Riverine Environments Research Articles

Elemental analysis of vertebrae discerns diadromous movements of threatened non-marine elasmobranchs.

River sharks (Glyphis spp.) and some sawfishes (Pristidae) inhabit riverine environments, although their long-term habitat use patterns are poorly known. We investigated the diadromous movements of the northern river shark (Glyphis garricki), speartooth shark (Glyphis glyphis), narrow sawfish (Anoxypristis cuspidata), and largetooth sawfish (Pristis pristis) using in situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) on vertebrae to recover elemental ratios over each individual's lifetime. We also measured elemental ratios for the bull shark (Carcharhinus leucas) and a range of inshore and offshore stenohaline marine species to assist in interpretation of results. Barium (Ba) was found to be an effective indicator of freshwater use, whereas lithium (Li) and strontium (Sr) were effective indicators of marine water use. The relationships between Ba and Li and Ba and Sr were negatively correlated, whereas the relationship between Li and Sr was positively correlated. Both river shark species had elemental signatures indicative of prolonged use of upper-estuarine environments, whereas adults appear to mainly use lower-estuarine environments rather than marine environments. Decreases in Li:Ba and Sr:Ba at the end of the prenatal growth zone of P. pristis samples indicated that parturition likely occurs in fresh water. There was limited evidence of prolonged riverine habitat use for A. cuspidata. The results of this study support elemental-environment relationships observed in teleost otoliths and indicate that in situ LA-ICP-MS elemental characterization is applicable to a wide range of elasmobranch species as a discriminator for use and movement across salinity gradients. A greater understanding of processes that lead to element incorporation in vertebrae, and relative concentrations in vertebrae with respect to the ambient environment, will improve the applicability of elemental analysis to understand movements across the life history of elasmobranchs into the future.

Speciation and repeated origins of hypertrophied lips in parallel adaptive radiations of cyprinid fish from East Africa.

The evolution of convergent phenotypes is one of the most interesting phenomena of repeated adaptive radiations. Here, we examined the repeated patterns of thick-lipped or "rubberlip" phenotype of cyprinid fish of the genus Labeobarbus discovered in riverine environments of the Ethiopian Highlands, East Africa. To test the adaptive value of thickened lips, identify the ecological niche of the thick-lipped ecomorphs, and test whether these ecomorphs are the products of adaptive divergence, we studied six sympatric pairs of ecomorphs with hypertrophied lips and the normal lip structure from different riverine basins. Trophic morphology, diet, stable isotope (δ15N and δ13C) signatures, as well as mtDNA markers and genome-wide SNP variation, were analyzed. Our results show that thick-lipped ecomorphs partition trophic resources with generalized ecomorphs in only one-half of the examined sympatric pairs despite the pronounced divergence in lip structure. In these thick-lipped ecomorphs that were trophically diverged, the data on their diet along with the elevated 15N values suggest an invertivorous specialization different from the basal omnivorous-detritivouros feeding mode of the generalized ecomorphs. Genetic data confirmed an independent and parallel origin of all six lipped ecomorphs. Yet, only one of those six thick-lipped ecomorphs had a notable genetic divergence with sympatric non-lipped ecomorphs based on nuclear SNPs data (F ST = 0.21). Sympatric pairs can be sorted by combinations of phenotypic, ecological, and genetic divergence from an ecologically non-functional mouth polymorphism via ecologically functional polymorphism to a matured speciation stage via divergent evolution.

AN OVERVIEW OF THE RIVER ECOLOGICAL DIVERSITY, STRUCTURAL-FUNCTIONAL CHANGES, AND POLLUTION ASSESSMENT

The most significant sources of freshwater are rivers, and many different uses are made of their water. Cities near rivers have recently had a significant detrimental impact on the water quality, causing the rivers to get worse every day. This is due to the increased urbanization of these areas. The relationship between biodiversity and ecological functions is currently a major scientific topic that requires understanding and prediction. Studies conducted on terrestrial ecosystems, for instance, have shown how species-specific traits and functional biodiversity affect key ecosystem structures and functions related to the storage and cycling of organic material. Many changes occur in ecosystem biomass because of polluting contaminants. Others are in the hydrophone structure type, while some are in the biomass summary. Greater biomass densities and a lack of diversity distinguish the contaminated river flow from the surrounding environment. Many different strategies and underlying concepts have been employed in environmental protection initiatives. Assessing the potential of any or all ecosystem components is necessary for identifying hazards. Hazard assessment describes the degree of harm any potentially harmful chemical or action will cause to ecosystem components. The assessment method needs to be extremely specific due to the changing nature of the riverine environment.

