Biotic Effects Research Articles

Improvement of wastewater and water quality via a full-scale ozonation plant? – A comprehensive analysis of the endocrine potential using effect-based methods

Micropollutants (MPs), especially endocrine disrupting compounds (EDCs), are mainly released from WWTPs into surface water bodies and can subsequently lead to adverse effects in biota. Treatment with ozone proved to be a suitable method for eliminating such MPs. This method was implemented at the WWTP Aachen-Soers by commissioning the largest full-scale ozonation plant in Europe at the moment. Recently, effect-based methods (EBMs) have been successfully proved for compliance monitoring, e.g. estrogenic compounds. Therefore, the impact of ozone treatment on endocrine potential (agonistic and antagonistic) of treated wastewater was investigated using the ERα- and AR CALUX assays. Additionally, the impact on the receiving stream and a potential preload of the water body was assessed. Therefore, the current study could deal as a case study for small rivers being highly impacted by WWTPs.The estrogenic potential was nearly fully eliminated after ozone treatment. Contrary, the antagonistic (anti-estrogenic and anti-androgenic) potential did not show a clear elimination pattern after ozone treatment independent of the applied ozone dosage and control system. Therefore, further investigations are required regarding the antagonistic potential. Additionally, preloading of the receiving stream was found during the study period. One significant impact is a rain overflow basin (ROB) located upstream of the WWTP effluent. The highest endocrine potential was found after a ROB overflow (2.7 ng EEQ/L, 2.4 μg TMX-EQ/L, 104 μg FLU-EQ/L), suggesting that such runoff events after a heavy rainfall may act as a driver of endocrine loading to the water body. This manuscript contributes significantly to the basic understanding of the efficiency of eliminating the endocrine potential of ozone treatment by, e.g., showing that there is a further need for improving the removal efficiency of antagonistic potential. Moreover, it highlights the need to include other point sources, such as ROBs, to assess polluted surface waters comprehensively.

Protists modulate fungal community assembly in paddy soils across climatic zones at the continental scale

Soil fungi have important functions in agricultural ecosystems. They promote crop growth by driving soil nutrient cycling and by forming mycorrhizal symbioses with crop species. Most studies on soil fungi have focused on detecting the edaphic factors that structure fungal communities, but little is known about how climate influences the soil microbiome. Moreover, a profound understanding of how soil fungal communities are modulated by other soil organisms, such as protist predators, is lacking. We investigated the spatial succession of fungal assemblages in China and their potential predator-prey relationships with protists across four climatic zones using 18S rDNA amplicon sequencing. Although stochastic processes dominated the assembly of fungal communities, deterministic drivers of community assembly were more important in high-latitude climatic zones (that is, in the temperate and continental zones) than in low-latitude climatic zones (that is, in the tropics and subtropics). Random forest and variation partitioning analyses showed that biotic effects influenced fungal communities as much as abiotic effects. Biotic factors were better predictors of the abundance of several saprophytic and mycorrhizal fungi than abiotic factors. This finding was further supported by a network analysis, which indicated that the intensity of fungi-protist interactions may stimulate the divergence of prey fungal communities.Our results reveal for the first time the nonnegligible effects of biotic factors on soil fungal community assembly across substantially different climatic zones. The biological mechanisms underlying these effects can be well understood within a predator-prey relationship framework in which protists exert strong top-down control on fungal communities.

Natural attenuation mechanism of hexavalent chromium in a wetland: Zoning characteristics of abiotic and biotic effects

