Hydrobiologia

Tidal flats cover less than 1% of the surface of our planet, but they provide important ecosystem functions and services, like carbon sequestration and nutrient (re-)mineralization, primary, sec-ondary, and food production, and habitats for a variety of species. Despite their importance, they are threatened by environmental stressors and anthropogenic impacts. Hence, a better under-standing of the interaction between macrozoobenthos, their metabolic activity, and their contri-bution to carbon and nitrogen cycling is important. Therefore, we conducted in-situ pulse-chase tracer experiments at a Pacific oyster (Magallana gigas) reef in the Eastern Scheldt (Southwest Dutch Delta, Netherlands) in summer and autumn 2020. During these experiments, we provided the submerged benthic community with 13C and 15N-enriched bacterioplankton and incubated it in seawater enriched in 1% deuterium oxide (2H2O) for one tidal cycle (~9 h), before the benthic community was kept at in situ conditions for another 14 d. Our aim was (1) to assess seasonal variations in 13C and 15N processing by macrozoobenthos, (2) to evaluate potential life-stage de-pendent differences in 2H uptake - a proxy for metabolic activity, and (3) to identify the macro-zoobenthos taxon which had the highest metabolic turnover rate (MTR). In summer, most bacte-rioplankton-derived 13C- and 15N was taken up by sponges (Halichondria panicea), limpets (Crepidula fornicata), and clams (Ruditapes philippinarum), whereas in autumn, H. panicea, C. fornicata and the sponge Hymeniacidon perlevis dominated 13C and 15N incorporation. Statisti-cally significant differences in 2H uptake between life stages (juvenile/ small vs. adult) was de-tected in Malacostraca (i.e., Rhithropanopeus harrisii), but not in Polychaeta or Bivalvia. There-fore, this difference between taxonomic classes might be linked to mold-intermolt periods. Sea-sonal differences in MTR of H. panicea and M. gigas (i.e., the species with the highest MTRs in summer and autumn) might be linked to seasonal environmental variability, such as temperature and food availability.

1. Atlantic salmon (Salmo salar) are an anadromous fish with a broad distribution from eastern North America to western Europe, with ecological, economic, and cultural significance. Despite their expansive range, wild populations across the North Atlantic have experienced decline. Survival to reproductive age is a management concern, with a focus on identifying factors affecting the juvenile freshwater life stage. Specifically, research is needed to identify potential bottlenecks limiting freshwater productivity. 2. We addressed this research gap with a case study on the Exploits River, Newfoundland - a watershed that receives one of the largest anadromous Atlantic salmon returns in North America. We aimed to identify biotic, chemical, and physical predictors of food resources for juvenile salmon (i.e., invertebrates) and food resources for invertebrates (i.e., periphyton). To test our hypotheses, we collected data on a suite of biotic (e.g., invertebrates and periphyton), chemical (e.g., total dissolved N), and physical (e.g., wetted width) variables at 42 sites within and around this watershed. 3. We observed evidence for relationships between invertebrate biomass and biotic and temporal variables. Specifically, invertebrate biomass was higher at sites with high periphyton biomass that were sampled later in the season. In addition, we observed that periphyton biomass was related to biotic, chemical, and physical variables. Here, we present evidence for bottom-up control, with increased periphyton biomass supporting increased invertebrate biomass. 4. We expect knock-on effects where increased invertebrate biomass results in increased juvenile Atlantic salmon biomass. Our large sample size revealed some predictors of invertebrate biomass and periphyton biomass. However, we found no evidence of correlation between invertebrate biomass and chemical or physical variables. The low productivity of our maritime boreal forest system could be an outlier in expected biotic, chemical, and physical relationships in streams. 5. Our findings provide an important step forward in furthering boreal stream ecology, producing novel invertebrate and periphyton knowledge for watershed managers.

