The study combined four modeling domains: a global model, or G-SDM, and independently calibrated models for the Asia–Pacific native range, Europe and North America. Each geographic model had separate terrestrial and nearshore components. The terrestrial component represented environmental conditions associated with the crab’s freshwater phase, whereas the nearshore component represented brackish-water conditions potentially relevant to reproduction and early development. This division reflected the species’ catadromous life cycle, in which juvenile and growth phases occur in freshwater before reproductive migration toward marine environments. The nearshore outputs were interpreted as potentially suitable environments, not confirmed spawning grounds or nursery habitats.

The researchers compiled 4,408 occurrence records from the Global Biodiversity Information Facility, published literature and field investigations. These were records gathered before spatial filtering, not the final number used by every model. To reduce spatial sampling bias and autocorrelation, the records were thinned to retain no more than one record per 10 × 10 km grid cell, then intersected with the appropriate terrestrial or nearshore predictor layers. After thinning and intersection, the native-range model retained 56 terrestrial and 31 nearshore records; the global model retained 685 and 271; the European model retained 472 and 216; and the North American model retained 67 and 28. Eight algorithms—including artificial neural networks, classification trees, generalized boosting, generalized linear models, multivariate adaptive regression splines, MaxEnt, random forests and surface range envelopes—were fitted with repeated pseudo-absence sampling and random holdout validation.

Random holdout validation indicated generally good discrimination, but spatial block cross-validation produced lower performance, as expected when nearby records cannot be divided randomly between training and testing data. Across the four geographic models, mean spatial-validation ROC-AUC values ranged from 0.77 to 0.94 and mean true skill statistic values from 0.55 to 0.77, indicating moderate to good discriminatory ability under spatially separated validation. The study also used a multivariate environmental similarity surface analysis to identify where future conditions fell outside the current calibration range. Negative similarity values occurred mainly in Western Europe and along the North Sea coast, parts of coastal North America, and coastal East Asia. Some of these extrapolation areas overlapped cells projected as suitable, making those predictions less secure.

Regional models identified different environmental associations for terrestrial suitability. In the native range, the leading predictors were annual mean temperature, distance to the shoreline, isothermality, mean temperature of the wettest quarter and annual precipitation. Distance to the shoreline ranked first in Europe, followed by annual mean temperature, wettest-quarter temperature, isothermality and annual precipitation. In North America, annual precipitation was the leading predictor, followed by annual mean temperature and precipitation of the warmest quarter. Using the central 95% ranges associated with high suitability, the native range extended from 9.3°C to 20.4°C in annual mean temperature, compared with 4.3°C to 15.7°C in Europe and 3.8°C to 15.4°C in North America. The invaded regions therefore contained cooler conditions within their modeled high-suitability ranges. The authors cautioned that such differences can arise from regional environmental availability, range occupancy, environmental filtering and calibration coverage; they do not by themselves demonstrate climatic adaptation, niche evolution or greater physiological tolerance.

The nearshore models showed more consistent predictor rankings. Water depth, mean chlorophyll concentration, mean sea-surface temperature and mean salinity were the principal predictors in all three regional models. The central 95% high-suitability range for mean sea-surface temperature was 13.8°C to 25.5°C in the native range, 7.3°C to 18.7°C in Europe and 7.0°C to 24.5°C in North America. Chlorophyll ranges were narrower in both invaded regions than in the native range. Despite this relative consistency, the terrestrial and nearshore outputs frequently failed to overlap. For example, some parts of Newfoundland and the northern Mediterranean were classified as suitable by only one component. The study did not show that these mismatches restrict reproduction, because the models did not include hydrological connectivity, actual dispersal pathways or confirmed reproductive sites.

Under the low-emissions SSP1-2.6 pathway, projected changes were relatively limited. With SSP2-4.5 and especially SSP5-8.5, terrestrial suitability shifted northward in all three regional models. Europe projected gains across Scandinavia and northern European Russia, including extensive areas north of 60°N in the later high-emission periods. North America projected increasing suitability in eastern Canada, Newfoundland, Labrador, the Gulf of St Lawrence and southern Alaska. In the native-range domain, suitability increased in northeastern China, the Korean Peninsula and other regions north of 40°N while declining across eastern and southern China. By the 2090s under SSP5-8.5, high-suitability areas in eastern China were nearly absent in the native-range projection. The global model likewise projected new high-latitude areas in northern Europe, northern North America and the Russian Far East, together with losses along the lower-latitude margins of the current modeled range.

Nearshore projections changed less dramatically than terrestrial ones, but this did not produce complete life-cycle overlap. In Europe, terrestrial suitability expanded into northern Scandinavia and northern European Russia without a corresponding expansion of suitable nearshore brackish-water conditions under later SSP2-4.5 and SSP5-8.5 scenarios. North American projections showed a similar discordance: new terrestrial areas appeared around Newfoundland, Labrador and farther north even where suitable nearshore conditions were absent. A shared principal-component analysis of the terrestrial projections quantified changes in environmental space. Current–future overlap generally declined toward later periods and higher-emission scenarios, reaching its lowest value in all three regions under SSP5-8.5 in the 2090s. The native range’s 95% kernel-density area declined from about 6.6 to 4.1 squared principal-component units, while its convex-hull area fell from about 16.5 to 10.7 squared units. North America’s corresponding areas declined from approximately 9.2 to 6.3 and from 23.0 to 16.0 squared units under the same scenario.

Europe followed a different trajectory in the environmental-space analysis. Its 95% kernel-density breadth remained comparatively stable, while occupied grid-cell counts and convex-hull extent increased under several future scenarios, peaking at approximately 575 cells and 24.3 squared principal-component units under SSP1-2.6 in the 2090s. Expansion into environmental space outside the current suitable range remained small everywhere, ranging from 0.2% to 2.7%. The unfilling index—the portion of current suitable environmental density not covered under future conditions—rose to 0.032–0.170 in the native range and 0.063–0.237 in North America by the 2090s, compared with 0.018–0.042 in Europe. These are terrestrial projections within predefined regional domains, so the native-range contraction does not imply loss across a wider area beyond that model’s northern boundary.

The results point to a geographically uneven reorganization of potential habitat rather than a uniform increase in the crab’s modeled range. Europe retained more of its current terrestrial environmental space, whereas the native range and North America showed stronger contraction and redistribution under late high-emission conditions. River-network post-processing identified candidate areas in Europe and North America where predicted terrestrial suitability, selected river systems and predicted nearshore suitability spatially coincided, but these were screening zones rather than estimates of actual dispersal distance or hydrological connectivity. The study’s main limitation is that the models estimate environmental suitability rather than actual establishment: they omit dispersal constraints, biotic interactions, verified reproductive sites, river-flow direction and demographic responses. Independent field observations, reproductive records and process-based investigations will therefore be needed to determine whether the projected shifts correspond to changes in Chinese mitten crab populations.

Subject of Research: Climate-driven redistribution of potential Chinese mitten crab habitat across native and invaded regions

Article Title: Assessing the Potential Distribution of Eriocheir sinensis Under Climate Change: Regional Contrasts and Spatial Mismatches in Terrestrial and Nearshore Suitability

Article References: Gong, H., Yang, X., Bidegain, G., Wang, Y., Jiang, Y., Han, T., Dong, J., & Zhang, X. (2026). Assessing the Potential Distribution of Eriocheir sinensis Under Climate Change: Regional Contrasts and Spatial Mismatches in Terrestrial and Nearshore Suitability. Ecology and Evolution, 16(10), Article e74351. https://doi.org/10.1002/ece3.74351

Image Credits: AI Generated

DOI: 10.1002/ece3.74351

Keywords: Chinese mitten crab, Eriocheir sinensis, species distribution models, climate change, habitat suitability, nearshore ecology, freshwater ecosystems, CMIP6 projections, invasive species, catadromous life cycle, Assessing, Potential

The core challenge the study addresses is confounding bias, the chronic curse of observational environmental research. Unlike a laboratory experiment, a river cannot be randomly assigned to treatment and control conditions. Wastewater discharges arrive at particular points along a waterway, and the downstream reaches differ from upstream ones in ways that have nothing to do with the effluent: differences in geology, catchment land use, flow regime, season, and the natural downstream drift of organisms all shape what ecologists observe. Traditional before-after-control-impact designs, the workhorse of impact assessment since the early 1990s, attempt to disentangle these signals, but they require carefully planned sampling campaigns and still struggle when natural spatiotemporal variability is large relative to the impact of interest.

