Search

Streams and river ecosystems contribute to global carbon cycle via collecting, storing, transforming and producing organic matter. The general paradigm is that most stream ecosystems are heterotrophic, respiring more carbon than they produce, nonetheless, many streams are autotrophic for some time, and a few may autotrophic on an annual scale. Periodic autotrophy is associated with high light, low disturbance, and low watershed carbon inputs, but limited examples of annual-scale autotrophy make it difficult to estimate how frequently net autotrophy occurs and what drives this net storage or export of carbon. Here, we use a spatially and temporally extensive dataset of 236 rivers across the continental USA with 921 years of daily metabolism data to assess the scale of annual and seasonal autotrophy and estimate its strongest covariates. Only 6% of rivers in this dataset were consistently autotrophic on an annual timescale, but 67% of rivers experienced at least one autotrophic event lasting longer than 7 days. These periodic autotrophic events frequently began in spring and summer. By comparing the 37 annually autotrophic rivers identified in our dataset to examples in the literature, we found that anthropogenically driven autotrophy arising from agricultural and urban land use is underrepresented in the study of riverine metabolism. We used quantile regression models to test hypothesized drivers of autotrophy and a sparse lasso technique to broadly explore a range of 86 watershed and in-stream covariates. Our models support previous findings that high light, long periods between disturbances, and low terrestrial production covary with more autotrophy. Additionally, through sparse regression, we found that elevation and river width may be useful synthesis variables that explain the distribution of autotrophic rivers. [ABSTRACT FROM AUTHOR]

Production of synthetic plastic obtained from fossil fuels are considered as a constantly growing problem and lack in the management of plastic waste has led to severe microplastic pollution in the aquatic ecosystem. Plastic particles less than 5mm are termed as microplastics (MPs), these are pervasive in water and soil, it can also withstand longer period of time with high durability. It can be broken down into smaller particles and can be adsorbed by various life-forms. Most marine organisms tend to consume plastic debris that can be accumulated easily into the vertebrates, invertebrates and planktonic entities. Often these plastic particles surpass the food chain, resulting in the damage of various organs and inhibiting the uptake of food due to the accumulation of microplastics. In this review, the physical and chemical properties of microplastics, as well as their effects on the environment and toxicity of their chemical constituents are discussed. In addition, the paper also sheds light on the potential of microorganisms such as bacteria, fungi, and algae which play a pivotal role in the process of microplastics degradation. The mechanism of microbial degradation, the factors that affect degradation, and the current advancements in genetic and metabolic engineering of microbes to promote degradation are also summarized. The paper also provides information on the bacterial, algal and fungal degradation mechanism including the possible enzymes involved in microplastic degradation. It also investigates the difficulties, limitations, and potential developments that may occur in the field of microbial microplastic degradation. [ABSTRACT FROM AUTHOR]

The Microsporidia, an often overlooked fungal lineage, exhibit increasing diversity and taxonomic understanding with the use of genomic techniques. They are obligate parasites infecting a diversity of hosts, including crustaceans. Crustacea are, in essence, ancient insects and their relationship with the Microsporidia is both diverse and convoluted. Relationships between crayfish and their microsporidian parasites display geospatial and taxonomic diversity. Through classical (histological, ultrastructural, developmental) and genomic (phylogenetic, phylogenomic) approaches, we expand the known diversity of crayfish-infecting microsporidia into the genus Nosema by describing three novel species from North America: Nosema astafloridana n. sp. infecting Procambarus pictus and Procambarus spiculifer, Nosema rusticus n. sp. infecting Faxonius rusticus, and Nosema wisconsinii n. sp. infecting Faxonius propinquus and Faxonius virilis. Additionally, we provide SSU sequence data for further Nosema diversity from Procambarus clarkii and Pacifasticus gambelii. The taxonomy of aquatic crustacean-infecting Nosema have been under scrutiny among microsporidiologists—using genomic data we solidify this systematic relationship. Our genomic data reveal phylogenomic divergence between terrestrial insect-infecting Nosema and aquatic crustacean-infecting Nosema but place our novel species within the Nosema. Comparative genomic analysis reveal that Nosema rusticus n. sp. is a tetraploid organism, making this the first known polyploid from the genus Nosema. Annotation of the genomic data highlight that crayfish-infecting Nosema have distinct proteomic differences when compared to amphipod and insect-infecting microsporidians. Alongside the new diversity uncovered and genome-supported systematics, we consider the role of these new 'invasive' parasites in biological invasion systems, exploring their relationship with their invasive hosts. [ABSTRACT FROM AUTHOR]

Nano-phytoremediation is a novel green technique to remove toxic pollutants from the environment. In vitro regenerated Ceratophyllum demersum (L.) plants were exposed to different concentrations of chromium (Cr) and exposure times in the presence of titania nanoparticles (TiO2NPs). Response surface methodology was used for multiple statistical analyses like regression analysis and optimizing plots. The supplementation of NPs significantly impacted Cr in water and Cr removal (%), whereas NP × exposure time (T) statistically regulated all output parameters. The Firefly metaheuristic algorithm and the random forest (Firefly-RF) machine learning algorithms were coalesced to optimize hyperparameters, aiming to achieve the highest level of accuracy in predicted models. The R2 scores were recorded as 0.956 for Cr in water, 0.987 for Cr in the plant, 0.992 for bioconcentration factor (BCF), and 0.957 for Cr removal through the Firefly-RF model. The findings illustrated superior prediction performance from the random forest models when compared to the response surface methodology. The conclusion is drawn that metal-based nanoparticles (NPs) can effectively be utilized for nano-phytoremediation of heavy metals. This study has uncovered a promising outlook for the utilization of nanoparticles in nano-phytoremediation. This study is expected to pave the way for future research on the topic, facilitating further exploration of various nanoparticles and a thorough evaluation of their potential in aquatic ecosystems. [ABSTRACT FROM AUTHOR]

In the present work, graphitic carbon nitride/GO/V2O5 nanocomposite was synthesized via a single stage and utilized this photocatalyst for the degradation of the pesticide Chlorpyrifos. The nanocomposite was prepared using the hydrothermal method. The crystal structure was determined using powder X-ray diffraction of ternary nanocomposite material crystallite size, phase, and defects. Scanning electron microscopy (SEM) and FT-IR evaluated surface morphologies and functional groups. FTIR heterocycle C–N and C=N stretching modes due to bands of 1200–1650 cm−1 During the course of the experiment, the impacts of the experimental parameters (such as pH, time, H2O2 concentration, and Catalyst Dose) on the degradation of Chlorpyrifos were investigated. The photocatalytic studies indicated that the graphitic carbon nitride/GO/V2O5 composites significantly outperformed the pure versions of g-C3N4 in photocatalytic degradation of Chlorpyrifos. The excellent photocatalytic removal efficiency of more than 88% in 120 min obtained using a graphitic carbon nitride/GO/V2O5 catalyst pointed toward a great alternative catalyst for the treatment of Chlorpyrifos and other hazardous pesticides from wastewater. By using 0.1% H2O2, the photocatalytic elimination of Chlorpyrifos was further increased from 88 to 90.5%. The g-C3N4/GO/V2O5 catalyst has outstanding recycling performance and a high level of stability. [ABSTRACT FROM AUTHOR]