Plant communities of sub-Arctic and Arctic regions are undergoing changes due to rapid climate change. Permafrost degradation is one of the key drivers of habitat change in these environments and it is considered to impact the biodiversity of northern peatlands. However, the empirical evidence linking permafrost thaw to biodiversity change remains limited. Here, we conducted a vegetation survey of the plant communities (including vascular plants, bryophytes, and lichens) of 14 palsa mires to quantify biodiversity change along different stages of permafrost degradation. We quantified changes in community composition, indicator species, alpha- and beta diversity as well as in two biodiversity indicators. Our results showed that permafrost degradation significantly affected both the plant community composition and the biodiversity of palsa mires. The most pronounced changes in biodiversity were associated with mires from which the permafrost had thawed completely. However, those mires that represented high stage of degradation but still retained remnant permafrost features, were still maintaining plant communities comparable to palsas with low stages of degradation. Thus, our results indicate that collapsing palsas are a clear tipping point for local biodiversity. Almost a complete loss of lichens was observed in completely thawed mires. Furthermore, the shifts in the vascular plant community were recognized to have potential to affect the biodiversity of palsa mires beyond vegetation. This study underscores the role of permafrost sustaining the compositional and taxonomic diversity of plants in palsa mires while also highlighting the varying responses of vascular plants, bryophytes, and lichens to permafrost degradation. Overall, our findings illustrate how the climate-induced changes in habitats and loss of environmental heterogeneity impact the biodiversity and the ecological resilience of the permafrost peatlands.

Mesozooplankton is a vital component of pelagic food webs, serving as a key trophic link between primary producers and higher marine organisms, and driving coastal and oceanic biogeochemical cycles. This study investigated the abundance, biovolume, community structure, and spatial distribution of mesozooplankton in relation to hydrographic variables in the Northeastern Arabian Sea (NEAS 15{whitebullet}N - 21{whitebullet}N) during the Spring Intermonsoon (March 2019) on board FORV Sagar Sampada. Sampling across 14 stations comparing coastal (> 50 m) and oceanic (< 1000 m) waters revealed distinct environmental gradients. Both Sea Surface Temperature (SST: 24.33{whitebullet}C - 28.68{whitebullet}C) and Sea Surface Salinity (SSS: 35.25 - 36.65) exhibited a declining trend toward northern latitudes, whereas Dissolved Oxygen (DO: 4.55 - 5.24 ml * L-1) increased northward. Chlorophyll concentrations were significantly higher in coastal regions (mean 1.45 mg * m-3) than in oceanic waters (mean 0.36 mg * m-3). Correspondingly, mesozooplankton biovolume (excluding large gelatinous taxa) was threefold higher in coastal waters (mean 1.39 mL * m-3) compared to oceanic waters (mean 0.38 mL * m-3). Mean numerical abundance was also higher coastally (605 ind. * m-3) than oceanically (524 ind. * m-3). A total of 21 mesozooplankton taxa were identified. Copepods dominated the community structure across both regimes (coastal: 61.07%; oceanic: 56.69%). In coastal waters, Chaetognatha (14.76%), Cladocera (9.39%), and Decapod larvae (5.69%) were the secondary drivers, with localised salp and siphonophore swarms observed at 17{whitebullet} - 19{whitebullet}N. In oceanic waters, Ostracoda (22.93%) and Salpidae (12.51%) were major secondary contributors. These results indicate that during the Spring Intermonsoon, the NEAS exhibits moderate productivity representative of a receding winter cooling regime.

Microorganisms, found in every environment, play an important role in recycling matter and providing energy to the ecosystem. Here, we used 18S and 16S metabarcoding to study bacteria, cyanobacteria and protist community diversity and functional ecology among different environments of typical lake, river, marine and soil from the Yangtze Delta of China. The results showed that the similarity of cyanobacteria and protozoa communities in soil and aquatic environments was both higher than that of bacteria and microalgae communities. While the diversity of cyanobacteria and bacteria in lake was higher than that in river, marine and soil, the diversity of microalgae and protozoa in river was higher than that in lake, marine and soil. The {beta} diversity of cyanobacteria and bacteria marked differences in lake from other environments. But The distribution of dominant families of cyanobacteria, bacteria, microalgae and protozoa is similar to diversity. While significant positive correlations were found among dominant species of cyanobacteria, protozoa, bacteria and microalgae in lake the dominant species among bacteria, microalgae and protozoa in river, marine and soil all showed more negative correlations. Our study provides the basis for understanding the functional ecology of microbes in the micro-food webs of different environments.