Hatami’s approach recasts an earlier validated causal architecture into a modular, reproducible workflow built on the structural causal model framework formalised by computer scientist Judea Pearl. Structural causal models describe a system as an interconnected network of variables linked by equations, in which each variable is generated from its direct causes plus random variation. Crucially, such models allow researchers to perform hypothetical interventions: instead of merely conditioning on an observation, the analyst mathematically reaches into the system, fixes a driver at a chosen value, and propagates that change through the entire supported network of equations. The result is a genuine counterfactual prediction of what the ecosystem would look like had the intervention occurred, not a passive correlation.

The workflow proceeds in distinct stages. First, community-level ecological responses are linked to an interconnected environmental network that represents the causal pathways connecting discharge-related drivers to water quality variables and, ultimately, to the biological community. Second, the framework tests structural sufficiency, checking whether the hypothesised causal structure is actually supported by the data rather than imposed by assumption. Third, once the spatiotemporal structure of the system has been modelled and validated, intervention effects can be estimated along the entire river continuum, from the point of discharge downstream. This explicit separation of model construction, structural validation, and counterfactual prediction is what makes the workflow modular, since each component can be audited, updated, or re-run independently as new data arrive.

The headline result is striking in its specificity. When the relevant discharge-related drivers were hypothetically reduced to one-tenth of their observed values, the model predicted that conductivity, total organic carbon, total phosphorus, nitrate, and chlorophyll a would all shift back towards baseline conditions. Even more telling, the downstream macroinvertebrate community, the biological yardstick most regulators rely upon, no longer exhibited a detectable effluent-related shift under that scenario. In other words, the model did not simply say that less pollution would be better; it identified a concrete reduction target at which a recognisable ecological signature of the discharge disappears from the biota.

Because the magnitude of improvement could be traced across the whole network of linked variables, the framework also provides something policy has long lacked: an estimate of the scale of reduction required for ecological recovery. Water managers facing investment decisions on wastewater treatment upgrades can use such estimates to compare scenarios, asking not only whether a proposed intervention will help but by how much, through which chemical and physical pathways, and where along the river the benefit will materialise. This positions the tool squarely within the movement towards probabilistic and quantitative environmental risk assessment, which argues that robust management decisions require explicit numbers with attendant uncertainty rather than qualitative judgments.

The technical machinery underlying the workflow draws on well-established statistical foundations. Multivariate techniques rooted in Legendre’s numerical ecology tradition, distance-based redundancy analysis for testing multispecies responses, and principal components methods for dimension reduction all feature in the analytical chain, alongside mixed effects models for handling the hierarchical structure of environmental data. The study also engages directly with the recent surge of interest in causal inference within ecology, citing work on applying structural causal models to observational ecological data and on causal methods for time series. The timing is significant: recent assessments have warned that roughly one quarter of freshwater fauna are threatened with extinction, and ecologists have increasingly argued that biodiversity change detection and attribution demand causal rather than purely correlative tools.

What distinguishes this contribution from earlier causal modelling efforts in the field is its extension from explanation to appraisal. Previous applications of structural equation modelling and Bayesian networks in environmental management have largely been used to explain observed variation, to test competing hypotheses about how a system works, or to organise expert knowledge. Hatami’s workflow takes the additional step of using a validated causal structure to run quantitative what-if analyses, simulating intervention scenarios that have not yet occurred. The framework’s focus on estimating how far stressors must be reduced to achieve ecological benefit, and on identifying the intervention targets most relevant to wastewater management, directly connects the abstract mathematics of causal inference to the practical economics of sewage treatment and freshwater ecosystem protection.

Transparency and reproducibility are baked into the study. The data and R code supporting the findings are publicly available in a GitHub repository named counterfactual-prediction, meaning that any regulator, consultant, or researcher can inspect the model structure, verify the validation tests, and rerun the intervention analyses with their own parameters. The work builds on the author’s earlier PhD research at La Trobe University, which developed protocols for environmental impact studies using causal modelling with particular reference to wastewater discharges to freshwater systems, and on published methods for controlling spatiotemporal confounding, including a practical method published in MethodsX in 2018. That lineage matters, because the credibility of a counterfactual prediction rests entirely on the credibility of the causal structure beneath it.

The broader implications reach beyond a single river or a single discharge. If the workflow proves portable to other systems, it could shift the entire framing of environmental impact assessment, moving agencies from asking whether an impact exists towards asking how large an intervention must be and where it should be applied for the greatest ecological return. It also offers a coherent answer to the long-standing complaint that BACI-style designs are reactive, detecting harm only after it has happened. By quantifying the relationship between discharge-related drivers and downstream ecological responses within a validated causal network, managers gain a forward-looking instrument: the ability to predict, before a single upgrade is funded, whether a tenfold reduction in a stressor will pull a river’s chemistry and its invertebrate communities back towards the conditions that define ecological health. For freshwater ecosystems under mounting pressure from multiple stressors across the globe, that kind of quantitative foresight may prove to be exactly the tool the field has been waiting for.

Subject of Research: Causal modelling for spatiotemporal ecological impact assessment and counterfactual prediction of wastewater intervention effects in freshwater ecosystems

Article Title: A causal modelling workflow for spatiotemporal ecological impact assessment with quantified counterfactual prediction of intervention effects

Article References: Hatami, R. (2026). A causal modelling workflow for spatiotemporal ecological impact assessment with quantified counterfactual prediction of intervention effects. Environmental Monitoring and Assessment, 198(9), Article 1005. https://doi.org/10.1007/s10661-026-15813-0

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15813-0

Keywords: causal modelling, counterfactual prediction, ecological impact assessment, freshwater ecosystems, wastewater discharge, macroinvertebrates, spatiotemporal confounding, intervention analysis, water quality, structural causal models, river continuum, environmental monitoring

The three species at the heart of the database all hail from North America, and all three are among the most damaging aquatic invaders Europe has ever faced. Faxonius limosus, the spiny-cheek crayfish, originates from the Atlantic watershed of North America. Pacifastacus leniusculus, the signal crayfish, comes from the north-western United States. Procambarus clarkii, the red swamp crayfish, is native to the southern United States and north-eastern Mexico. Together they drive biodiversity loss, restructure food webs and undermine the ecosystem services that lakes provide, from clean water to fisheries. Several introduced crayfish species are listed as species of Union Concern under EU Regulation 1143/2014, a designation that reflects their severe ecological and economic toll and obliges member states to manage their spread.

Freshwater ecosystems are exceptionally vulnerable to human-mediated species introductions, and invasive crayfish rank among the worst offenders on the continent. Yet scientists have long struggled with fragmented and incomplete spatial data, which makes it fiendishly difficult to assess the true costs of these invasions. Significant gaps persist in reporting the economic damage caused by crayfish worldwide, and the absence of comprehensive records hampers both research and the design of effective management strategies. By mobilising FAIR data — a term meaning Findable, Accessible, Interoperable and Reusable — the new database directly addresses that deficiency, allowing long-term analyses of invasion dynamics that were previously impossible at a regional scale.

The study area spans an impressive gradient of lake types, from large, deep glacial basins such as Lake Maggiore to small, shallow waterbodies of fluvial and tectonic origin scattered across the Piedmont plain. Two of the study lakes, Maggiore and Orta, belong to the national Long-Term Ecological Research network known as LTER Italy, meaning they are monitored continuously as sentinels of environmental change. The remaining lakes carry conservation designations: they are registered as Special Areas of Conservation, Special Protection Areas, or components of the European Union’s Natura 2000 network under the Birds Directive. That such heavily protected waters harbour thriving populations of North American crayfish underscores how thoroughly these invaders have penetrated even the continent’s most safeguarded habitats.

The fieldwork behind the database combined standardised trapping with meticulous taxonomic verification. Sampling sites were chosen where sediment type and vegetation cover offered suitable crayfish habitat, and where the animals had been confirmed or suspected previously. The number of sites per lake was scaled to surface area, with four stations in Lake Mergozzo and six in Lake Orta. At each site, 13 interconnected traps, spaced two to three metres apart, were deployed on the shallow lake bottom overnight for roughly 12 hours, coinciding with peak crayfish activity. Each cylindrical trap, measuring 30 by 60 centimetres with a one-square-centimetre mesh, was baited with 20 grams of cat food — an unconventional but effective lure. The catch per unit effort, calculated as total catch divided by the number of traps multiplied by nights, provided a comparable abundance index across lakes and years.

Quality control was equally rigorous. Geographic coordinates were verified using Google Maps, and every specimen was identified to species level by taxonomic experts using standard identification keys, with molecular analyses performed whenever a doubtful case demanded certainty. This precision matters, because the three invaders can be confused with one another, and because Faxonius limosus was itself reclassified taxonomically, having formerly been known as Orconectes limosus following a major revision of crayfish nomenclature in 2017. All native species caught incidentally in the traps were immediately released unharmed, ensuring the monitoring programme did not itself become a further disturbance to the lakes’ fragile ecological balance.

