After a long-term monitoring campaign spanning 1999-2025, the populations of Nymphaeids growing in Sardinia were comprehensively investigated. Within the family Nymphaeaceae, Nuphar lutea and Nymphaea alba are native species on the island, while two other taxa are alien: Nymphaea mexicana and N. × marliacea, both currently naturalized in Sardinia. Two additional taxa, one native (Nymphoides peltata) and one alien (Nelumbo nucifera) remain unconfirmed: the former was reported only once in 1827, and the latter was recorded as naturalized twenty years ago, but with no precise location or subsequent observations. Overall, we recorded the occurrence of N. alba at 166 sites (eight of which are now locally extinct) and N. lutea at 38 sites (two of which are now locally extinct). Regarding N. alba, its populations in northern Sardinia have all been described in detail, with numerous metapopulations documented, particularly within the hydrographic basins of the Coghinas, Temo, and Posada rivers, as well as in other smaller basins. Moreover, some stations in South Sardinia have been confirmed after more than a century. In addition, N. candida is definitively excluded from Sardinian flora. As for Nuphar lutea, its localities have been further refined, all concentrated in the Coghinas River basin, whereas the only known sites in the South have now disappeared. Moreover, an updated and verified distribution of exotic waterlily populations in Sardinia is provided. Furthermore, the ecological requirements, the main threats and conservation issues affecting native taxa on the island are identified.
Freshwater ecosystems of the Mediterranean basin are increasingly exposed to hydroclimatic fluctuations, often interacting with sustained anthropogenic pressures. However, in North African rivers, the ecological patterns of endemic aquatic invertebrates remain poorly documented. In this context, the Upper Loukkos Watershed (northern Morocco), a mountainous system within the Intercontinental Mediterranean Biosphere Reserve, provides a relevant setting to examine how environmental gradients and seasonal dynamics influence these assemblages. Endemic macroinvertebrates were sampled across 18 sites during four sampling campaigns (spring and autumn 2014-2015), capturing contrasting hydro-seasonal conditions from drought-induced low flows to post-flood periods. A total of 667 individuals belonging to 24 endemic species were recorded, including Moroccan, Maghrebian, and Ibero-Maghrebian taxa. Diversity metrics varied across sites and seasons, with a clear peak in spring, coinciding with increased flow permanence and partial recovery of hydrological connectivity. The mayfly Choroterpes atlas was the most abundant taxon, whereas the genus Hydraena showed the highest diversity. Multivariate analyses (NMDS, CCA) revealed that environmental gradients strongly structured species distribution. Sites characterized by elevated organic load and suspended solids were associated with disturbance-tolerant taxa (mainly Coleoptera and Hemiptera), whereas well-oxygenated lotic habitats supported rheophilic Ephemeroptera and Plecoptera. Spatial and seasonal patterns revealed a marked turnover in endemic assemblages based on their temporal stability, dominated by intermittent taxa (41.7%); only Hydraena allomorpha was classified as permanent, being recorded throughout all sampling periods. The Jaccard similarity index revealed consistently low overlap in community composition among sampling campaigns, indicating pronounced temporal turnover in the macroinvertebrate assemblage. The predominance of Ibero-Maghrebian taxa underscores the biogeographical significance of the Betico-Rifan region as a link between Europe and Africa. Overall, these findings identify Rif headwaters as key habitats for range-restricted freshwater taxa and highlight their potential role as climatic refugia under increasing hydroclimatic variability. This underscores the need for sustained, long-term monitoring and for explicitly incorporating intermittent and headwater streams into conservation frameworks, which remain underrepresented despite their ecological importance in North African river networks.