The decline in fishery yields in Japan's enclosed coastal seas has been accompanied by a reduction in phytoplankton biomass, suggesting a widespread decrease in ecosystem productivity. Oligotrophication in Mikawa Bay has caused substantial declines in phytoplankton biomass and Manila clam (Ruditapes philippinarum) production. To assess whether external nutrient enhancement could stimulate phytoplankton growth, a controlled demonstration experiment using treated effluent from two sewage treatment plants (WWTPs) was conducted (spanning fiscal years 2022 to 2024) based on analysis using a three-dimensional non-hydrostatic model. Although effluent DIP and nitrogen concentrations were increased, model results showed that WWTP-derived nutrients represent only a minor portion of the total nutrient budget. Field observations revealed limited increases in surface water phosphorus, strong seasonal variability, and only temporary rises in chlorophyll-a and clam harvests. Monthly TP data demonstrated that seasonal DIP pulses, especially spring phosphorus bursts, dominate nutrient dynamics and overshadow external loading effects. Laboratory experiments further showed that phosphate is efficiently fixed by Fe(III) under oxidizing conditions and rapidly released during reductive dissolution of [FeOOH-HPO4]2- complexes, confirming iron as the principal regulator of internal P cycling. Because current numerical models omit iron-driven internal cycling, they cannot accurately predict bioavailable P or ecosystem responses. Overall, the study indicates that localized nutrient enhancement is insufficient to counter long-term oligotrophication, and effective management must integrate nitrogen limitation, internal Fe and P cycling, oceanic exchange, and seasonal variability in Ise and Mikawa Bays.

The rapid global expansion of dams has significantly reshaped freshwater ecosystems, yet long-term trophic dynamics and food-web stability within reservoirs remain underexplored. This study examines the reorganization of fish communities induced by the trophic surge following dam construction and river impoundment. We used the predator-to-consumer mass ratio (PCMR) as a proxy for trophic pyramid structure to track changes in fish biomass distribution across three large boreal reservoirs in Quebec, Canada, over 20 years, using data from before and after impoundment. We found transient top-heaviness events (i.e., PCMR values > 1; predator accumulation), characterized by a hump-shaped trajectory of the PCMR values in two reservoirs (Opinaca and Robert Bourassa). The third reservoir (Caniapiscau) showed a gradual increase in top-heaviness but did not exhibit a clear transient pattern. The magnitude and duration of top-heaviness varied across reservoirs, potentially due to differences in the system's capacity to receive and accumulate nutrients, which are driven by water residence time and reservoir size. This research provides a conceptual framework for understanding the long-term trophic dynamics of reservoirs, which can help inform the development of more effective management strategies to preserve ecological health in these ecosystems.

The spiraling tooth of the narwhal (Monodon monoceros) has long intrigued scientists, but the growth rates of its "tusk" are poorly constrained due to the difficulty to age narwhal. To learn more about the population dynamics and life history of this exploited species, previous studies have used sectioned teeth to age narwhals and calibrate other ageing methods based on aspartic acid racemization, radiocarbon or trace element analysis. However, few such studies have been conducted due to the method's difficulty and the need to sacrifice the tooth. In this study, computed tomography (CT) was used on five teeth as a non-destructive means of estimating the age of narwhals, revealing different growth rates between erupted and embedded teeth during adolescence. Moreover, in combination with our reanalysis of all relevant literature, CT data clarify the annual growth rates of narwhal tusks, which peak before the age of 10 (~100 mm yr-1). This approach will be useful for investigating private and museum collections, and might also better constrain the use of trace element proxies in narwhal teeth and support sustainable harvest management.

