Abundance In Rivers Research Articles

GIS-driven Hydro Energy Potential Estimation for Technoeconomic Assessment of Hydro Power Plant in Bawean, Gresik

This study aims to assess the spatial distribution of hydropower capacity on Bawean Island using a Geographic Information System (GIS). The objective of this study is to provide a valuable contribution to the progress of sustainable energy transition initiatives in Indonesia. The primary objective of the hydropower map is to enhance the process of strategic planning and implementation of hydropower infrastructure, with a particular emphasis on supplying electricity to rural regions. The essential components required for the successful implementation of hydropower are the head, which represents the vertical distance between the water source and the water outflow, which refers to the rate at which water is discharged from the system. Bawean Island, located in the eastern region of Java, possesses a unique topographical structure distinguished by an abundance of rivers, making it a promising site for the establishment of hydropower infrastructure. The utilization of ArcGIS was applied for the aim of hydropower mapping. The estimation of water discharge was conducted using the Soil Conservation Service-Curve Number (SCS-CN) approach. The current investigation utilized the Multi-Criteria Decision Analysis (MCDA) framework, which incorporated the Analytical Hierarchy Process (AHP) and the Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS) to ascertain the most advantageous choice of hydropower plant types for deployment in the Bawean region. The classifications comprise pico-hydro, micro-hydro, mini-hydro, and large-scale hydropower installations.The Multi-Criteria Decision Analysis (MCDA) framework incorporates various criteria, including cost, policy, social concerns, technology assistance, integration, and natural catastrophe considerations. The results indicate that the hydropower potential on Bawean Island peaks in January, coinciding with the rainy season, while it is at its lowest in August, corresponding to the dry season. Moreover, the spectrum of hydropower installations suitable for Bawean Island includes pico-hydro systems, which have a power generation capacity of up to 5 kW. Additionally, mini-hydro plants are categorized into two classes: class A, with a power generation capacity ranging from 5 to 100 kW, and class B, with a power generation capacity ranging from 100 to 200 kW. The utilization of Multi-criterion Decision Analysis (MCDA) reveals the results of the techno-economic assessment, emphasizing the importance of cost, social factors, and policy as the key criterion for decision-making. The factors mentioned above are allocated weights of 0.44, 0.17, and 0.17, correspondingly. Pico-hydro is a suggested category of hydropower plants that are being considered for the development of hydropower infrastructure in the Bawean region.

НОВЫЕ ДАННЫЕ О ВОЗВРАТЕ ДРЕВНЕГО ОРОШАЕМОГО ЗЕМЛЕДЕЛИЯ В ТУВЕ

According to the conducted research, the Republic of Tuva is an area of ancient agriculture, which was facilitated by the geographical location and natural conditions, first of all, the mountainous terrain and the abundance of rivers in this territory. Practically in all river valleys of the region there are various irrigation systems corresponding to the capabilities of technology and the organization of social labor of certain historical periods. Here you can observe all the stages of irrigation development. According to В.А. Latynin’s classification, it is the stage of early irrigated agriculture, the stage of the simplest types of irrigation channels that turn into complex fan irrigation systems. The presence of the rudiments of agriculture in the Neolithic is evidenced by the finds of pollen of cultivated barley aged 6–5 thousand years in the valley of the Small Yenisei, made by S.B. Potakhin. Mining and ore production contributed to the development of agriculture in the Bronze Age — there are large copper deposits in the bowels of Tuva. According to the conducted research, developed irrigated agriculture existed in this territory in the Xiongnu period (Ubsunur basin, SOAN-9199; East Tuva Highlands, SOAN-9201). In 2022, radiocarbon dating was obtained for the first time, confirming the presence of irrigated agriculture in Tuva in the 1st millennium BC, Scythian-Saka time.