The data reveal striking patterns in how the invaders partition the lakes. In Lake Maggiore, 80 occurrence records from 75 sampling points collected between April 2017 and July 2018 captured all three species, but Faxonius limosus dominated, particularly in May, achieving a mean catch per unit effort of 1.14. In Lake Orta, monthly sampling from June 2021 to May 2022 generated 186 records and documented something ecologically remarkable: the coexistence of F. limosus and Procambarus clarkii, with the red swamp crayfish accounting for more than 80 percent of total abundance from May to December. Lake Mergozzo, by contrast, hosted only F. limosus, whose abundance peaked between June and October 2021 before thinning to occasional records by the following spring.

The seasonal signature in the data is unmistakable. Both F. limosus and P. clarkii reached peak densities in the summer and autumn months, and the pronounced summer predominance of the red swamp crayfish reinforces its reputation as a warm-water invader, flourishing as lake temperatures climb. Pacifastacus leniusculus, meanwhile, made a far more restricted appearance: it was recorded only once, in July 2018, in the northernmost part of Lake Maggiore on Swiss territory. The most recent dataset, gathered between June and October 2025 across all 17 lakes, recorded presence or absence in each waterbody and found crayfish absent in seven of them. Intriguingly, that survey also documented P. clarkii for the first time in Lakes Pistono, San Michele and Sirio, extending the known invasion frontier, while mean abundance of the red swamp crayfish varied from more than 1.5 individuals per unit effort in Candia and Pistono down to less than 0.5 in five other lakes.

Some of the findings hint at shifting dynamics that will repay close monitoring. Catch rates of Faxonius limosus in Lakes Orta and Maggiore during 2025 fell well below those recorded in 2021 and 2022, and the mean catch per unit effort of both species in Lake Orta was significantly altered in 2025 compared with the earlier survey. Researchers hypothesise that the occurrence of non-native crayfish across the region is shaped by hydrological connectivity between waterbodies, predator-prey interactions, and even illegal human activities, such as unauthorised introductions. A further curiosity emerged from Lake Orta, where scientists reported a new morphotype of Procambarus clarkii bearing atypical marbled colouration remarkably similar to the marbled crayfish P. virginalis, a species famous for its ability to reproduce without males.

The database is far more than an archival exercise. Because each of the four datasets carries its own Digital Object Identifier and is published under an open licence, the records can be linked to global invasive species registers, including those maintained by the Invasive Species Specialist Group and the Global Register of Introduced and Invasive Species. The data have already fed into several peer-reviewed studies on crayfish biometry, habitat preferences and invasion history, and they now provide an evidence base for regional management strategies in Piedmont and Lombardy. As invasions accelerate across freshwater systems worldwide, this first consolidated picture of three North American crayfish in 17 Italian lakes offers both a warning and a template: rigorous, standardised, openly shared data is the indispensable foundation for defending vulnerable aquatic ecosystems before the invaders dig in for good.

Subject of Research: Occurrence and distribution of three invasive North American crayfish species in lakes of north-western Italy

Article Title: First database of invasive crayfish in north-western Italian lakes

Article References: Kamburska, L., Zaupa, S., Orlandi, M., Garzoli, L., & Boggero, A. (2026). First database of invasive crayfish in north-western Italian lakes. Biodiversity Data Journal, 14, Article e189983. https://doi.org/10.3897/bdj.14.e189983

Image Credits: AI Generated

DOI: 10.3897/BDJ.14.e189983

Keywords: invasive crayfish, Faxonius limosus, Pacifastacus leniusculus, Procambarus clarkii, GBIF, freshwater ecosystems, Piedmont, Lombardy, Lake Maggiore, biodiversity data, Darwin Core Archive, Natura 2000

The African sharptooth catfish is one of the world’s most widely introduced freshwater fish, exported globally for aquaculture because of its rapid growth, disease resistance, tolerance of crowded ponds, and ability to breathe atmospheric oxygen and even disperse overland. Adults commonly exceed one metre in length. Those same traits, however, make it a formidable invader, and the species has been linked elsewhere to the displacement of native fish, food web disruption, and parasite transmission. In Türkiye, it has gained a foothold in a section of the Sakarya River warmed by springs, where it now coexists with the Wels catfish, a species that is native and declining in the region even though it behaves as a damaging invader in other parts of Europe.

To measure predation pressure directly, the team ran comparative functional response experiments, a standard tool in invasion science that quantifies how efficiently a predator consumes prey as prey density rises. Wild-caught catfish of both species were offered two prey fish at densities from one to 64 individuals in 90-litre tanks held at 21.5 degrees Celsius, matching the average temperature of the collection sites. One prey was the native bleak Alburnus escherichii, the dominant small fish at the study site; the other was gibel carp, Carassius gibelio, an invasive cyprinid now widespread across the country. The number of prey eaten after 24 hours was used to estimate each predator’s attack rate and handling time.

Every predator-prey combination produced a Type II functional response, the classic pattern in which consumption is disproportionately high when prey are scarce, a dynamic that can drive prey populations toward local collapse. The critical difference emerged between prey species. Both catfish took significantly longer to handle gibel carp than bleak, and the functional response ratio, which integrates attack rate and handling time into a single measure of predatory impact, was roughly three times higher on the native prey. Clarias gariepinus posted a ratio of 203.5 on the bleak compared with 61.3 on gibel carp; for Silurus glanis the corresponding figures were 123.5 and 49.0. Clarias gariepinus also attacked the native bleak at a significantly higher rate than the Wels catfish did.

The researchers attribute the gibel carp’s partial refuge from predation to its deeper body shape and to the predators’ lack of evolutionary experience with it, whereas slender-bodied bleak closely resemble South African minnows and barbs whose populations have crashed following sharptooth catfish invasions. Because both predators converge on the same native prey, their combined presence could destabilize bleak populations faster than either predator acting alone, a concern sharpened by the fact that the invaders consumed more of the native prey per unit time under the study’s warm conditions.

Laboratory results, however, can oversimplify natural food webs, so the team also analysed stable isotopes of carbon and nitrogen in muscle tissue from fifteen wild specimens of each species. Nitrogen isotope ratios placed both predators at similar trophic positions, with the Wels catfish slightly higher at 3.57 versus 3.30 for the African catfish. Yet their isotopic niches barely overlapped: the African catfish’s niche ellipse overlapped only 5.4 percent of the Wels catfish’s at the 95 percent level, and a negligible 0.3 percent at the core 40 percent level. The narrower isotope signature of the African catfish suggests it feeds on a more specialized subset of resources in the wild, consistent with the idea that generalist invaders can shrink their trophic niche when sharing waters with a native competitor, easing direct conflict while maintaining pressure on shared prey.

The third strand of the study looked outward in space and forward in time. Using nine modelling algorithms and quality-controlled occurrence records filtered for spatial errors and autocorrelation, the researchers built ensemble ecological niche models for both predators and both prey, then projected habitat suitability under two CMIP6 climate scenarios, an intermediate SSP1-2.6 pathway and a high-emission SSP5-8.5 pathway, for mid-century and end-of-century horizons. Model performance was strong, with True Skill Statistics above 0.6 for all species and reaching 0.93 or higher for the Wels catfish and gibel carp in the best algorithms.

The projections tell a coherent story about climate niches. The African catfish is associated with thermally stable environments with moderate seasonal variability, while the Wels catfish prefers regions with pronounced seasonal temperature swings and is sensitive to cold-quarter temperatures. The native bleak is likewise governed by temperature-related variables and favours areas with distinct seasons but low daily fluctuation. Under future scenarios, both predators are projected to expand their ranges, and their overlapping habitat increases, raising the probability of interspecific encounters and competition. The Wels catfish’s climatic tolerance aligns more closely with bleak habitat across temperate Europe, meaning the native predator may threaten the native prey over a broader area than the invader, at least climatically.

The authors are careful to frame the models as risk maps rather than prophecies. Species distribution models identify where interactions could plausibly occur, but they cannot predict the outcome of competition or predation because they omit behavioural flexibility, diet switching, and density-dependent processes. Fully forecasting predator dynamics under climate change, they note, would require individual-based or mechanistic multispecies models parameterized with interaction data that do not yet exist. The study also acknowledges limits in its field evidence: isotope samples came only from the sympatric site, so niche separation could not be confirmed where the species occur apart, and factors such as dissolved oxygen, flow, habitat structure, and pollution were outside the modelling scope.