Integrative Taxonomic Reappraisal and Evolutionary Biogeography of the Most Diverse Freshwater Mussel Clade from Southeast Asia (Pseudodontini)

Freshwater mussels belonging to the tribe Pseudodontini (Bivalvia: Unionidae: Gonideinae) play a keystone role in riverine and lacustrine environments throughout Southeast Asia. Many of them are narrowly endemic and habitat specialists, which need special conservation efforts. Unfortunately, the systematics of this group is rather poorly understood. Here, we show that Pseudodon inoscularis, the type species of the genus Pseudodon, belongs to the eastern clade of the tribe (Southeast Asia, east of the Salween Basin), and, more certainly, clusters with members of the genus Monodontina. Hence, the latter genus becomes a synonym of Pseudodon, while the subtribe Pseudodontina (=Pilsbryoconchina syn. nov.) should be used as a name for the eastern clade. In turn, the genus Indopseudodon stat. rev. and the subtribe Indopseudodontina subtr. nov. must be applied as valid names for the western clade of the Pseudodontini (Ayeyarwady to Salween). We present a revision of the genus Indopseudodon with an updated synonymy and a description of a new species, I. indawgyiensis sp. nov. We also link four species-level genetic lineages from the Mekong to available taxonomic names in the genera Pseudodon and Sundadontina (Pseudodon cambodjensis, P. vagulus, Sundadontina harmandi, and S. sulcata). Based on morphological features, we revise the taxonomic position of several recent and fossil species that were traditionally placed in the Pseudodontini and transfer them to the genera Parvasolenaia, Pseudodontopsis, Ptychorhynchus, Simpsonasus nom. nov. (a new name for Nasus Simpson, 1900) (Gonideinae: Gonideini), Pseudobaphia (Unioninae: Unionini), Balwantia and Lamellidens (Parreysiinae: Lamellidentini).

Australian country paper: Integrated approaches to irrigation management in the future

AbstractIrrigation in Australia expanded dramatically during the early to mid‐twentieth century under an economic and social development regime of government. This led to overallocation and overuse of many of the country's water resources to the detriment of the rivers and riverine environments. To address this degradation federal and state governments have come together to implement a range of reforms at national, basin and catchment level to return water to the rivers but not at the expense of rural communities and a range of policy reforms to implement water resource best management practice including cost recovery pricing, accuracy in measurement (resource availability and extraction). The three most significant components of these reforms are the Murray–Darling Basin Plan, the National Water Initiative and the Sustainable Rural Water Use and Infrastructure Programme (SRWUIP). These actions are complemented by infrastructure and management improvements at on‐ and off‐farm levels and examples are documented.

Assessment of the effect of short-term weathering on the molecular-level chemical composition of crude oils in contact with aquatic environments.

Multiple studies have focused on the effect of long-term weathering processes on oils after spill events, without considering the chemical compositional changes occurring shortly after the release of oil into the environment. Therefore, the present study provides a broad chemical characterization for understanding of the changes occurring in the chemical compositions of intermediate (°API = 27.0) and heavy (°API = 20.9) oils from the Sergipe-Alagoas basin submitted to two simulated situations, one under marine conditions and the other in a riverine environment. Samples of the oils were collected during the first 72 h of contact with the simulated environments, followed by evaluation of their chemical compositions. SARA fractionation was used to isolate the resins, which were characterized at the molecular level by UHRMS. The evaporation process was highlighted, with the GC-FID chromatographic profiles showing the disappearance of compounds from n-C10 until n-C16, as well as changes in the weathering indexes and pristane + n-C17/phytane + n-C18 ratios for the crude oils submitted to the riverine conditions. Analysis of the resins fraction showed that basic polar compounds underwent little or no alterations during the early stages of weathering. The marine environment was shown to be much less oxidative than the riverine environment. For both environments, a feature highlighted was an increase of acidic oxygenated compounds with the increase of weathering, especially for the crude oil with °API = 27.0.