Extensive abundances and characteristics of microplastic pollution in the karst hyporheic zones of urban rivers

Cities are potential areas for microplastic pollution due to large-scale production and the use of plastic products. The karst ecosystem in southwestern China is fragile, and pollutants are more likely to be transported over long distance, resulting in higher pollution risks. Understanding the abundance and composition of microplastics in karst urban water systems is crucial for microplastic pollution management in a karst region. This study investigates the abundances and characteristics of microplastics typically found in river sediments in 10 cities in karst regions of Southwest China. The results show that the abundance of microplastics in sediments ranged from 800 items·kg−1 to 4400 items·kg−1, with an average of 2273 ± 775 items·kg−1 (n = 30), indicating high abundance. Polyamide (PA) was the most common plastic polymer types in all sediment samples. The abundance of microplastics in the downstream (2527 ± 698 items·kg−1) was higher than that in the midstream (2350 ± 999 items·kg−1) and upstream areas (1943 ± 370 items·kg−1), indicating a gradual accumulation effect in the karst water systems. Microplastic abundance in cities (2119 ± 838 items·kg−1) was lower than in counties (2427 ± 671 items·kg−1). No significant correlation was found between microplastic abundance in rivers of urban areas and the level of regional population and economy, but significantly negatively correlated with the efficiency of urban sewage treatment. The results obtained from this study provided insights into the management of microplastic pollution in urban river of a karst region.

Brook trout occupancy in rivers and streams of the Mixedwood Plains Ecozone, Ontario

AbstractBrook trout (Salvelinus fontinalis) are an iconic freshwater salmonid native to northeastern North America. They prefer cold, clean rivers and lakes, and have been culturally, socially and economically valued for decades. Overharvest and deforestation associated with European settlement in southern Ontario, Canada led to notable declines in brook trout abundance in rivers and streams by the late 1800s. Today, they are threatened by further habitat degradation, non‐native species, and climate change. In this study, we document brook trout occupancy in rivers and streams of the Mixedwood Plains Ecozone in southern Ontario, between 1970–1980 and 2000–2010. We used generalised linear models to determine occupancy variation between the two time periods at five spatial scales spanning multiple watershed levels. We detected a decline in occupancy between time periods for the tertiary (from 23% to 17%) and quaternary (from 35% to 22%) watershed scales. In the Credit River‐Sixteen Mile Creek watershed, mean occupancy decreased to a third of past estimate (from 31% to 10%). For a subset of 86 sites with overlapping sampling in both periods no temporal trend was detected, but a post‐hoc analysis indicated low statistical power (0.07), which suggested that more intensive sampling would be needed to better quantify brook trout occupancy changes at this scale. The occupancies quantified for the past period in our study may serve as benchmarks for brook trout restoration efforts.

Microplastic abundance in the Thames River during the New Year period

Microplastic pollution is widely studied; however, research into the effects of large-scale firework displays and the impact on surrounding waterways appears to be lacking. This study is potentially the first to look at microplastic abundance in rivers after a major firework event. To assess the impact of the 2020 New Year's firework display in London, a 3 litre water sample was collected over nine consecutive days at Westminster on the River Thames. A total of 2760 pieces of microplastics (99% fibres) were counted using light microscopy, and further analysis was performed on representative plastic samples (354) using Fourier Transform Infrared Spectroscopy (FTIR). Whilst anthropogenic microfibres made up 11%, most microplastic identified (13.3%) were polychloroprene. This study demonstrates the occurrence of a short-term influx of microplastics in the River Thames following the New Year fireworks, which will have an additional detrimental impact on the ecology and aquaculture of the river and neighbouring waterways.

Tracing microplastics from raw water to drinking water treatment plants in Busan, South Korea

The increasing amount of plastic waste has raised concerns about microplastics (MPs) in aquatic environments. MPs can be fragmented into nanoplastics that can pass through water treatment processes and into tap water; potentially threatening human health because of their high adsorption capacity for hazardous organic materials and their intrinsic toxicity. This case study investigates the identification, fate, and removal efficiency of MPs in Korean drinking water treatment plants. Two sites on the Nakdong River, two lake reservoirs (raw water sources), and four corresponding drinking water treatment plants were targeted to trace the amounts, types, and sizes of MPs throughout the treatment process. Monthly quantitative and qualitative analyses were conducted by chemical image mapping using micro-Fourier-transform infrared spectroscopy. MPs larger than 20 μm were detected, and their sizes and types were quantified using siMPle software. Overall, the number of MPs in the river sites (January to April and October to November) exceeded those in the reservoirs, but only slight differences in the number of MPs between rivers and lake reservoirs were detected from June to October. The annual average number of MPs in River A, B and Lack C and D was not distinctively different (2.65, 2.48, 2.46 and 1.87 particles/L, respectively). The majority of MPs found in raw waters were polyethylene (PE)/polypropylene (PP) (> 60%) and polyethylene terephthalate (PET)/poly(methyl methacrylate) (PMMA) (20%), in addition to polyamide (<10%) in the river and polystyrene (<10%) in the lake reservoirs. Approximately 70–80% of the MPs were removed by pre-ozonation/sedimentation; 81–88% of PE/PP was removed by this process. PET/PMMA was removed by filtration. Correlation of MPs with water quality parameters showed that the Mn concentration was moderately correlated with the MP abundance in rivers and lake reservoirs, excluding the lake with the lowest Mn concentration, while the total organic carbon was negatively correlated with the MP abundance in both rivers (A and B) and lake reservoir C.