The conservation implications extend well beyond one Turkish river. Hot-spring refugia like Eminekin act as invasion beachheads, and connectivity during warm months is expected to strengthen as the climate warms, allowing thermally tolerant invaders to disperse outward. Meanwhile the Wels catfish, historically a keystone structure in these fish communities, is being squeezed by overfishing, pollution, drought, and now competition from a functionally similar invader prized by some anglers, whose translocations and stocking practices may further shape future distributions. The researchers argue for habitat restoration, vigilant monitoring of predator-prey dynamics, stricter regulation of aquaculture and stocking, and climate-adaptive biosecurity planning, coupled with transboundary cooperation across Eurasia. As their integrated evidence shows, warming waters do not merely shift species ranges on a map; they can raise the per-capita predatory power of an invasive fish, redraw the boundaries of its conflict with native predators, and leave vulnerable native prey caught between both.

Subject of Research: Trophic interactions and climate-driven range dynamics of invasive and native catfish in Turkish freshwater ecosystems

Article Title: Trophic interactions and climate-driven range dynamics of native and invasive catfish in freshwater ecosystems

Article References: Başkurt, S., Emiroğlu, Ö., Aksu, S., Köse, E., Mol, O., Çınar, E., South, J., & Tarkan, A. S. (2026). Trophic interactions and climate-driven range dynamics of native and invasive catfish in freshwater ecosystems. NeoBiota, 105, 67-88. https://doi.org/10.3897/neobiota.105.174895

Image Credits: AI Generated

DOI: 10.3897/neobiota.105.174895

Keywords: invasive species, Clarias gariepinus, Silurus glanis, functional response, stable isotope analysis, ecological niche modelling, climate change, freshwater ecosystems, predation, Sakarya River, biodiversity conservation, species distribution models

The formulation in question is nanoatrazine encapsulated in poly(ε-caprolactone), or nATZ-PCL, a nanocarrier system designed to make herbicide application more efficient while reducing the total amount of active ingredient released into the environment. Polymer nanoencapsulation is one of the flagship ideas of agricultural nanotechnology: by controlling the release of the herbicide, improving its stability and solubility, and limiting off-target drift and leaching, such formulations promise more sustainable weed control. But the very nanoscale properties that make these carriers attractive in the field also change how they behave once they enter an aquatic ecosystem. Particle size, surface chemistry, and polymer composition all influence how a nanopesticide interacts with water, dissolved organic matter, and living cells, which means its environmental fate cannot simply be inferred from decades of data on conventional atrazine.

To probe that fate, researchers at Embrapa Environment and São Paulo State University designed a two-step experiment tracing nATZ-PCL through a simplified freshwater food chain, from the microalga Raphidocelis subcapitata, a standard ecotoxicological test species and primary producer, to the water flea Daphnia magna, a grazing zooplankter that feeds on algae. The team first characterized the nanoparticles using dynamic light scattering, finding a mean hydrodynamic diameter of 226 nanometers, a low polydispersity index of 0.12, and a negative zeta potential of about minus 25 millivolts, all signs of a relatively homogeneous and physically stable suspension. Encapsulation efficiency, established in earlier work, was high at roughly 86.7 percent, meaning most of the atrazine was locked inside the polymer matrix rather than floating free in solution.

Stability, however, proved to be matrix-dependent. When the nanoparticles were suspended in the algal culture medium, their hydrodynamic diameter and polydispersity index climbed steadily over seven days, a signature of aggregation or surface interactions driven by the ionic composition of the medium and possibly by the formation of an abiotic eco-corona, a coating of natural organic molecules that adsorbs onto nanoparticle surfaces and reshapes their biological identity. Natural organic matter, or NOM, is ubiquitous in real water bodies, and the researchers included it at an environmentally relevant concentration of 10 milligrams per liter using Suwannee River humic substances. In most other test media the formulation remained comparatively stable, but the progressive growth of particle size in the algal medium hinted that clumping could alter how much herbicide actually reaches algal cells.

Exposure concentrations were anchored to sublethal effect levels determined in previous toxicity work: the EC10 and EC25, the concentrations causing 10 and 25 percent growth inhibition in the alga. Without NOM these were 0.040 and 0.103 milligrams per liter; with NOM they dropped to 0.020 and 0.043 milligrams per liter, indicating that organic matter itself modulates toxicity. Algae were exposed for seven days under controlled conditions, then harvested, washed, freeze-dried, and analyzed for atrazine using a micro-QuEChERS extraction protocol coupled to high-performance liquid chromatography with diode-array detection. Because each two-liter culture yielded only about 100 to 150 milligrams of dry biomass, the team had to repeat the cultures twelve times to accumulate enough material for reliable chemical quantification, a logistical feat that underscores how demanding nanopesticide bioaccumulation studies can be.

The results were clear: Raphidocelis subcapitata did accumulate atrazine. Measured concentrations in exposed algal biomass ranged from 0.25 to 0.89 micrograms per gram, with the highest value, roughly 0.89 micrograms per gram, recorded under the EC25 condition without natural organic matter, significantly above all other treatments. When NOM was present at EC25, accumulation fell to about 0.33 micrograms per gram, consistent with the idea that organic molecules adsorbing onto nanoparticle surfaces form an eco-corona that alters colloidal behavior and reduces bioavailability to algal cells. A control centrifugation assay ruled out a mundane artifact: no visible nanoparticle pellet formed when clean nATZ-PCL suspensions were spun under the same conditions used to harvest algae, so the detected atrazine was not simply co-sedimenting nanoparticles masquerading as cellular uptake, although the authors note the measured residue may include both internalized herbicide and strongly associated particles that washing could not remove.

The critical question came next: would that algal burden travel up the food web? To find out, the researchers fed Daphnia magna with the nATZ-PCL-exposed algae at a standardized density of four million cells per milliliter for 48 hours, followed by a 24-hour depuration period in clean medium. In a parallel experiment, daphnids were exposed directly to nATZ-PCL in reconstituted water at their own species-specific EC10 and EC25 values of 2.05 and 5.69 milligrams per liter. Pooled daphnid samples were analyzed first by liquid chromatography and then, to push sensitivity further, by high-resolution LC-QTOF mass spectrometry targeting the protonated atrazine ion at mass-to-charge ratio 216.1016. The verdict was unambiguous: atrazine was not detected above the method detection limit of 0.373 micrograms per gram in any dietary or direct exposure treatment.

Several non-exclusive mechanisms could explain this apparent decoupling of bioaccumulation from trophic transfer. The aggregation observed in the algal medium may have reduced the bioavailability of the nanoparticles to both producer and consumer. Daphnia’s limited assimilation efficiency for engineered nanomaterials, documented in earlier studies, may have prevented meaningful uptake from the gut. Rapid depuration is another candidate; previous work on conventional atrazine shows that uptake steady states in algae and Daphnia are reached within hours, while elimination occurs within minutes for algae and hours for microcrustaceans, leaving little time for residues to build up. The researchers also suggest that nATZ-PCL particles may simply have adhered to the daphnids’ carapace and swimming appendages rather than being absorbed, and that the small daphnid biomass available limited analytical sensitivity, meaning trace transfer below the detection limit cannot be excluded. The authors are careful to stress that their experiments identify the absence of measurable transfer without pinpointing which mechanism dominates.

The broader significance of the study lies in what it says about how we assess nanopesticide risk. For conventional hydrophobic pollutants and metals, bioaccumulation at the base of a food web is often a red flag for biomagnification up the chain. This work demonstrates that the same logic cannot be automatically applied to nanostructured formulations: accumulation in primary producers does not necessarily translate into efficient transfer to consumers, because aggregation state, eco-corona formation, bioavailability, assimilation efficiency, and toxicokinetics all intervene at each step. Earlier work by some of the same group had already found no significant adverse effects in Daphnia following trophic exposure to nanoatrazine, and the new data reinforce that picture. At the same time, the team cautions that real freshwater food webs involve far more species, greater ecological complexity, and concomitant exposure to transformed nanoparticles and other pollutants, all of which limit generalization from a single producer-consumer pair tested in the laboratory.

There is also a regulatory gap. Despite the rapid growth of nanopesticide products, no internationally accepted framework yet exists for evaluating their environmental risks, and laboratory toxicity data from a handful of model species remain a fragile basis for protecting the enormous diversity of freshwater life. The authors call for longer, more elaborate trophic-chain protocols, in situ physicochemical characterization of nanoparticles throughout exposure, and toxicokinetic studies across multiple trophic levels to determine whether the apparent containment of nanoatrazine at the producer level holds under field-realistic conditions. For now, the message is twofold: nanoencapsulation may genuinely curb the movement of a persistent herbicide through aquatic food webs, but proving that promise will require watching not just where the particles go, but what they become along the way.