Natural wetland has great retention effect on Cr(VI) migration due to its abiotic and biotic reduction abilities, however, the zoning characteristics of dominating reduction mechanism along Cr(VI) pollution plume in wetland is still unclear. In this study, a Cr(VI) contaminated natural wetland was explored to investigate the distributions of Cr and Fe in groundwater and sediment, and their relationship with microorganisms according to metagenomics, aiming to reveal the natural attenuation mechanism of Cr(VI) from the perspective of zoning characteristics of abiotic and biotic effects. The wetland was divided into contaminated zone, transition zone and uncontaminated zone according to the contamination states of groundwater and sediment. At the upstream of contaminated zone, Cr(VI) concentration in groundwater was as high as 26.7 mg L−1, which has significant inhibition effect on microbial growth, and thus chemical reduction of Cr(VI) by natural organic matters (NOMs) dominated in this area, leading to the increasing of H/C and O/C ratios of NOMs because of the oxidation of aromatic moieties. At the downstream of contaminated zone, Cr(VI) concentration in groundwater decreased to less than 4.46 mg L−1 resulting from dilution and attenuation, but the microbial community was altered substantially, chromate resistant bacteria with ChrA, ChrR, NemA and AzoR genes were enriched, such as Sphingomonas, Mesorhizobium and Comamonadaceae, and thus the direct microbial reduction of Cr(VI) dominated in this area. While at the transition zone, which is located at the front edge of the pollution plume, Cr(VI) could only reached in this area intermittently, and the microbial community remained similar to that of the uncontaminated zone, dominated by Chloroflexi and Acidobateria phylum with dissimilatory ferric iron reduction capacity, and thus Cr(VI) was indirectly reduced by Fe2+ intermediately in this area.

Disentangling biotic and abiotic drivers of intraspecific trait variation in woody plant seedlings at forest edges.

In fragmented forests, edge effects can drive intraspecific variation in seedling performance that influences forest regeneration and plant composition. However, few studies have attempted to disentangle the relative biotic and abiotic drivers of intraspecific variation in seedling performance. In this study, we carried out a seedling transplant experiment with a factorial experimental design on three land‐bridge islands in the Thousand Island Lake, China, using four common native woody plant species. At different distances from the forest edge (2, 8, 32, 128 m), we transplanted four seedlings of each species into each of three cages: full‐cage, for herbivore exclusion; half‐cage, that allowed herbivore access but controlled for caging artifacts; and no‐cage control. In the 576 cages, we recorded branch architecture, leaf traits, and seedling survival for each seedling before and after the experimental treatment. Overall, after one full growing season, edge‐induced abiotic drivers and varied herbivory pressure led to intraspecific variation in seedling performance, including trade‐offs in seedling architecture and resource‐use strategies. However, responses varied across species with different life‐history strategies and depended on the driver in question, such that the abiotic and biotic effects were additive across species, rather than interactive. Edge‐induced abiotic variation modified seedling architecture of a shade‐tolerant species, leading to more vertical rather than lateral growth at edges. Meanwhile, increased herbivory pressure resulted in a shift toward lower dry matter investment in leaves of a light‐demanding species. Our results suggest that edge effects can drive rapid directional shifts in the performance and intraspecific traits of some woody plants from early ontogenetic stages, but most species in this study showed negligible phenotypic responses to edge effects. Moreover, species‐specific responses suggest the importance of interspecific differences modulating the degree of trait plasticity, implying the need to incorporate individual‐level responses when understanding the impact of forest fragmentation on plant communities.

Soil biotic effects and competition; What are the mechanisms behind being a successful invader?

The global threat of plant invasions to native ecosystems mandates an understanding of the mechanisms that determine invasion success. While some exotic species establish, spread and impact native ecosystems, others establish with little or no measurable impact. Competitive ability has been highlighted as a key mechanism influencing invasion success and impact, but there is growing evidence that interactions between plants and soil biota may also be important. In particular, escape from natural enemies during the early stages of establishment may give exotic species an advantage over native species subject to their own natural enemies in the soil. Here, we evaluated whether the invasion success and impact of exotic grass species could be explained by competitive superiority over resident native species, advantages gained from the positive effects of native soil communities, or both. We assessed the competitive abilities of six grass species that vary in their invasion success relative to three widespread native grasses, quantified the effects of native soil microbial communities on the performance of both native and exotic grass species, and determined whether there was an interaction between competitive and soil effects. Overall, we found that exotic species were stronger competitors than natives and that native soil effects were weak and did not predict invasiveness. Differences in species relative competitive abilities also did not correlate with invasiveness but demonstrate how some exotic species could outcompete natives and suppress their growth during the invasion process.