Operational Impacts of a Water Management Structure on the Surrounding Fish Assemblages in a Restored Backwater and a Large Floodplain River

Water management structures (WMS) are used to regulate water levels between large floodplain river backwaters and their adjacent river systems offering a balance between maintaining quality backwater habitat and providing benefits to the river systems. The design and operation of these WMS is dependent on unique management goals, and their impacts on the surrounding ecosystem are understudied. From 2016–2018 we quantified the response of the surrounding fish assemblages (i.e., backwater and river abundance and composition) to the WMS operation at the Emiquon Preserve, a 2723 ha restored floodplain lake located adjacent to the main channel of the Illinois River, U.S.A. Environmental conditions were recorded, and fish were collected using boat electrofishing on both sides of the WMS under three operational levels: closed and no flow, gravity flowing water, and mechanically pumping water to the river. Multivariate analyses determined that there was no difference in fish community composition within the Emiquon Preserve among operation levels. Within the river there were differences in community composition when the WMS was closed and mechanically pumping water. Environmental parameters varied seasonally and WMS operation level varied but indicated an increase in chlorophyll-a in the river when the WMS was mechanically pumping water, although the chlorophyll-a decreased within 200 m downstream of the WMS in the Illinois River. This study suggests that managed connections between restored backwater and habitats operated like this WMS have variable, spatially isolated impacts on fish communities despite supplying chlorophyll-a to large river ecosystems.

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

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

3种不同营养水平的河流浮游植物群落结构及其与环境因子的相关性

PDF HTML阅读 XML下载 导出引用 引用提醒 3种不同营养水平的河流浮游植物群落结构及其与环境因子的相关性 DOI: 10.5846/stxb201911112382 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 贵州科学院青年基金（黔科院J字[2018]05&[2018]24）；贵州省科学技术基金项目（20161141） Phytoplankton's community structure and its relationships with environmental factors in three rivers with different nutrition levels Author: Affiliation: Fund Project: Youth Fund of Guizhou Academy of Sciences(J[2018]05& [2018]24)；Guizhou Science and Technology Funding Project（20161141） 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了更好地了解人类活动干扰下，河流水质和浮游植物群落结构的变化情况以及河流生态系统的演变过程，于2019年6月对贵州境内3种不同营养类型的河流（锦江河、湘江河和南明河）进行调查。研究了3条河流的理化因子、浮游植物种类组成及密度，结合冗余分析（RDA）研究了它们之间的关系，并应用聚类分析法研究3条河流浮游植物的空间分布特征。结果表明：水体富营养化程度排序为南明河>湘江河>锦江河，3条河流的综合营养指数分别为61.76、48.76和36.05。锦江河共有浮游植物6门19属21种，其中硅藻门种类最多，占总种数的57.14%；湘江河共有浮游植物6门34属43种，其中硅藻门和绿藻门种类最多，分别占总种数的41.86%和37.21%；南明河共有浮游植物6门32属46种，其中硅藻门和绿藻门种类最多，分别占总种数的39.13%和32.61%，锦江河、湘江河、南明河水体中浮游植物细胞数的平均值分别为12.66×105、38.66×105、132.61×105个/L。浮游植物细胞密度与溶解氧呈显著正相关（P<0.05），浮游植物细胞密度与电导率、溶解性总固体、盐度、总氮、总磷、氨氮、硝酸盐氮也呈显著正相关（P<0.01）。锦江河的电导率、盐度、溶解性总固体和营养盐含量最低，南明河的最高。此外，聚类分析显示3条河流的浮游植物群落按结构特征可分为两大类。这表明，随着人类活动的加强，河流的电导率、盐度、溶解性总固体、营养盐含量升高，浮游植物的细胞密度增加，其群落结构会由硅藻门占优势，逐渐转变为蓝藻门占优势。 Abstract:In order to know more about the change of water quality, phytoplankton's community structure and the evolution of river ecosystem by human activities. In June 2019, the phytoplankton samples and water samples were collected from 21 locations in three rivers with different nutrition levels, which included Jinjiang River, Xiangjiang River and Nanming River. Physicochemical factors, species composition and abundance of phytoplankton were studied, and combined with the result of Redundancy analysis (RDA) studied the relationship of these indexs, the spatial distribution characteristic of phytoplankton was analyzed using the clustering analytical method simultaneously. The results showed that the eutrophication level of the three rivers were in order of Nanming River > Xiangjiang River > Jinjiang River, the comprehensive trophic level index (TLI) of the three rivers were 61.76, 48.76 and 36.05, respectively. Twenty-one species of 19 genera in 6 phyla phytoplankton were found in Jinjiang River, in which Bacillariophyta was the predominant species, and accounted for 57.14% of the total species. Forty-three species of 34 genera in 6 phyla phytoplankton were found in Xiangjiang River, in which Bacillariophyta and Chlorophyta were the predominant species, accounted for 41.86% and 37.21% of the total species respectively. Forty-six species of 32 genera in 6 phyla phytoplankton were found in Nanming River, in which Bacillariophyta and Chlorophyta were the predominant species, accounted for 39.13% and 32.61% of the total species respectively. The cell density of phytoplankton in water sample of Jinjiang River, Xiangjiang River and Nanming River were 12.66×105 cells/L, 38.66×105 cells/L, and 132.61×105 cells/L, respectively. The cell density of phytoplankton was positive correlation with dissolved oxygen (P<0.05), and it was positive correlation with conductivity, total dissolved solids (TDS), salinity, total nitrogen, total phosphorus, ammonia nitrogen, and nitrate nitrogen (P<0.01). The conductivity, salinity, TDS, and nutrient concentration in Jinjiang River were the lowest, however, these indexes in Nanming River were the highest. The result from hierarchical cluster analysis showed that community structures of phytoplankton in the three rivers were different, and these samples were divided into two groups, in which the samples of Jinjiang River and Xiangjiang River were one group, the samples of Nanming River were the other group. These studies suggested that with the intensifying of human activity, the conductivity, salinity, TDS, nutrient concentration and phytoplankton abundance in rivers increased, the abundance of Bacillariophyta decreased, otherwise, the abundance of Cyanophyta increased. 参考文献 相似文献 引证文献