In this study, response surface methodology (RSM) was used to optimize in vitro regeneration of the Brazilian micro sword (Lilaeopsis brasiliensis) aquatic plant, followed by data prediction and validation using machine learning algorithms. The basal salt, sucrose and Benzyaminopurine (BAP) concentrations were derived from Box-Behnken design of RSM. The response surface regression analysis revealed that 1.0 g/L MS + 0.1 mg/L BAP + 25 g/L sucrose was optimized for maximum regeneration (100%), shoot counts (63.2), and fresh weight (1.382 g). The RSM-based predicted scores were fairly similar to the actual scores, which were 100% regeneration, 63.39 shoot counts, and 1.44 g fresh weight. Pareto charts analysis illustrated the significance of MS for regeneration and fresh weight but remained insignificant. Conversely, MS × BAP was found to be the most crucial factor for the shoot counts, with MS coming in second and having a major influence. The analysis of the normal plot ascertained the negative impact of elevated MS concentration on shoot counts and enhanced shoot counts from the combination of MS × BAP. Results were further optimized by constructing contour and surface plots. The response optimizer tool demonstrated that maximum shoot counts of 63.26 and 1.454 g fresh weight can be taken from the combination of 1.0 g/L MS + 0.114 mg/L BAP + 23.94 g/L. Using three distinct performance criterias, the results of machine learning models showed that the multilayer perceptron (MLP) model performed better than the random forest (RF) model. Our findings suggest that the results may be utilized to optimize various input variables using RSM and verified via ML models. Key message: Optimization of in vitro whole plant regeneration of Brazilian sword wood using response surface methodology Data analysis through ANOVA, response surface regression anlaysis and machine learning Graphical presentation of data via Pareto charts, normal plots, contour plots and surface plots for optimization Better performance of ANN-based MLP model compared to decision tree based RF model [ABSTRACT FROM AUTHOR]

Di-nitrogen (N2) fixation rates, and the diversity of the organisms that fix N2, remain largely unconstrained in the aquatic landscapes or aquascapes (e.g., lakes, wetlands, streams, rivers, estuaries) between land and sea. As a result, we lack a mechanistic understanding of the controls and contributions of N2 fixation across disparate aquatic environments, and cannot accurately incorporate this process into local and global nitrogen (N) budgets. This special issue brings together papers highlighting current advances in understanding of N2 fixation within and across all aquatic habitats, integrating novel methodology for studying N2 fixation, quantification of N2 fixation fluxes in understudied habitats, the role of N2 fixation in biotic assemblages, and the rate and fate of fixed N in heterogeneous landscapes. Together, these papers address important gaps in understanding and highlight the frontiers of research on N2 fixation in aquatic habitats. [ABSTRACT FROM AUTHOR]

The threat of invasive species to biodiversity and ecosystem structure is exacerbated by the increasingly concerning outlook of predicted climate change and other human influences. Developing preventative management strategies for invasive plant species before they establish is crucial for effective management. To examine how climate change may impact habitat suitability, we modeled the current and future habitat suitability of two terrestrial species, Geranium lucidum and Pilosella officinarum, and two aquatic species, Butomus umbellatus and Pontederia crassipes, that are relatively new invasive plant species regionally, and are currently spreading in the Pacific Northwest (PNW, North America), an area of unique natural areas, vibrant economic activity, and increasing human population. Using North American presence records, downscaled climate variables, and human influence data, we developed an ensemble model of six algorithms to predict the potential habitat suitability under current conditions and projected climate scenarios RCP 4.5, 7.0, and 8.5 for 2050 and 2080. One terrestrial species (P. officinarum) showed declining habitat suitability in future climate scenarios (contracted distribution), while the other terrestrial species (G. lucidum) showed increased suitability over much of the region (expanded distribution overall). The two aquatic species were predicted to have only moderately increased suitability, suggesting aquatic plant species may be less impacted by climate change. Our research provides a template for regional-scale modelling of invasive species of concern, thus assisting local land managers and practitioners to inform current and future management strategies and to prioritize limited available resources for species with expanding ranges. [ABSTRACT FROM AUTHOR]

Climate change can exacerbate the effects of environmental pollutants on aquatic organisms. Pollutants such as human antidepressants released from wastewater treatment plants have been shown to impact life-history traits of amphibians. We exposed tadpoles of the wood frog Lithobates sylvaticus to two temperatures (20 °C and 25 °C) and two antidepressants (fluoxetine and venlafaxine), and measured timing of metamorphosis, mass at metamorphosis, and two behaviors (startle response and percent motionless). Antidepressants significantly shortened time to metamorphosis at 20 °C, but not at 25 °C. At 25 °C, tadpoles metamorphosed significantly faster than those at 20 °C independent of antidepressant exposure. Venlafaxine reduced body mass at 25 °C, but not at 20 °C. Temperature and antidepressant exposure affected the percent of tadpoles showing a startle response. Tadpoles at 20 °C displayed significantly more responses than at 25 °C. Exposure to fluoxetine also increased the percent of tadpoles showing a startle response. Venlafaxine reduced the percent of motionless tadpoles at 25 °C but not at 20 °C. While our results showed that antidepressants can affect the timing of metamorphosis in tadpoles, warmer temperatures overrode these effects and caused a reduction in an important reaction behavior (startle response). Future studies should address how warmer global temperatures may exacerbate or negate the effects of environmental pollutants. [ABSTRACT FROM AUTHOR]

In recent decades, microplastics (MPs < 5 mm) are ubiquitous and considered a serious emerging environmental problem. However, due to the limited recovery and long-lasting durability MPs, debris is frequently accumulating in riverine ecosystems, thereby impacting microbial activity and its communities. The presence of MPs may alter the microbial richness, variety, and population, thereby impacting the transformation of biogeochemical cycles. The occurrence, fate, and transport of MPs in marine and terrestrial ecosystems and their impact on biogeochemical or nutrient cycling are reported in the scientific fraternity. Yet, the global scientific community is conspicuously devoid of research on impact of MPs on riverine greenhouse gas (GHG) emissions. The presented view point provides a novel idea about the fate of MPs in the riverine system and its impact on GHG emissions potential. Literature reveals that DO and nutrients (organic carbon, NH4+, NO3−) concentrations play an important role in potential of GHG emission in riverine ecosystems. The proposed mechanism and research gaps provided will be highly helpful to the hydrologist, environmentalist, biotechnologist, and policymakers to think about the strategic mitigation measure to resolve the future climatic risk. [ABSTRACT FROM AUTHOR]

Anthropogenic salinisation of inland waters worldwide causes diverse social, economic and ecological impacts, including shifts in the composition of biological communities. I used published data on occurrence of aquatic invertebrate taxa in relation to salinity to develop a novel Invertebrate-Based Salinity Index (IBSI) suitable for purposes such as indicating the ecological impact of anthropogenic salinisation and charting faunal recovery after salinity mitigation. Testing of the index with data independent of those used in its derivation showed a stronger association with salinity than prior Australian salinity indices based on macroinvertebrates. IBSI is applicable to both running and standing inland waters across Australia, and could be extended to other countries. Potential limitations of IBSI and its underlying salinity tolerance values are discussed, and suggestions are made for future index refinement and testing. [ABSTRACT FROM AUTHOR]

Shifts in plant functional groups associated with climate change have the potential to influence peatland carbon storage by altering the amount and composition of organic matter available to aquatic microbial biofilms. The goal of this study was to evaluate the potential for plant subsidies to regulate ecosystem carbon flux (CO2) by governing the relative proportion of primary producers (microalgae) and heterotrophic decomposers (heterotrophic bacteria) during aquatic biofilm development in an Alaskan fen. We evaluated biofilm composition and CO2 flux inside mesocosms with and without nutrients (both nitrogen and phosphorus), organic carbon (glucose), and leachates from common peatland plants (moss, sedge, shrub, horsetail). Experimental mesocosms were exposed to either natural sunlight or placed under a dark canopy to evaluate the response of decomposers to nutrients and carbon subsidies with and without algae, respectively. Algae were limited by inorganic nutrients and heterotrophic bacteria were limited by organic carbon. The quality of organic matter varied widely among plants and leachate nutrient content, more so than carbon quality, influenced biofilm composition. By alleviating nutrient limitation of algae, plant leachates shifted the biofilm community toward autotrophy in the light-transparent treatments, resulting in a significant reduction in CO2 emissions compared to the control. Without the counterbalance from algal photosynthesis, a heterotrophic biofilm significantly enhanced CO2 emissions in the presence of plant leachates in the dark. These results show that plants not only promote carbon uptake directly through photosynthesis, but also indirectly through a surrogate, the phototrophic microbes. [ABSTRACT FROM AUTHOR]