Subject of Research: Bioaccumulation and trophic transfer of polymeric nanoencapsulated atrazine in a freshwater algae-zooplankton food chain

Article Title: Decoupling bioaccumulation and trophic transfer: nanoatrazine accumulates in microalgae but shows limited transfer to zooplankton

Article References: Braga, A. P. A., Vallim, J. H., Mendes, M. D. L., Levanteza, V. O., Assalin, M. R., Tavares, M. M., Fraceto, L. F., do Espírito Santo Pereira, A., & de Castro, V. L. S. S. (2026). Decoupling bioaccumulation and trophic transfer: nanoatrazine accumulates in microalgae but shows limited transfer to zooplankton. Environmental Monitoring and Assessment, 198(9), Article 1021. https://doi.org/10.1007/s10661-026-15831-y

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15831-y

Keywords: nanopesticides, atrazine, bioaccumulation, trophic transfer, Raphidocelis subcapitata, Daphnia magna, aquatic food web, nanoecotoxicology, polymer nanoparticles, natural organic matter, freshwater ecosystems, environmental monitoring

The new assessment deliberately departs from earlier approaches. Türkiye’s only previous national list, published in 2020, tallied 872 non-native species, but it included every species ever recorded in the country regardless of whether those populations had actually taken hold. The distinction matters enormously for management. A species that has been introduced but has not formed a self-sustaining population poses uncertain and often negligible risk, whereas an established species is far more likely to spread and exert ecological or economic impacts. By filtering out native, cryptogenic, and non-established records, the researchers reduced the national total to roughly a quarter of the earlier figure, producing a dataset that reflects genuine biological reality rather than a catalogue of historical sightings.

The taxonomic composition of the list is strikingly lopsided. Marine species dominate with 198 of the 271 established non-natives, followed by 42 terrestrial species, 27 freshwater species, three species occupying both terrestrial and freshwater habitats, and one freshwater-marine species. Among phyla, Chordata leads with 111 species, followed by Mollusca with 67 and Arthropoda with 52. The most species-rich class is Actinopterygii, the ray-finned fishes, with 100 species, ahead of Gastropoda with 48 and Malacostraca with 26. At the family level, ants of the Formicidae top the ranking with 14 established species, followed by the small parasitic snails of Pyramidellidae with nine, penaeid shrimp with eight, pufferfishes of Tetraodontidae with seven, and cardinalfishes of Apogonidae with five.

This marine dominance is not accidental. Türkiye’s extensive coastline along the Black, Aegean, and Mediterranean Seas provides a vast array of habitats, and these waters are under intense pressure from maritime traffic, aquaculture, and fisheries, all well-documented pathways for species introductions. The prominence of fish, snails, and crustaceans in the list mirrors the constant movement of ships, ballast water discharge, and farmed organisms through Turkish waters. By contrast, the comparatively low numbers of terrestrial and freshwater species likely reflect a combination of genuine ecological constraints and significant gaps in research and reporting. Türkiye has a long history of plant introductions for agriculture and horticulture, but the relatively small number of vascular plants in the dataset probably signals under-surveying rather than true absence.

The geographic pattern of establishment follows the pulse of human activity. Drawing on more than 10,000 occurrence records from the Global Biodiversity Information Facility, the researchers found that established non-native species concentrate in the western part of the country and decline eastwards. The provinces of Kayseri and Muğla each host 37 established non-native species, with Antalya close behind at 34. Urban and coastal areas, with their dense populations, robust trade networks, and well-developed infrastructure, offer multiple routes for species introductions, including maritime transport, the ornamental plant and pet trades, and ballast water discharge. Remote inland and mountainous regions show far fewer invasions, consistent with global patterns linking invasion intensity to human footprint.

Notably, a handful of birds dominate the occurrence data. The rose-ringed parakeet alone accounts for 5,080 records, or 49.3 percent of the total, with the Alexandrine parakeet contributing 2,166 records and the common myna another 879. Together these three species represent nearly 79 percent of all GBIF records for established non-native species in Türkiye, a reminder that detection effort is heavily skewed toward conspicuous, well-studied organisms in accessible locations. The apparent scarcity of non-natives in remote regions may therefore partly reflect a lack of surveying rather than a genuine absence of invasion.

Tracing the geographic origins of 256 established species, the study found that the Indo-Malayan realm is the dominant source, contributing 116 species or 45.3 percent of the total. Australasia follows with 52 species, then the Palearctic with 39, the Afrotropical realm with 17, the Nearctic with 16, and the Neotropical with six. This pattern underscores Türkiye’s role as a hub in global invasion networks, receiving organisms from across the tropical and subtropical world, largely through trade and transport corridors that connect it to Asia, Africa, and beyond.

Perhaps the most sobering finding concerns what remains unknown. Only 47 of the 271 established species, or 17 percent, have documented ecological or economic impacts within Türkiye, although the proportion rises to 41 percent when impacts reported anywhere in the world are considered. Among species with known impacts, ecological and environmental effects are the most frequently cited, followed by economic and socio-cultural harms. Competition is the most commonly reported impact mechanism, ahead of predation and rapid growth, with habitat alteration and disease transmission also recorded. The reporting gap is uneven across environments: freshwater species show a documented impact ratio of 38 percent, nearly double the 19 percent for marine species, while among phyla, Tracheophyta lead at 28 percent and Chordata trail at 14 percent. This bias toward well-known invaders means many threats may be growing silently, undetected until they become costly or irreversible.

Risk screening adds a further layer of urgency. Using the Aquatic Species Invasiveness Screening Kit, a decision-support tool comprising 55 questions covering basic and climate-change risk assessments, the researchers compiled results for 62 established species, roughly 23 percent of the national total. Under current climate conditions, 4.8 percent of screened species posed a very high risk of invasiveness, 40.3 percent a high risk, and 53.2 percent a medium risk. Under predicted climate change conditions, the picture darkens dramatically: the share of very high-risk species jumps to 21 percent, meaning that more than 60 percent of screened species fall into the high or very high risk categories as warming shifts the Turkish climate. Warming waters may allow tropical invaders arriving through the Suez Canal and shipping lanes to establish and spread more readily, turning today’s medium-risk species into tomorrow’s crises.

The study’s authors argue that this inventory provides a critical foundation for strengthening biosecurity policy, guiding targeted monitoring, and coordinating management responses at local, national, and international scales. They call for systematic impact assessments targeting under-studied groups and habitats, expanded screening of terrestrial animals and plants using recently developed tools, and a prioritization framework that weighs both risk scores and impact potential to allocate limited conservation resources where they matter most. Given that established populations in one region can serve as stepping stones for secondary spread within the country, through activities such as recreational angling and aquaculture, prevention at points of entry must be paired with vigilance against internal translocations. For a country whose rich biodiversity underpins agriculture, fisheries, and tourism, the message of this first national census is clear: the window for proactive management is open now, but it will not remain so indefinitely.

Subject of Research: National assessment of established non-native species in Türkiye

Article Title: The first national assessment of established non-native species in Türkiye

Article References: Tarkan, A. S., Yapıcı, S., Kurtul, I., Błońska, D., Vilizzi, L., Baş Sermenli, H., Farooq, S., Aldemir, C., Uçma Uysal, T., Giannetto, D., Bilge, G., Çiftçioğlu, M., Najafi-Majd, E., Aktay-Sözüer, L., Kaya, C., Bayçelebi, E., Aydın, İ., Haubrock, P. J., Briski, E., & Soto, I. (2026). The first national assessment of established non-native species in Türkiye. NeoBiota, 105, 297-317. https://doi.org/10.3897/neobiota.105.176362

Image Credits: AI Generated

DOI: 10.3897/neobiota.105.176362

Keywords: invasive species, non-native species, Türkiye, biodiversity, biosecurity, marine invasions, freshwater ecosystems, climate change, risk assessment, biological invasions, species monitoring, NeoBiota

The plant itself is a formidable adversary. Originating in the Amazon Basin, Eichhornia crassipes escaped its native range in the 1800s and has since earned a place on the International Union for Conservation of Nature’s list of the world’s 100 worst invasive species. Its secret is a buoyant architecture: swollen, air-filled petioles keep rosettes afloat while fibrous roots dangle below, and clonal growth through stolons allows populations to double with astonishing speed. In nutrient-rich, slow-moving waters, mats can reach biomass densities exceeding 60 kilograms per square meter. These floating carpets block sunlight, starve aquatic plants of photosynthesis, deplete oxygen and collapse native biodiversity. The socioeconomic toll is equally severe, as clogged waterways disrupt transport and fishing, and control campaigns drain local economies. Paradoxically, the same plant serves as a sensitive bioindicator, accumulating heavy metals and responding spectrally to pollutants such as endocrine disruptors and neonicotinoids, which makes it both a menace and a diagnostic tool.