Modelling spatial and temporal patterns in bioturbator effects on sediment resuspension: A biophysical metabolic approach

Tidal flats are biogeomorphic landscapes, shaped by physical forces and interaction with benthic biota. We used a metabolic approach to assess the overarching effect of bioturbators on tidal landscapes. The benthic bivalve common cockle (Cerastoderma edule) was used as model organism. The effect of C. edule on sediment resuspension was approximated as a function of the overall population metabolic rate per unit of area. We combined i) laboratory observations on how C. edule affect sediment resuspension along gradients of bioturbation activity, sediment cohesiveness and hydrodynamic force with ii) spatial data on the natural distribution of intertidal C. edule populations. This allowed us to build an integrated model of the C. edule effect on sediment resuspension along the tidal gradient. Owing to the temperature dependence of metabolic rate, the model also accounted for seasonal variation in bioturbators activity.Laboratory experiments indicated that sediment resuspension is positively related to the metabolic rate of the C. edule population especially in cohesive sediments. Based on this observation, we predicted a clear spatial and seasonal pattern in the relative importance of C. edule contribution to sediment resuspension along a tidal transect. At lower elevations, our model indicates that hydrodynamics overrules biotic effects; at higher elevations, inter-tidal hydrodynamics should be too low to suspend bioturbated sediments. The influence of C. edule on sediment resuspension is expected to be maximal at the intermediate elevation of a mudflat, owing to the combination of moderate hydrodynamic stress and high bioturbator activity. Also, bio-mediated sediment resuspension is predicted to be particularly high in the warm season.Research into metabolic dependency of bio-mediated sediment resuspension may help to place phenomenological observations in the broader framework of metabolic theories in ecology and to formulate general expectations on the coastal ecosystem functioning.

Efficient Dye Degradation via Catalytic Persulfate Activation using Iron Oxide-Manganese Oxide Core-Shell Particle Doped with Transition Metal Ions

Organic-pollutants released into water bodies pose serious concerns because of its detrimental effects in aquatic biota, environment and economy. Water remediation using persulfate based advanced oxidation process is one of the emerging techniques. In this study, we have developed iron oxide-manganese oxide core–shell nanoparticles doped with transition metal ions for the efficient degradation of bromophenol blue dye, for the first time. Here, the transition metal ion doped MnOx shell enables efficient persulfate activation while the magnetic core facilitate in the effective recovery of used particles. The synthesized particles were characterized by X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and vibrating sample magnetometer. The presence of dopants is found to significantly change the ratio of Mn3+ to Mn4+, reactivity and mobility of lattice oxygen in doped samples. Silver ion doped MnOx showed the highest dye degradation efficiency of ~91% with 1.8 wt% nanoparticles, due to the enhanced reactivity and mobility of lattice oxygen activity of the core–shell nanoparticle in presence of Ag ions in persulfate activation. From the experimental results, the mechanism of activation of persulfate by nanoparticles is elucidated. Our findings provide a new platform for efficient water remediation using dual functional core shell magnetic nanoparticles.

Influence of hail suppression systems over silver content in the environment in Aragón (Spain). I: Rainfall and soils

In several countries, hail is considered as the most harmful climatic phenomenon from an agricultural perspective. The surroundings of the Gallocanta Lake (North-East Spain), is one of the areas where the storms affecting the Ebro Valley are formed. For this reason, silver iodide from hail suppression systems has been emitted to the atmosphere for half a century.Nowadays, there is an increasing social concern about the potential environmental consequences of this activity, which has promoted the analysis of the influence of hail suppression systems regarding the amount of silver concentration in the ecosystem. This study focuses on silver atmospheric deposition and its accumulation in soils.To this end, silver concentrations in rainfall (5 gauges, 16 samples per site, from April 2017 to March 2019) and soils (72 samples) distributed across the hail suppression network managed by the Anti-hail Consortium of Aragón, were analysed.The results show that the amount of silver is much higher in rainfall gauges and soils close to ground-based silver iodide generators (85 μg/m2·day and 10 mg/kg soil, respectively), but concentrations considerably decrease when samples are collected far from them (downing to 0.3 μg/m2·day and 0.1 mg/kg soil).Apart from the samples obtained nearby silver iodide generators, most of the other soil samples display silver concentrations below the legal threshold established for the most vulnerable activities (1 mg/kg soil in agricultural and forestry land uses). Nevertheless, silver content, both in precipitation and in soils, is higher in regions where hail suppression has been developed for decades when compared to nearby areas in which silver iodide emissions did not occur.Silver content observed in soils is not high, but their cumulative effect in sediments and biota should be analysed, which is the aim of the second part of the present study.