Plastics enter the environment, amongst others, from synthetic textiles, which shed microplastic fibers (microfibers) during their production, use and disposal. We tested whether short- and long-term effects of microfibers on the aquatic worm, Lumbriculus variegatus, depend on the synthetic microfiber material. Microcosms containing L. variegatus were exposed to no microfibers (control) or one of three polymer treatments (nylon, polyester, or olefin) at 5 g of microfibers kg-1 of sediment for 48 h or 28 days. Following exposure, L. variegatus were counted, weighed, and the number of microfibers ingested determined. Polyester microfibers occurred in higher quantities (10–12) than nylon and olefin (< one) per individual after 48 h and 28 days. Only the olefin per individual doubled after 28 days compared to 48 h. These findings indicate that polyester microfibers are more likely to affect L. variegatus and have greater potential to be ingested by higher trophic levels than other polymers. [ABSTRACT FROM AUTHOR]

Concentrations of metals along with pH, potential redox (Eh), total dissolved solid (TDS), electrical conductivity (EC) and salinity were measured for sediments of different layers, pore and surface water in the Anzali wetland. Also, the diffusive flux of metals was calculated ad compared with the values in other aquatic bodies. The abundance of metals in sediments was Al > Fe > Ca > Ti > Mn > Zn > V > Cr > Ni > Cu > Pb > Co > As > Mo > Ag > Cd, while the pore-water results indicated a different concentration profile: Ca > Mn > Fe > Al > V > Mo > As > Ni > Cu > Co. Anzali wetland is classified within a high ecological risk. Pore-water toxicity test showed it is in non-polluted condition. Eh–pH diagrams showed that all species of elements are in a stable state in surface and pore-waters. However, Mn and Co (in some layers) are in soluble form and free ions and thus are bioavailable to the organisms. V and As are also present in the form of hydrogen compounds and Ni in the form of hydroxides, therefore, they are toxic to aquatic animals due to their solubility and ionic forms. Diffusive fluxes for As, Al, Fe, Ca, Cu, Mn, Mo, Ni and V are 0.43, 1.80, 48.52, 43,147.50, 0.12, 1.47, 0.15, 1.28, 0.21 µg/m2/day, respectively. Cluster analysis showed that in a solid phase of sediments, elements such as Cr, As and Ti are of petroleum and terrestrial origin. In pore-waters, Cu is of petroleum and biological origin, and Mo, As, Cu and Co are controlled by pH. [ABSTRACT FROM AUTHOR]

Water bodies or aquatic ecosystem are susceptible to heavy metal accumulation and can adversely affect the environment and human health especially in underdeveloped nations. Phytoremediation techniques of water bodies using aquatic plants or macrophytes are well established and are recognized as eco-friendly world over. Phytoremediation of heavy metals and other pollutants in aquatic environments can be achieved by using Ceratophyllum demersum L. — a well-known floating macrophyte. In vitro regenerated plants of C. demersum (7.5 g/L) were exposed to 24, 72, and 120 h to 0, 0.5, 1.0, 2.0, and 4.0 mg/L of cadmium (CdSO4·8H2O) in water. Results revealed significantly different relationship in terms of Cd in water, Cd uptake by plants, bioconcentration factor (BCF), and Cd removal (%) from water. The study showed that Cd uptake by plants and BCF values increased significantly with exposure time. The highest BCF value (3776.50) was recorded for plant samples exposed to 2 mg/L Cd for 72 h. Application of all Cd concentrations and various exposure duration yielded Cd removal (%) between the ranges of 93.8 and 98.7%. These results were predicted through artificial intelligence–based models, namely, random forest (RF), extreme gradient boosting (XGBoost), and multilayer perceptron (MLP). The tested models predicted the results accurately, and the attained results were further validated via three different performance metrics. The optimal regression coefficient (R2) for the models was recorded as 0.7970 (Cd water, mg/L), 0.9661 (Cd plants, mg/kg), 0.9797 bioconcentration factor (BCF), and 0.9996 (Cd removal, %), respectively. These achieved results suggest that in vitro regenerated C. demersum can be efficaciously used for phytoremediation of Cd-contaminated aquatic environments. Likewise, the proposed modeling of phytoremediation studies can further be employed more comprehensively in future studies aimed at data prediction and optimization. [ABSTRACT FROM AUTHOR]

Seagrasses have some of the highest rates of carbon burial on the planet and have therefore been highlighted as ecosystems for nature-based climate change mitigation. However, information is still needed on the net radiative forcing benefit of seagrasses inclusive of their associated greenhouse gas (GHG) emissions. Here, we report simultaneous estimates of seagrass-associated carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) air–water emissions. Applying in situ sampling within a south-east Australian seagrass ecosystem, this study finds atmospheric GHG emissions from waters above seagrasses to range from − 480 ± 15.96 to − 16.2 ± 8.32 mg CO2-equivalents m2 d−1 (net uptake), with large temporal and spatial variability. Using a combination of gas specific mass balance equations, dissolved stable carbon isotope values (δ13C) and in situ time-series data, CO2-e flux is estimated at − 21.74 mg m2 d−1. We find that the net release of CH4 (0.44 µmol m2 h−1) and net uptake of N2O (− 0.06 µmol m2 h−1) effectively negated each other at 16.12 and − 16.13 mg CO2-e m2 d−1, respectively. The results of this study indicate that temperate Australian seagrasses may function as net sinks of atmospheric CO2-e. These results contribute towards filling key emission accounting gaps both in the Australian region, and through the simultaneous measurement of the three key greenhouse gas species. [ABSTRACT FROM AUTHOR]

Microplastics are plastic fragments with a size less than 5 mm in length. In addition to a threat to the marine environments where these are abundantly present, these have also started polluting freshwater ecosystems. However, the uptake of microplastics by living organisms differs depending on their habitats and feeding behaviors. We investigated the presence, size, type, and color of microplastics in the gastrointestinal tract contents of two water snakes, namely Natrix natrix and Natrix tessellata. The snakes were collected from different regions of Turkey and preserved as museum materials. Our results showed that fibers constituted the predominant polymer type in both snake species (94.7% for N. natrix and 87.9% for N. tessellata), whose dimensions ranged from 250 to 3750 µm. We did not find any significant difference in the number of microplastics ingested between the two species. In addition, the uptake of microplastics did not relate to the size and weight of snakes. Microplastics were not consistently present all years, and similarly, these were not detected in all samples within the distribution area. These results could be attributed to the environment and diet of two snake species. [ABSTRACT FROM AUTHOR]

Microplastics are an emerging threat and a big challenge for the environment. The presence of microplastics (MPs) in water is life-threatening to diverse organisms of aquatic ecosystems. Hence, the scientific community is exploring deeper to find treatment and removal options of MPs. Various physical, chemical and biological methods are researched for MPs removal, among which few have shown good efficiency in the laboratory. These methods also have a few limitations in environmental conditions. Other than finding a suitable method, the creation of legal restrictions at a governmental level by imposing policies against MPs is still a daunting task in many countries. This review is an effort to place all effectual MP removal methods in one document to compare the mechanisms, efficiency, advantages, and disadvantages and find the best solution. Further, it also discusses the policies and regulations available in different countries to design an effective global policy. Efforts are also made to discuss the research gaps, recent advancements, and insights in the field. [ABSTRACT FROM AUTHOR]