The review traces how observation technology matured through distinct eras. In the mid-2000s, manned airborne campaigns using the HyMap hyperspectral sensor over the Sacramento–San Joaquin River Delta established the methodological baseline, proving that narrow spectral bands could separate water hyacinth from co-occurring vegetation. Handheld spectroradiometers such as the ASD FieldSpec Pro provided ground-truth precision, revealing in South African experiments that red-edge indices could detect chlorophyll changes caused by heavy metals and biocontrol weevils. The real transformation came with satellites. Early platforms like SPOT-5 and MODIS offered broad coverage but coarse resolution, while Landsat’s four-decade archive enabled retrospective analyses. The decisive turning point arrived in 2015 with Sentinel-2, whose 10-to-20-meter pixels, five-day revisit and red-edge bands made it the dominant platform in recent studies, appearing in 31 percent of the reviewed literature.

Each sensor family brings distinct strengths. Hyperspectral instruments, capturing hundreds of contiguous bands, excel at species-level discrimination and phenological tracking. Drone-mounted versions have pushed this capability to remarkable scales: a study using the Nano-Hyperspec sensor on a UAV achieved 94 percent overall accuracy in the California Delta, outperforming the 85 percent of an airborne HyMap survey, and successfully separated water hyacinth from structurally similar plants like Pontederia cordata and Trapa natans using indices built around near-infrared reflectance at 780 and 900 nanometers. Multispectral satellites trade spectral depth for scalability and continuity. Sentinel-2’s red-edge bands improved classification accuracy by nearly 10 percent compared with Landsat, and long NDVI archives have linked water hyacinth presence to urban wastewater inputs in small reservoirs worldwide.

Synthetic Aperture Radar adds an entirely different dimension: the ability to see through clouds, at night, in any season. This matters enormously in the tropics, where persistent cloud cover blinds optical sensors precisely when infestations explode. Studies in Vembanad Lake in India and the Winam Gulf of Lake Victoria in Kenya demonstrated that dense water hyacinth mats alter radar backscatter enough to be distinguished from open water, with true-positive rates of 90 to 98 percent over thick infestations. Five-year Sentinel-1 time series have mapped the weed’s expansion across Lake Victoria and tracked seasonal dynamics in Indian wetlands, where temporal variations in the VV polarization channel closely matched actual coverage. Yet radar has limits. Detection rates collapsed to 35 to 40 percent in low-density patches, exactly the regime that matters most for early warning, and wind-roughened water can mimic the volumetric scattering of vegetation.

On the analytical side, the field has climbed what the authors call an analytical ladder. Simple NDVI thresholds, such as values above 0.3 or 0.4 to flag floating vegetation, remain popular for their simplicity and compatibility with decades of Landsat data. NDVI values between 0.6 and 0.95 tracked seasonal biomass in Lake Tana, Ethiopia, and median reservoir NDVI correlated with water hyacinth cover with an R-squared of 0.91 in Portuguese studies. But where multiple floating species coexist, spectral confusion undermines thresholds. Machine learning classifiers, particularly Random Forest and Support Vector Machines, now routinely exceed 85 percent accuracy, and object-based image analysis that segments imagery into meaningful patches has pushed detection accuracies above 99 percent in some settings. Deep learning represents the frontier: U-Net segmentation of five-band drone imagery achieved a mean Intersection over Union of 97 percent, while a two-dimensional CNN trained on Sentinel-2 data reached 95.9 percent accuracy in detecting invasive aquatic plants along Spain’s Guadiana River.

The review also delivers a sobering reality check on accuracy claims. Overall accuracy figures above 95 percent are often inflated by the vast open-water background that dominates aquatic scenes. One study reported nearly 99 percent overall accuracy but only 67 percent user’s accuracy for water hyacinth itself, meaning a third of detections were false positives. Another recorded 85 percent overall accuracy yet just 70 percent producer’s accuracy for the target species, the worst among eight plants studied, owing to confusion with similar floating species. Validation design compounds the problem: when reference samples come from the same imagery being classified, systematic errors escape scrutiny entirely. The authors call for consistent reporting of class-specific metrics and spatially independent validation as prerequisites for credible cross-study comparison.

Perhaps the most actionable insight concerns timing. Chlorophyll-sensitive indices such as the Normalized Difference Chlorophyll Index consistently rise before NDVI signals canopy growth, and in Lake Tana, peaks in chlorophyll-a and suspended sediment preceded water hyacinth biomass peaks by about a month. This lead time of days to weeks offers a genuine early-warning window. Environmental correlations reinforce the predictive potential: lake levels, turbidity with a two-month lag, nutrient concentrations and surrounding urban land cover all statistically anticipate infestation expansion. In Sri Lanka, high-resolution Planet imagery has even been used to estimate recoverable biomass across 28 water bodies, converting invasion maps into circular-economy opportunities for biochar, compost and bioenergy production.

What distinguishes this review is its insistence that detection alone is not management. Since 2021, multi-platform studies combining drones with satellites have surged, with 37 percent of the analyzed research now using two or more platforms. Drone orthomosaics at 5-to-6-centimeter resolution calibrate Sentinel-2 classifications, replacing laborious ground-truthing, while satellite data guide UAV deployment to priority hotspots. The authors distill these practices into a decision-support framework built on five pillars: multi-scale sensor fusion anchored by weekly optical-radar time series; classification schemes that encode species identity, anchorage state and phenological stage rather than mere presence; a scalable analytical ladder matching algorithmic complexity to management urgency; early-warning indicators exploiting pre-emergence physiological signals; and feedback loops that feed monitoring results back into intervention planning and evaluation. Knowing whether a mat is flowering or senescent, free-floating or rooted, determines whether harvesters, netting or biological control is the right response.

The challenges that remain are as much institutional as technical. Data harmonization across platforms, model transferability between ecosystems, and the persistent gap between published methods and field operations all constrain progress. The review’s own limitations, including its restriction to English-language, DOI-traceable literature, mean that valuable operational knowledge from affected regions may be missing. Still, the trajectory is unmistakable. As climate variability and nutrient pollution intensify pressure on freshwater systems worldwide, the convergence of free satellite archives, cheap drones and increasingly accessible machine learning offers resource-strapped managers something they have never had: a responsive, scalable early-detection system for a weed that has historically outpaced every attempt to contain it. The lavender blooms may keep coming, but for the first time, the watchers above the water are seeing them coming first.

Subject of Research: Remote sensing methods and decision-support frameworks for monitoring and managing the invasive aquatic plant Eichhornia crassipes (water hyacinth)

Article Title: Remote sensing for monitoring and managing Eichhornia crassipes: a review of methods, applications, and decision-support frameworks

Article References: Salim, D. H. C., Mello, C. C. S., Pereira, G., Maretto, R. V., & Amorim, C. C. (2026). Remote sensing for monitoring and managing Eichhornia crassipes: a review of methods, applications, and decision-support frameworks. Environmental Monitoring and Assessment, 198(9), Article 1024. https://doi.org/10.1007/s10661-026-15788-y

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15788-y

Keywords: water hyacinth, Eichhornia crassipes, remote sensing, invasive species, Sentinel-2, Sentinel-1 SAR, UAV monitoring, hyperspectral imaging, machine learning, deep learning, NDVI, freshwater ecosystems

The investigation focused on four large lakes and four smaller reservoirs, sampling twice annually to capture seasonal variations in fish assemblages. Researchers utilized cast nets, kick nets, and gill nets to collect a total of 9,105 individual fish representing 41 species from 11 families. Among these, the invasive alien species accounted for a substantial portion of the catch, with bluegill and largemouth bass together comprising 43.35% of all individuals collected in the lake sites. This high relative abundance indicates that these non-native fish have established dominant positions within the food webs of these ecosystems, often outcompeting or preying upon native species.

Statistical analysis of the collected data demonstrated a clear negative correlation between the density of invasive species and the diversity of native fish communities. Using Poisson-based analysis of variance models, the study found that sites with higher densities of largemouth bass and bluegill exhibited significantly lower Shannon diversity indices. The effect of bluegill density was particularly strong, with a highly significant impact on diversity, while largemouth bass density also showed a significant negative effect. Furthermore, the interaction between the two invasive species was significant, suggesting that their combined presence exacerbates the decline in native species richness and evenness more than either species alone.