Seasonal Variations in Flocculation and Erosion Affecting the Large‐Scale Suspended Sediment Distribution in the Scheldt Estuary: The Importance of Biotic Effects

AbstractMany estuaries exhibit seasonality in the estuary‐scale distribution of suspended particulate matter (SPM). This SPM distribution depends on various factors, including freshwater discharge, salinity intrusion, erodibility, and the ability of cohesive SPM to flocculate into larger aggregates. Various authors indicate that biotic factors, such as the presence of algae and their excretion of sticky transparent exopolymer particles (TEP), affect the flocculation and erosion processes. Consequently, seasonality in these biotic factors may play a role in the observed seasonality in SPM. Whereas the impact of abiotic factors on seasonality in SPM is well studied, the relative contribution of biotically induced seasonality is largely unknown. In this study, we employ two approaches to assess the aggregated importance of biotically induced seasonality in flocculation and erosion on seasonality in SPM in the Scheldt estuary. In the first approach, we focus on seasonality of in situ observations in the Scheldt estuary of turbidity, floc size, Chlorophyll‐a, and TEP, showing that the abiotic parameters show seasonality, while seasonality in TEP is ambiguous. The second approach concerns a reverse engineering method to calibrate biotically affected parameters of a coupled sediment transport‐flocculation model to turbidity observations, allowing us to compare the modeled SPM concentrations to the observations. Driven by seasonality in freshwater discharge, the model captures the observed seasonality in SPM without requiring biotically induced seasonality in flocculation and erosion, which is supported by the absence of seasonality in TEP.

Bio-climate affects hillslope and fluvial sediment grain size along the Chilean Coastal Cordillera

Sediment dynamics in river catchments are controlled by tectonics, climate, and biota effecting material production on hillslopes and transport of sediment from their source to the catchment outlet. Tectonics create topography and control erodibility of the bedrock material, whereas climate controls the efficiency of weathering and transporting processes. In contrast, the effects of biota (i.e. vegetation) are more ambiguous. Vegetation accelerates bio-chemical weathering and effects mass wasting through uprooting, trapping and stabilizing hillslope material. Furthermore, vegetation exerts a strong control on the grain size distribution of hillslope sediments and thus on sediment rooting through catchments.In this study we compare grain size distributions of hillslope and channel sediments collected in four headwater catchments located in the Chilean Coastal Cordillera covering a strong bio-climatic gradient. 76 volumetric bulk samples were taken with grain sizes ranging from clay (d = 0.3 μm) to boulders (d > 300 mm).Results show that the production of fine material is strongly dependent on bio-chemical weathering intensity and hence humidity. The coarse fraction in hillslope material and channel sediments increases from arid to sub-humid conditions, presumably reflecting a higher intensity of mass wasting processes. Channels show varying degrees of armouring reflecting nonselective and thus transport-limited conditions under arid climate that are contrasted by relatively well sorted and armoured channel sediments in the humid and vegetated catchments, indicating size selective and supply-limited transport conditions. Channel grain sizes generally show high similarity to hillslope grain sizes of the same catchment, revealing the strong dependency of channel sediments on hillslope supply, at least in headwater catchments, transferring a bio-climatic control from the hillslopes to the channel system.

Resolving the effects of environmental micro- and nanoplastics exposure in biota: A knowledge gap analysis.

The pervasive spread of microplastics (MPs) and nanoplastics (NPs) has raised significant concerns on their toxicity in both aquatic and terrestrial environments. These polymer-based materials have implications for plants, wildlife and human health, threatening food chain integrity and ultimate ecosystem resilience. An extensive - and growing - body of literature is available on MP- and NP-associated effects, including in a number of aquatic biota, with as yet limited reports in terrestrial environments. Effects range from no detectable, or very low level, biological effects to more severe outcomes such as (but not limited to) increased mortality rates, altered immune and inflammatory responses, oxidative stress, genetic damage and dysmetabolic changes. A well-established exposure route to MPs and NPs involves ingestion with subsequent incorporation into tissues. MP and NP exposures have also been found to lead to genetic damage, including effects related to mitotic anomalies, or to transmissible damage from sperm cells to their offspring, especially in echinoderms. Effects on the proteome, transcriptome and metabolome warrant ad hoc investigations as these integrated "omics" workflows could provide greater insight into molecular pathways of effect. Given their different physical structures, chemical identity and presumably different modes of action, exposure to different types of MPs and NPs may result in different biological effects in biota, thus comparative investigations of different MPs and NPs are required to ascertain the respective effects. Furthermore, research on MP and NP should also consider their ability to act as vectors for other toxicants, and possible outcomes of exposure may even include effects at the community level, thus requiring investigations in mesocosm models.