With the continued growth in plastic production, its ubiquitous use and insufficient waste management and disposal, the increased levels of plastics in the environment have led to growing ecological concerns. The breakdown of these plastic macromolecules to smaller micro and nanosized particles and their detection in the aerial, aquatic, marine and terrestrial environments has been reviewed extensively, especially for thermoplastics. However, the formation of micro and nanoplastics has typically been explained as a physical abrasion process, largely overlooking the underlying chemical structure-morphology correlations to the degradation mechanisms of the plastics. This is particularly true for the common commodity thermosets. This review focuses on the degradation pathways for the most widely produced commodity thermoplastics and thermosets into microplastics (MP)s and nanoplastics (NP)s, as well as their behaviour and associated toxicity. Special emphasis is placed on NPs, which are associated with greater risks for toxicity compared to MPs, due to their higher surface area to volume ratios. This review also assesses the current state of standardized detection and quantification methods as well as comprehensive regulations for these fragments in the aquatic environment. [ABSTRACT FROM AUTHOR]

Use of benthic macroinvertebrates has been in vogue as indicator organisms for water quality monitoring since long. Traditional methods of water quality monitoring incorporate mostly monitoring of physicochemical parameters. However, it is the biomonitoring studies that could help in more accurate water quality monitoring. Due to anthropogenic impact at water sources, integrated water quality monitoring has become a necessity. An integrated study comprising physicochemical parameters and biomonitoring using benthic macroinvertebrates was carried out at six sites along the Mahi river basin, the command area of which has witnessed tremendous economic and cultural progress over a period of time. Diversity Score and Saprobic Score were calculated, and Water Quality Class was determined as per Biological Monitoring Working Party score given by Central Pollution Control Board and results in moderate pollution at all locations, whereas Water Quality Class as per ISI-IS 2296–1982 at M-1, M-4, M-7 and M-12 shows slight pollution. Jaccard's similarity index compared the biodiversity of benthic macroinvertebrates at all the sites from upstream to downstream locations. It was maximum, i.e., 52.94% between the locations at M-4 and M-7. Species richness (S) has also been monitored at the said locations. The Diversity Score 0.83 is maximum at the Galteshwar (M-12) location of the Mahi river, which indicates that the location was the most ecologically diverse region among all. [ABSTRACT FROM AUTHOR]

The persistent and accumulative nature of the pesticide of indiscriminate use emerged as ecotoxicological hazards. The bioconcentration factor (BCF) is one of the key elements for environmental assessments of the aquatic compartment. Limitations of prediction accuracy of global model facilitate the use of local predictive models in toxicity modeling of emerging compounds. The BCF data of diverse organophosphate (n = 55) was collected from the Pesticide Properties Database and used as a model data set in the present study to explore physicochemical properties and structural alert concerning BCF. The structures were downloaded from Pubchem, ChemSpider database. Two splitting techniques (biological sorting and structure-based) were used to divide the whole dataset into training and test set compounds. The QSAR study was carried out with two-dimensional descriptors (2D) calculated from PaDEL by applying genetic algorithm (GA) as chemometric tools using QSARINS software. The models were statistically robust enough both internally as well as externally (Q2: 0.709–0.722, Q2Ext: 0.717–0.903, CCC: 0.857–0.880). Overall molecular mass, presence of fused, and heterocyclic ring with electron-withdrawing groups affect the BCF value. The developed models reflected extended applicability domain (AD) and reliable predictions than the reported models for the studied chemical class. Finally, predictions of unknown organophosphate pesticides and the toxic nature of unknown organophosphate pesticides were commented on. These findings may be useful for the scientific community in prioritizing high potential pesticides of organophosphate class. [ABSTRACT FROM AUTHOR]

Identifying waterbodies where fish methylmercury concentrations are elevated is critical for development of consumption guidelines. However, mercury concentrations vary among waterbodies and fishes due to a suite of environmental conditions and detection of elevated mercury concentrations is imperfect, resulting in inaccurate consumption guidelines. Occupancy models may be a useful approach for addressing these issues but have not been used for these purposes. Our objectives were to use occupancy modeling to (1) estimate number of samples needed to detect mercury levels surpassing >0.30 mg/kg wet weight in fish at a waterbody (2) identify individual fish-level factors associated with detection probability, and (3) identify environmental-level factors linked to elevated mercury levels in fish at a waterbody. Mercury concentrations were estimated from >500 largemouth bass Micropterus salmoides and walleye Sander vitreus from 30 waterbodies throughout Iowa, USA to identify individuals with concentrations > or <0.30 mg/kg. Probability of detecting mercury concentrations >0.30 mg/kg varied between species and increased with fish length; consequently, more samples were needed to detect elevated mercury concentrations in small versus large fish. The probability of a waterbody having fish with elevated mercury levels increased with the percent grassland and declined with percent agriculture in the watershed, providing prioritization metrics for mercury surveillance programs. Our results demonstrate that occupancy models can be a valuable tool for mercury surveillance due to their ability to estimate necessary sample sizes and identify fish sizes and waterbodies with elevated mercury concentrations while accounting for imperfect detection probabilities. [ABSTRACT FROM AUTHOR]

Viruses are found in almost all biomes on Earth, with bacteriophages (phages) accounting for the majority of viral particles in most ecosystems. Phages have been isolated from natural environments using the plaque assay and liquid medium-based dilution culturing. However, phage cultivation is restricted by the current limitations in the number of culturable bacterial strains. Unlike prokaryotes, which possess universally conserved 16S rRNA genes, phages lack universal marker genes for viral taxonomy, thus restricting cultureindependent analyses of viral diversity. To circumvent these limitations, shotgun viral metagenome sequencing (i.e., metaviromics) has been developed to enable the extensive sequencing of a variety of viral particles present in the environment and is now widely used. Using metaviromics, numerous studies on viral communities have been conducted in oceans, lakes, rivers, and soils, resulting in many novel phage sequences. Furthermore, auxiliary metabolic genes such as ammonic monooxygenase C and β-lactamase have been discovered in viral contigs assembled from viral metagenomes. Current attempts to identify putative bacterial hosts of viral metagenome sequences based on sequence homology have been limited due to viral sequence variations. Therefore, culture-independent approaches have been developed to predict bacterial hosts using single-cell genomics and fluorescentlabeling. This review focuses on recent viral metagenome studies conducted in natural environments, especially in aquatic ecosystems, and their contributions to phage ecology. Here, we concluded that although metaviromics is a key tool for the study of viral ecology, this approach must be supplemented with phage-host identification, which in turn requires the cultivation of phage-bacteria systems. [ABSTRACT FROM AUTHOR]