Microplastics on the sea surface of the semi-closed Tokyo Bay

Microplastics (MPs) pollution surveys were conducted in Tokyo Bay using neuston nets (May 2019 and January 2020). Although the pollution level in Tokyo Bay was high (3.98 pcs/m3, May), it was lower than reported in other semi-closed bays because of differences in the Enclosed Index. It was found that polyethylene fragments dominated the retrieved MPs; the mode of MPs size was 800 μm. As MPs abundance in rivers had the same seasonality as found in the inner bay, rivers were considered the main source of MPs. The seawater residence time is shorter than the time required for the density of MPs to become greater than that of seawater; therefore, it was considered that MPs are transported out of the bay instead of sinking. MPs were aggregated into a convergence zone by residual currents (the thermohaline front) in May (January). These findings will improve understanding of MPs pollution in other bays.

Salmon on the lam: Drivers of escaped farmed fish abundance in rivers

Abstract The production of Atlantic salmon in aquaculture has grown substantially over the last 40 years. The unintentional release of domesticated salmon poses a significant risk to the long‐term persistence of wild Atlantic salmon populations through ecological interactions and genetic introgression. Our ability to link aquaculture production to farmed escaped salmon in rivers is still limited and hinders identifying the appropriate production capacity of salmon aquaculture to reduce unwanted interactions between wild and escaped Atlantic salmon. Here we use a 14‐year dataset of farmed escapee abundance in rivers to model how the a priori selected covariables of wild salmon abundance, aquaculture intensity, river discharge, hydropower and fjord placement of the river affects escapee abundance across 54 rivers in western Norway. Then, we evaluate the predictive strength of the model to provide context for its use to minimize escapees. We found that the abundance of escaped farmed Atlantic salmon in rivers is correlated to aquaculture intensity. Furthermore, the abundance of wild Atlantic salmon, mean yearly discharge, and the interaction between fjord placement and wild salmon abundance were important predictors of escapee abundance in rivers. The model was 40% accurate when predicting the abundance of farmed escaped salmon in rivers. However, the accuracy improved to 75% when using risk categories derived from modelled intrusion rates that induced long‐term genetic changes to the wild population (low &lt; 4%, medium 4%–10%, and high &gt; 10% escaped farmed salmon). Synthesis and applications. This study links aquaculture production, at relevant spatiotemporal scales (75 km from rivers), to the abundance of escaped farmed Atlantic salmon in rivers, and provides governmental agencies with a tool to help regulate domesticated salmon production based on the carrying capacity of the system to buffer against introgression between conspecifics. Furthermore, understanding this relationship will be beneficial when establishing new aquaculture sites in pristine ecosystems where they would overlap with wild Atlantic salmon. Finally, future mitigation efforts should continue to focus on new technologies (e.g. triploid females) that can eliminate the risk of introgression without limiting aquaculture production.

