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Understanding the mechanism by which non‐native fish species integrate into native communities is crucial for evaluating the possibility of their establishment success. The genus Pangasianodon, comprising Pangasianodon gigas and Pangasianodon hypophthalmus, has been introduced into reservoirs, which are non‐native habitats, for fishery stock enhancement. P. gigas and P. hypophthalmus often successfully establish and co‐occur in several Thai reservoirs, but there is little information on differences in food resource use between the two species. To investigate the trophic niche width of P. gigas and P. hypophthalmus in a Thai reservoir, we conducted stable carbon and nitrogen ratio (δ13C and δ15N) analyses. We examined the degree of individual specialization in both species using the δ13C and δ15N values of muscle and liver tissues, which provides long‐ and short‐term diet information. The isotopic niches did not overlap between P. gigas and P. hypophthalmus. The δ15N value of P. gigas was significantly higher than that of P. hypophthalmus, whereas the δ13C value did not significantly differ between the two species. The isotopic niche sizes were larger in P. hypophthalmus than in P. gigas. Individual specialization was observed in P. hypophthalmus but not in P. gigas, indicating that intraspecific variation in food resource use was larger in P. hypophthalmus compared to P. gigas. These findings suggest that trophic niche partitioning was one of the factors facilitating the establishment success of P. gigas and P. hypophthalmus in a reservoir, but the establishment process may differ between the two species. [ABSTRACT FROM AUTHOR]

River ecosystems host a continuum of various discontinuities, such as dams and tributary inflows, which shape the habitats of aquatic organisms; this makes it important to evaluate the interactions among discontinuities and effects of a single discontinuity point. Herein, we focused on tributaries in dammed rivers to elucidate a manner to mediate discontinuities and hypothesized that the effects of the tributary inflow on the downstream river were mediated by the (1) distance between the dam and tributary inflow, (2) size ratio between the dam and tributary, and (3) ability of the tributary to transport fine sediments, such as sand and gravel. We conducted field investigations to measure 24 environmental factors, including the water column, riverbed, and river topography, along eight dammed rivers to test the three hypotheses. Only five factors differed significantly between the upstream and downstream sites of the tributary confluence, whereas 12 factors differed significantly between the tributary and mainstem. We also classified the variation pattern using principal component analysis (PCA). The correlation between each PCA axis and environmental factors suggests that the modifications of the water quality factors by tributary inflow were significantly correlated with the distance between the dam and the tributary inflow, and that the flux of various riverbed factors, that is, was significantly correlated with the ability to resupply of fine riverbed sediments by the tributary. Overall, tributary‐inflow downstream of a dam has the potential to be applicable in environmental restoration, especially in terms of resupplying fine sediment. [ABSTRACT FROM AUTHOR]

Copepods play a key trophic role as secondary producers, transferring primary production to higher trophic levels such as fish. Copepod production contributes significantly to successful fish recruitment. Despite their importance, knowledge of copepod dynamics over several decades remains limited due to the lack of long‐term data series with adequate sampling and analysis. However, an understanding of long‐term copepod dynamics is urgently required to strive toward better management for sustainable aquatic ecosystems and fish recruitment.Sedimentary DNA (sedDNA) has been developing as a useful tool for reconstructing past plankton dynamics. This study evaluates whether sedDNA targeting the pelagic copepod, Eodiaptomus japonicus, in Lake Biwa (Japan) can be an effective tool for elucidating its past population dynamics.We applied a quantitative polymerase chain reaction method targeting the mitochondrial cytochrome c oxidase subunit I gene on two sediment cores and compared the detected sedDNA concentrations with the unique long‐term dataset of demographic traits, biomass, specific growth rate, production, subitaneous eggs, and resting eggs of E. japonicus.The sedDNA concentration of E. japonicus recovered from sediment layers correlated significantly with in situ production, biomass, and production of immediately hatching eggs but not with resting eggs or specific growth rate. Our study provides evidence for the effective use of sedDNA as a tracking tool for assessing past copepod production dynamics. [ABSTRACT FROM AUTHOR]

Caspian terns (Hydroprogne caspia Pallas, 1770) present a sub‐cosmopolitan but scattered distribution, and many of its colonies are in a vulnerable state. The species has been listed in the Red Data Book of the Russian Federation and is covered by the Agreement on the Conservation of African‐Eurasian Migratory Waterbirds. We observed the colonies of Caspian terns repeatedly in the breeding season from May to June on the islands of Lake Chany from 1985 to 2011. We recorded clutch size, eggshell coloration and measured egg length and width to the nearest 0.1 mm with a caliper. Furthermore, we recorded the fate and hatching date of individual eggs and determined the clutch initiation date. Head, bill, tarsus length, and body weight of newly hatched chicks were measured. Caspian tern colony size changed between years from 50 nests in 1985 to 513 in 1999; therefore, the sample size of measured eggs varied from 90 to 1045. A total of 4137 eggs and 570 chicks were measured. We provide new information for this species nesting in west Siberia, which is important to compare with other local results. The presented data set is a novel long‐term data set on an isolated population of this species in center of Eurasian continent. The complete data set for this abstract published in the Data Article section of the journal is available in electronic format in MetaCat in JaLTER at http://db.cger.nies.go.jp/JaLTER/metacat/metacat/ERDP-2023-02.1/jalter-en. [ABSTRACT FROM AUTHOR]