Artificial light at night (ALAN) is one of the fastest growing anthropogenic disturbances to animals across many ecosystems, yet little is known about how ALAN influences fish and aquatic ecosystems. Our current understanding of the effects of ALAN on fish behavior and physiology tend to be based on research conducted during night, with comparatively little research on whether ALAN influences subsequent behavior during diurnal periods. We used wild-caught Bluegill Lepomis macrochirus as a model to assess whether ALAN of differing intensities comparable to what would be experienced in the wild near human-altered landscapes (i.e., 0.5 lux, 4 lux, 9 lux) alters subsequent diurnal behavior relative to controls (i.e., dark, 0 lux). We assessed a number of behavioral traits in a laboratory setting known to relate to performance and fitness in wild teleost fish including exploration, activity levels, space usage, and risk aversion. Exploration behavior, space use, and risk-taking behaviors were similar among treatments. Only locomotor activity differed among treatments with Bluegill in the 0.5 and 9 lux treatments swimming significantly less than controls after being exposed to ALAN overnight. This difference in behavior was found at light intensities commonly found at waterways today and thus may already be affecting fish communities and aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Climate change may facilitate the expansion of non-native invasive species (NIS) in aquatic and terrestrial systems. However, empirical evidence remains scarce and poorly synthesized at scales necessary for effective management. We conducted a literature synthesis to assess the state of research on the observed and predicted effects of climate change on a suite of 398 aquatic and terrestrial NIS now present in or a major threat to aquatic and terrestrial ecosystems of the Pacific Northwest (PNW), USA and British Columbia. Surprisingly, very few studies (n = 15) have investigated the observed effects of climate change on the distribution, abundance, spread, or impact of the focal NIS, with only five studies focusing on terrestrial (n = 2) or aquatic (n = 3) species within the PNW. Only 93 studies predicted the future dynamics of the focal NIS somewhere in their non-native range using climate model projections, yielding 117 species-specific predictions. However, only 30 of those studies generated predictions that overlapped with the PNW, and only six focused specifically on the expansion or abundance of NIS (n = 11 species) entirely within the region. Although our understanding of how climate change may interact with biological invasions is notably lacking, some evidence suggests that climate-induced NIS expansions are already underway in the PNW, particularly in aquatic ecosystems, and will be exacerbated by future changes in temperature and precipitation regimes. Better information is urgently needed for managers to implement strategic prevention, early detection, and proactive actions that ameliorate ecologically and economically devastating impacts of NIS. [ABSTRACT FROM AUTHOR]

The number of non-native plant species established outside of cultivation in the New Zealand archipelago is higher than for any other islands worldwide. Faced with this scale of plant invasions, there has been considerable investment in the scientific and operational aspects of prevention, eradication and control. As a result, New Zealand is ideally placed to illustrate the many challenges that plant invasions present worldwide as well as the possible solutions. New Zealand has been at the forefront of biosecurity policy developments to tackle plant invasions being one of the first countries to: (a) implement national legislation to address the management of non-native plants; (b) establish a national permitted list (white-list) for plant imports; and (c) introduce bans on the sale, distribution, or propagation of non-native plant species. However, these preventative measure are only effective where there are also adequate border inspection regimes, compliance monitoring of the horticulture industry, and surveillance of internet trade. While New Zealand has successfully eradicated several non-native plant species from its territory, the small number of successes reflects the short-term, local and often uncoordinated efforts to manage non-native plants rather than national programmes backed by legislation and financed over several decades. New Zealand supports a world-leading biological control programme, but this has led to sustained, large-scale control for only a handful of species. In natural areas, most management attempts using mechanical or herbicide treatments have failed to achieve control and there has been a progressive reduction in the area, and frequency of these programmes over time. This is illustrative of the challenges facing those responsible for managing non-native plants in any region of the world. A general insight is that a shift in mindset is required that overcomes significant cognitive biases that include succumbing to the pressure to always intervene, underestimating the non-linear trajectories of invasions, failing to articulate the values at stake, and underestimating the time programmes require to succeed. Important lessons of global relevance include the need for managers to: (a) recognise when and where sleeper weeds are likely to become a national issue, especially as a result of climate change; (b) quantify impacts on those values that stakeholders most cherish rather than those that are easy to measure; (c) provide accurate estimates of the potential future extent of the invasion in the absence of management; and (d) identify clear indicators of successful progress over the course of a long-term management programme. [ABSTRACT FROM AUTHOR]

Our understanding of how ecosystems function has changed from an equilibria-based view to one that recognizes the dynamic, fluctuating, nonlinear nature of aquatic systems. This current understanding requires that we manage systems for resilience. In this review, we examine how resilience has been defined, measured and applied in aquatic systems, and more broadly, in the socioecological systems in which they are embedded. Our review reveals the importance of managing stressors adversely impacting aquatic system resilience, as well as understanding the environmental and climatic cycles and changes impacting aquatic resources. Aquatic resilience may be enhanced by maintaining and enhancing habitat connectivity as well as functional redundancy and physical and biological diversity. Resilience in aquatic socioecological system may be enhanced by understanding and fostering linkages between the social and ecological subsystems, promoting equity among stakeholders, and understanding how the system is impacted by factors within and outside the area of immediate interest. Management for resilience requires implementation of adaptive and preferably collaborative management. Implementation of adaptive management for resilience will require an effective monitoring framework to detect key changes in the coupled socioecological system. Research is needed to (1) develop sensitive indicators and monitoring designs, (2) disentangle complex multi-scalar interactions and feedbacks, and (3) generalize lessons learned across aquatic ecosystems and apply them in new contexts. [ABSTRACT FROM AUTHOR]

Heavy metals are one of the main problems in aquatic systems as they affect the ecological balance of the water body. Biological availability of a metal is dependent on its chemical form. Speciation of metals in aquatic systems is of high importance and can provide a proper framework for managers to determine the probable risks resulted from metals. Therefore, this study was performed in Anzali Wetland to investigate the speciation of heavy metals and metalloids, and determine the factors controlling them. For this purpose, six stations were sampled and the relations among water quality parameters were identified by cluster analysis. Water chemistry software (HSC Chemistry) was used to draw Eh/pH diagrams. According to the results, oxidation–reduction potential (Eh) values ranged from − 280 to + 135 mV. The metals including arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), mercury (Hg), cerium (Ce), copper (Cu), aluminum (Al) and iron (Fe) were affected by Eh and pH. Salinity played a significant role in controlling nickel (Ni), magnesium (Mg), calcium (Ca) and strontium (Sr) in the water. The HSC Chemistry diagrams showed that all the studied metals were within the two lines of water stability range. As, Cd, Co, Cr, Ni, lead (Pb), Al, Ca, Ce, Fe, manganese (Mn), Mg, silicon (Si) and Sr were present in a bioavailable species in the wetland water. Some metals such as As, Cd, Cr, and Fe existed in very toxic forms. It was found that changes in the Eh–pH values as a result of anthropogenic and different activities in the wetland can alter the speciation of metals. Eh/pH diagrams also showed that the elements can exceed the water stability range and become unstable in three states (pH < 5, Eh < − 380 mV or Eh > 780 mV). [ABSTRACT FROM AUTHOR]

We present a comprehensive survey of the scientific literature pertaining to non-indigenous and invasive zooplankton published across the first decades of the twenty-first century (i.e., 2000–2018). We provide a concise summary of the manner in which the scientific community has allocated its efforts to this issue in recent decades, and to illuminate trends that emerge from the literature. Our search yielded 620 publications encompassing 139 invasive zooplankton species, with invasive zooplankton reported from every region of the planet—including the Arctic and Antarctic. Most taxa were reported in a small number of publications, with the majority being mentioned in only a single paper. In contrast, approximately half of the surveyed publications concerned just four species: Bythotrephes longimanus, Mnemioposis leidyi, Cercopagis pengoi, and Daphnia lumholtzi. Our survey reveals strong geographic patterns among the literature, with most publications arising from economically developed western nations. We found that the majority of publications pertained to holoplanktonic organisms from freshwater habitats, especially from the North American Great Lakes. Based on these results, we present several recommendations for future research topics that may hold considerable opportunity for growth in our understanding of the invasion process. [ABSTRACT FROM AUTHOR]