Exposure to sublethal concentrations of the glyphosate-based herbicide Faena® increases sensitivity in the progeny of the American cladoceran Daphnia exilis (Herrick, 1895).

The use of herbicides has increased over the last decades. Glyphosate is the most widely used herbicide commercialized in more than 750 formulations. While information about glyphosate's toxicity on different non-target aquatic organisms has been vastly documented, we know little about the transgenerational effects in aquatic biota. This study determined the cross-generation effects produced by the glyphosate-based herbicide Faena® on the American cladoceran Daphnia exilis. Measured endpoints were survival, reproductive responses, metabolic biomarkers, and the size of neonates. D. exilis was exposed to glyphosate concentrations of 2.09, 2.49, and 3.15 (mg L-1) (as content in Faena®) during 21 days starting from neonates, at 25°C, 16:8 photoperiod, fed with 8 × 105 cells mL-1 of Pseudokirchneriella subcapitata. The LC50 was 4.22 mg L-1. Survival, accumulated progeny, and the number of clutches in the parental generation (P1) were significantly higher than those observed in the first generation (F1). Exposure to the herbicide completely inhibited reproduction in the F1. The size of the neonates varied among treatments and broods in P1; nevertheless, neonate size (body and total lengths, as well as body width) was significantly affected in F1. Toxic effects on the survival and reproduction of D. exilis were significantly increased in the F1 exposed to Faena®. Results warn about the augmented effect on progeny where parents were exposed to this herbicide. Multigenerational adverse effects could be expected in freshwater zooplankton exposed to Faena®. The frequently claimed low toxicity of glyphosate must be revised to control the indiscriminate use of this herbicide.

Biogeomorphological domination of forest landscapes: An example from the Šumava Mountains, Czech Republic

Biogeomorphological and ecological succession following a disturbance or the exposure of new ground often proceeds in stages, from domination by abiotic, geophysical factors through stages characterized by increasing effects of biota, biotic-abiotic feedbacks, and eventual domination by ecological processes. However, some studies in forest settings have found more varied development patterns, including persistence of states dominated by biogeomorphic feedbacks. In this study we investigated this phenomenon In Norway spruce (Picea abies (L.) Karst.) dominated forests on the main ridge of the Šumava Mountains in the Czech Republic along the German and Austrian borders. Throughout most of the Holocene, Picea has strongly influenced microtopography and soil/regolith characteristics so as to inhibit hydrological connectivity and development of surface drainage, and maintain hydromorphic soil conditions. These strongly historically and geographically contingent ecosystem engineering effects create and maintain habitat that favors spruce over other trees. These interactions have maintained a landscape dominated by biogeomorphic feedbacks.

Inter-annual climatic variability modulates biotic interactions on early Nothofagus pumilio community development

ABSTRACT Background: Despite extensive efforts to understand how biotic interactions and community dynamics respond to changes in environmental conditions many knowledge gaps remain. Assessing biotic interactions involving little studied organisms, such as the biological soil crust (BSC), can widen our understanding of ecosystem functioning. Aims: (1) to quantify the effects of two pioneer communities, one of shrubs and the other of BSC, on the survival and early growth of Nothofagus pumilio tree seedlings on land exposed after glacier retreat, and (2) evaluate how these biotic effects changed according to variations in environmental conditions. Methods: We conducted seedling transplants, at four glacier forelands in the Patagonian Andes across a precipitation gradient in three microsite types: bare soil, soil-covered BSC, low-stature vegetation cover by the creeping dwarf-shrub Empetrum rubrum (ER). Results: N. pumilio seedling survival was related to inter-annual climatic variations, with higher survival in cool-wet years. These effects depended on microsite conditions, with a tendency towards highest survival in BSC. Conversely, microsite type was the dominant factor affecting seedling leaf area, with a trend towards bigger leaves in bare soil. Conclusions: At regional scales, inter-annual climatic variability modulates N. pumilio colonisation. However, microenvironmental differences imposed by cover type introduce important variations. Accounting for interactions between climate and pre-existing communities is essential for predicting climate change impacts on plant community development.