Groundwater ecosystems host highly specialised and frequently endemic faunas, yet their biodiversity remains poorly explored. Although Italy is recognised as a hotspot of subterranean diversity, knowledge of its stygobitic ostracods (i.e., species that are obligate inhabitants of subterranean waters) remains fragmentary. Here we report new data on ostracods collected from 15 natural caves, a mine and an aquifer across mainland Italy and Sicily between 2009 and 2018, with the aim of documenting new occurrence records from poorly investigated subterranean sites, discussing their taxonomic implications, and reassessing the diversity and endemism of Italian stygobitic ostracods in a broader European context. Nineteen taxa belonging to 12 genera and five families were identified, several of which are regarded as strictly stygobitic. These include representatives of Mixtacandona (Candonidae), among which several putative undescribed species of the laisi-chappuisi group were detected. Particularly noteworthy is the occurrence of Mixtacandona cf. botosaneanui in southern Italy: if its identity with the nominal species is confirmed, this record would considerably extend its known geographical range and provide the first description of the male, thereby adding important taxonomic information for a poorly known subterranean lineage. We also report a new record of Typhlocypris cf. eremita and specimens referable to Pseudolimnocythere, further expanding the known distribution of these genera within Italian subterranean habitats. Although some specimens could be assigned only tentatively because well-preserved adults were scarce, the new records substantially refine current knowledge of Italian groundwater ostracod diversity and distribution patterns at both regional and European scales. An updated checklist raises the number of Italian stygobitic ostracods to more than 30 taxa, representing approximately 30% of the currently known European groundwater ostracod diversity. This proportion is remarkable given the limited extent of Italian territory, and the high frequency of endemic and potentially undescribed species further highlights the Italian peninsula and its islands as important centres of diversification for subterranean ostracods. These results emphasize the need for continued biospeleological surveys and integrative taxonomic approaches combining morphology and molecular data to resolve species boundaries, phylogenetic relationships and colonization histories in subterranean lineages.
We present the first isotopic dataset for two shallow, slightly brackish Mediterranean lakes in Sicily colonised by Chara baltica (Lago Preola) and Najas marina (Lago Murana). Seasonal stable isotopes (δ13C, δ15N) and elements concentration (C%, N%) were measured in macrophytes and sediments over one year. Lago Murana sediments were more 13C-depleted than Lago Preola. Both lakes showed similar seasonality: 13C-enriched and 15N-depleted values in spring–summer, lower in autumn–winter. Greater seasonal variability in Preola indicates macrophyte-derived organic matter input to sediments, whereas Murana reflects run-off from surrounding pastures and vineyards. These results offer a preliminary framework for future work.
Dreissena polymorpha, the zebra mussel, is one of the most widespread and ecologically disruptive invasive species in European freshwater systems. Despite its long presence in Latvia, genetic information on local populations has been lacking. This study provides the first comprehensive assessment of genetic diversity and population structure of D. polymorpha across seven Latvian waterbodies, representing lakes, a reservoir, and a river system. Individuals were genotyped using five polymorphic microsatellite loci. Genetic variation was analysed through the standard genetic parameters, namely, number of alleles and frequency, heterozygosity estimates and genetic differentiation was estimated using FST statistics, Bayesian clustering, PCA, and Nei’s genetic distance. All loci were polymorphic, and no evidence of null alleles or recent bottlenecks was detected. Populations exhibited high genetic diversity. Significant heterozygote deficits were found in most populations. Genetic differentiation among populations was moderate overall, though three geographically proximate lakes showed minimal differentiation. Bayesian clustering and PCA identified four distinct genetic groups, indicating that hydrological isolation and limited dispersal contribute to population structuring. These findings demonstrate that Latvian D. polymorpha populations maintain substantial genetic diversity and exhibit clear spatial genetic structuring. This genetic information provides an essential foundation for monitoring invasion dynamics and informing management strategies aimed at limiting further spread and ecological impact.
