Invasive non-native plants can cause ecological, economic, and health impacts worldwide, yet how these impacts cascade from a primary producer to multiple consumers remains poorly understood. Using aquatic microcosms, we examined how replacing the native reed Phragmites australis with the morphologically similar invader Arundo donax (0–100% leaf litter biomass gradient) alters water physicochemistry, microeukaryote assemblages, and the development of Culex pipiens mosquito larvae in northeastern Spain. Microeukaryotes are key players in microbial food webs, and mosquito larvae are microbial consumers. Increased A. donax leaf litter % disrupted microeukaryote taxonomic composition and functional guild structure, mainly due to changes in the density of flagellates, planktonic ciliates, and micrometazoa. Mosquito larval development was mainly driven by changes in water physicochemistry, flagellates, and amoebae. Microcosms with A. donax produced more mosquito pupae of greater weight and shorter development times. Effects emerged even when only 25% of P. australis biomass was replaced by A. donax, suggesting potentially strong nutrient limitations from P. australis leaf litter and posing challenges for defining a management “safe threshold” for A. donax when eradication is unfeasible. This study highlights A. donax leaf litter as a potential promoter of mosquito development and underscores the role of water chemistry and microeukaryotes in mediating its effects.

Nature-Based Solutions (NBS) for water treatment can mitigate pollution while enhancing aquatic biodiversity. However, their safe and effective implementation requires improved understanding of multitrophic impacts to key contemporary stressors, such as invasive fish species and nutrient imbalances. This study addresses this critical knowledge gap by examining how Gambusia holbrooki, a widely distributed invasive fish, and high nitrate levels, typical of European Nitrate Vulnerable Zones, influence the ecological performance of experimental water-treatment ponds. We assessed impacts on water quality, mosquito proliferation, and the overall planktonic and benthic community in a 11-week outdoor mesocosm study. Gambusia holbrooki did not significantly affect water physicochemistry or nutrient levels, nor did it contribute to mosquito control, as larvae were absent in all treatments. However, the fish significantly altered ecosystem functioning by modulating organic matter processing, increasing benthic chlorophyll-a, and reducing specific zooplanktonic and benthic taxa. Nitrate addition acted as a powerful "bottom-up" driver, shifting the community structure toward primary producers such as Tetraedron and Cosmarium, while reducing consumer richness and biomass at the whole-mesocosm scale. These findings suggest that the presence of G. holbrooki may undermine the dual function of pond-based NBS to treat water and support native biodiversity. Further studies could use the tolerant taxa identified in this study to optimize the ecological functionality of pond-based NBS designed to intercept and treat agricultural pollutants.

Infectious agents shape fish populations by inducing lethal and sublethal changes that alter nutrient metabolism and metal bioaccumulation. These shifts can manifest as changes in the ionome—the specific combination of essential and non-essential chemical elements defining the whole-body composition of an individual. Understanding how pathogens shape the fish ionome is critical for developing advanced monitoring tools and clarifying the ecological roles of hosts and their pathogens. This study reports the first documented outbreak of Citrobacter freundii, Pseudomonas aeruginosa, Pseudomonas mosselii, and Shewanella xiamenensis bacterial infections in wild-caught eastern mosquitofish (Gambusia holbrooki) from three populations in Extremadura, southwestern Spain. Under laboratory-controlled conditions, we established associations between these bacterial outbreaks and the whole-fish body ionome of G. holbrooki. We compared 19 chemical elements and seven elemental ratios among diseased fish, healthy fish at the outbreak, and individuals fully recovered 100 days post-infection following antibiotic treatment. The fish ionome clearly discriminated between diseased and healthy states, and the response was consistent across all three populations. Our findings support the utility of whole-fish body elemental composition in G. holbrooki as a biomarker for environmental monitoring. Furthermore, as the bacterial infections were associated with the capture and transport-induced stress of wild individuals, this study provides critical data on the opportunistic pathogens that may be co-introduced into recipient ecosystems through the release of this widely distributed invasive fish species.