Boreal forested streams receive substantial inputs of terrestrial carbon (C) from riparian vegetation in the form of leaf litter, which is processed by litter-associated microorganisms. In addition to these leaf-litter C inputs, boreal streams also receive significant concentrations of dissolved organic carbon (DOC), which may represent an alternative major resource pool for litter-associated microorganisms. As leaf litter quality decreases over the process of decomposition, DOC may increasingly become a more suitable C source for the microbial communities. We investigated how DOC availability, litter type, and microbial succession influenced respiration and decomposition. Alder, birch, and spruce litter were incubated for 65 days in 12 outdoor experimental channels supplied with natural boreal stream water. Higher time-adjusted DOC concentrations were associated with higher respiration and lower relative mass remaining, whereas DOC flux received less support. Respiration and mass loss followed litter-specific trajectories, with birch showing a respiration peak that was not matched by proportional mass loss. Prokaryotic and eukaryotic communities differed among litter types and changed through time but explained process variation only for specific litter types and responses. Our results suggest that DOC can sustain litter-associated microbial activity and partly decouple respiration from litter decomposition, thereby affecting boreal stream C processing.

Introduction: Despite decades of investment, stream restoration often fails to recover diverse benthic macroinvertebrate communities, as restored reaches tend to remain dominated by pollution-tolerant taxa. This shortfall in recovery is commonly attributed to either poor habitat quality or dispersal limitation of aquatic macroinvertebrate taxa, yet these hypotheses are rarely tested directly. Objectives: We conducted a manipulative field experiment in the eastern Piedmont region (Maryland, USA) within the Chesapeake Bay Watershed to evaluate whether restored streams can support pollution-sensitive taxa when dispersal barriers are removed. Methods: We translocated whole macroinvertebrate communities from three nearby reference streams into three restored streams using standardized habitat substrates and quantified macroinvertebrate survival after 28 days. We also assessed how effective leaf vs rock substrates were for accumulating diverse and abundant macroinvertebrate communities for translocation. Results: Across all sites, 77% of translocated individuals and 16 of 22 taxa sensitive and moderately sensitive to pollution persisted under restored stream conditions, demonstrating that restored reaches can support short-term survival of pollution-sensitive taxa that typically fail to recover. Substrate comparisons revealed that leaf packs accumulated higher macroinvertebrate abundances, whereas both substrates accumulated macroinvertebrate communities with similar taxa richness, EPT richness, and Shannon Diversity. Conclusions: This work suggests that dispersal limitation, rather than unsuitable habitat, may be an underappreciated constraint limiting macroinvertebrate recovery in restored streams. These findings challenge the assumption that habitat restoration alone is sufficient for biological recovery and highlight the potential for whole-community translocations to accelerate recovery and ecological uplift as part of stream restoration practices. Implication for Practice: Our study highlights the need to consider habitat connectivity and dispersal pathways during stream restoration designs. Restoring streams to meet habitat requirements of pollution-sensitive macroinvertebrate taxa may not be sufficient for their populations to recover if these taxa are unable to reach the restored stream. In scenarios where restoring connectivity to source populations is infeasible, whole community translocations may offer a novel restoration tool to overcome dispersal barriers and accelerate biological recovery in restored streams.

Context Pumping stations pose a threat to fish globally through land use change, habitat fragmentation and entrainment risk, with the catadromous and critically endangered European eel particularly impacted. Objectives/methods Establish, model, assess and understand the present-day distribution of European eel and resident fishes in 152 pumping station catchments in a once extensive wetland (The Fens) using eDNA metabarcoding (855 samples over two and half years), with specific focus on anthropogenic influences on hydrological connectivity and habitat quality. A removal survey design maximised confidence in negative results while minimising time and consumable costs. Results Eel occurrence upstream of pumping stations was low (occupancy = 28.3%) and positively associated with catchment area, fish species richness and natural hydrological connectivity (gravity drainage or flooding) and negatively associated with distance from the tidal limit. Fish species richness replaced catchment area and improved model performance, potentially acting as a biotic indicator of habitat quality and connectivity. Pumped catchments with manually operated upstream water transfers had reduced eel presence, potentially linked to the direction of water flow or the timing of operation. By contrast, fish species richness increased in these catchments during summer, suggesting displacement into unsuitable long-term habitats. Physical habitat maintenance had no detectable effect on eel occurrence or fish species richness. Conclusions This study provides the first landscape-scale assessment of European eel distribution and drivers of occurrence in pumped river catchments. The highly novel and comprehensive insights have implications for European eel conservation as well as infrastructure and catchment management, including compliance with legislation (EC Regulation No. 1100/2007).