Although environmental DNA (eDNA) metabarcoding is an exceptionally useful and powerful tool for monitoring biodiversity, little is known about whether the traits of organisms and their ecosystem characteristics affect eDNA metabarcoding performance. Nationwide surveys can provide more detailed insights, yet such studies have rarely been conducted.In order to evaluate eDNA metabarcoding performance in broad‐scale monitoring, we examined the effects of species ecological/biological traits and ecosystem characteristics on species detection rates and the implications for community analysis. In addition, we tested the effects of sample mixing and transportation methods, including cooling and freezing, on eDNA metabarcoding. On a nationwide scale, we conducted eDNA metabarcoding for fish communities in 18 Japanese lakes.By comparing species records, we observed that certain traits, including body size, body shape, saltwater tolerance and habitat preference, influenced eDNA detection. In addition, the proportion of species detected decreased significantly with an increase in lake surface area owing to ecosystem size effect on species detection.We conclude that species traits, including habitat preference, body size and ecosystem size, should be considered when assessing the eDNA metabarcoding performance in broad‐scale monitoring. [ABSTRACT FROM AUTHOR]

Predator‐induced plasticity is an adaptive response inprey to predation risks. Considering that size‐selective predation affects the body‐size distribution of prey populations, we hypothesised that the body size of species determines their expression of predator‐induced plasticity. However, as a result of variations in expression among species, an integrated understanding of the relationships between traits remains lacking. We considered the predator‐induced plasticity of Daphnia species separately for their body size, defensive morphology and life‐history traits. The aim of this study was to compare the predator‐induced plasticity of Daphnia against size‐selective predators: phantom midge Chaoborus larvae and fish.This meta‐analysis included 75 studies and nine plasticity traits for 15 Daphnia species. Daphnia were analysed separately according to phylogeny (subgenera Ctenodaphnia, Daphnia and Hyalodaphnia) and body size (large >3.0 mm, medium 2.0 mm and small 1.0 mm).Size‐dependent analyses showed that at least three of the nine plasticity traits were expressed in Daphnia against fish. Among the three subgenera, Daphnia induced the greatest plasticity against both predators (five key traits against Chaoborus and four against fish).The relationship between size and age at first reproduction showed that Daphnia exhibited different degrees of plasticity against Chaoborus and fish. Daphnia had only one set of life‐history response to fish, namely, decreased size at maturity and early reproduction. By contrast, Daphnia exhibited three sets of life‐history responses to Chaoborus larvae: decreased size and delayed reproduction, increased size and delayed reproduction, and increased size and early reproduction. Overall, predator‐induced plasticity was expressed well in small and medium‐sized Daphnia, and was more evident in small Daphnia than would be expected from size‐selective predation.This study shows that the body size of Daphnia is a key trait influencing its plasticity expression and evolution. We detected novel pattern among life‐history traits, but found no strong associations between morphological defences and life‐history traits. We suggest that prey size, predation preference and body size are important factors for understanding and explaining the evolution of phenotypic plasticity. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) has recently been developed for detecting the distribution of macroorganisms in aquatic systems and for estimating biomass/abundance. Although positive relationships between eDNA concentrations of species and biomass/abundance have been observed in previous studies, estimation of total biomass in a particular ecosystem based on eDNA concentration has not been investigated.To test this, we sampled eDNA from the littoral and pelagic zones of eight small ponds in Japan. Then, we drained ponds to capture all fish inhabiting each pond. We compared the eDNA copies measured by quantitative real‐time polymerase chain reaction analysis with the captured biomass of three dominant fish species (common carp, bluegill sunfish, and largemouth bass) obtained by direct capture. Differences in eDNA concentrations were compared between the littoral and pelagic zones of each pond.We found positive relationships between the eDNA copies and the whole captured biomass of all target species using Type II logarithmic equations, and the eDNA copies appeared to be saturated at a higher total biomass.We found positive correlations between the total number of eDNA copies and the total captured biomass of three fish species. This demonstrated the first step in estimating the population biomass of target fish species under natural conditions using eDNA measurement. [ABSTRACT FROM AUTHOR]

Species invasion in conventional ecosystems is an impedance to ecosystem management. The extensive invasion of American bullfrogs (Lithobates catesbeiana) and red swamp crayfish (Procambarus clarkii) is seriously harmful to aquatic systems worldwide, including Japan. In recent years, the methods involving environmental DNA (eDNA) have significantly contributed to the detection of invasive alien species. These methods for the above two species had already been developed in previous studies overseas, but could be unsuitable for detection of the species in Japan due to matching of the polymerase chain reaction (PCR) primers with the sequence of the co‐existing species. The present study developed two eDNA detection methods for L. catesbeiana and P. clarkii in Japanese habitats. The eDNA of both invasive alien species was detected in all ponds where they had been captured and observed. A positive relationship was elucidated between the traditional survey (i.e., frog male calling detection or direct catch) and the presence or concentration of eDNA. The eDNA method applied in this study could be useful for monitoring the distribution of L. catesbeiana and P. clarkii in Japan. [ABSTRACT FROM AUTHOR]