Peatlands and peat-like habitats are among the most vulnerable ecosystems to climate change. Owing to their specific microclimatic conditions, which maintain high and stable moisture levels, they host assemblages dominated by hydrophilous taxa, including several groups of tardigrades. Despite this, tardigrade diversity in peat-related habitats remains poorly known. Here, we conducted an extensive taxonomic survey of tardigrades based on 35 samples collected from alpine fens in northern Italy. We detected 30 species-level tardigrade taxa, of which 23 were successfully DNA barcoded. One species of the genus Crenubiotus is new to science and is formally described herein as Crenubiotus meg sp. nov. We also provide updated morphological and taxonomic information for two enigmatic taxa, Fontourion secchii and Microhypsibius minimus, which have long been hindered by data deficiency. Notably, the assemblage recovered comprises several taxa with boreo-alpine or cold-adapted affinities, highlighting alpine peatlands as potential refugial habitats for relict tardigrade lineages. In addition, we performed phylogenetic analyses to resolve the placement of the newly described Crenubiotus species and to clarify the relationships of four Murrayon lineages recovered in this study. This work represents the first integrative taxonomic inventory of tardigrades inhabiting peat-like habitats and contributes an extensive, curated set of reference DNA sequences for this understudied habitat. These data provide an essential foundation for high-throughput biodiversity assessments using mega- and metabarcoding approaches and offer new insights into tardigrade taxonomy and evolutionary relationships.
Invasive aquatic macrophytes represent an increasing concern for freshwater ecosystems, where they alter biodiversity, ecosystem functioning, and water-related services. Among them, the submerged species Elodea nuttallii has rapidly expanded across many European waterbodies, yet its ecology in regulated lowland rivers remains insufficiently explored, particularly compared to that in artificial canals, ponds, and lakes. This study investigates the environmental, hydrological, and biotic factors shaping the occurrence and distribution of E. nuttallii in an urban river system. Field surveys conducted in 2025 documented macrophyte assemblages and habitat conditions in the Po River, the longest Italian river, flowing through the city of Turin. A total of 150 presence-absence points for E. nuttallii were recorded, spaced at least 200 meters apart, along the urban stretch of the river, collecting information on temperature, dissolved oxygen, pH, conductivity, as well as the presence of other macrophytes and the extent of plant populations. The results show that most vegetated patches are dominated by E. nuttallii, which is associated with depositional areas characterised by soft sediments and significantly related to the presence of Myriophyllum spicatum, as demonstrated by Phi correlation analysis. Although interspecific competition appears to limit E. nuttallii’s relative abundance during the seasonal macrophyte community peak, when its mean relative cover drops from 89.2% to 60%, its extended vegetative season likely contributes to its persistence. Moreover, substrate type emerged as the primary abiotic factor shaping spatial distribution in a regulated lowland river, with sand and silt providing optimal conditions for its establishment. We further highlight the need for early season and site-specific management interventions. Given the ecological and recreational significance of the Po River and its role as a dispersal corridor, understanding the invasion dynamics of E. nuttallii is critical for informing management strategies, particularly in light of its designation as an EU-priority alien invasive species.
Freshwater lakes are fundamental ecosystems that provide essential ecosystem services for humans and support high plant diversity, often including specialized and rare species. Nevertheless, in Italy, botanical knowledge of lake ecosystems remains fragmented, and floristic data are scattered across heterogeneous sources. DataLake is a dataset designed to integrate and standardize existing floristic knowledge on aquatic and riparian vascular plants occurring in 30 natural freshwater lakes of central-southern Italy. Records included in DataLake derive from both literature sources and original field surveys conducted by the authors. Overall, DataLake comprises 5140 georeferenced floristic records referring to 213 taxa, 97 genera and 43 families. The dataset highlights a markedly uneven distribution of taxa and records among lakes, with large tectonic and volcanic basins accounting for the highest floristic richness and number of records. The taxonomic composition is dominated by Cyperaceae, Potamogetonaceae and Juncaceae, while at the species level Myriophyllum spicatum L., Ceratophyllum demersum L., Phragmites australis (Cav.) Trin. ex Steud., Potamogeton perfoliatus L. and Stuckenia pectinata (L.) Börner are the most frequently recorded taxa. A substantial proportion of taxa is included in regional (39% of the dataset) and national (10.8%) conservation risk categories, underlining the role of lacustrine ecosystems as important reservoirs for plant species of conservation concern. Alien species were recorded in 14 lakes, and among these, 12 taxa are classified as invasive, including Paspalum distichum L., Elodea canadensis Michx. and Bidens frondosa L.. Biological and chorological spectra reflect the strong ecological dependence of lacustrine plant species on hydrological conditions, with dominance of hydrophytes and helophytes and multizonal taxa. By integrating heterogeneous floristic data into a single, coherent and openly accessible resource, DataLake provides a solid reference base for future floristic research, as well as for supporting long-term monitoring activities and actions aimed at conserving natural Mediterranean freshwater lake ecosystems.