Antarctic benthic ecosystems are currently threatened by global change and direct human impact. Pollution from local human activities is among the most relevant emerging hazards affecting Antarctic organisms. Micro-litter (ML) has already been found in Antarctic marine ecosystems, including diverse benthic fauna. This study characterised and quantified ML in a common soft-bottom filter-feeding solitary ascidian, Cnemidocarpa verrucosa (Lesson, 1830), along the Antarctic Peninsula from 62° S to 67° S, focusing particularly on Deception Island. Study sites included Johnsons' Bay (Livingston Island), Deception Island (South Shetland Islands), Uruguay Island (Yalour Islands), and Ryder Buttress (Ryder Bay, Adelaide Island). More than half of the analysed organisms contained at least one ML particle, with an average of 0.14 ± 0.26 items per gram (viscera wet weight) and 1.62 ± 1.79 items per individual. Microplastics represented 37 % of the total ML items found. Along the Antarctic Peninsula, significantly higher amounts of ML were found in Johnsons' Bay and Uruguay Island. Within Deception Island, significantly higher ML abundances were found in Murature, at the innermost part of the island. The most common items found were black or blue cellulosic fibres within the smallest size range analysed (100-500 μm). We suggest that variations in ML among sites could be mainly due to the different intensity of anthropogenic activities, although environmental characteristics of the locations (i.e. currents, bottom type) also played a key role in its distribution. To the best of our knowledge, this is the first study to assess ML pollution in an Antarctic ascidian and it also represents the southernmost benthic invertebrate study regarding ML along the Antarctic Peninsula. We believe this research may contribute to the development of policies to protect the Antarctic marine benthos from human pollution and improve their management.

Studies that investigate the effects of a given invasive exotic species within real-world contexts are essential for informing effective management decisions. Here, we used extensive surveys of stream reaches in north-eastern Spain to test whether the presence of the widely distributed invasive exotic riparian plant Arundo donax is detrimental to the conservation of riverine fishes. To explore potential impacts of A. donax at different temporal scales, we examined fish responses using indicators of relatively recent effects (body-condition index) and longer lasting effects (functional diversity indices, taxonomic richness, and the relative abundance of 12 fish species). We found correlative evidence for net positive effects of the presence of A. donax on native fish richness and body condition but negative effects on the overall functional diversity of fish assemblages, including invasive exotic and translocated native fish species. Our analyses also revealed significant interactions between A. donax and local stream conditions, suggesting that these net effects of the plant on fish might shift in direction in some circumstances. In particular, several indicators at the fish community scale support that the presence of A. donax may be beneficial to fishes in streams with high Strahler order values, in-stream habitat diversity and lack of channelization. The plant may provide shelter and refugia to fish in these medium, low-land Mediterranean streams with typically poor cover of high riparian vegetation. Therefore, without overlooking the serious threats caused by biological invasions, this study illustrates that, at least under specific environmental conditions, the local removal of A. donax alone may not achieve the desired ecological outcomes if pre-existing fish-habitat relationships are not taken into account.

Marine microdebris (MD) seem to be widespread in benthic invertebrates, even in the most remote areas of the planet such as Antarctica, although the information available is still very scarce. Here we provide a detailed quantification and characterization of the MD found on three common bivalve species (Aequiyoldia eightsii, Thracia cf. meridionalis, and Cyclocardia astartoides) inhabiting shallow areas in Johnsons’ Bay, Livingston Island (South Shetland Islands, Antarctica) as a snapshot of the MD present. On average, these bivalves contained 0.71 ± 0.89 items per individual and 1.49 ± 2.35 items per gram, being comparable to the few previous existing studies in other Antarctic areas. Nearly half of the organisms analysed here (45.6 %), contained at least one item. No significant differences were found in the three bivalve species. As far as we know, this is the first study to analyse and compare MD in three bivalve species in the Antarctic Peninsula. Although our results indicate bivalves are as not as polluted as in other areas of the planet, this is remarkable since this is considered one of the last pristine areas of the world. Our results point to local activities as the main source of MD pollution in Livingston Island, although global pollution cannot be discarded. We believe this research provides a useful baseline for future studies and will contribute to develop policies and strategies to preserve Antarctic marine ecosystems from MD pollution.