Mercury occurrence and speciation in sediments from hard coal mining in Czechia

This study examines Hg distribution in stream sediments impacted by hard coal mining in the Upper Silesian Coal Basin (USCB), Czechia. By means of a comparative analysis, geological samples and samples from stream sediments were used to carry out a comprehensive assessment of the effects of anthropogenic activities on Hg distribution and speciation. Total Hg (THg), total organic and inorganic carbons (TOC and TIC), and total sulphur (TS) were measured in the samples to reveal a potential relationship. In addition, THg and TS species were discussed in order to elucidate their mobility pattern in the environment. The results have shown that there are no correlations between THg, TS, and TOC indicating overlapping Hg sources attributed to industrial processes. Geological samples, particularly coal and associated sedimentary rocks, contained lower Hg concentrations compared to a variety of stream sediments. The main Hg species identified in the samples was a stable β-HgS, which decreases its mobility in the riverine environment. It follows that Hg enrichment and speciation is linked to industrial processes, which are the main origin/cause for Hg enrichment and transformation. Minor proportions of HgO in some samples show Hg oxidation upon diagenesis, while HgCl2 is attributed to the chemical loads from the former coking plant.

An Assessment of the Toxicity of Pesticide Mixtures in Periphyton from Agricultural Streams to the Mayfly Neocloeon triangulifer.

Residual concentrations of pesticides are commonly found outside the intended area of application in Ontario's surface waters. Periphyton are a vital dietary component for grazing organisms in aquatic ecosystems but can also accumulate substantial levels of pesticides from the surrounding water. Consequently, grazing aquatic organisms are likely subjected to pesticide exposure through the consumption of pesticide-contaminated periphyton. The objectives of the present study were to determine if pesticides partition into periphyton in riverine environments across southern Ontario and, if so, to determine the toxicity of pesticides in periphyton when fed to the grazing mayfly Neocloeon triangulifer. Sites with low, medium, and high pesticide exposure based on historic water quality monitoring data were selected to incorporate a pesticide exposure gradient into the study design. Artificial substrate samplers were utilized to colonize periphyton in situ, which were then analyzed for the presence of approximately 500 pesticides. The results demonstrate that periphyton are capable of accumulating pesticides in agricultural streams. A novel 7-day toxicity test method was created to investigate the effects of pesticides partitioned into periphyton when fed to N. triangulifer. Periphyton collected from the field sites were fed to N. triangulifer and survival and biomass production recorded. Survival and biomass production significantly decreased when fed periphyton colonized in streams with catchments dominated by agricultural land use (p < 0.05). However, the relationship between pesticide concentration and survival or biomass production was not consistent. Using field-colonized periphyton allowed us to assess the dietary toxicity of environmentally relevant concentrations of pesticide mixtures; however, nutrition and taxonomic composition of the periphyton may vary between sites. Environ Toxicol Chem 2023;42:2143-2157. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Exploring a multi-objective optimization operation model of water projects for boosting synergies and water quality improvement in big river systems