Driven by global economic and population growth, the diversion of streamflow, via pipeline networks, for agricultural, livestock, or domestic purposes, has had a significant impact on water demand. These processes have created an urgent need for sustainable water resource management. Environmental flow regimes have become a key tool in watershed-wide management plans, as they enable appropriate water allocation while maintaining the functionality of riverine ecosystems. The northwestern region of the State of Baja California, Mexico, is characterized by a mediterranean climate, an average annual precipitation lower than 400 mm, and a critical water availability situation due to the overexploitation of aquifers for agriculture and urban development. The present study proposes environmental flow modeling to support the habitat connectivity of the endemic trout Oncorhynchus nelsoni (Evermann, 1908) in a third-order stream in a basin forming part of the Mexican region of what is known as Mediterranean California, due to its specific climatic characteristics. The modeling was achieved via an adaptation of the hydrobiological Instream Flow Incremental Methodology (IFIM) that adhered to the procedures stipulated under Official Mexican Standard NMX-AA-159-SCFI-2012. Given special protection status under Official Mexican Standard NOM-059-ECOL-2010, this endemic trout is currently threatened by various anthropogenic activities and natural factors, including climate change. The present study developed a riverine habitat model in the El Potrero Stream, a representative site in the distribution range of the trout of interest, to evaluate the environmental flow required to maintain aquatic habitat connectivity. A minimum environmental flow of 0.02 m3s-1 was identified as sufficient to ensure habitat connectivity, while a value of 0.01 m3s-1 was determined as sufficient for the formation of a discontinuous stream with isolated pools that could serve as temporary thermic refuges for the trout during prolonged multi-year drought conditions. The present study found that levels exceeding the optimal water volume did not increase access to a suitable habitat for the endemic trout and may even become detrimental to it during high-flow events. We recommend the continued implementation of hydrological monitoring programs in the El Potrero Stream, along with the inclusion of representative sites such as the San Antonio de Murillos stream (type locality), which is currently threatened by anthropogenic activities. Monitoring these streams will enable a more robust characterization of temporal streamflow variability under seasonal climatic conditions and will contribute to a better understanding of the hydraulic connectivity between stream segments throughout the annual cycle.