Water input is a key component of the ecosystems. Water defines the functionality, composition, and structure of biomes; therefore, any change in its availability would have an impact on ecosystem features. Moreover, a change in the water balance of an ecosystem affects its persistence as well as biochemical cycles, such as the carbon and nitrogen. Forests are ecosystems structured using high amounts of water. Thus, trees, the oldest living plants, are the prime species in these ecosystems and are the main managers of this abiotic element. Trees uptake water from the soil, store it in their biomass, and exchange it with the environment through leaf stomata. They also intercepted rainfall and fog with their canopies. All of this water is also transmitted to the entire biological diversity that inhabits these ecosystems. Any change in water input affects the web described above. The ability of trees to modify their anatomy or processes, that is, to acclimate to novel climates, is of great advantage in maintaining the characteristics of ecosystems. In this study, we took advantage of a precipitation exclusion experiment to reveal the acclimation of shade-tolerant understory trees, which will be the main component of a cold temperate rainforest in the future. We evaluated different anatomical and physiological leaf traits involved in the use of water by these species. We hypothesized that, as observed in similar experiments, species would adopt more conservative water-use strategies by adjusting their functional traits accordingly. Contrary to our hypotheses, we found that understory tree species inhabiting this temperate ecosystem will not become more conservative when using water. In minimal, but significant differences, most of the studied species displayed traits, in the precipitation exclusion treatment, that were demonstrated to be water spender, rather than conservative. We attributed these contrasting changes to root metabolism alleviation due to the flooded soils of Chiloe inhabited by these forests.

Urbanization has been previously shown to affect evolution of plants and animals by restricting gene flow, increasing genetic drift, and causing divergent selection between rural and urban populations, however, the effect of urbanization on terrestrial gastropod evolution has only been minimally researched. Most research on terrestrial gastropods primarily focusing on invasive pest species, and little attention is given to native species like Ariolimax columbianus (Pacific banana slug). There is no current published research on the phylogeography of A. columbianus. In this study, surface epithelial cells from 66 Ariolimax columbianus individuals were collected from 11 locations around Corvallis, Oregon, and one site in northern California. These samples were amplified and sequenced at two loci: cytochrome oxidase 1 (CO1) and the internal transcribed spacer 2 (ITS-2). This data was used to generate maximum-likelihood phylogenetic trees to better understand the population genetics of these local native gastropods. The CO1 phylogenetic analysis showed two major haplotypes around the city of Corvallis - northwestern and southern, while the ITS-2 phylogenetic analysis showed three general haplotypes around the city - northern, western, and southern. The results in this study show the presence of genetic breaks between many of these populations, possibly due to a combination of factors including anthropogenic fragmentation, natural barriers, and the low active dispersal ability of A. columbianus. However, the extent that each of those factors has on disrupting gene flow and explaining patterns of genetic variation in this species requires further research. The present study acts as a foundation for the development of future research on banana slug phylogenetics and population genetic structure.