The environmental DNA (eDNA) method, which is widely applied in biomonitoring, is limited to laboratory analysis and processing. In this study, we developed a filtration/extraction component using a microfluidic channel, the Biryu‐Chip (BC), and a filtration/extraction method, the BC method, to minimize the volume of the sample necessary for DNA extraction and subsequent PCR amplification. We tested the performance of the BC method and compared it with that of the Sterivex filtration/extraction method using aquarium and river water samples. We observed that using the BC method, the same concentration of extracted DNA was obtained with 1/20–1/40 of the filtration volume of the Sterivex method, suggesting that the BC method can be widely used for eDNA measurement. In addition, we performed on‐site measurements of eDNA within 30 min using a mobile PCR device, demonstrating that filtration and extraction can be performed easily and quickly using the BC method. The PCR results obtained using the BC method were similar to those obtained using the Sterivex method. The BC method requires fewer steps; therefore, the risk of DNA contamination can be reduced. When combined with mobile PCR, the BC method can be applied to easily detect eDNA within 30 min from the collection of water sample, even on‐site. [ABSTRACT FROM AUTHOR]

Molecular methods, including those for environmental DNA (eDNA), provide essential information for biological and conservation sciences. Molecular measurements are often performed in the laboratory, which limits their scope, especially for rapid on‐site analysis. eDNA methods for species detection provide essential information for the management and conservation of species and communities in various environments. We have developed an innovative novel method for on‐site eDNA measurements using an ultrarapid mobile PCR platform. We tested the ability of our method to detect the distribution of silver carp, Hypophthalmichthys molitrix, in rivers and lakes. Our method reduced the measurement time to 30 min and provided high detectability of aquatic organisms compared to national observation surveys that use multiple fishing nets and laboratory extraction/detection using a benchtop qPCR platform. Our on‐site eDNA method can be immediately applied to various taxa and environments. [ABSTRACT FROM AUTHOR]

Summary: Investigation of seasonal variation in fungal communities is essential for understanding biodiversity and ecosystem functions. However, the conventional sampling method, with substrate removal and high spatial heterogeneity of community composition, makes surveying the seasonality of fungal communities challenging. Recently, water environmental DNA (eDNA) analysis has been explored for its utility in biodiversity surveys. In this study, we assessed whether the seasonality of fungal communities can be detected by monitoring eDNA in a forest stream. We conducted monthly water sampling in a forest stream over 2 years and used DNA metabarcoding to identify fungal eDNA. The stream water contained DNA from functionally diverse aquatic and terrestrial fungi, such as plant decomposers, parasites and mutualists. The variation in the fungal assemblage showed a regular annual periodicity, meaning that the assemblages in a given season were similar, irrespective of the year or sampling. Furthermore, the strength of the annual periodicity varied among functional groups. Our results suggest that forest streams may act as a 'trap' for terrestrial fungal DNA derived from different habitats, allowing the analysis of fungal DNA in stream water to provide information about the temporal variation in fungal communities in both the aquatic and the surrounding terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

Information on α‐ (local), β‐ (between habitats), and γ‐ (regional) diversity is fundamental to understanding biodiversity as well as the function and stability of community dynamics. Methods like environmental DNA (eDNA) metabarcoding are currently considered useful to investigate biodiversity.We compared the performance of eDNA metabarcoding with visual and capture surveys for estimating α‐ and γ‐diversity of river fish communities, and nestedness and turnover in particular.In five rivers across west Japan, by comparison to visual/capture surveys, eDNA metabarcoding detected more species in the study sites (i.e. α‐diversity). Consequently, the overall number of species in the region (i.e. γ‐diversity) was higher. In particular, the species found by visual/capture surveys were encompassed by those detected by eDNA metabarcoding.Estimates of community diversity within rivers differed between survey methods. Although we found that the methods show similar levels of community nestedness and turnover within the rivers, visual/capture surveys showed more distinct community differences from upstream to downstream. Our results suggest that eDNA metabarcoding may be a suitable method for community assemblage analysis, especially for understanding regional community patterns, for fish monitoring in rivers. [ABSTRACT FROM AUTHOR]

Dam‐mediated biological invasions are a serious problem all over the world. Once established in reservoirs, the invasive species have catastrophic impacts on the river ecosystems downstream, and thus, rapid monitoring of invasive species is an urgent issue for the effective removal of them and the conservation management of native ecosystems. Here, we verified the utility of environmental DNA (eDNA) analysis as a tool to effectively monitor three invasive fish species (bluegill, largemouth bass, and smallmouth bass) in reservoirs using multiplex real‐time PCR. First, to determine the optimal sampling location and season to detect eDNA from these species, we analyzed the eDNA in water samples from shore and offshore sites in three reservoirs all year around. We found that eDNA detection rates either did not differ between sampling locations or were higher for shore than offshore sites. In addition, eDNA detection rates were higher in spring (breeding season of target species) and/or summer than winter. Second, we extensively surveyed the distribution of the three species in 30 reservoirs in Japan using eDNA analysis. Consequently, a single eDNA‐based surveillance in summer allowed to match approximately 90% of the presence/absence of the invasive fish species known from 27 yr of administrative capture‐based surveillances. Given these results, we recommend collecting the replicated water samples from shore sites in summer or the breeding season for the effective detection of invasive fish eDNA in reservoirs. Our eDNA assays with multiplex real‐time PCR enable the rapid and sensitive monitoring of invasive fish distribution in reservoirs. [ABSTRACT FROM AUTHOR]