Lake Skadar is the largest freshwater body on the Balkan Peninsula. It is recognized as a wetland of international importance under the Ramsar Convention and holds the status of a national park in Montenegro. The results presented in this study indicate a significant downward trend in monthly water levels during the period 1948-2021, ranging from -14.9 cm in September to -24.0 cm per decade in May. Water levels show significant variation both seasonally and annually (cm per decade): from -16.8 (autumn) to -21.7 (spring), i.e., -19.3 (year). Standardized deviations suggest that the most pronounced decline began in 1981, a pattern further confirmed by the Rescaled Adjusted Partial Sums. Total precipitation in Lake Skadar's drainage basin has shown little to no change. However, there has been a significant increase in air temperature, and thus increased evaporation. According to ERA5-Land data, the annual total evaporation trend in the lake basin reaches up to 10.0 mm per decade. The substantial increase in evaporation has probably resulted in a significant reduction in runoff (Y) derived from precipitation contributing to stream flow. The trend of the mean annual runoff (Y) from 1 m2 is -45 mm per decade, and the flow of the Morača River, the main tributary of the lake, -2.5% per decade. Notably, over the past 14 years, Lake Skadar recorded both its highest water level (2010) and its lowest (2017). We appreciate that the long-term trend of falling water levels is influenced by significant warming of the atmosphere, which has led to increased water evaporation. Short-term fluctuations in lake water levels are primarily driven by variations in precipitation within the catchment area, which are likely linked to atmospheric oscillation patterns. In addition, human impact is evident near the confluence of the Morača River and Lake Skadar, particularly due to the intensive extraction of gravel and sand. To preserve the ecology and economy of Lake Skadar, its natural and cultural heritage, urgent measures are necessary by the countries (Montenegro and Albania) within whose territories this natural gem is located.
We report new occurrence records and an updated global distribution of Limnias novemceras Meksuwan, Jaturapruek & Maiphae, 2018 (Rotifera: Flosculariaceae) based on citizen-science observations and published data. Twenty-two records were compiled, 19 from social media, extending the species range from its presumed endemic area in southern Thailand to Nearctic, Neotropical, Afrotropical, Palearctic, Sino-Japanese, and Oriental realms. Morphological features were consistent across populations, while minor corona variation and ecological traits indicate behavioral flexibility.
The endangered anchialine squat lobster Munidopsis polymorpha is restricted to northern Lanzarote. To understand genetic isolation and conservation risks, we genotyped 26 individuals at eight microsatellite loci from four sites in La Corona lava tube and Charcos de Luis. Lava tube sites shared most alleles and were effectively undifferentiated, whereas Charcos de Luis harbored nine private alleles, the highest allelic richness, and clear differentiation from the lava tube complex. We detected no Hardy-Weinberg deviations among testable locus x site combinations and no linkage disequilibrium. These results are consistent with two candidate management units: La Corona lava tube and Charcos de Luis. We outline genomic priorities to guide future conservation plans. To account for our reduced sampling size, we screened for null alleles and repeated the analyses on a reduced set of loci passing conservative quality filters, obtaining congruent patterns of differentiation.
Aquatic Diptera are a diverse and widely distributed group of insects globally. In Perú, knowledge about this group is limited, with existing studies focusing mainly on aquatic community ecology, water quality, and heavy metal pollution. This study aimed to analyze the composition and structure of aquatic Diptera and their relationship with environmental variables in the lower Quilca-Chili River Basin in southern Perú. Environmental variables were measured and Diptera samples were collected from 16 stations during June and October 2022. Community structure and its relationship with environmental parameters were analyzed under conditions of high and low river flow. The results revealed 13 families and 29 genera, with Chironomidae, Simuliidae, Empididae, Ceratopogonidae, Dolichopodidae, and Muscidae being the most abundant. The analysis of similarity and the non-metric multidimensional showed clear separation in dipteran composition and structure among rivers in June, while in October, only Quilca River differed significantly. The greatest variation in taxon richness between low and high flow seasons was observed in the Vitor and Quilca rivers. Diversity indices were compared across rivers and seasons using Kruskal-Wallis and Mann-Whitney tests (p<0.05). Significant differences occurred in evenness (June) and all indices (October). Among the physicochemical parameters, temperature and pH remained relatively stable across all rivers, while conductivity and total dissolved solids were consistently high. The canonical correspondence analysis indicated that in June, the abundance of Polypedilum and Forcipomyia was associated with organic matter. The genera Tabanus, Holorusia, Podonomus, Paltostoma, and Simulium were associated with dissolved oxygen. In October, Polypedilum abundance was positively related to turbidity, dissolved oxygen, salinity, and electrical conductivity, while Podonomus, Paltostoma, Tabanus, Bezzia, and Simulium were associated with river flow. These findings demonstrate that environmental variables significantly influence river conditions and determine the distribution of Diptera. This study contributes valuable insights into the aquatic Diptera communities of semi-arid river systems.