Non-metric multidimensional scaling analyses further illustrated distinct community groupings based on waterbody type and the presence of invasive species. The ordination plots revealed that fish assemblages in lakes and reservoirs clustered separately, confirming size-related differences in community structure. Notably, Buckchosan Reservoir plotted distinctly from other sites after a complete removal project for largemouth bass was implemented in 2020. Following this intervention, no invasive alien species were detected in subsequent years, leading to a measurable increase in diversity and species richness. This case study provides empirical evidence that active management can reverse some of the ecological damage caused by invasive populations.

The distribution patterns of the two invasive species differed markedly between lakes and reservoirs. Bluegill were predominantly found in the larger lake sites, where they often acted as dominant or subdominant species. In contrast, largemouth bass were more prevalent in the reservoirs, although their abundance varied significantly across sites. In Gwanglyeong Reservoir, the relative abundance of invasive species reached 99.19%, indicating a severely degraded community where native fish were nearly displaced. This extreme imbalance highlights the vulnerability of smaller, enclosed water bodies to biological invasion, where limited habitat complexity and resources make native species more susceptible to disruption.

Historical context reveals that both species were intentionally introduced to Korea to improve fishery resources and address food shortages. Largemouth bass were introduced from North America in 1973, while bluegill arrived from Japan in 1969. Since then, both species have spread rapidly through rivers and reservoirs, adapting to local conditions and occupying higher trophic levels. Their generalist feeding habits allow them to exploit a wide range of prey, including aquatic invertebrates, small fish, and fish eggs. This predatory pressure, combined with competition for habitat and food, has led to a decline in the abundance of native species and a reduction in overall ecosystem health.

The study also examined the impact on Korean endemic species, which are particularly vulnerable to invasive competition. The average percentage of endemic species in Korea is estimated at 25.9%, but most study sites recorded lower proportions, with only Lake Chuncheon exceeding this baseline. The endangered species Pseudopungtungia nigra was captured once in 2019 but has not been recorded since, suggesting a potential local extinction due to invasive pressure. These findings emphasize that invasive alien species are not only reducing general biodiversity but also threatening unique and irreplaceable components of the local fauna, contributing to the broader global loss of freshwater biodiversity.

Management implications from the research suggest that strategies must be tailored to different habitat scales and waterbody types. The successful removal of largemouth bass from Buckchosan Reservoir demonstrates that targeted interventions can restore community balance, but such efforts require sustained monitoring to prevent re-invasion. The study recommends continued long-term monitoring to track population dynamics and assess the effectiveness of management actions. Additionally, expanding the number of sampling locations across different river basins is necessary to generalize these findings and develop robust policies for invasive species control in other regions of Korea.

As international trade and industrial development continue to facilitate the spread of alien species, the ecological and economic costs of inaction are becoming increasingly apparent. The global economic loss due to invasive species is estimated at approximately 530 trillion KRW annually, with freshwater ecosystems bearing a disproportionate share of the biodiversity loss. This five-year study provides a foundational dataset for understanding the long-term impacts of largemouth bass and bluegill in Korean waters, offering valuable insights for conservationists and policymakers. By identifying the specific mechanisms through which these species disrupt native communities, the research supports the development of more effective and targeted management strategies to preserve the integrity of freshwater ecosystems.

Subject of Research: Impacts of invasive alien fish species— Micropterus salmoides and Lepomis macrochirus (Actinopterygii, Centrarchiformes, Centrarchidae)—on freshwater fish communities in lakes and reservoirs of Korea: A five-year monitoring study

Article Title: Impacts of invasive alien fish species— Micropterus salmoides and Lepomis macrochirus ( Actinopterygii , Centrarchiformes , Centrarchidae )—on freshwater fish communities in lakes and reservoirs of Korea: A five-year monitoring study

Article References: Cho, Y. J., Kim, J.-W., Park, C.-W., Lee, S. I., & Kim, J.-G. (2025). Impacts of invasive alien fish species— Micropterus salmoides and Lepomis macrochirus (Actinopterygii, Centrarchiformes, Centrarchidae)—on freshwater fish communities in lakes and reservoirs of Korea: A five-year monitoring study. Acta Ichthyologica et Piscatoria, 55, 281-289. https://doi.org/10.3897/aiep.55.164833

Image Credits: AI Generated

DOI: 10.3897/aiep.55.164833

Keywords: Impacts, invasive, alien, fish, species, Micropterus, salmoides, Lepomis, macrochirus, Actinopterygii, Centrarchiformes, Centrarchidae

The research team, working at 17 long-term monitoring sites across Slovakia’s Western Carpathian streams, put DNA metabarcoding head-to-head with the conventional morphological approach that has underpinned national biomonitoring for decades. The conventional method is exactly what it sounds like: kick-net the stream bed, sort the animals under a microscope, and identify each one by eye, a process that demands scarce taxonomic expertise and, in Slovakia’s case, typically examines only about 20 percent of each collected sample. The molecular alternative reads the same material differently, extracting DNA from the sample and matching genetic barcodes against reference databases to produce a species list without anyone peering down a microscope.

The headline result is striking. DNA metabarcoding detected roughly 30 percent more species than fifteen years of conventional monitoring had accumulated at the same sites, spanning records from 2007 to 2022. At one site on the Morava River, thirteen conventional samples collected over many years had yielded between 12 and 30 species per sampling event; a single metabarcoding sample recorded 82 species. At the Rimava River, where both methods were applied simultaneously, the molecular approach outdetected morphology by 37 species. In total, 40 percent of all species captured across both approaches were found exclusively by metabarcoding, while only about 27 percent were exclusive to the conventional method.

The study also compared three ways of feeding DNA to the sequencer, and the verdict was clear. Bulk samples, meaning the entire preserved mass of collected invertebrates homogenised and extracted whole, captured on average 85 percent of all species detected at each site. Environmental DNA filtered from the water column managed only about 30 percent, and sediment eDNA just under 14 percent. Yet the eDNA samples were not useless: they uniquely recorded entire classes of animals, including rotifers, sponges and other soft-bodied organisms that bulk sampling misses entirely, hinting that a combined strategy could deliver the fullest picture of stream life.

Behind those percentages lies a deeper story about hidden biodiversity. The metabarcoding data revealed cryptic diversity, cases where one named species actually comprises several genetically distinct lineages, in 87 of the 463 species detected. The midge family Chironomidae, notorious among taxonomists for its difficulty, was the richest example: 23 recognised species resolved into 51 genetic units. Groups that morphologists struggle with, such as flies, worms and mayflies, were precisely where the molecular method pulled furthest ahead, with Diptera species detected at more than double the rate of conventional identification.

The crucial question, of course, is whether all this extra detection actually changes the regulatory verdict. Under the Water Framework Directive, species lists feed into multimetric indices that produce an Ecological Quality Ratio, which places each water body into one of five status classes ranging from high to bad. Slovakia’s system uses between six and eleven metrics per stream type, some depending on species abundances and others simply on which species are present. If metabarcoding produced wildly different scores, regulators could not adopt it without rewriting the rulebook.

Encouragingly, the answer was mostly reassuring. For abundance-dependent metrics such as the Saprobic Index, where the researchers used sequencing read counts as a proxy for how many individuals of each species were present, the two approaches agreed closely, typically within a single ecological quality class. The real divergence appeared in presence-absence metrics such as EPT taxa, the BMWP score and the number of families, which are sensitive to every additional species detected. Because metabarcoding simply sees more species, these metrics often scored higher, sometimes shifting the assessment by two or even three quality classes, and generally in the direction of a better grade.

That pattern played out in the final status assessments too. At ten of the seventeen localities, the molecular approach assigned a higher ecological class than the conventional record: four sites moved from moderate to good status, and six improved from good to high. Seven sites were unchanged. The researchers attribute much of this inflation not to flattery but to calibration: the reference thresholds that define each class were originally derived from morphology-based data, so a method that detects more species will inevitably overshoot thresholds built for a blunter instrument. Recalibrating those thresholds for molecular data, they argue, would likely close most of the gap.

None of this means metabarcoding is a finished product. The technique has well-documented weaknesses, from false positives caused by nuclear copies of mitochondrial genes to errors and gaps in reference databases, and read counts remain an imperfect stand-in for true abundance since they can be skewed by PCR bias and do not distinguish life stages. The team mitigated these problems by filtering low-confidence matches, verifying species against Slovak freshwater checklists, and drawing on the growing regional barcode library AquaBOL.SK. Molluscs, notably, were detected less well by DNA than by morphology, a reminder that the two methods each have blind spots the other partially fills.