The recent development of the environmental DNA (eDNA) technique has dramatically facilitated investigations of the distribution and abundance of macroorganisms in the natural environment. Various real‐time polymerase chain reaction (PCR)‐based methods have been proposed for the detection and quantification of eDNA by independent researchers or groups. Although several eDNA reviews have outlined the critical requirements for experimental processes and provided guidelines for best practice, clear standardization of eDNA protocols is lacking. Here, we collected the PCR conditions of previous eDNA studies using real‐time PCR (n = 190), that is, the volume of the DNA template, PCR cycles, number of PCR replicates and PCR inhibition tests. Then, we synthesized the current development of real‐time PCR techniques for eDNA studies. Our synthesis has identified the critical issues that need to be addressed to design standardized protocols for eDNA monitoring that will enable broader uptake of eDNA technology. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) is a useful tool for biological monitoring of a target species by detecting DNA contained in environmental samples. However, the suppression of eDNA degradation after sample collection is a major issue when estimating the presence of a target species. Recently, benzalkonium chloride (BAC) was shown to dramatically suppress the degradation of eDNA in fish species from freshwater environments. However, the effect of this inexpensive reagent has not yet been tested in the other fish and shellfish species. We examined changes in eDNA concentrations for three target species (Corbicula japonica, Lateolabrax japonicus, and Anguilla japonica). eDNA was measured in samples containing added BAC. The effects of storage temperature (25°C, 4°C, and −30°C) and storage periods (periods up to 21 d) were also measured to determine how sample degradation was affected. We observed that BAC addition was effective in suppressing eDNA degradation, and its influence was similar among species but not storage temperatures. The concentrations of eDNA with BAC for all three species did not decrease with storage period, except for L. japonicus at 25°C and 4°C. Our results suggest that BAC affects eDNA degradation universally for a variety of species inhabiting both freshwater and brackish water. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) analysis has seen rapid development in the last decade, as a novel biodiversity monitoring method. Previous studies have evaluated optimal strategies, at several experimental steps of eDNA metabarcoding, for the simultaneous detection of fish species. However, optimal sampling strategies, especially the season and the location of water sampling, have not been evaluated thoroughly. To identify optimal sampling seasons and locations, we performed sampling monthly or at two‐monthly intervals throughout the year in three dam reservoirs. Water samples were collected from 15 and nine locations in the Miharu and Okawa dam reservoirs in Fukushima Prefecture, respectively, and five locations in the Sugo dam reservoir in Hyogo Prefecture, Japan. One liter of water was filtered with glass‐fiber filters, and eDNA was extracted. By performing MiFish metabarcoding, we successfully detected a total of 21, 24, and 22 fish species in Miharu, Okawa, and Sugo reservoirs, respectively. From these results, the eDNA metabarcoding method had a similar level of performance compared to conventional long‐term data. Furthermore, it was found to be effective in evaluating entire fish communities. The number of species detected by eDNA survey peaked in May in Miharu and Okawa reservoirs, and in March and June in Sugo reservoir, which corresponds with the breeding seasons of many of fish species inhabiting the reservoirs. In addition, the number of detected species was significantly higher in shore, compared to offshore samples in the Miharu reservoir, and a similar tendency was found in the other two reservoirs. Based on these results, we can conclude that the efficiency of species detection by eDNA metabarcoding could be maximized by collecting water from shore locations during the breeding seasons of the inhabiting fish. These results will contribute in the determination of sampling seasons and locations for fish fauna survey via eDNA metabarcoding, in the future. [ABSTRACT FROM AUTHOR]