Riparian forests play a crucial role in aquatic ecosystems by regulating light, temperature, channel stability and nutrient cycling. However, these forests are highly vulnerable to invasion by alien plant species, which can alter leaf litter inputs and decomposition dynamics, thereby impacting freshwater ecosystem functions. This study explores the decomposition rates of native black alder (Alnus glutinosa) and two riparian invaders, Japanese knotweed (Fallopia japonica) and Canada goldenrod (Solidago canadensis), in both headwater streams and pond mesocosms in Central Europe. We conducted experiments with 169 litter bags to assess decomposition rates and test the home-field advantage hypothesis. The hypothesis assumes that native litter decomposes faster due to the evolutionary adaptation of local decomposer communities. We found that invasive S. canadensis decomposed significantly faster than native A. glutinosa in both lotic and lentic environments. On the other hand, invasive F. japonica decomposed at a comparable rate (streams) or at a slower rate (ponds) than the native species. These findings contradict the home-field advantage hypothesis, suggesting that decomposition rates are primarily driven by litter nutrient content rather than geographic origin. The rapid breakdown of S. canadensis is likely driven by the low C:P ratio of its litter. The rapid decomposition of this litter may lead to short-term nutrient boosts that are quickly lost due to microbial activity, whereas the slow decomposition of F. japonica may limit immediate nutrient availability but extend their accessibility over longer periods. Overall, the invasion of riparian zones by species with litter traits distinct from those of native species can disrupt ecosystem processes, leading to cascading effects on aquatic food webs and nutrient cycling. Understanding the effects of riparian forest invasions on organic matter processing is essential for managing biodiversity and maintaining ecosystem integrity in freshwater environments.
Groundwater copepods in lowland Europe remain insufficiently studied compared to those from mountainous regions. Here, we present the results of a faunistic and ecological survey of lowland springs, conducted in the context of earlier research on groundwater copepods from over 100 wells in the same region. Springs, as natural interfaces between aquifers and surface waters, provide more diverse habitats and favorable conditions for groundwater-affiliated fauna. We examined copepod assemblages in 36 lowland springs in northeastern Poland, representing rheocrene, limnocrene, and helocrene types, which were sampled in summer and autumn. We identified a total of 23 species of Copepoda, comprising 13 Cyclopoida and 10 Harpacticoida. Most of these species were associated with hyporheic or groundwater habitats. Cyclopoida dominated in terms of abundance, especially in limnocrene springs, and showed little seasonal variation, while Harpacticoida exhibited markedly higher diversity and abundance in summer. The Cyclopoida assemblage was dominated by Eucyclops serrulatus, Diacyclops bicuspidatus, and Cyclops strenuus, whereas Harpacticoida were represented mainly by Attheyella crassa, Canthocamptus staphylinus, and by five Bryocamptus species. Many of the common copepod species were also found in groundwater wells in the same region. Still, overall richness, particularly of Harpacticoida, was higher in springs due to the presence of heterogeneous benthic microhabitats. We identified three Cyclops species in the springs that were not recorded in the groundwater (wells) of this region. Conversely, we did not detect C. furcifer in the studied springs, despite its presence in nearby wells and temporary puddles. To present taxonomic relationships within the genus Cyclops, we applied an integrative taxonomic approach that combined morphological traits with 12S rRNA and ITS-1 markers. This confirmed the presence of three distinct species: C. strenuus, C. insignis, and C. borealis (considered a senior synonym of C. heberti), for which we provide descriptions of key morphological traits together with molecular data. These findings highlight the function of lowland springs as ecotonal habitats fostering distinct copepod assemblages, including taxa characteristic of both groundwater and benthic microhabitats.