Freshwater biodiversity of the United States has long been recognized for its high level of species richness. The US crayfish fauna is richer than that found in any other country or continent in the world. Crayfishes are critically important members of freshwater ecosystems and have long been utilized for human consumption. Combined, these factors argue for effective conservation. When compared to other diverse aquatic groups such as fishes or unionid mussels, conservation efforts for US crayfishes are lacking. We review here, knowledge gaps that prevent effective conservation and past and ongoing crayfish conservation and management activities. We conclude by proposing a strategy of actions to improve the conservation standing of this important group of organisms. These action items include improved outreach efforts, funding and research to fill numerous knowledge gaps, and the inclusion of crayfishes in broader scale aquatic conservation activities. [ABSTRACT FROM AUTHOR]

A representative suite of 276 samples was used to study the isotopic and elemental geochemistry of kerogens from the Bazhenov horizon (Bazhenov Formation and its age equivalents) of the western Siberian sedimentary basin and to map the variations in the elemental composition of kerogen in the area. The elemental composition of the kerogen was used to determine the types of organic matter (H and C contents), the initial components of the living matter that were the source of the kerogen (H and N contents), the diagenetic history of organic matter (S content), and the level of catagenetic transformation of the kerogen (C and O contents). Kerogen from the central, western, and southern parts of the western Siberian basin, up to the pinch-out boundary of the Bazhenov horizon, shows strong enrichment in hydrogen (up to 8–9%) and 12С (δ13С‰ from –35 to –29), suggesting its derivation from polymer lipids of aquatic origin. Kerogen from the Bazhenov horizon (catagenetic grade MC1) in the northeast of the basin contains much lower hydrogen concentrations (2–4%). A map of the types of organic matter in the Bazhenov horizon is constructed. [ABSTRACT FROM AUTHOR]

The fungus Batrachochytrium dendrobatidis (Bd) is a generalist amphibian pathogen responsible for chytridiomycosis. It was documented for the first time in Cuba in 2007, the apparent cause of the decline in one species of toad. In a recent survey, Bd was reported only for the highlands of Central Cuba. In the present study, we reexamined the geographic distribution and level of impact of Bd in Cuba by conducting an island-wide sampling in 10 localities and collecting skin swabs from 18 species and 28 environmental samples. We report detection of Bd in 60% of sampled sites and in 58% of sampled taxa. We show that Bd is associated with riparian, arboreal and terrestrial species, and it was estimated to occur in approximately 30% of the aquatic habitats we sampled. In addition, we confirmed that a dying individual of the species Eleutherodactylus casparii was severely infected with Bd. We also rise concern about the endanger toad Peltophryne longinasus and about three species of endemic riparian frogs that were not detected during our surveys. This study demonstrates that this pathogen is widespread throughout Cuba and provides relevant evidence to advance our understanding of its detection in amphibians and the aquatic environment in Cuba and about the occurrence of Bd in species with different ecologies. We provide valuable baseline information for Bd risk assessment and decision-making processes to mitigate its negative impact on Cuban amphibians. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) analysis is a rapid, non-invasive, cost-efficient biodiversity monitoring tool with enormous potential to inform aquatic conservation and management. Development is ongoing, with strong commercial interest, and new uses are continually being discovered. General applications of eDNA and guidelines for best practice in freshwater systems have been established, but habitat-specific assessments are lacking. Ponds are highly diverse, yet understudied systems that could benefit from eDNA monitoring. However, eDNA applications in ponds and methodological constraints specific to these environments remain unaddressed. Following a stakeholder workshop in 2017, researchers combined knowledge and expertise to review these applications and challenges that must be addressed for the future and consistency of eDNA monitoring in ponds. The greatest challenges for pond eDNA surveys are representative sampling, eDNA capture, and potential PCR inhibition. We provide recommendations for sampling, eDNA capture, inhibition testing, and laboratory practice, which should aid new and ongoing eDNA projects in ponds. If implemented, these recommendations will contribute towards an eventual broad standardisation of eDNA research and practice, with room to tailor workflows for optimal analysis and different applications. Such standardisation will provide more robust, comparable, and ecologically meaningful data to enable effective conservation and management of pond biodiversity. [ABSTRACT FROM AUTHOR]

Aquatic environments are widely affected by anthropogenic activities and efficient remediation of these areas requires detailed studies for each natural ecosystem. This research aimed to evaluate the natural phytoremediation potential of Hydrocotyle ranunculoides L., a floating aquatic macrophyte located in a polluted aquatic environment in South of the Rio Grande do Sul, Brazil. Nutrients such as P, K, Ca, Mg, and S and heavy metals such as Cu, Zn, Fe, Mn, Na, Cd, Cr, Ni, Pb, Al, As, Co, and V content in the roots and shoots of the plants were evaluated through nitric perchloric acid digestion (HNO3-HClO4) methods and quantified by ICP-OES. Bioconcentration factor (BCF), translocation factor (TF), plant effective number (PEN), and potential phytoremoval (mg m−2) were carried out. H. ranunculoides showed a substantial ability for phytoextracting P, Na, and As, since showed ability of uptake these elements from the water and translocate them to the shoots of the plants. H. ranunculoides also showed potential for application in rhizofiltration of Mg, S, Cu, Zn, Fe, Mn, Cd, Cr, Ni, Pb, Al, and V, since exhibited high potential to uptake higher levels in the roots. The highest potential for bioremoval (mg m−2) of the H. ranunculoides was detected for K, Ca, P (recommending thus the use for phytoextraction), Fe, and Al (highly recommended for rhizofiltration). Therefore, this species under study showed high potential for in situ phytoremediation at Santa Bárbara stream, and as a widespread species, it might be tested for phytoremediation in other sites. [ABSTRACT FROM AUTHOR]

Human activities such as industrialisation, urbanisation and agriculture have adversely impacted terrestrial and aquatic ecosystems. Water pollutants such as heavy metals and nanoparticles can undergo bioaccumulation and bioaugmentation. Heavy metals cannot be degraded and are hence added permanently. Nanoparticles are a potential threat because of their small size and unique properties. This article reviews the impact of various pollutants on aquatic biota and presents remediation methods. Benthic macroinvertebrates can be used as bioindicators to study the impact of pollutants on aquatic ecosystems. Fishes occupy the highest trophic level in the aquatic food chain and can therefore accumulate large amounts of metal from water, ultimately leading to biomagnification. Some organic compounds such as pesticides and fungicides are carcinogenic and sometimes resistant to degradation. [ABSTRACT FROM AUTHOR]

Antifouling chemicals are legacy contaminants in aquatic ecosystems. Previous experiments have shown that a 14-day exposure to the antifouling chemical medetomidine delays metamorphosis and reduces body mass in wood frog tadpoles. In the present study, we exposed wood frog tadpoles to medetomidine for 3, 7, and 10 days at 100 nM, 1 μM, and 10 μM. We also exposed American toad tadpoles to medetomidine for 3 days at four concentrations (10 nM, 100 nM, 1 μM, and 10 μM) in static renewal experiments. In each experiment, we measured growth, frequency and time to metamorphosis, and mass at metamorphosis. In both species, medetomidine significantly slowed development as measured by the Gosner stage. After 34 days in culture, wood frog tadpoles exposed to 1 and 10 μM medetomidine for as few as 3 days were significantly less developed compared to controls. Toads exposed to 1 μM medetomidine for 3 days were also significantly less developed on day 27, but by day 34, there was no difference from controls. For wood frogs, medetomidine significantly affected time to metamorphosis with a trend for tadpoles at lower concentrations metamorphosing sooner than those at higher concentrations. While medetomidine affected time to metamorphosis in wood frogs, it did not affect fresh mass, dry mass, or mortality compared to controls. Wood frog tadpoles that did not metamorphose after over 90 days in culture were more frequent in high-concentration groups than in the control. In toads, 10 μM medetomidine was 100% lethal within 23 days, but at the same concentration and duration, no wood frog tadpoles died. Lower concentrations were also significantly lethal to toads compared to controls, but tadpoles that survived in 10 and 100 nM metamorphosed sooner than those in 1 μM. Fresh mass of toad tadpoles exposed to 1 μm was significantly smaller at metamorphosis compared to that of controls. Medetomidine also affected the behavior of tadpoles. In toads, medetomidine significantly reduced both percent activity and startle response. In wood frogs, medetomidine significantly reduced percent activity, but increased startle response. We discuss our finding of low-dose stimulation and high-dose inhibition of different life history endpoints in terms of hormetic mechanisms. The differential sensitivity between species in terms of mortality, frequency of metamorphosis, and behavior highlights the potential negative environmental effects of medetomidine to amphibians. [ABSTRACT FROM AUTHOR]