Renewable energy resources can potentially solve global warming issues that arise from the large amounts of CO2 emissions from currently used energy resources. Microbial fuel cells (MFC) can produce electrical energy from the environment, making them attractive for energy harvesting. The structures and mechanisms of MFC have been studied for a few decades, and the performance of MFC has constantly been improved using new materials in the devices or by interacting microbial species on the anode chamber of MFC. However, the ecological phenomena, especially inter‐species interactions, within the microbial community in MFC are still largely unknown. Analysis and control of the microbial community have high potential to improve the MFC performance. In this idea paper, I have provided ways to analyze the species interactions in the microbial communities of MFC: (a) empirical dynamic modeling for detecting species interactions in MFC, and (b) network analysis to explore the core microbe species in the MFC. The interaction analyses of the microbial communities in MFC devices can potentially contribute to improving the performance of MFC. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) techniques utilizing DNA fragments from water have recently been developed to investigate the distribution and abundance/biomass of aquatic organisms. The eDNA technique is based on the analysis of DNA fragments in sampled water; thus, an unmanned aerial vehicle (UAV; drone) would be a useful way of collecting water for eDNA sampling, and may consequently allow us to extend eDNA surveys both spatially and temporally. Here, we developed a new method of water collection by using UAV with bleachable equipment, to avoid DNA contamination. To test the performance and contamination risk of UAV water sampling in eDNA surveys, we sampled water from a dam reservoir, detected eDNA from two fish species, and compared the water samples obtained by UAV with those obtained by boat. Additionally, we investigated contamination using blank samples. The results revealed that our UAV water sampling method performed similar to the boat sampling method. No positive signals were detected in the blank samples, including those used for UAV sampling, transportation, filtering, and PCR blanks. Our UAV method can be used to investigate species distributions using eDNA. Combinations of UAV technologies, including remote and thermal sensing, will enable efficient environmental monitoring in various waterbodies. [ABSTRACT FROM AUTHOR]

Understanding behavioral differences between intraspecific genotypes of aquatic animals is challenging because we cannot directly observe the animals underwater or visually distinguish morphologically similar counterparts. Here, we tested a new monitoring tool that uses environmental DNA ( eDNA), an assemblage of DNA in environmental water, to specifically detect Japanese native and introduced non-native genotypes of common carp ( Cyprinus carpio) in Lake Biwa, Japan, and estimated differences between the two genotypes in the use of inland habitats. We monitored the ratios of native and non-native single nucleotide polymorphism alleles of a mitochondrial locus of common carp in a lagoon connected to Lake Biwa for 3 years using eDNA. We observed seasonal dynamics in the allele frequency showing that the native genotype frequency peaked every spring, suggesting that native individuals migrated to the lagoon for spawning and then returned to the main lake, whereas non-native individuals tended to stay in the lagoon. The estimated migration patterns corresponded with the estimates of a previous study, which were based on commercial fish catch data. Our findings suggest that eDNA-based monitoring can be useful tool for addressing intraspecific behavioral differences underwater. [ABSTRACT FROM AUTHOR]

Life cycles of animals and plants worldwide are shifting in response to recent climate change. Macroecology, which deals with biological patterns and processes at a large scale, is ideally suited to address this global phenomenon, thus providing a more general and generalizable understanding of the impacts of climate change on ecosystems. To date, a macroecological approach to examining phenological changes based on historical ground observations remains mostly unexplored, as the phenological studies have been conducted at local scales, while the recent new technologies, e.g., remote sensing, can extend phenological study to global scales. Because phenology is probably the most widely used bioindicator of climate change, thus allowing for studies at the macroscale. Some meta-analyses have indeed employed broad-scale, long-term datasets to estimate overall shift rates in the timing of plant and animal phenological events. However, none has provided a convincing macroecological view of current phenological shifts, and few attempts have been made to make global-scale predictions of phenological responses under future climatic scenarios. Understanding spatial variability and clines may be essential for comprehending phenological variations stemming from future climate change. Here, we discuss how ecological mechanisms discovered in macroecology may provide new insights for understanding spatial variation of sensitivity of phenology to climate change. [ABSTRACT FROM AUTHOR]

The recently developed environmental DNA (eDNA) analysis has been used to estimate the distribution of aquatic vertebrates by using mitochondrial DNA (mtDNA) as a genetic marker. However, mtDNA markers have certain drawbacks such as variable copy number and maternal inheritance. In this study, we investigated the potential of using nuclear DNA (ncDNA) as a more reliable genetic marker for eDNA analysis by using common carp ( Cyprinus carpio). We measured the copy numbers of cytochrome b (CytB) gene region of mtDNA and internal transcribed spacer 1 (ITS1) region of ribosomal DNA of ncDNA in various carp tissues and then compared the detectability of these markers in eDNA samples. In the DNA extracted from the brain and gill tissues and intestinal contents, CytB was detected at 95.1 ± 10.7 (mean ± 1 standard error), 29.7 ± 1.59 and 24.0 ± 4.33 copies per cell, respectively, and ITS1 was detected at 1760 ± 343, 2880 ± 503 and 1910 ± 352 copies per cell, respectively. In the eDNA samples from mesocosm, pond and lake water, the copy numbers of ITS1 were about 160, 300 and 150 times higher than those of CytB, respectively. The minimum volume of pond water required for quantification was 33 and 100 mL for ITS1 and CytB, respectively. These results suggested that ITS1 is a more sensitive genetic marker for eDNA studies of C. carpio. [ABSTRACT FROM AUTHOR]