Monitoring presence and abundance of two gyrodactylid ectoparasites and their salmonid hosts using environmental DNA

AbstractBackgroundInvasive species represent a major challenge for the conservation of biodiversity. The invasive ectoparasitic fluke Gyrodactylus salaris is considered one of the major threats to the Atlantic salmon (Salmo salar), and the parasite has so far been detected in 50 rivers in Norway.AimsWe investigate environmental DNA (eDNA) as a tool for detecting and assessing relative abundance of G. salaris and Atlantic salmon, upstream and downstream of a recently constructed artificial migration barrier in the River Driva in Norway. In addition, we also use eDNA to assess abundance of the less pathogenic G. derjavinoides and its main host, the brown trout (S. trutta).Material &amp; MethodsWe filtered 1 L and 10 L of water through a 0.45 μm cellulose filter and a 2.0 μm glass fiber filter, respectively, at nine different localities along the river. Concentrations of eDNA were assessed using droplet digital PCR (ddPCR) and compared to parasite abundance based on conventional methodology using electrofishing and the counting of individual parasites on juvenile salmon.ResultsAll four species could successfully be detected from water samples using two different protocols varying in sample volumes, filter types, and DNA‐isolation methods. However, eDNA‐occupancy modeling revealed that the probability of detecting the two gyrodactylid species was higher when filtering 10 L water through a 2.0 μm glass fiber filter (p &gt; .99) than when filtering 1 L water through a 0.45 μm cellulose filter (p = .48–.78). The eDNA concentrations of the two fish species were markedly higher below the migration barrier, reflecting the expected higher biomass of fish. For the two gyrodactylid parasites, eDNA concentrations showed a peak upstream of the migration barrier and decreased below the migration barrier. The observed pattern was consistent with parasite abundance based on conventional methodology.DiscussionAssessing abundance in rivers using eDNA is challenging and potentially influenced by downstream accumulation and dilution from tributaries, but our results suggest that G. salaris eDNA concentrations were indicative of parasite abundance.ConclusionWe conclude that eDNA is an efficient way of monitoring gyrodactylid parasites and their salmonid hosts, and we suggest that eDNA should be incorporated into future monitoring of G. salaris.

El río Amazonas

Las características físicas de Colombia en cuanto a su riqueza fluvial representan unas ventajas difíciles de igualar por otros países de la región, pero su manejo inadecuado y sin proyección impiden el desarrollo y la explotación requeridos. Para ello se deben establecer metas que, más allá de un resultado económico favorable, ubiquen el país a la vanguardia geopolítica del continente. De acuerdo con este escenario, el artículo se plantea la siguiente pregunta: ¿puede el río Amazonas, como corredor estratégico, proyectar a Colombia geopolíticamente en el espacio oceánico del Atlántico sur? Para responderla, se llevó a cabo una investigación propositiva y prospectiva, que expone cómo el Estado colombiano se debe proyectar en una región que aún no cuenta con una participación positiva en el escenario nacional.

Environmental DNA analysis as a non-invasive quantitative tool for reproductive migration of a threatened endemic fish in rivers.