The study highlights the importance of biological monitoring as an effective tool for assessing the impact of chemical substances on living organisms. It offers significant advantages in detecting ecological changes and contributes to a deeper understanding of environmental risks. The application of biological observation supports the protection of both public health and natural ecosystems. Aim of the study was to determinate impact of cadmium on periphytic diatoms biodiversity, structure under laboratory conditions and evaluate application of diatoms as cadmium bioindicators. Species diversity was found to decrease with increasing cadmium concentration in the water: 85 taxa of diatoms were identified in the control sample, and decreased with changing cadmium concentration, from 59 species at 0.01 mg Cd/l to 52 at 0.1 mg Cd/l. The concentration of cadmium in environment was reliably indicated by Navicula lanceolata, N. gregaria and N. rostellata, whose cell proportion significantly decreases with increasing cadmium, and Achnanthidium spp., and Fragilaria spp., whose proportion in the samples increases with increasing cadmium level. The frequency of frustule and theca carpel deformations increases at higher cadmium concentrations: at 0.01 mg Cd/l more than 8% of diatom cells become deformed, and at 0.04 mg Cd/l – 12%. It was determined that N rostellata is the most prone to deformation, therefore, from the bioindicative point of view, it is the most valuable species of periphytic diatoms among those studied.
Methane (CH4) production in oxygenated freshwater systems remains an active area of research in biogeochemistry. This study investigates CH4 dynamics in Honey Harbour’s North Bay, a stratified freshwater oligotrophic embayment of Georgian Bay (Lake Huron), by integrating microbial community analyses, and geochemical measurements. The field study was conducted in 2021, with four sampling campaigns carried out during the months of July, August, September, and October. During stable stratification, CH4 is present in oxic surface water with a maximum of 4.69 μg/L in September. The abundance of Synechococcus in surface waters indicates that CH4 formation may be driven by methylphosphonate (MPn) degradation under phosphorus limitation conditions. Additionally, methanogenic archaea were detected in oxic waters, indicating possible methanogenesis in oxic surface freshwaters. The CH4 oxidation possibly was supported by Fe- and Mn-reducing bacteria such as Geothrix and Methylobacter, which increased at depths below chemocline. Redundancy analysis (RDA) demonstrated strong positive correlations between CH4, photosynthetically active radiation (PAR), and microbes linked to CH4 cycling. Our study shows that CH4 production in surface waters is influenced by phototrophic and archaeal activity, whereas deeper waters exhibit CH4 oxidation coupled to metal cycling and Fe- and Mn-reducing bacteria. This study provides novel insights into microbial and geochemical interactions regulating CH4 emissions in oligotrophic freshwaters of Georgian Bay embayment.
Red algae belonging to Batrachospermales are important contributors to the energy input of lotic ecosystems. Given the importance of these algae for the lotic food web, we tested the photosynthetic performance of a relatively widespread and sensitive species (Virescentia viride-brasiliensis) in multi-stressor scenarios. Experiments were performed by exposing algal samples to three nominal concentrations (0.05 mg/L, 0.6 mg/L, and 1.2 mg/L) of tebuthiuron, a commonly used pesticide in Brazil, combined with three projected temperatures due to climate change (21.6ºC, 23.9ºC, and 26ºC). We observed a decrease in photosynthetic yield (Y(II)), regulated energy dissipation (Y(NPQ)), net photosynthetic rate (NPR), and dark respiration rate (DRR), while an increase in non-regulated energy dissipation (Y(NO)) was recorded, all of which indicate stress responses. Furthermore, we observed a dose-dependence relationship in which the negative effects increased with increasing tebuthiuron concentrations and in the scenario with a more severe temperature increase (26ºC). The high sensitivity of V. viride-brasiliensis to tebuthiuron highlights its potential bioindicator status because the tebuthiuron concentration accepted as safe for drinking water (0.05 mg/L) was sufficient to decrease its photosynthetic yield. Ultimately, these results show the importance of managing pesticide usage, especially considering the simultaneous occurrence of global warming.