Due to excessive nutrient enrichment and rapidly increasing water demand, the occurrence of riverine environment deterioration events such as algal blooms in rivers of China has become more frequent and severe since the 1990s, which has imposed harmful consequences on riverine ecosystems. However, tackling river algal blooms as an important issue of restoring riverine environment is very challenging because the complex interaction mechanisms between the causes are impacted by multiple factors. The contributions of our study consist of: (1) optimizing joint operation of water projects for boosting synergies of water quality and quantity, and hydroelectricity; and (2) preventing algal bloom from perspectives of hydrological and water-quality conditions by regulating water releases of water projects. This study proposed a multi-objective optimization methodology grounded on the Non-dominated Sorting Genetic Algorithm to simultaneously minimize the excess values of algal bloom indicators (water quality, O1), minimize the used reservoir capacity for water supply (water quantity, O2), and maximize the hydropower generation (hydroelectricity, O3). The proposed methodology was applied to several catastrophic algal bloom events that took place between 2017 and 2021 and thirteen water projects in the Hanjiang River of China. The results indicated that the proposed methodology largely stimulated the synergistic benefits of the three objectives by reaching a 36.7% reduction in total nitrogen and phosphorus concentrations, a 33.1% improvement in the remaining reservoir capacity, and a 41.0% improvement in hydropower output, as compared with those of the standard operation policy (SOP). In addition, the optimal water release schemes of water projects would increase the minimum streamflow velocity of downstream algal bloom control stations by 8.6%–9.4%. This study provides a new perspective on water project operation in the environmental improvement in big river systems while boosting multi-objectives synergies to support environmentalists and decision-makers with scientific guidance on sustainable water resources management.

The rate and quality of post-mortem hair root changes in relation to melanin content

Hairs is a relatively environmentally resistant biological material that is often found at crime scenes. Human hair is more durable than other biological traces such as blood or urine, and its collection and storage does not require specific preservation procedures. Melanin is the hair pigment, which is the main determinant of hair colour. There are two pigments present in human hair: eumelanin, predominant in dark hair, and pheomelanin, responsible for red colour. Eumelanin is more resistant and has photoprotective properties, while pheomelanin is phototoxic and shows lower resistance to environmental factors. The differences in the properties of eu- and pheomelanin are the basis of the present study, which aimed to examine the rate and quality of taphonomic changes in hair roots in relation to the predominant melanin type, under the influence of selected environmental factors, such as soil pH, degree of exposure to solar radiation, temperature and water from a natural watercourse (river) and chemically pure water. Therefore, changes in blonde, dark, grey, red and dyed hair roots were microscopically documented for six months under the influence of the above factors. The results of the study indicated the strongest degradation potential among acidic soil and a riverine environment, as well as the protective role of eumelanin against environmental taphonomic factors. Degradation occurred most rapidly in the river environment, where microbial activity was additionally observed. Distilled water, exposure to sunlight and low temperature did not lead to decomposition changes. The results of our team's research provide the basis for an extended analysis of the changes occurring in hair under the influence of environmental factors in relation to melanin content.

Reconstructing long-term settlement histories on complex alluvial floodplains by integrating historical map analysis and remote-sensing: an archaeological analysis of the landscape of the Indus River Basin

Alluvial floodplains were one of the major venues of the development and long-term transformation of urban agrarian-based societies. The historical relationship between human societies and riverine environments created a rich archaeological record, but it is one that is not always easy to access due to the dynamism of alluvial floodplains and the geomorphological processes driven their hydrological regimes. Alluvial floodplains are also targeted for urban and agricultural expansion, which both have the potential to pose threats to cultural heritage and the environment if not carefully managed. Analysis that combines Historical Cartography and Remote Sensing sources to identify potential archaeological sites and river palaeochannels is an important first step towards the reconstruction of settlement patterns in different historical periods and their relationship to the history of hydrological networks. We are able to use different computational methods to great effect, including algorithms to enhance the visualization of different features of the landscape; and for processing large quantity of data using Machine-Learning based methods. Here we integrate those methods for the first time in a single study case: a section of the Indus River basin. Using a combined approach, it has been possible to map the historical hydrological network in a detail never achieved before and identify hundreds of potential archaeological sites previously unknown. Discussing these datasets together, we address the interpretation of the archaeological record, and highlight how Remote Sensing approaches can inform future research, heritage documentation, management, and preservation. The paper concludes with a targeted analysis of our datasets in the light of previous field-based research in order to provide preliminary insights on how long-term processes might have re-worked historical landscapes and their potential implications for the study of settlement patterns in different Historical periods in this region, thereby highlighting the potential for such integrated approaches.