Reservoirs are a globally significant source of methane (CH4) to the atmosphere. However, emission rate estimates may be biased low due to inadequate monitoring during brief periods of elevated emission rates (that is, hot moments). Here we investigate CH4 bubbling (that is, ebullition) during periods of falling water levels in a eutrophic reservoir in the Midwestern USA. We hypothesized that periods of water-level decline trigger the release of CH4-rich bubbles from the sediments and that these emissions constitute a substantial fraction of the annual CH4 flux. We explored this hypothesis by monitoring CH4 ebullition in a eutrophic reservoir over a 7-month period, which included an experimental water-level drawdown. We found that the ebullitive CH4 flux rate was among the highest ever reported for a reservoir (mean = 32.3 mg CH4 m−2 h−1). The already high ebullitive flux rates increased by factors of 1.4-77 across the nine monitoring sites during the 24-h experimental water-level drawdown, but these emissions constituted only 3% of the CH4 flux during the 7-month monitoring period due to the naturally high ebullitive CH4 flux rates that persist throughout the warm weather season. Although drawdown emissions were found to be a minor component of annual CH4 emissions in this reservoir, our findings demonstrate a link between water-level change and CH4 ebullition, suggesting that CH4 emissions may be mitigated through water-level management in some reservoirs. [ABSTRACT FROM AUTHOR]

The antimicrobial triclosan (TCS) has been detected in household wastewaters (untreated and treated) and receiving environments across the globe. The toxic effects of TCS on temperate standard aquatic test organisms have been widely reported with microalgae being the most sensitive. However, environmental differences between tropical and temperate regions may have selected different trait compositions between these two regions, which in turn may lead to a difference in species sensitivity. Therefore, additional information is required to better characterize risks to organisms in tropics and ensure biodiversity in these regions is not adversely impacted. This study aims to supplement existing TCS toxicity data with five aquatic invertebrates found in tropics and to compare the sensitivity between aquatic invertebrate species from tropical and temperate regions. In addition, the effect of pH on the toxicity of neutral and ionized forms of TCS to microalgae (Chlorella ellipsoidea) was investigated. The reported 96-h LC50 values for the studied invertebrate species ranged from 72 to 962 μg/L. There was no significant difference between the sensitivity of aquatic invertebrate species from tropical and temperate regions. EC50 values for C. ellipsoidea, with and without pH buffer, were significantly different. The findings of this study can be used to support site-specific water quality criteria and environmental risk assessment for TCS in tropical regions. However, further chronic and semi-field experiments with TCS could potentially enable a refined assessment of direct and indirect effects on tropical aquatic communities and further explore functional endpoints of tropical ecosystems. [ABSTRACT FROM AUTHOR]

Rising temperatures likely affect the trophic interactions in temperate regions as global warming progresses. An open question is how a temperature rise may affect consumer pressure and plant abundance in shallow aquatic ecosystems, where most consumers are omnivorous. Interestingly, herbivory (plant-eating) is more prevalent toward low latitudes in ectotherms such as fish and aquatic invertebrates, and this may be temperature driven. We used pond snails (Lymnaea stagnalis L.) as a model aquatic ectotherm species and tested their consumption of both animal prey (Gammarus pulex L.) and plant material (Potamogeton lucens L.) at three different temperatures (15, 20, and 25°C). Higher temperatures led to higher consumption rates by the omnivore on both plant food and animal prey when fed separately. When the food was offered simultaneously, the pond snails consistently preferred animal prey over plant material at all tested temperatures. However, the omnivore did consume plant material even though they had enough animal prey available to them. Based on our experiments, we conclude that with increasing temperatures, L. stagnalis will only increase their consumption rates but not change food preference. Further studies are needed to test the generality of our findings across aquatic species to predict the effect of warming on aquatic plant consumption. [ABSTRACT FROM AUTHOR]

Antifouling chemicals have a long history of causing toxicity to aquatic organisms. We measured growth and developmental timing in wood frog tadpoles exposed to the antifouling chemical medetomidine (10 nM-10 μM) starting at two different developmental stages in static renewal experiments. For tadpoles hatched from egg masses and exposed for 3 weeks to 100 nM and 1 μM, head width/total body length ratio was significantly shorter compared to control. For field-collected tadpoles at Gosner stage 24-25 and exposed for 2 weeks, 1 and 10 μM medetomidine significantly slowed development as measured by Gosner stage. Medetomidine (1 and 10 μM) significantly increased the time to metamorphosis by over 16 days on average, and at 100 nM and 1 μM, it significantly decreased mass at metamorphosis. We discuss the possible effects of antifouling chemicals containing medetomidine on globally threatened groups such as amphibians. [ABSTRACT FROM AUTHOR]

Non-native species are a major component of global environmental change, and aquatic systems are especially vulnerable to non-native species impacts. Much of the research on aquatic non-native species impact has occurred at the local or site level. In reality, non-native species impacts play out across multiple spatial scales on heterogeneous landscapes. How can we 'scale up' our understanding of site-level impacts to the broader landscape scale? To address this disconnect, we synthesize our current understanding of key components of landscape-scale non-native species impacts: geographic range, abundance, and local impacts. Most aquatic non-native species have small ranges, while a few have large ranges. However, aquatic non-native species are often far from saturated on landscapes, and occurrence records are often woefully incomplete. Aquatic non-native species are often at low abundances where they are present, reaching high abundance in a small number of locations. Finally, local-scale impact can be estimated from abundance, but this requires knowledge of the abundance-impact relationship. Considering these multiple components enables understanding of non-native species impacts at broader spatial scales. Although the landscape-level impacts of aquatic non-native species may be high, the spatial distribution of site-level impacts is uneven, and highly impacted sites may be relatively uncommon. This heterogeneity in impacts provides an opportunity to optimize and prioritize non-native species management and prevention efforts. [ABSTRACT FROM AUTHOR]

We used highly realistic temperature treatments based on down-scaled global circulation models for 1990-2000 (control) and 2100 (warming treatment) to experimentally assess the impacts of altered temperature regimes on the emerging adults of aquatic insect communities. Experiments were run for 6 weeks and emerging adults of insects were identified and measured for length. There were clear responses to the warming treatment, but responses were taxa- and gender-specific. Males of mayfly Ulmerophlebia pipinna Suter 1986 (Leptophlebiidae) emerged faster under 2100 temperatures. This resulted in a change in the sex ratio that could compromise populations. Mean body size of some insects decreased under warming conditions, which is in agreement with the general hypothesis of reduced body size in response to climate change. However, the degree to which organism size was affected by temperature varied within and between taxa. These changes show the potential for changed temperature regimes to impact ecological systems at individual, population, and community levels. Changes in body size and species composition of emerging insects are likely to impact different levels in both the aquatic and terrestrial communities, for example through disruption of interactions between emerging insects and riparian predators which rely on those resources. [ABSTRACT FROM AUTHOR]