Phylogenetic diversity efficiently and accurately prioritizes conservation of aquatic macroinvertebrate communities

AbstractLand degradation is a leading cause of biodiversity loss, and understanding its consequences on freshwater ecosystems remains a priority for improving the effectiveness of restoration practices and ecosystem assessments. Freshwater monitoring programs use macroinvertebrates to assess the biotic effects of degradation and management actions, often using the ratio of observed to expected taxa at a site—O/E—for this purpose. Despite the power of the O/E approach, large amounts of data are required to generate an expectation and it can be difficult to define a threshold value for degraded sites. An alternative assessment tool is phylogenetic diversity, which is widely used in academic biology but rarely applied in management despite empirical correlations between phylogenetic diversity and management targets such as ecosystem structure and function. Here, we use macroinvertebrate data from 1400 watersheds, collected since 1998, to evaluate the potential for phylogenetic metrics to inform evaluations of management practices. These watersheds were chosen because their low disturbance levels and high habitat heterogeneity have made them problematic to assess with O/E. Phylogenetic diversity detected degradation of assemblages and was sensitive enough to parse impacts to inform management actions. This is particularly notable given the phylogenetic metrics, unlike O/E, did not require additional “baseline” data. Site disturbance and broader environmental drivers strongly predicted site phylogenetic structure, providing management objectives to increase site quality. We call on others to consider using phylogenetic diversity to complement existing O/E schemes, particularly in systems where O/E is insufficient to prioritize management objectives.

Trace elements in aquatic environment. Origin, distribution, assessment and toxicity effect for the aquatic biota

Trace elements contamination and accumulation in bottom sediment represents a risk to environment and aquatic biota. Their anthropogenic or natural discharge, extension and cumulation can cause large scale of ecological destructions. Bioaccumulation and biomagnification is capable of leading to toxic level of these chemical substances in fish and other fresh water organisms (benthos, zooplankton), even when the exposure is low. The fish contamination through trophic structure can cause serious consequences to human health.The aim of the manuscript was to assemble and summarize the latest literature on the environmental and the aquatic biota effects of trace element contamination of bottom sediments. The article is also a review of new methods for trace elements elimination and their assessment to impact on aquatic organisms. Based on collected scientific publications in last 20 years the most common and important trace elements in aquatic ecosystem are Chromium, Arsenic, Mercury, Cadmium and Copper. These compounds are dangerous for living organisms and can disrupt their homeostasis as well as a cardiovascular, nervous and digestive system. Nowadays exist many instrumental methods, which are available to determine the trace element concentration such as PMF, INNA, BCR, XRF and bioassay. In searched studies the most preferred and used analyse of trace element concentration in aquatic bottom sediments is bioassay. This biological method is good complement to physical and chemical analyses in procedures of sediment quality assessment. Bioassay method can indicate sensitive response of planktonic organisms to various trace elements and provide information about the real risk to aquatic life.

Soil biota suppress maize growth and influence root traits under continuous monoculture

This study investigated maize-soil biota interactions as well as the soil legacy effects of continuous monoculture (CM) on maize performance. We conducted a glasshouse experiment that compared the performance of maize inoculated with living or sterilized soil inocula collected from experimental field plots with cropping histories of 1 to 5 years of continuous maize monoculture, where the soil type is Nicollet clay loam with moderate fertility. We measured the biomass, yield, root traits and leaf nutrients of maize as well as eukaryotic soil organisms. Inoculation with living soil dramatically reduced maize biomass and yield compared to inoculation with sterilized soil, showing CM to have strong negative soil biotic legacy effects on maize. Nonetheless, the strength of soil biotic effects on most maize variables were relatively stable over time under CM. The response of maize total biomass to living soil inoculation correlated positively with arbuscular mycorrhizal (AM) fungal abundance but negatively with soil fauna abundance, whereas it did not relate with the abundance of plant pathogenetic fungi or herbivorous nematodes. The roots showed acquisitive syndromes (high specific root length but low root diameter) in sterilized soil but conservative syndromes (opposite traits) in living soil. The responses in root system structure were tightly related with AM fungal diversity and community composition. Our study shows strong and stable negative effects of soil biota on maize under CM. The complex effects of soil biota on maize performance highlight the need to explore the functions of different groups of soil organisms to better understand and control negative soil legacy effects in agroecosystems.