Quantitative information regarding reproduction is essential for conserving endangered animals; however, some conventional quantitative methods can be damaging to the target population and their habitats. In the present study, the reproductive migration of a threatened endemic fish, three‐lips (Opsariichthys uncirostris uncirostris), was non‐invasively monitored by quantitative PCR of species‐specific environmental DNA (eDNA), the usefulness of which has been not sufficiently explored. Water sampling and from‐shore visual inspection were performed weekly along a tributary of Lake Biwa (Japan), where adult fish seasonally migrate upstream to reproduce as well as at lake sites near the river mouth. Species‐specific eDNA was collected at all locations at times when the fish were visually observed and at certain sites where the fish were not observed. Log‐transformed individual counts from visual inspection were positively correlated with log‐transformed eDNA concentration in the river sites, indicating that eDNA analysis can be a reliable quantitative tool for fish abundance in rivers. Furthermore, distance from the lake did not influence eDNA concentration, suggesting that eDNA transport by river flow had a negligible effect on eDNA quantification. Both eDNA concentration and individual counts gradually increased from May–July, and decreased in August. Importantly, eDNA analysis showed that the fish occupied more habitats in the peak reproductive season and stayed for longer time at any given site. An additional underwater survey confirmed unexpected eDNA detections as true positives. eDNA analysis has great potential to quantitatively monitor reproductive fish migrations under certain conditions.

Ancestry and Adaptation of Rainbow Trout in Yosemite National Park

California's Central Valley contains an abundance of rivers with historical and potential productivity for anadromous salmonids, which are currently limited by impacts such as dams, water diversions, and high temperatures. We surveyed genetic variation in Rainbow Trout Oncorhynchus mykiss within the upper Tuolumne and Merced rivers in and around Yosemite National Park to evaluate both population origins (ancestry) and the evolutionary response to natural and artificial barriers to migration (adaptation). This analysis revealed that despite extensive stocking with hatchery Rainbow Trout strains throughout the study area, most populations retained largely indigenous ancestry. Adaptive genomic variation associated with anadromy was distributed throughout the study area, with higher frequencies observed in populations connected to reservoirs that are known to support adfluvial life history variants. Fish in southern Central Valley rivers experience temperatures near the upper thermal limit for salmonids and represent an important reservoir of genomic diversity for adaptation to climate change. These results highlight the importance of local adaptation as well as the potential for resident Rainbow Trout populations above barrier dams to contribute to the recovery of steelhead (anadromous Rainbow Trout) once migratory connectivity is restored between upstream spawning and rearing habitats and the ocean.

Landscape influence on the local distribution of western pond turtles

AbstractSpatial and temporal scales are important for understanding habitat associations because organisms have neither unbounded mobility nor perfect knowledge of their environment, but still must make decisions on where to seek food, shelter, and mates. Semi‐aquatic turtles exemplify the need to evaluate potential habitat characteristics at a range of scales, because their ectothermy makes these animals particularly sensitive to local environmental conditions, yet their limited mobility spatially constrains selection of microsites. Microsite choice may also be sensitive to larger geographic context. We explored site occupancy and abundance of western pond turtles (Actinemys [Emys] marmorata) as a function of environmental variables over a range of spatial scales up to that of the entire watershed. We modeled occupancy at ponds and abundance at river sites using data from surveys conducted at 50 ponds and 58 river locations throughout the South Umpqua, Umpqua, and North Umpqua watersheds in western Oregon, USA in 1999–2000. The South Umpqua supported the greatest abundance of western pond turtles in rivers and the highest rates of occupancy in ponds. No turtles were detected in rivers of the North Umpqua, and only low numbers were detected in ponds in that watershed. Increasing amount of potential relative solar radiation was associated with increased probability of pond occupancy, particularly in the North Umpqua watershed. Pond turtle abundance in rivers increased with increasing distance to nearest pond, decreasing area of nearby ponds, and increasing area of nearby wetland habitat of all types, particularly in the Klamath Mountain and Coast Range physiographic provinces, which dominate the South Umpqua and Umpqua watersheds, respectively. Western pond‐turtle occupancy and abundance varied with both broad‐scale and fine‐scale habitat features, not solely to the fine‐scale features that are most often measured.

Towards Mechanistic Hydrological Limits: A Literature Synthesis to Improve the Study of Direct Linkages between Sediment Transport and Periphyton Accrual in Gravel-Bed Rivers.