Exposure to human antidepressants has been shown to disrupt locomotion and other foot-mediated mechanisms in aquatic snails. We tested the effect of three selective serotonin reuptake inhibitor (SSRI)- and one selective serotonin-norepinephrine reuptake inhibitor (SNRI)-type antidepressants on the righting response in the marine snail, Ilyanassa obsoleta. All four antidepressants (fluoxetine, sertraline, paroxetine, venlafaxine) significantly increased righting time compared with controls with an exposure time as short as 1 h. Dose responses were nonmonotonic with effects seen mainly at the lowest exposure concentrations and shortest duration. The lowest concentration to show an effect was 3.45 μg/L fluoxetine with a 2-h exposure period and is about 3.71 times higher than environmental concentrations. Our results highlight rapid disruption of another foot-mediated behavior in aquatic snails by SSRI-type antidepressants. We discuss these and other reported nonmonotonic dose responses caused by antidepressants in terms of the various possible physiological mechanisms of action in nontarget aquatic species. [ABSTRACT FROM AUTHOR]

Aquatic monitoring programs vary widely in objectives and design. However, each program faces the unifying challenge of assessing conditions and quantifying reasonable expectations for measured indicators. A common approach for setting resource expectations is to define reference conditions that represent areas of least human disturbance or most natural state of a resource characterized by the range of natural variability across a region of interest. Identification of reference sites often relies heavily on professional judgment, resulting in varying and unrepeatable methods. Standardized methods for data collection, site characterization, and reference site selection facilitate greater cooperation among assessment programs and development of assessment tools that are readily shareable and comparable. We illustrate an example that can serve the broader global monitoring community on how to create a consistent and transparent reference network for multiple stream resource agencies. We provide a case study that offers a simple example of how reference sites can be used, at the landscape level, to link upslope management practices to a specific in-channel response. We found management practices, particularly areas with high road densities, have more fine sediments than areas with fewer roads. While this example uses data from only one of the partner agencies, if data were collected in a similar manner they can be combined and create a larger, more robust dataset. We hope that this starts a dialog regarding more standardized ways through inter-agency collaborations to evaluate data. Creating more consistency in physical and biological field protocols will increase the ability to share data. [ABSTRACT FROM AUTHOR]

Wetlands are repositories of unique biodiversity. Wetland organisms are well adapted to their habitat, lying at the interface of aquatic and terrestrial environments. In order to understand their adaptations in a better way, it is essential to grasp the basic properties of the medium in which various organisms live. This is attempted here by first examining the properties of the two contrasting environments, terrestrial and aquatic. We focus primarily on locomotion, touching upon related life processes like respiration, body size and maintaining body balance by employing basic principles of biology and physics. [ABSTRACT FROM AUTHOR]

Four blocks of terrestrial-aquatic ecotones, namely, aquatic, fluctuation, dynamic, and distant ecotones, have been distinguished and characterized. The blocks are differentiated in space and time and represent a complete formation. This is proved by species saturation at the level of the modern structure and previous area genetic relations. [ABSTRACT FROM AUTHOR]

In rivers of the upper Neosho basin, Kansas, USA, lowhead dams influence the downstream dispersal of zebra mussels ( Dreissena polymorpha). We quantified density of planktonic zebra mussel larvae and abundance of recruited individuals at 13 sites in this river-reservoir system to examine potential effects of four lowhead dams on dispersal dynamics of this invasive species. Density and abundance declined downstream from reservoir sources but repeatedly increased at sites inundated by lowhead dams compared to free-flowing areas, with colonization extending 189 river-km. The pattern of zebra mussel dispersal in these rivers is best described by the downstream-march model, with lowhead dams acting as stepping stones. Even though these zebra mussel populations are likely not self-recruiting behind lowhead dams, reproduction at these dams could lead to recruitment downstream. Thus, in rivers with lowhead dams, control of zebra mussel metapopulations may not be accomplished solely by limiting source-sink dynamics from upstream infested lakes. [ABSTRACT FROM AUTHOR]

Freshwater ascomycetes are the predominant fungal colonizers of ligno-cellulosic substrates submerged in freshwater habitats. Although considered important decomposers and a food resource in freshwater food webs, little is known about the influence of environmental factors on their geographical distribution patterns, species richness and community structure. We undertook a study of the distribution of freshwater lignolytic ascomycetes in the Madre de Dios River basin in Peru along an elevational gradient from the headwater regions dominated by the Inambari and Araza Rivers to the lowlands of the Madre de Dios River. The gradient extended from 218 to 3870 m; collections were made at low (<300 m), medium (300-1000 m) and high (>1000 m) elevations. Three separate collecting trips were conducted during the dry seasons over 3 years. Samples of submerged woody debris were returned to the University of Illinois where they were incubated in moist chambers and examined for the presence of sexual and asexual reproductive structures, which were used for identification. GPS location, altitude, water temperature and pH were measured at the time of collection. A total of 2187 vouchered fungal collections representing 268 fungal taxa were collected. One hundred and fifty-nine taxa were collected at low elevations, 201 at middle elevations and 56 at high elevations. Only 33 of 268 taxa occurred at all three elevational ranges. Canonical analyses of principal coordinates and Sørensons Similarity Index of species based on presence/absence data revealed different structuring of freshwater fungal communities at low, middle, and high elevations, indicating a change in species composition along the Andes to Amazon elevation gradient. Mantel's tests demonstrated that beta diversity is strongly impacted by both elevation and pH as rapid taxonomic turnover was associated with both these factors. Of 140 species found in their sexual reproductive state, only ten occurred at all three elevational ranges. The most commonly occurring species was Annulatascus velatisporus, a species with a worldwide distribution. Of 128 taxa found in their asexual reproductive state, 23 occurred at all three elevational ranges. The most commonly collected species was Candelabrum broccchiatum, also a species with a worldwide distribution. Most of the taxa reported from Peru have been reported previously from Asian and/or Australian freshwater tropical habitats. One hundred and three species are new records for South America and 137 species are new records for Peru. About 80 species found in Peru have a pan-tropical distribution. Whether these distribution patterns exist due to vicariance or geodispersal remains to be determined. This study indicates that the composition of fungal communities in mountainous areas is influenced by elevation and has implications for the effects of global warming. [ABSTRACT FROM AUTHOR]

The invasive aquatic plant species Elodea nuttallii could pose a considerable risk to European freshwater ecosystems based on its current distribution, rate of spread and potential for high biomass. However, little research has been conducted on the impacts of this species on native biota. This study takes an ecosystem-wide approach and examines the impact of E. nuttallii on selected physicochemical parameters (dissolved oxygen and pH), algae, invertebrate and macrophyte communities. Elodea nuttallii had small but significant impacts on plant, invertebrate and algal species. The richness of algal periphyton was lower on E. nuttallii than on native macrophytes. The taxonomic composition of invertebrate communities associated with E. nuttallii differed from that associated with similar native plant species, but did not differ in terms of total biomass or species richness. Macrophyte species richness and total cover were positively correlated with percentage cover of E. nuttallii. Not all macrophyte species responded in the same way to E. nuttallii invasion; cover of the low-growing species, Elodea canadensis and charophytes were negatively correlated with E. nuttallii cover, whilst floating-rooted plants were positively correlated with E. nuttallii cover. All observed differences in the macrophyte community were small relative to other factors such as nutrient levels, inter-annual variation and differences between sites. Despite this, the observed negative association between E. nuttallii and charophytes is a key concern due to the rarity and endangered status of many charophyte species. [ABSTRACT FROM AUTHOR]