The environmental DNA (eDNA) method has been used to estimate the distributions of aquatic species, and both ethanol precipitation and filtration-based methods are commonly employed to capture eDNA from sampled water. Although filtration-based methods can capture more eDNA than that by ethanol precipitation, by processing larger volumes of water (e.g., 1 L vs. 15 mL), ethanol precipitation can immediately preserve eDNA on site and ease downstream processing, which are especially advantageous for eDNA studies conducted with limited resources, such as electric equipment, labor, and time. However, the ethanol precipitation method is limited by small volume of water that can be processed (i.e., 15 mL in a reaction volume of 50 mL). As an alternative, isopropanol could potentially be used to increase the volume of sample water processed, since lower volumes of isopropanol are required for precipitation. Therefore, in the present study, we compared the copy numbers of carp eDNA captured using isopropanol and ethanol precipitation in both mesocosm and field experiments. In both cases, we found that isopropanol precipitation recovered double the amount of eDNA recovered by ethanol precipitation, when the reaction volumes were equal. Therefore, isopropanol precipitation is a superior option for eDNA capture when surveys are conducted under resource-limited conditions. [ABSTRACT FROM AUTHOR]

1. Environmental DNA (eDNA) analysis for detecting the presence of aquatic and terrestrial organisms is an established method, and the eDNA concentration of a species can reflect its abundance/biomass at a site. However, attempts to estimate the abundance/biomass of aquatic species using eDNA concentrations in large stream and river ecosystems have received little attention. 2. We determined the eDNA concentration and abundance/biomass of a stream fish, Plecoglossus altivelis, by conducting a snorkelling survey in the Saba River, Japan. Furthermore, we evaluated the relationship between eDNA concentrations and the estimated abundance/biomass of P. altivelis, and determined its spatial distribution within the river. 3. Across the three seasons from spring to autumn, we found significant correlations between the eDNA concentration of P. altivelis and its abundance/biomass at study sites within the river. We detected the eDNA at the sites where we found only feeding traces on stones (where P. altivelis was not directly observed), but not at sites without feeding traces. Additionally, we tested the optimal number of qPCR replicates needed for the eDNA evaluation of P. altivelis abundance and biomass; only a small number of replicates was required when the eDNA concentration was high. 4. Our findings suggest that eDNA analysis is a useful tool to estimate fish abundance/biomass as well as their spatial distribution in rivers. [ABSTRACT FROM AUTHOR]

Climate change is expected to affect tree leaf phenology by extending the length of the growing season (LGS), which will affect the productivity and nutrient cycling of forests. Interactions between plants and microbes will mediate the ecosystem processes further through microbe-mediated plant-soil feedback (PSF). To investigate the possible consequences of interactions between the extension of the growing season (GS) and PSF under various conditions, we developed a simple theoretical model (LGS-PSF model). The LGS-PSF model predicts that microbe-mediated PSF will intensify the negative effects of increasing temperature on the size of soil carbon stock when compared with simulations without the PSF effect. The combined effects of increasing temperature and PSF on the size of soil carbon stock occurs through enhanced activity of individual microbes and increased microbial population size. More importantly, the model also demonstrated that a longer GS mitigates this negative effect on carbon accumulation in soil, not through increased net primary production, but through intensified competition for nutrients between plants and microbes, thus suppressing microbial population growth. Our model suggested that the interactive effects of the LGS and PSF on carbon and nitrogen dynamics in forests should be incorporated into larger scale quantitative models for better forecasting of future forest functions under climate change. [ABSTRACT FROM AUTHOR]

The invasion of non-native species that are closely related to native species can lead to competitive elimination of the native species and/or genomic extinction through hybridization. Such invasions often become serious before they are detected, posing unprecedented threats to biodiversity. A Japanese native strain of common carp ( Cyprinus carpio) has become endangered owing to the invasion of non-native strains introduced from the Eurasian continent. Here, we propose a rapid environmental DNA-based approach to quantitatively monitor the invasion of non-native genotypes. Using this system, we developed a method to quantify the relative proportion of native and non-native DNA based on a single-nucleotide polymorphism using cycling probe technology in real-time PCR. The efficiency of this method was confirmed in aquarium experiments, where the quantified proportion of native and non-native DNA in the water was well correlated to the biomass ratio of native and non-native genotypes. This method provided quantitative estimates for the proportion of native and non-native DNA in natural rivers and reservoirs, which allowed us to estimate the degree of invasion of non-native genotypes without catching and analysing individual fish. Our approach would dramatically facilitate the process of quantitatively monitoring the invasion of non-native conspecifics in aquatic ecosystems, thus revealing a promising method for risk assessment and management in biodiversity conservation. [ABSTRACT FROM AUTHOR]

Predator diversity and abundance are under strong human pressure in all types of ecosystems. Whereas predator potentially control standing biomass and species interactions in food webs, their effects on prey biomass and especially prey biodiversity have not yet been systematically quantified. Here, we test the effects of predation in a cross-system meta-analysis of prey diversity and biomass responses to local manipulation of predator presence. We found 291 predator removal experiments from 87 studies assessing both diversity and biomass responses. Across ecosystem types, predator presence significantly decreased both biomass and diversity of prey across ecosystems. Predation effects were highly similar between ecosystem types, whereas previous studies had shown that herbivory or decomposition effects differed fundamentally between terrestrial and aquatic systems based on different stoichiometry of plant material. Such stoichiometric differences between systems are unlikely for carnivorous predators, where effect sizes on species richness strongly correlated to effect sizes on biomass. However, the negative predation effect on prey biomass was ameliorated significantly with increasing prey richness and increasing species richness of the manipulated predator assemblage. Moreover, with increasing richness of the predator assemblage present, the overall negative effects of predation on prey richness switched to positive effects. Our meta-analysis revealed strong general relationships between predator diversity, prey diversity and the interaction strength between trophic levels in terms of biomass. This study indicates that anthropogenic changes in predator abundance and diversity will potentially have strong effects on trophic interactions across ecosystems. [ABSTRACT FROM AUTHOR]