Relationships between Land Use Changes and Benthic Macroinvertebrates’ Community Structure in an East African Riverine Environment

Anthropogenic land use activities affects the health status of river ecosystems in supporting aquatic biodiversity. Undisturbed wetlands ensure water bodies are ecologically healthy for community livelihoods. Recent years have witnessed degradation of aquatic ecosystems and this has devastating effects on the environment and community livelihoods. One of such wetlands is river Isiukhu of western Kenya. This study analysed water physico-chemical parameters and benthic macroinvertebrates’ assemblages of River Isiukhu between August to November, 2022. Four sampling stations were selected along the longitudinal river gradient based on anthropogenic impact and dominance of land use activities. Sampling stations were classified as ‘very high’, ‘high’, ‘moderate’ and ‘low’ and rated 4,3,2 and 1 respectively, depending on the anthropogenic impact. Macroinvertebrates were sampled using D-frame net and classified using appropriate keys. Anthropogenic activities and habitat characteristics were noted and recorded. Water quality parameters were determined in situ. Macroinvertebrates’ population indices were calculated to determine community structure. Sorenson’s Coefficient quantified similarities of species in different stations. Pearson correlation and ANOVA tested the study hypothesis. About 1,391 invertebrates were collected belonging to 12 orders, 32 families and 30 genera. Orders Ephemeroptera, Hemiptera, Diptera and Coleoptera recorded highest percentage taxonomical composition. Upper pristine stations (F and G) supported more species richness and diversity than lower stations (L and T). Macroinvertebrates’ communities in terms of diversity, abundance, richness, evenness, and functional feeding groups responded differently to impacts of anthropogenic activities, due to their varied adaptation traits. Water quality varied significantly between sampling stations (ρ &lt;0.05). Close relationship existed between land use activities and species diversity (r=0.8; ρ &lt; 0.05); richness (r=0.8779; ρ &lt; 0.05); evenness (r=0.1067; ρ &lt; 0.05); and abundance (r=0.962; ρ &lt; 0.05). The study recommends the need to conserve riparian vegetation as a way of mitigating and adapting to the impact climate change on stream ecosystem.

Allometric equations for estimating peak uprooting force of riparian vegetation.

Uprooting caused by flood events is a significant disturbance factor that affects the establishment, growth, and mortality of riparian vegetation. If the hydraulic drag force acting on riparian plants exceeds the peak uprooting force originate from their below-ground portion, it may result in the uprooting of these plants. Despite previous studies have documented and investigated the uprooting processes and factors influencing the peak uprooting force of plants, most of these studies have focused on how the root morphological traits of tree and shrub seedlings affect peak uprooting force or mainly collected data in indoor experiments, which may limit the extrapolation of the results to natural environments. To address these limitations, we assume that the peak uprooting force can be estimated by the morphological traits of the above-ground portion of the vegetation. In this study, we conducted in-situ vertical uprooting tests on three locally dominant species: Conyza canadensis, Daucus carota, and Leonurus sibiricus, in a typical riverine environment. The three species were found to have the highest abundance based on the outcomes of the quadrat method. We measured the peak uprooting force, plant height, stem basal diameter, shoot and root wet biomass, and shoot and root dry biomass of each plant and compared them between species. Furthermore, we quantified the influence of morphology on peak uprooting force. Our results showed significant differences in morphological traits and peak uprooting force among the three species. We found a significant positive correlation between peak uprooting force and the morphological traits of the three species. The peak uprooting force increases with plant size following a power law function which is analogous to allometric equations. The allometric equation provided a convenient and non-destructive method to estimate the peak uprooting force based on the above-ground morphological traits of the plants, which may help to overcome the limitations of measuring root morphological traits.

Paleodiets of hunter‐gatherers from the central Patagonian coast: Reviewing scopes and limitations of stable isotope analyses