Still, the implications for Europe’s rivers are hard to ignore. Routine biomonitoring is expensive, slow and increasingly constrained by the shrinking pool of experts able to identify larvae by eye, and the study demonstrates that metabarcoding under real field conditions, at real regulatory sites, can deliver assessments that are faster, broader and largely consistent with the legacy method. With reference databases improving every year and thresholds awaiting recalibration, the authors conclude that DNA-based monitoring is already a viable alternative rather than a distant promise. For the invertebrates quietly grading Europe’s streams, and for the agencies charged with protecting them, the microscope may finally be getting a molecular assistant.

Subject of Research: DNA metabarcoding for assessing ecological status of streams under the EU Water Framework Directive

Article Title: Evaluating the potential of DNA metabarcoding for ecological status assessment under the Water Framework Directive: A case study on benthic invertebrates from Western Carpathian streams

Article References: Šamulková, M., Beracko, P., Macko, P., Vargovčík, O., Tuhrinová, K., Čiamporová-Zaťovičová, Z., Lešťáková, M., Mišíková Elexová, E., & Čiampor Jr, F. (2025). Evaluating the potential of DNA metabarcoding for ecological status assessment under the Water Framework Directive: A case study on benthic invertebrates from Western Carpathian streams. Metabarcoding and Metagenomics, 9, Article e163640. https://doi.org/10.3897/mbmg.9.163640

Image Credits: AI Generated

DOI: 10.3897/mbmg.9.163640

Keywords: DNA metabarcoding, Water Framework Directive, benthic macroinvertebrates, ecological status, environmental DNA, biomonitoring, freshwater ecosystems, Slovakia, Carpathian streams, multimetric index, cryptic species, bulk samples

The research team, working at the University of Barcelona, set out to address a persistent gap in invasion ecology. Most studies of invasive plants examine one or two links in the food web, but the impacts of a non-native species can ripple across many trophic levels at once. Leaf litter decomposition is one of the main routes through which invasive plants reshape ecosystems: as leaves break down in water, they release chemicals and nutrients that alter bacterial and fungal communities, which in turn feed the tiny animals that graze on them. Among these grazers are microeukaryotes, a catch-all group that includes protozoa such as amoebae, flagellates and ciliates, as well as small metazoans like rotifers and nematodes. Despite their central role in microbial food webs, microeukaryotes have been largely overlooked in studies of plant invasion.

The experiment focused on two morphologically similar reeds. Arundo donax, the giant reed, is considered one of the world’s worst invasive plant species and forms dense stands in Mediterranean streams, ponds and ditches, displacing natives such as Phragmites australis, the common reed. Both plants are abundant along the Delta del Llobregat near Barcelona, where the researchers collected freshly fallen leaves of both species from the same channels in June 2022. The leaves were dried, fragmented and mixed in five different proportions, ranging from microcosms containing 100 percent native reed litter to mixtures with 25, 50, 75 and 100 percent giant reed litter. Each one-litre glass jar received one gram of leaf material, ultrapure water and a splash of pond water containing a natural microbial community.

After allowing fifteen days for the leaves to leach and the microbes to colonise, the team added twenty first-instar larvae of Culex pipiens, the northern house mosquito, to each microcosm. This species was chosen deliberately: it is native to Europe, Africa and Asia, and its adults can transmit pathogens of serious human and veterinary concern, including West Nile virus, St. Louis encephalitis virus, filariasis and avian malaria. The larvae were fed exclusively by the microbial food web growing on the decaying leaves, with no artificial supplements, so that any differences in their development could be traced back to the leaf litter itself. Jars containing only water and pond inoculum, with no leaves at all, served as negative controls, and every larva in them died, confirming that leaf litter was the essential fuel for the entire system.

Before the larvae were introduced, the researchers characterised the microeukaryote communities under a phase-contrast microscope, counting and identifying organisms drop by drop. The results were striking. Leaf litter of any kind boosted microbial life compared to leaf-free controls, but increasing the share of giant reed litter significantly raised both the total density and the taxonomic richness of microeukaryotes. The composition of the community also shifted markedly: flagellates such as Peranema, planktonic ciliates like Cyclidium, lecanid rotifers and the testate amoeba Euglypha became characteristic of the giant reed treatments. Viewed through the lens of functional guilds, the densities of flagellates, planktonic ciliates and micrometazoa all climbed as the invader’s share increased, a pattern the authors interpret as evidence of enhanced bacterial productivity driven by nutrients released from the giant reed leaves.

The mosquito responses mirrored these microbial shifts, and in a direction the researchers did not expect. Because previous work had shown giant reed tissues to be unpalatable and nutritionally poor for herbivores and detritivores, the team had predicted that the native reed would best support larval development. Instead, microcosms with giant reed litter produced more pupae that were heavier and reached pupation sooner than those in jars with only native reed litter. Pupae mass increased progressively with the proportion of invasive litter, while the effects on pupae number and development time became pronounced once just a quarter of the native biomass had been replaced, and then levelled off. The proportion of females, notably, did not change across treatments.

To understand what was driving these effects, the team measured an extensive suite of water properties at the end of the experiment, including pH, dissolved oxygen, conductivity, dissolved organic carbon, ammonium and a long list of elements released during decomposition, from essential nutrients such as phosphorus, potassium and sulphur to potential pollutants such as zinc, copper, arsenic and lead. A principal component analysis revealed that microcosms with pure giant reed and pure native reed separated clearly along the first axis, which loaded heavily on conductivity, ammonium, aluminium, copper, zinc and silicon. The giant reed generally enriched the water with ions, with the notable exception of silicon, compared with the native reed at similar rates of leaf mass loss.

Statistical modelling showed that water chemistry explained mosquito performance better than the microeukaryote densities measured after pupation. Pupae numbers and total pupae mass rose with the first principal component scores, while mean development time fell with both major axes of water chemistry. Female proportion was positively related to the second axis, which captured arsenic, iron and lead, and to amoebae density. Some weaker but significant microeukaryote effects emerged as well: pupae number and mass decreased with flagellate density, hinting at either competition between larvae and nanoflagellates for bacteria or direct predation by larvae on these microbes. Fungal filaments, although more abundant with increasing giant reed litter, did not significantly explain any mosquito trait.

The abrupt, threshold-like responses in both microbes and mosquitoes point to nutrient limitation in the native reed treatments. Elements such as phosphorus, potassium, sulphur, sodium and magnesium, all higher in the giant reed microcosms, are essential for physiological regulation in mosquitoes, and their scarcity in the native litter may have constrained both microbial growth and larval development. Silicon in the native reed may also have hampered larval browsing, as it does for amphipod shredders. Although some measured concentrations of zinc and copper exceeded water quality standards, and arsenic and lead were detectable, both mosquito larvae and microeukaryotes appeared to tolerate these conditions well.

The authors argue that these findings carry practical weight for both invasion management and mosquito control. Because effects emerged when only 25 percent of the native reed biomass had been replaced, defining a safe threshold for giant reed invasion appears challenging where eradication is unfeasible. Heavier pupae imply female mosquitoes with greater reproductive potential and longevity, potentially increasing biting nuisance and disease transmission risk, while faster development narrows the window during which control services can target larvae, the most efficient stage for intervention. The researchers recommend prioritising early removal of the giant reed and restoring invaded sites with native vegetation, integrated with established tools such as Bacillus thuringiensis israelensis and natural predators. They also caution that real populations depend on factors outside the experiment, including where female mosquitoes choose to breed, and call for future work on how invasive litter reshapes the internal microbiota of mosquitoes, a key frontier in vector biology.

Subject of Research: Effects of invasive giant reed leaf litter on water chemistry, microeukaryote communities and mosquito larval development

Article Title: Invasive plant-induced shifts in water chemistry and microeukaryotes enhance mosquito development

Article References: Cano-Rocabayera, O., Bonilla, Y. Y., Salvadó, H., Garcia-Bargalló, M., Sobhy, I. S., Berry, C., Vilà, M., Sabater, F., Aranda, C., & Maceda-Veiga, A. (2026). Invasive plant-induced shifts in water chemistry and microeukaryotes enhance mosquito development. NeoBiota, 106, 265-286. https://doi.org/10.3897/neobiota.106.167149

Image Credits: AI Generated

DOI: 10.3897/neobiota.106.167149

Keywords: invasive species, Arundo donax, Phragmites australis, leaf litter, microeukaryotes, Culex pipiens, mosquito development, water chemistry, trophic cascade, freshwater ecosystems, public health, NeoBiota