Species-abundance distribution (SAD) is one of the most basic descriptions of an ecological community. Vigorous controversy surrounded SAD from the 1940s to 1960s, and has since persisted. Isao Motomura first published a notable paper in 1932 to describe findings on SAD, and to provide an empirical model; nevertheless, this work has often been overlooked or incorrectly cited, probably due to being published in Japanese. Here, we introduce the works of Motomura with an English translation of the paper, and the subsequent research history of SAD. We also introduce the work of Numata et al., another Japanese paper, which provided the biological explanation for Motomura's model of SAD, although it was rarely cited by subsequent studies. We summarize that Motomura was the first to fit a statistical model to observed SAD, and that Numata et al. attempted to explain the observed SAD via underlying biological mechanisms. [ABSTRACT FROM AUTHOR]

Ecologists have focused on food-chain length (FCL) for the past eight decades as an index of food-web structure. Here, I review the hypotheses determining FCL with a focus on resource productivity and availability effects on FCL. First, I introduce the mainstream hypotheses to explain FCL variations: productivity, ecosystem size, and disturbance. For the existing productivity and productive space hypotheses, I stress the importance of using resource availability to estimate the productivity effect on FCL. Using a FCL dataset from 15 ponds, I tested the resource stoichiometry effect on FCL for ponds with between carbon:nitrogen ratio of primary producers and FCL. Moreover, I provide a perspective for studying resource availability and stoichiometry effects on FCL and of the alternative hypotheses of productive-space and ecosystem size. Finally, I suggest the future directions of the FCL study: a resource subsidy and climate change effects on FCL and food-web structure. [ABSTRACT FROM AUTHOR]

Climate change has significant impacts on phenology of various organisms in a species-specific manner. Facing this problem, the match/mismatch hypothesis that phenological (a)synchrony with resource availability strongly influences recruitment success of a consumer population has recently received much attention. In this article, we discuss extending the conventional pairwise concept and demonstrate a community module-based approach as an initial step for exploring community consequences of species-specific phenological shifts caused by climate change. Our multispecies match/mismatch perspective leads to the prediction that phenological (a)synchrony among interacting species critically affects not only population recruitment of species but also key dynamical features of ecological communities such as trophic cascades, competitive hierarchies, and species coexistence. Explicit identification and consideration of species relationships is therefore desirable for a better understanding of seasonal community dynamics and thus community consequences of climate change-induced phenological shifts. [ABSTRACT FROM AUTHOR]

Compound-specific stable isotope analysis (CSIA) of amino acids is a new method that enables estimates of trophic position for consumers in food webs. We examined the nitrogen isotopic composition (δN) of amino acids of Japanese social insects (three bee, three wasp, and four hornet species) to evaluate the potential of CSIA of amino acids in studies of terrestrial food webs. For wasps, we also examined samples at different growth stages (ranging from egg to adult) to assess the effect of metamorphosis on CSIA estimates of trophic position. The δN values of bulk tissues for Japanese social insects are only weakly correlated with the biologically expected trophic positions. In contrast, the trophic positions estimated from the δN values of amino acids (yielding values of between 2.0 and 2.3 for bees, between 2.8 and 3.3 for wasps, and between 3.5 and 4.1 for hornets) are consistent with the biologically expected trophic positions for these insects (i.e., 2.0 for bees, 3.0 for wasps, and 3.0-4.0 for hornets). Although large variability is observed among the δN values of individual amino acids (e.g., ranging from 3.0 to 14.9‰ for phenylalanine), no significant change is observed in the trophic position during wasp metamorphosis. Thus, the CSIA of amino acids is a powerful tool for investigating not only aquatic food webs but also terrestrial food webs with predatory insects. [ABSTRACT FROM AUTHOR]

1. The vertical and horizontal distribution of unionoid mussels (Pronodularia japanensis) were examined in spring, late summer and winter for different size classes, including juveniles (<20 mm) and large adults (>50 mm), in an agricultural drainage channel in Central Japan. 2. A large number of small-sized juveniles were found at the surface (0-3 cm depth) in spring, whereas approximately half of the adults remained in the deep layer (3-8 cm depth). Most individuals were found in the surface layer irrespective of size classes in summer, and approximately 70% of all individuals descended to the deep layer in winter. 3. Horizontal distribution did not substantially change across seasons and high density patches were consistently found in the areas where substrate appeared to be stable or hydraulically sheltered. Spatial distribution of small juveniles was relatively well predicted by the abundance of adults. 4. The size-frequency distribution was multi-modal in three seasons and estimated numbers of newly recruited juveniles were highly variable in recent years, suggesting that juveniles were rarely found owing to irregular reproduction and/or recruitment not the overlooked habitat preferred by small-sized juveniles. 5. As P. japanensis is characterized by the behaviour of burrowing down to a depth of ∼10 cm, maintaining the processes of sediment deposition appears to be one of the critical criteria for the conservation of mussel habitats in agricultural drainage channel systems, which are commonly lined with smooth concrete materials. [ABSTRACT FROM AUTHOR]