AbstractThis work reviews paleodietary reconstructions of hunter‐gatherers from the northeast province of Chubut, Argentina. The isotopic record of human bone can complement information from zooarchaeological and technological studies with its particular resolution on the long‐term diet of individuals. Previous δ13C and δ15N studies found dietary differences between the coastal area and the lower basin of the Chubut River, both in the proportion of marine resources in the diet and the trophic positions of prey. However, it is challenging to test hypotheses concerning human diets in northeastern Patagonia, where C3 and CAM plants grow and terrestrial, riverine, and marine prey are available. Here, we focus on the local isotopic ecology to assess the scopes and limitations of δ13C and δ15N stable isotopes analyses. We provide new data on native faunas spanning different trophic levels of terrestrial, riverine, and marine environments. After establishing the basic patterns in the local isotope record, we reanalyze the available δ13Ccol, δ15N, and δ13Capa measurements from 23 individuals studied 15 years ago. That analysis reveals a relatively continuous distribution of several overlapping resources on the coast of northeastern Patagonia. Bayesian mixing models identified a combination of terrestrial and riverine resources aggregated as the main component of long‐term diets. However, it generated diffuse estimations. The Bayesian ellipses, describing isotopic niches, emphasized more the spatial variations in diet between coastal and valley groups.

River Commoning and the State: A Cross‐Country Analysis of River Defense Collectives

Grassroots initiatives that aim to defend, protect, or restore rivers and riverine environments have proliferated around the world in the last three decades. Some of the most emblematic initiatives are anti-dam and anti-mining movements that have been framed, by and large, as civil society versus the state movements. In this article, we aim to bring nuance to such framings by analyzing broader and diverse river-commoning initiatives and the state–citizens relations that underlie them. To study these relations we build on notions of communality, grassroots scalar politics, rooted water collectives, and water justice movements, which we use to analyze several collective practices, initiatives, and movements that aim to protect rivers in Thailand, Spain, Ecuador, and Mozambique. The analysis of these cases shows the myriad ways in which river collectives engage with different manifestations of the state at multiple scales. As we show, while some collectives strategically remain unnoticed, others actively seek and create diverse spaces of engagement with like-minded citizen initiatives, supportive non-governmental organizations, and state actors. Through these relations, alliances are made and political space is sought to advance river commoning initiatives. This leads to a variety of context-specific multi-scalar state–citizens relations and river commoning processes in water governance arenas.

Plastic-associated metal(loid)s in the urban river environments of Mongolia

The widespread distribution of plastic debris in riverine environment is one of the major concerns of environmental pollution because of its potential impact on the aquatic ecosystem. In this study, we investigated the accumulation of metal(loid)s on polystyrene foam (PSF) plastics collected from the floodplain of the Tuul River of Mongolia. The metal(loid)s sorbed on plastics were extracted from the collected PSF via sonication after peroxide oxidation. The size-dependent association of metal(loid)s with plastics indicates that PSFs act as vectors for pollutants in the urban river environment. The mean concentrations of metal(loid)s (i.e., B, Cr, Cu, Na, and Pb) indicate a higher accumulation of the metal(loid)s on meso-sized PSFs compared with macro- and micro-sized PSFs. In addition, the images from scanning electron microscopy (SEM) indicated not only the degraded surface of plastics showing fractures, holes, and pits but also the adhered mineral particles and microorganisms on the PSFs. The interaction of metal(loid)s with plastics was probably facilitated by the physical and chemical properties of altered surface of plastics through photodegradation, followed by an increase in surface area by size reduction and/or biofilm development in the aquatic environment. The enrichment ratio (ER) of metals on PSF samples suggested the continuous accumulation of heavy metals on plastics. Our results demonstrate that the widespread plastic debris could be a carrier of hazardous chemicals in the environment. Considering that the negative impacts of plastic debris on environmental health are major concerns to be addressed, the fate and behavior of the plastics especially their interaction with pollutants in aquatic environments should be further studied.

A New Species of Zanthoxylum (Rutaceae) from Colombia and Brazil

A new species of Zanthoxylum L. (Rutaceae) from Colombia and Brazil is described here, based upon morphological characters. Zanthoxylum palustre Londoño-Ech. &amp; Reynel is distributed in lacustrine, riverine, and swampy environments at very low altitude, and belongs to Zanthoxylum sect. Macqueria Comm. ex Triana &amp; Planch., the largest section of the genus; it is distinguished by several vegetative and reproductive characteristics.

