstream migration and estuarine habitat availability, thereby playing a crucial role in shaping the composition of these communities within rivers. Conserving gentle-gradient rivers with large estuaries would be crucial for preserving the diversity of diadromous fish species, which play a crucial role in shaping biodiversity especially in rivers of subtropical and tropical oceanic islands.

Characteristics of the River Islands of the Greater Zab River Between "Rizan Village and Its Mouth" Hydro Geomorphological Study

Characteristics of the River Islands of the Greater Zab River Between "Rizan Village and Its Mouth" Hydro Geomorphological Study

Influence of climate, physical and chemical variables on the taxonomic and functional responses of macroinvertebrate communities in tropical island rivers

Influence of climate, physical and chemical variables on the taxonomic and functional responses of macroinvertebrate communities in tropical island rivers

Insights into key threats and conservation status of the river lapwing, Vanellus duvaucelii (Lesson, 1826) in Northern India

Abstract The river lapwings are inhabitant of river banks with sand or gravel bars and river islands. In this study, we investigated vital threats (natural and anthropogenic) and the conservation status of river lapwing in the riverine ecosystem of Northern India. In this regard, we frequently visited selected study sites along the banks of the river Ganges in the district of Raebareli (Uttar Pradesh), India, from January 2016 to December 2019. To estimate perceived threats for river lapwing, we developed a questionnaire and collected threat scores. The line transect method was used to estimate the density of river lapwing. Predation and farming activities were the most potent threats influencing the survival and abundance of river lapwing. River lapwings were primarily observed at open unvegetated river banks and open unvegetated islands. They were seen in significant density near the water in the breeding season. We concluded that the population of river lapwing is relatively stable in the Gangetic plains of Northern India. However, it is declining in other parts of the world, for example, in Southern Laos. Though it is a relatively common species, robust scientific information about its population and habitat relation is mainly absent. Therefore, accurate counts from other parts of the world are needed to place the estimate for river lapwing into a comprehensible, inclusive perspective. Furthermore, detailed information on habitat relationships is also necessary to develop conservation strategies.

Temporal trends in sand bars and water bodies on the right side of the world's largest fluvial island - Javaés River

Bananal Island is the largest river island in the world, located in the Araguaia River basin in central-western Brazil. Studies on the Araguaia River have shown that changes in the main channel are linked to the increase in sediment input due to agricultural expansion in the Cerrado. However, very little is known about the Javaés River, on the opposite margin of Bananal Island. This study analyzed the temporal trends of sand bars and water masses in the Javaés River from 1985 to 2021. Annual mosaics of Landsat images were generated to identify the classes of water masses and sand bars. The Mann Kendall and Sen's Slope tests were used to identify trends and statistical significance of changes over time. The results indicated an increase of 57% (6.5 km²) in the areas of sand bars and a reduction of 39% (15.2 km²) in water bodies. The tests revealed significant trends with an increase in bars and a decrease in water bodies. It was observed that changes in the distribution and rates of regional precipitation, along with the expansion of anthropogenic occupation, are contributing to an increase in sediment input, in a cascade effect, affecting the balance between erosion and deposition in the Javaés River.

Urbane politike planiranja, upravljanja i stanovanja u evropskim gradovima na rekama i gradu Beogradu - studija slučaja

As a consequence of the lack of public policies and legal framework, and then the non-compliance with laws and regulations related to the use of rivers and coasts, the development of floating communities from their creation until today in Belgrade, has flowed predominantly from the bottom up, i.e. from individual and often illegal actions individuals to the gradual and increasingly current determination and then the implementation of public policies and the arrangement of the river area. Comparatively, some European cities on rivers and canals have, in the last few decades, increasingly paid attention to the careful planning of river and canal management and the potential opportunities for the realization of urban green housing projects through the creation of sustainable floating microriver communities on them. And the city of Belgrade gradually adapts to these needs. In the city of Belgrade, in addition to a large number of examples of bad practice of "floating communities" there are also some good examples of "micro river space" arrangement and good practice of living and living in an ecologically acceptable natural environment on the water. This is the case of the river island of Ada Međica in Belgrade, which can serve as a "good case" for other European cities on rivers. It is a sustainable community characterized by the symbiosis of people and the environment, where the strength of a small river community contributes to the preservation of the environment, the achievement of ecological balance and urban green living in a natural environment.

Application of Revised Universal Soil Loss Equation (RUSLE) model for the estimation of soil erosion and prioritization of erosion-prone areas in Majuli Island, Assam, India

Soil erosion is a serious issue, causing loss of agricultural productivity, increase in sediment deposit in the riverbeds, and damage to the ecological balance of the affected areas. Proper assessment of the soil erosion rate is essential for managing natural resources. The present study employs a GIS-based RUSLE (Revised Universal Soil Loss Equation) model to estimate annual soil loss in Majuli River Island of Assam, India. Annual average rainfall, soil properties, topographic characteristics, and LULC were taken as inputs to identify the soil erosion susceptible areas. The result revealed that annual soil loss of the study area ranges between 0 to 711 t ha−1 yr−1, with a mean annual soil loss of 23.02 t ha−1 yr−1. The entire region was classified into six soil loss severity classes, around 90 % of the area was found to be very slightly affected (< 5 t ha−1 yr−1) by soil erosion, around 5 % slightly affected (5 – 10 t ha−1 yr−1), roughly 3% moderately affected (10 – 20 t ha−1 yr−1), around 1% moderate high (20 – 40 t ha−1 yr−1), nearly 0.3 % area affected severely (40 -80 t ha−1 yr−1) and very severely affected areas (> 80 t ha−1 yr−1) contributes 0.1 %. A total of six priority levels of conservation were demarcated village-wise; priority level I requires immediate attention, and so on. The research outcome can help effectively implement conservation and management practices to check soil erosion in the study area.