Although ecologists have recognized the importance of spatial structure within food webs, this aspect of ecosystems remains difficult to characterize quantitatively. Stable-isotope techniques have recently been used to provide evidence of spatial structure within aquatic food webs. Here, I review current literature on spatial patterns of autochthonous and allochthonous resources in aquatic food webs in lakes and rivers. Across various habitats and ecosystems, the factors determining the major resources of aquatic food webs are primarily phytoplanktonic productivity, benthic algal productivity, and amount of subsidization from terrestrial habitats. Autochthonous and allochthonous resource availability in food webs shifts with gradients in water depth, nutrient concentrations, degree of canopy cover, and distance from terrestrial habitats. Size of lake and river ecosystem (i.e., lake volume and stream width) also affects the relative contribution of the resources to the food webs, as this factor determines the system primary productivity and linkage to terrestrial habitats. Human activities have fragmented river and lake ecosystems and have subsequently modified the structure of aquatic food webs. The responses of food webs to anthropogenic effects differ across ecosystems, and stable isotope techniques can help to quantitatively assess the effects of human impacts on aquatic food webs. [ABSTRACT FROM AUTHOR]

We investigated the photosynthesis–light intensity (P–I) relationships of phytoplankton collected from a sublittoral sand bank in the Seto Inland Sea, Japan, under different temperature conditions. In spite of low chlorophyll a concentration (<3 mg m−3), phytoplankton had considerably high photosynthetic potential (>10 mg C (mg chl a)−1 h−1) in the study area. Based on the P–I relationships, we conducted numerical simulation of areal primary production using published data on water temperature, chlorophyll a concentration, and irradiance. The areal primary production ranged between 159 and 187 g C m−2 year−1. This production was within the range of typical values reported previously in deeper areas of the Seto Inland Sea. The productivity in the sand bank area was discussed in relation to water current, allochthonous resource input, and fisheries. [ABSTRACT FROM AUTHOR]

Aim To estimate the potential effect of global climate change on the phenological responses of plants it is necessary to estimate spatial variations at larger scales. However, previous studies have not estimated latitudinal patterns in the phenological response directly. We hypothesized that the phenological response of plants varies with latitude, and estimated the phenological response to long-term climate change using autumn phenological events that have been delayed by recent climate change. Location Japan. Methods We used a 53-year data set to document the latitudinal patterns in the climate responses of the timing of autumn leaf colouring and fall for two tree species over a wide range of latitudes in Japan (31 to 44° N). We calculated single regression slopes for leaf phenological timing and air temperature across Japan and tested their latitudinal patterns using regression models. The effects of latitude, time and their interaction on the responses of the phenological timings were also estimated using generalized linear mixed models. Results Our results showed that single regression slopes of leaf phenological timing and air temperature in autumn were positive at most stations. Higher temperatures can delay the timing of leaf phenology. Negative relationships were found between the phenological response of leaves to temperature and latitude. Single regression slopes of the phenological responses at lower latitudes were larger than those at higher latitudes. Main conclusions We found negative relationships between leaf phenological responsiveness and latitude. These findings will be important for predicting phenological timing with global climate change. [ABSTRACT FROM AUTHOR]

We sampled Lake Katanuma from 1998 to 2002 at weekly or biweekly intervals, except in winter. This dimictic volcanic lake has a pH of 2.0-2.2. In summer, volcanic heat at the lake bottom results in a small water temperature difference of 3-7 Celsius between the epilimnion and hypolimnion. During the April-August stratification period in 1998, 1999, and 2002, the entire water column mixed for 1-8 d, when air temperature declined 4-8 Celsius from the epilimnion temperature. During these mixing events, anoxic, hydrogen sulfide-rich water from the hypolimnion spread over the entire lake. In contrast, distinct short-term turnover did not occur during the stratification period in 2000 or 2001. However, the early onset of autumn turnover in August 2000 and 2001 caused anoxic conditions with negative Eh values to persist for ∼2 weeks throughout the entire water column. Volcanic heat flux from the lake bottom fluctuated from 29.0 to 35.8 W m-2 from year to year. The frequency and duration of short-term holomixis thus depended on interannual variations in volcanic heat flux and weather. [ABSTRACT FROM AUTHOR]

The article talks about the American Society of Limnology and Oceanography (ASLO) Early Career Community (ECC) that is involved with the creation and organization of programs to benefit ASLO's early-career members. The community does not miss the opportunities to meet the needs of EC and student members. The survey was conducted to provide insights into how ASLO is and continues to promote younger members. The ASLO plans to introduce the Travel Awards that will account the distance traveled.