ITERATIVE REFRACTION-CORRECTION METHOD ON MVS-SFM FOR SHALLOW STREAM BATHYMETRY

Abstract. Extracting accurate bathymetric information from clear, shallow waters in complex riverine environments can be challenging, but it is crucial for many applications, such as hydraulic modeling, ecological monitoring, and sediment transport analysis. Multi-view stereo photogrammetry (MVS-SfM) has emerged as a promising technique for acquiring high-resolution bathymetric data from aerial imagery. However, the accuracy of MVS-SfM can be affected by various factors, including water refraction, which can distort the depth measurements. In this study, iterative Dietrich’s refraction-correction method is tested for extracting bathymetry from MVS-SfM in a complex riverine environment. Moreover, we proposed a workflow for applying the method using raster data files, which can be more readily available than point clouds. It also compared the obtained results with previous applications and evaluated them using statistical indices and ratios. For this case study, the multicamera refraction method produces bathymetric datasets with accuracies of ~0.019% of the flying height and precisions of ~0.07% of the flying height. This study contributes to increased confidence in exploiting aerial imagery for bathymetric mapping in photogrammetric procedures under field conditions and can facilitate the management and conservation of clear water systems.

In the right place, at the right time: the integration of bacteria into the Plankton Ecology Group model

BackgroundPlanktonic microbial communities have critical impacts on the pelagic food web and water quality status in freshwater ecosystems, yet no general model of bacterial community assembly linked to higher trophic levels and hydrodynamics has been assessed. In this study, we utilized a 2-year survey of planktonic communities from bacteria to zooplankton in three freshwater reservoirs to investigate their spatiotemporal dynamics.ResultsWe observed site-specific occurrence and microdiversification of bacteria in lacustrine and riverine environments, as well as in deep hypolimnia. Moreover, we determined recurrent bacterial seasonal patterns driven by both biotic and abiotic conditions, which could be integrated into the well-known Plankton Ecology Group (PEG) model describing primarily the seasonalities of larger plankton groups. Importantly, bacteria with different ecological potentials showed finely coordinated successions affiliated with four seasonal phases, including the spring bloom dominated by fast-growing opportunists, the clear-water phase associated with oligotrophic ultramicrobacteria, the summer phase characterized by phytoplankton bloom-associated bacteria, and the fall/winter phase driven by decay-specialists.ConclusionsOur findings elucidate the major principles driving the spatiotemporal microbial community distribution in freshwater ecosystems. We suggest an extension to the original PEG model by integrating new findings on recurrent bacterial seasonal trends.6DDRKdq8UhqLvueZRvryQwVideo

Fish Tissue Contamination with Organic Pollutants and Heavy Metals: Link between Land Use and Ecological Health

Under pressure from existing and emerging contaminants, lotic ecosystems are becoming increasingly susceptible to ecological deterioration. Therefore, investigations of the impacts of persistent organic pollutants (POPs) and heavy metals on riverine fish health, water quality, and biotic integrity are critical. We examined the effects of 52 POPs and heavy metals on ecological health and land use, based on the monitoring of fish assemblages and river water quality from 2007 to 2014. Among the 52 chemical species, 35 were present in water and fish tissues, including eight heavy metals. The concentrations of these POPs and heavy metals in 12 fish species are presented. Most POPs were either undetected or present at negligible levels in fish tissues, although a few polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs; dichlorodiphenyltrichloroethanes and heptachlor epoxide) were detected above the screening values (SVs). Hg, As, and Cd were detected in most water samples and fish species at concentrations above their SVs. Among the fish species in the investigated trophic guild, heavy metal contents were in the order of Zn &lt; Cr &lt; Cu &lt; Pb &lt; Se, while trophic levels were in the order of insectivorous &lt; omnivorous &lt; carnivorous. Agricultural cover showed an association with endosulfan II (R2 = 0.50, r = 0.70), followed by alachlor (R2 = 0.43, r = 0.66). For PAHs, all detected substances showed significant relationships with forest cover. Ecological health assessment revealed that most river sites are in poor condition, indicating the direct impacts of pollutants. In conclusion, of the 28 POPs detected, 16 PAHs and 3 OCPs (hexachlorobenzene, lindane, and heptachlor epoxide) were of significant concern, such that action is needed to curb their inflow to the riverine environment. The studied river basin is under substantial threat from harmful POPs that endanger ecological health and fish biodiversity.