This study assessed the impact of electrical conductivity (EC) on the microeukaryotic community and pollutant removal efficiency in full-scale wastewater treatment plants (WWTPs) in Catalonia, Spain. Monthly samples from seven WWTPs (2010-2021) were collected, with microbial communities identified by microscopy and effluent quality parameters measured. Linear mixed-effects models (LMER), indicator species analysis (IndVal), and structural equation modeling (SEM) were used to evaluate the effects of EC on WWTP operation and microbial communities. EC levels varied widely among WWTPs (800 to 15,000 mu S cm- (1)), with mean removal rates generally low, not exceeding 26 %. EC removal was inversely correlated with organic matter removal (p < 0.05). IndVal analysis revealed distinct microbial communities associated with each WWTPs along the EC gradient (e. g., Beggiatoa spp. and Epistylis sp. were associated with high and low EC, respectively). High EC and peaks negatively affected the abundance of certain microorganisms (e.g., Acineria uncinata) (p < 0.05). Ciliate genera were most affected by EC peaks, with different species showing different salinity tolerance ranges (e.g. Holophyra discolor was affected by EC >3000 mu S cm-(1)). Seasonal variations did not significantly alter community sensitivity to salinity (p > 0.05). LMER and SEM analyses revealed strong adverse effects of high EC and EC peaks on microbial diversity, richness, and the efficiency of organic matter and TKN removal (p < 0.05). This highlights the importance of monitoring and controlling EC levels in WWTP influent to maintain optimal treatment performance and the need for effective technologies or biological processes to mitigate saline discharges into rivers.

The bioindicator potential of the microeukaryotic community in a full-scale A2O wastewater treatment process was assessed after deactivating the internal recirculation in one of the two parallel treatment lines of the plant. The deactivation of the internal recirculation in one of the lines (NIR-line), led to a strong decrease in nitrogen removal efficiency (53 % ammonia-uptake in the NIR-line versus 97 % in the unaltered line or IR-line), as well as to a lower organic matter removal (95 % BOD5 removal versus 97 % in the IR-line). The microeukaryote community structure changed greatly confirming trends observed in experimental studies and showed a decrease in abundance and richness in the NIR-line. However, this line showed a significant higher abundance of certain ciliate species, such as Epistylis camprubii and Vorticellides infusionum, which are common species in conventional activated sludge. Conversely, the IR-line showed useful indicators of internal recirculation, associated with much higher ammonium and BOD5 removal. These results show that identification to ciliate species level provides a more reliable bioindication in nutrient removal systems, supporting the importance of research on biological parameters, mainly protists, as simple and useful tools for plant operators to manage nutrient removal processes. These observations extend the current boundaries of bioindication.

Microplastics (MP) have spread to every corner of the globe, reaching remote areas like Antarctica. Recent studies detected MP in marine environments, including biota. Benthic organisms suffer negative effects upon MP ingestion, leading to impacts on their populations. To address the current knowledge gap on how Antarctic benthic invertebrates interact with MP, we conducted an experiment exposing a bivalve (Aequiyoldia eightsii) and two ascidians (Cnemidocarpa verrucosa and Molgula pedunculata) to polyethylene microbeads (mb). Specimens of each species were exposed for 48 h to two different concentrations of microbeads, a low dose (100 mb/l) and a high dose (1000 mb/l), with the same proportion of four different microbead size fractions (Fine (10-20 μm), Small (45-53 μm), Medium (106-125 μm), and Large (850-1000 μm)). After exposure, all three species had ingested microbeads. Significant differences between doses were observed in A. eightsii and C. verrucosa but not in M. pedunculata. Both ascidians ingested microbeads of all size fractions, whereas the bivalve did not ingest the largest microbeads. No significant differences were found between species in the number nor sizes of microbeads ingested. Minor variations between taxa may be attributed to the specific biology and anatomy of each species. Our study highlights the need for a deeper understanding of Antarctic benthic ecosystems, suggesting that the interaction with MP is species-specific. We believe that this study provides a baseline for assessing MP pollution in Antarctic benthic invertebrates and will help to inform policy-makers in protecting and preserving Antarctic marine ecosystems from MP pollution.

Human activities are not only increasing salinization of rivers, they might also be altering the temporal dynamics of salinity. Here, we assess the effect of human activities on the temporal dynamics of electrical conductivity (EC) in 91 Spanish rivers using daily measures of EC from 2007 to 2011. We expected rivers weakly affected by human activities to have low and constant ECs, whereas rivers strongly affected by human activities should have high and variable ECs throughout the year. We collected information on land use, climate, and geology that could explain the spatiotemporal variation in EC. We identified four groups of rivers with differences in EC trends that covered a gradient of anthropogenic pressure. According to Random Forest analysis, temporal EC patterns were mainly driven by agriculture, but de-icing roads, mining, and wastewater discharges were also important to some extent. Linear regressions showed a moderate relationship between EC variability and precipitation, and a weak relationship to geology. Overall, our results show strong evidence that human activities disrupt the temporal dynamics of EC. This could have strong effects on aquatic biodiversity (e.g., aquatic organisms might not adapt to frequent and unpredictable salinity peaks) and should be incorporated into monitoring and management plans.