Despite the considerable progress that has been made in the field of taxonomy and genetics of freshwater fish, there is still a paucity of knowledge regarding their ecology and behaviour. We used PIT-telemetry to study movement and habitat use of native and non-native benthic fish species in a spring-fed irrigation stream, subject to seasonal macrophyte removal, in a rice field in North-Western Italy. This anthropogenically managed environment constitutes a habitat of high conservation value for some important endemisms, while hosting several non-native species. Fish were tracked both using manual tracking and stationary PIT-antennas, and telemetry data was complemented with catch data from electrofishing. The native P. bonelli and the non-native M. anguillicaudatus were tracked in sufficient numbers to allow quantitative analysis. While successfully tracked in the study area, both species were mostly stationary, but some fish registered movements in the study area of several hundred meters. M. anguillicaudatus showed a tendency of greater movements. With time, most fish disappeared from the study area but no direct migratory movement was detected. M. anguillicaudatus showed a clear preference for macrophyte-covered substrates while P. bonelli were frequently tracked both among macrophytes and on gravel substrates. Electrofishing data showed higher fish abundance in reaches subject to only partial macrophyte removal (fish-friendly management) compared to those subject to standard removal. Overall, movement seems to be an integral part of the ecology of benthic fish in this system, where vegetation appears to structure their spatial behavior.
Tropical monomictic lakes, characterized by a single annual mixing event and prolonged stratification, are particularly sensitive to climatic and anthropogenic pressures. Lake Yambo, a tropical monomictic lake in the Philippines, exemplifies such systems, with stratification prevailing during the southwest monsoon and full lake mixing occurring during the northeast monsoon. This study examined vertical and seasonal variations in environmental conditions and phytoplankton functional group composition in Lake Yambo to assess how seasonal stratification and mixing affect functional groups’ vertical structure. Monthly sampling from March 2024 to February 2025 was conducted from the subsurface to 30 meters at 5-meter intervals. In situ measurements of water temperature, dissolved oxygen, pH, and nitrate (NO₃⁻) were obtained using multiparameter probes, while chlorophyll-a, ammonia, and total phosphorus were analyzed in the laboratory. Phytoplankton samples were collected, identified, and counted, with species comprising at least 5% of the total phytoplankton biomass per period classified into their respective functional groups. Lake Yambo exhibited meso-eutrophic conditions characterized by high total phosphorus concentrations but comparatively low chlorophyll-a levels, suggesting that phytoplankton growth is likely limited by nitrogen availability. Seasonal patterns governed thermal stratification and mixing, which, in turn, regulated vertical nutrient gradients. Stratified conditions during the southwest monsoon led to nutrient trapping and hypolimnetic anoxia, while northeast monsoon mixing redistributed nutrients, particularly NO₃⁻. These transitions strongly influenced the functional group composition. Seven dominant functional groups (B, F, G, H1, J, LO, and P) comprised 81% to 97% of the total phytoplankton biomass. Most functional groups declined with depth, but seasonal and vertical variations were distinct: Group G and H1 thrived in warmer surface waters with low nitrate concentrations. Groups J and LO were associated with cooler, nitrate-enriched surface layers during peak mixing, while Groups B, F, and P were more abundant at deeper layers under the same conditions. These findings support the hypothesis that seasonally driven stratification and mixing in tropical monomictic lakes structure vertical nutrient availability and shape phytoplankton functional group dynamics. Notably, the bloom of Group H1 during post-peak mixing under extreme nitrogen limitation and elevated temperatures poses a health risk, as this group’s descriptor taxon, Dolichospermum, can produce cyanotoxins. Thus, tropical monomictic lakes experiencing greater eutrophication may face increased risks of these toxic blooms. As a representative tropical monomictic system, Lake Yambo offers valuable insights into how similar systems respond to seasonal mixing and nutrient limitations, providing a framework for understanding and managing ecological risks in these environments.