Diverse life history strategies allow species to spread risk across a mosaic of habitat conditions. In Chinook Salmon (Oncorhynchus tshawytscha), particularly in the Central Valley of California, this is expressed through varied adult run timings and juvenile outmigration strategies. Anthropogenic impacts, particularly dams, disrupt these fundamental life stage transitions, often forcing managed populations to adapt to homogenized, less stochastic hydrologic regimes. This is exemplified in the Sacramento River, where the conservation of endangered Sacramento River winter run Chinook salmon requires balancing complex water operations with the ecological needs of a population confined to a short stretch of suitable habitat downstream of Shasta Reservoir. Using a 23 year dataset (2002 to 2024), we evaluated the combined effects of flow, temperature, and spawner abundance on juvenile production and life history expression in this habitat. We found that flow and spawner abundance best predicted juvenile abundance at Red Bluff Diversion Dam while temperature had considerably less support. The proportion of juveniles migrating as smolts exhibited significant density dependence that was negatively correlated to both female spawner abundance and peak flows. These results suggest focusing on temperature management alone may be insufficient. Effective management strategies should consider flow variability and habitat restoration to facilitate varying migration strategies and expand upstream rearing capacity. By addressing these physical and hydrologic constraints, managers can better support the full suite of life history strategies necessary for the resilience of winter run Chinook salmon.

This research addresses a central question in Palaeolithic research: how hunter-gatherer mobility was structured across space and time in the Cantabrian Region (northern Iberia), which has human occupation evidence spanning from the Middle Pleistocene through the Holocene. A multidisciplinary framework integrating primarily {delta}3S isotope values, combined with {delta}{superscript 1}3C and {delta}{superscript 1}N, palaeoproteomics, Bayesian age modelling, palaeoclimatic reconstruction, isoscape mapping, and ecological diversity was developed. A total of 905 animal bone collagen samples, with evidence of anthropogenic modifications, from 16 key archaeological sites from the Mousterian to Mesolithic (Marine Isotopic Stage 5 to 1, between 100-7 ka BP) were analysed, permitting the reconstruction of spatial patterns of resource exploitation and human mobility. The {delta}3S isotope values show weak, inconsistent relationships with climatic proxies, suggesting that sulfur signatures are primarily driven by geographic and ecological factors rather than climate. Strong spatial trends are observed, with higher {delta}3S values in coastal zones and lower values inland. Diachronic trends reveal marked shifts in human mobility: smaller ranges during the Mousterian, increasing mobility through the Chatelperronian and especially the Aurignacian, followed by reduced mobility in the Gravettian and Solutrean, and renewed territorial expansion during the Magdalenian and, likely, the Azilian. In contrast, the Mesolithic is characterised by decreased mobility and thus increased territoriality in both coastal and inland contexts. Faunal isotope values and isoscape predictions reveal that some animals were acquired beyond local foraging ranges during the Palaeolithic, particularly in inland regions with lower {delta}3S values. Isotopic niche analyses indicate partial interspecific overlap consistent with ecological flexibility. Macromammal and micromammal diversity exhibit contrasting patterns, with a significant negative correlation in Simpson and Shannon indices. Macromammal diversity correlates negatively with {delta}3S values, linking increased hunting diversity to expanded catchment areas and longer-distance foraging, whereas micromammal diversity shows positive correlations with {delta}3S, {delta}{superscript 1}3C and {delta}{superscript 1}N reflecting stronger climatic influence. Overall, these results demonstrate that hunter-gatherer behaviour in northern Iberia during the Middle and Late Palaeolithic was highly dynamic, combining logistical and residential strategies that shifted in response to changing environmental conditions, resource distributions and cultural adaptations.

Okanagan sockeye salmon have shown a strong recovery over the past three decades, but the contribution of environmental conditions and management actions to this recovery has not been determined. We developed a hierarchical Bayesian model linking spawner abundances to fry emergence observations to evaluate how flow and water temperature during adult upstream migration and incubation periods influence spawner-to-fry production. Production declined by 62% in years with earlier onset and longer duration of periods when warm river temperatures created barriers to adult migration, indicating that migration conditions can have carry-over effects on reproductive success even when spawners successfully reach the spawning grounds. Additionally, production was 46% lower when flows fell above or below the management target range designed to minimize scour and desiccation during egg incubation. In contrast, we found little support for effects of pre-spawning flows or incubation temperature on production. These findings provide quantitative evidence that current flow management is increasing freshwater spawner-to-fry production and has likely contributed to the Okanagan sockeye recovery. Effective flow management may therefore help offset climate-driven impacts that increasingly threaten this population.