Network models and community phylogenetic analyses are applied to assess the composition, structure, and ecological assembly mechanisms of microbial communities. Here we combine both approaches to investigate the temporal dynamics of network properties in individual samples of two activated sludge systems at different adaptation stages. At initial assembly stages, we observed microbial communities adapting to activated sludge, with an increase in network modularity and co-exclusion proportion, and a decrease in network clustering, here interpreted as a consequence of niche specialization. The selective pressure of deterministic factors at wastewater treatment plants produces this trend and maintains the structure of highly functional and specialized communities responding to seasonal environmental changes.

Nature-based solutions including rooftop-water storage ponds are increasingly adopted in cities as new ecodesigns to address climate change issues, such as water scarcity and storm-water runoff. Macrophytes may be valuable additions for treating stored rooftop waters and provisioning other services, including aquaponics, esthetic and wildlife-conservation values. However, the efficacy of macrophyte treatments has not been tested with influxes of different labile carbon loadings such as those occurring in storms. Moreover, little is known about how macrophytes affect communities of metazoans and microbes, including protozoans, which are key players in the water-treatment process. Here, we experimentally investigated the effectiveness of two widely distributed macrophytes, Ceratophyllum demersum and Egeria densa, for treating drained rooftop water fed with two types of leaf litter, namely Quercus robur (high C lability) and Quercus rubra (low C lability). C. demersum was better than E. densa at reducing water conductivity (by 10 x336; 40 mu S/cm), TDS (by 10-18 mg/L), DOC (by 4-5 mg/L) and at increasing water transparency (by 4-9%), water O2 levels (by 19-27%) and daylight pH (by 0.9-1.3) compared to leaf-litter only microcosms after 30 days. Each treatment developed a different community of algae, protozoa and metazoa. Greater plant mass and epiphytic chlorophyll-a suggested that C. demersum was better at providing supporting habitat than E. densa. The two macrophytes did not differ in detritus accumulation, but E. densa was more prone to develop filamentous bacteria, which cause sludge bulking in water-treatment systems. Our study highlights the superior capacity of C. demersum and the usefulness of whole-ecosystem experiments in choosing the most adequate macrophyte species for nature-based engineered solutions.

This study aims at optimizing the anaerobic digestion (AD) of biomass in microalgal-based wastewater treatment systems. It comprises the co-digestion of microalgae with primary sludge, the thermal pretreatment (75 °C for 10 h) of microalgae and the role of the hydraulic retention time (HRT) in anaerobic digesters. Initially, a batch test comparing different microalgae (untreated and pretreated) and primary sludge proportions showed how the co-digestion improved the AD kinetics. The highest methane yield was observed by adding 75% of primary sludge to pretreated microalgae (339 mL CH4/g VS). This condition was then investigated in mesophilic lab-scale reactors. The average methane yield was 0.46 L CH4/g VS, which represented a 2.9-fold increase compared to pretreated microalgae mono-digestion. Conversely, microalgae showed a low methane yield despite the thermal pretreatment (0.16 L CH4/g VS). Indeed, microscopic analysis confirmed the presence of microalgae species with resistant cell walls (i.e., Stigioclonium sp. and diatoms). In order to improve their anaerobic biodegradability, the HRT was increased from 20 to 30 days, which led to a 50% methane yield increase. Overall, microalgae AD was substantially improved by the co-digestion with primary sludge, even without pretreatment, and increasing the HRT enhanced the AD of microalgae with resistant cell walls.

Biological wastewater treatment processes involve very complex microbial communities. Culture-independent molecular methods are feasible tools used to analyze and control the structure of different microbial communities, such as bacterial communities that remove nutrients. Here, we used the gBlocks gene fragments method, a new real-time PCR approach for the development of DNA standards, to quantify total bacterial cells, AOB, NOB, and Archaeal genes at two different WWTPs. PAOs were also quantified using the FISH technique. Our findings highlight a significant improvement in real-time PCR detection for the microorganisms studied. The qPCR and FISH technique applied allowed characterization of the microbial composition of two WWTPs operated as a conventional WWTP and a biological nutrient-removal WWTP. The results revealed a significant difference in the microbial profiles of the WWTPs, with a higher abundance of nitrifying bacterial communities and PAOs in the nutrient removal plant, which were in accordance with operational performance.