Altered hydrological, sediment, and nutrient regimes can lead to dramatic increases in periphyton abundance in rivers below impoundments. Flushing flows are a commonly adopted strategy to manage the excess periphyton that can accumulate, but in practice they often prove ineffective. Designing hydrological regimes that include flushing flows may be overlooking key processes in periphyton removal, particularly the role of abrasion and molar action induced by substrate movement. Setting flow targets which aim to initiate substrate movement are likely to improve periphyton removal, but an understanding of the site-specific thresholds for substrate entrainment and periphyton removal is required. Despite decades of entrainment studies accurate and consistent measurement and prediction of substrate entrainment remains elusive, making it challenging to study the relationship between substrate movement and periphyton removal, and to set flow targets. This paper makes a case for using substrate entrainment and transport thresholds as the target metric for flushing flows to manage excess periphyton accrual. This paper critically reviews the determinants of periphyton accrual and associated management methods. This paper also aims to provide a reference for interdisciplinary research on periphyton removal by summarising the geomorphic and hydraulic literature on methods for estimating and measuring substrate entrainment and transport. This will provide a basis for ecologists to identify tools for quantifying entrainment and transport thresholds so they are better placed to explore the direct linkages between phases of sediment transport and periphyton accrual. These linkages need to be identified in order for river managers to set effective flushing flow targets.

Microplastics in freshwater river sediments in Shanghai, China: A case study of risk assessment in mega-cities.

Microplastics, which are plastic debris with a particle diameter of less than 5mm, have attracted growing attention in recent years. Its widespread distributions in a variety of habitats have urged scientists to understand deeper regarding their potential impact on the marine living resources. Most studies on microplastics hitherto are focused on the marine environment, and research on risk assessment methodology is still limited. To understand the distribution of microplastics in urban rivers, this study investigated river sediments in Shanghai, the largest urban area in China. Seven sites were sampled to ensure maximum coverage of the city's central districts, and a tidal flat was also included to compare with river samples. Density separation, microscopic inspection and μ-FT-IR analysis were conducted to analyze the characteristics of microplastics and the type of polymers. The average abundance of microplastics in six river sediment samples was 802 items per kilogram of dry weight. The abundance in rivers was one to two orders of magnitude higher than in the tidal flat. White microplastic spheres were most commonly distributed in river sediments. Seven types of microplastics were identified, of which polypropylene was the most prevailing polymers presented. The study then conducted risk assessment of microplastics in sediments based on the observed results, and proposed a framework of environmental risk assessment. After reviewing waste disposal related legislation and regulations in China, this study conclude that in situ data and legitimate estimations should be incorporated as part of the practice when developing environmental policies aiming to tackle microplastic pollution.

The relative importance of water temperature and residence time in predicting cyanobacteria abundance in regulated rivers

Despite a growing awareness of the problems associated with cyanobacterial blooms in rivers, and particularly in regulated rivers, the drivers of bloom formation and abundance in rivers are not well understood. We developed a Bayesian hierarchical model to assess the relative importance of predictors of summer cyanobacteria abundance, and to test whether the relative importance of each predictor varies by site, using monitoring data from 16 sites in the four major rivers of South Korea. The results suggested that temperature and residence time, but not nutrient levels, are important predictors of summer cyanobacteria abundance in rivers. Although the two predictors were of similar significance across the sites, the residence time was marginally better in accounting for the variation in cyanobacteria abundance. The model with spatial hierarchy demonstrated that temperature played a consistently significant role at all sites, and showed no effect from site-specific factors. In contrast, the importance of residence time varied significantly from site to site. This variation was shown to depend on the trophic state, indicated by the chlorophyll-a and total phosphorus levels. Our results also suggested that the magnitude of weir inflow is a key factor determining the cyanobacteria abundance under baseline conditions.

Link between estuarine fish abundances and prey choice of the great cormorant Phalacrocorax carbo (Aves, Phalacrocoracidae)

Prey choice of opportunistic piscivorous birds, such as Phalacrocoracidae, may primarily depend on prey abundance in rivers. Estuaries, the most downstream river stretches, often represent important feeding sites for piscivorous birds, but are usually characterised by highly dynamic fish assemblages. Thus, studies of the composition of diets of estuarine birds also require up-to-date information on prey abundances. In this study, interactions between diet composition and prey abundance by species and size were investigated for the great cormorant Phalacrocorax carbo in the natural setting of a typical European estuary. Moderate to high overlap between diet composition and estuarine prey abundances indicated that prey abundance represented the major factor driving prey choice of cormorants. However, differences in length distributions between cormorant diet and estuarine fish fauna suggested that prey size in particular species was another factor influencing prey choice of cormorants. While small-sized individuals of main prey species, especially European smelt Osmerus eperlanus, were underrepresented, large-sized individuals of twaite shad Alosa fallax were overrepresented in the cormorant diet. Flexible selection of prey in relation to particular species and size classes may be the result of the superabundance of potential prey in a highly productive environment such as an estuary.