Discrimination of species and populations of the genus Cichla (Cichliformes: Cichlidae) in rivers of the Amazon basin using otolithic morphometry

ABSTRACT The genus Cichla is a highly diverse group, with 16 species already described. Externally, some species are very similar and discriminating between them may be very difficult. Nevertheless, discrimination of fish stocks is essential for management purposes. Morphometric analyses of otoliths have been successfully used to distinguish species and fish stocks, especially in marine environments. This study evaluated whether sagittal otolith shape can be used to discriminate among the species Cichla temensis, C. monoculus, and C. orinocensis, as well as within populations of C. temensis in rivers of the Amazon. Shape indices and Fourier coefficients were used to describe the shape of the otoliths. Among the groups of species, the morphology of the sagittal otolith of C. temensis was totally distinct from the species C. monoculus and C. orinocensis. While among populations of C. temensis, individuals from the Negro and Jatapú Rivers were different, regardless of the methods used. These results confirm the ability to differentiate species and populations by using the morphology of otoliths. However, more research is needed to verify the role of genetic versus environmental and biotic effects, and thus be able to explain the discrimination observed in otoliths.

Drivers of Change in Estuarine and Coastal Marine Environments: An Overview

Anthropogenic climate and non-climate drivers of change are causing significant impacts on estuarine and coastal marine environments. Climate change poses a particular threat to the structure and function of biotic communities in these environments because it acts on the most extensive temporal and spatial scales relative to other anthropogenic drivers of change. The interaction of multiple environmental drivers exacerbates degradation of ecosystem condition. Estuaries are most susceptible to climate-change mediated biotic shifts and direct anthropogenic impacts due to burgeoning human population growth and development in coastal watersheds. Multiple anthropogenic drivers of change, which often interact synergistically, alter physical, chemical, and biological characteristics. Ecological responses may be increasingly nonlinear, with cumulative effects manifested by marked changes in organism abundance, distribution, diversity, and productivity. Detrimental biotic effects in impacted coastal environments cascade up from individual organisms to population and community levels, culminating in ecosystem-level changes including reduced services. Multiple drivers of change and their impacts are increasing in estuarine and coastal marine environments with greater anthropogenic forcing in the coastal zone and global effects of climate change, creating greater challenges for environmental management and conservation programs.

The impacts of waterbird-mediated elemental enrichment on chironomid assemblages from island ponds in Lake Ontario

Ring-billed gulls (Larus delawarensis) and double-crested cormorants (Phalacrocorax auritus) have nested in dense colonies across the Laurentian Great Lakes since their rapid population expansions during the early- and mid-20 th century, respectively. Dated sediment cores from ponds located near nesting sites have been used to track the history of these large colonies on islands in eastern Lake Ontario. However, less is known about avian-mediated biotransport of contaminants to these nesting sites and its effects on aquatic biota at mid-trophic levels, such as chironomids. Here, we used a paleolimnological approach to determine the extent of possible avian- mediated metal(loid) contamination of ponds in nesting sites compared to reference sites. Water from avian-im- pacted ponds had higher concentrations of Al, Cd, Cu, Fe, Pb, and Se than the reference ponds, and exceeded the Canadian Council of Ministers of the Environment (CCME) guidelines for the protection of aquatic life at some sites. Down-core geochemical analysis of elements in sediments showed that concentrations of Cd, Se, and Zn were significantly higher in impacted ponds than in reference sites and correlated significantly with stable nitrogen isotopes, a marker of avian-derived nitrogen. In sites impacted by ring-billed gulls, Cd and Zn concentrations in sediments exceeded or approached those at which frequent adverse biotic effects are expected. Metal contamination was linked to altered chironomid assemblages, with subfossil remains in the avian-impacted sites including more taxa tolerant of heavy metal contamination than reference sites. Notably, chironomids were largely absent from the sites with the highest metal concentrations. These findings have implications for understanding and managing contaminant cycling in the Great Lakes, as waterbirds that nest in dense colonies can act as biovectors that transport metals to new and unexpected locations.