This work aims at comparing the ability of two kinds of electrochemical technologies, namely electrocoagulation (EC) and electro-Fenton (EF), to disinfect primary and secondary effluents from municipal wastewater treatment plants. Heterotrophic bacteria, Escherichia coli, enterococci, Clostridium perfringens spores, somatic coliphages and eukaryotes (amoebae, flagellates, ciliates and metazoa) were tested as indicator microorganisms. EC with an Fe/Fe cell at 200 A m(-2) and natural pH allowed >5 log unit removal of E. coli and final concentration below 1 bacteria mL(-1) of coliphages and eukaryotes from both effluents in ca. 60 min, whereas heterotrophic bacteria, enterococci and spores were more resistant. A larger removal was obtained for the primary effluent, probably because the flocs remove higher amount of total organic carbon (TOC), entrapping more easily the microbiota. EF with a boron-doped diamond (BDD) anode and an air-diffusion cathode that produces H2O2 on site was first performed at pH 3.0, with large or even total inactivation of microorganisms within 30 min. A more effective microorganism removal was attained as compared to EC thanks to (OH)-O-center dot formed from Fenton's reaction. A quicker disinfection was observed for the secondary effluent owing to its lower TOC content, allowing the attack of greater quantities of electrogenerated oxidants on microorganisms. Wastewater disinfection by EF was also feasible at natural pH (similar to 7), showing similar abatement of active microorganisms as a result of the synergistic action of generated oxidants like active chlorine and coagulation with iron hydroxides. A sequential EC/EF treatment (30 min each) was more effective for a combined decontamination and disinfection of urban wastewater. (C) 2017 Elsevier Ltd. All rights reserved.

An in-depth, long-term, multidisciplinary study was conducted in order to study the microeukaryote community in a partial nitritation (PN) reactor prior to anammox. The PN reactor operated with moving bed biofilm reactor (MBBR) technology, using plastic supports (carriers) for biofilm development. The microeukaryote community from the biofilm (BF) and the surrounding media (mixed liquor or ML) were analysed separately. Despite the physicochemical conditions under which the PN-MBBR operated (an average of 305.9±117mg TAN l-1 and 328.4±131.9mg N-NO2- l-1), up to 24 microeukaryotic taxa were observed by microscope. Microeukaryote species showed an uneven distribution in the PN-MBBR, thus suggesting the existence of two habitats: the BF, preferred by species with specific structures for adhering to a substrate, such as the stalked Peritrichia, and the ML, preferred by free-swimming or non-substrate dependent species. The results indicated that most ciliate population dynamics mainly responded to the nitrous acid and free ammonia concentrations and, to a lesser extent, to sCOD values. In the BF, variations in the population of Epistylis camprubii and Opercularia coarctata suggest the existence of competition between these species due to niche overlap. A V4 18S rDNA molecular survey (Illumina) was carried out for some samples with the aim of obtaining maximum coverage of the main eukaryote species that were microscopically detected throughout the study. The diversity and abundance data provided by both detection methods were compared. The study helped identify broader tolerance ranges of the microeukaryote taxa to the physicochemical parameters analysed.

Skeletochronology allows estimation of lizard age with a single capture (from a bone), making long-term monitoring unnecessary. Nevertheless, this method often involves the death of the animal to obtain the bone. We tested the reliability of skeletochronology of phalanges (which may be obtained without killing) by comparing the estimated age from femurs and humeri with the age estimated from phalanges. Our results show skeletochronology of phalanges is a reliable method to estimate age in lizards as cross-section readings from all bones studied presented a high correlation and repeatability regardless of the bone chosen. This approach provides an alternative to the killing of lizards for skeletochronology studies.

Nowadays, biofilms are one of the principal targets of community ecotoxicology in aquatic ecosystems with a high potential for future use in ecotoxicology. A large set of methods derived from biofilm ecology has successfully been applied in ecotoxicology providing a diverse and comprehensive toolbox. Our ability to quantify the effects of pollution on different biofilm components, allows the direct effects of pollutants on the most sensitive community and their indirect effects on the rest of biofilm components to be evaluated. Biofilms are also a site for biotransfomation and/or transfer of chemicals to other aquatic organisms, supporting a more generalized use of biofilms in environmental chemistry. Investigations aiming to describe processes at biofilm scale, like nutrient dynamics and those including simple food chains, have recently been applied, providing the opportunity of upscaling the effects of pollutants on biofilms to food webs and ecosystems. Finally, biofilm ecotoxicology should now focus on providing the theoretical background for understanding the complex set of responses of natural communities to pollution. This knowledge should also be the basis for guiding the selection of the most appropriate tools and the development of new approaches for a better detection of the impact of pollution on aquatic life.