The management of Atlantic bluefin tuna (Thunnus thynnus) is currently defined by a long-standing life-history paradox: a stark divergence in maturation schedules between the Eastern and Western stocks. While the Mediterranean contingent matures at approximately 104 cm straight fork length (SFL; age 3-5), the western stock has long been characterized as a late-maturing, at [~]190 cm SFL (age 8+), and as late as age 15.8, based on size-at-catch data in the presumed exclusive spawning areas of the Gulf of Mexico. This discrepancy defies maturity states confirmed by endocrine hormones as well as established life-history principles that link metabolic energetics to reproductive biology. To resolve this critical issue in stock assessment, we present a sensitivity analysis based on the first histological evidence of spawning- capable individuals from 42 bluefin females (97-244 cm curved fork length or [~]95- 236 cm SFL) sampled in June 2025 within the Slope Sea, Northwest Atlantic. This historically overlooked, temperate spawning ground must be recognized and past estimates of stock productivity reevaluated. Our data provide a conservative estimate of length-at-50% maturity, L50 for females at 123.3 cm SFL, effectively reconciling the reproductive parameters of the two stocks based on histology. Our findings align established bluefin tuna metabolic and evolutionary symmetries in life history, irrespective of management boundaries. Incorporating this previously unrecognized spawning group (i.e., smaller, younger fish) calls for a substantial upward revision of Western spawning stock biomass (SSB). This biomass represents an intrinsic biological buffer that could contribute to the Atlantic bluefins adaptation and resilience. Appreciating demographic diversity is critical to accurately diagnosing stock vulnerability, ensuring that management frameworks protect long-term population stability in the face of climate-driven oceanographic shifts and ongoing exploitation pressure.

Bottom trawling is the most widespread human disturbance on the seafloor, known to affect seabed structure and benthic biota. Yet, its impact on benthic communities remains documented mainly for taxa identifiable through morphology, leaving microscopic benthic communities largely overlooked. The Gulf of Lion continental shelf has been trawled for decades by French and Spanish fleets, to the point that encountering untrawled reference areas became elusive. Here, we examined prokaryote, protist and Animalia benthic communities at eight stations, using eDNA metabarcoding of core sediment samples, with five primer-pairs. Benthic communities were cross-referenced with contrasted trawling impacts, integrated across three periods: over one month, three years or ten years preceding the sampling. The community composition was primarily structured by ecological habitats, yet, trawling pressure showed association with prokaryotes and Animalia diversity. Diversity was higher at sites trawled more intensively in the preceding month, whereas long-term trawling was associated with a significant erosion of Animalia alpha diversity. Unexpectedly, communities did not display consistent vertical structure and the relative contributions of trawling and hydrodynamic reworking remain unresolved due to the absence of untrawled sites. Overall, our results show that trawling effects extend to prokaryotic compartments rarely considered in impact assessments, providing a proof of concept for eDNA-based assessment, and underline a pervasive long-term effect on Animalia communities. This study also highlights the importance of the timescale used to quantify fishing pressure and underscores the complexity of impact assessment when monitoring begins too late to establish a clear baseline, particularly when no reference site remains.

Heavy metal contamination of aquatic environments poses persistent risks to ecosystems and human health. Aquatic macrophytes such as Pistia stratiotes are increasingly used for phytoremediation due to their capacity to accumulate contaminants without displaying symptoms of abiotic stress. However, the molecular mechanisms underlying their metal tolerance remain poorly understood. Metallothioneins (MTs) are cysteine-rich proteins involved in metal binding and detoxification in plants. In this study, genome-wide analysis was performed to identify and characterise candidate MT genes in P. stratiotes and to assess their transcriptional response to copper exposure. Six novel MT genes (PsMT2f, PsMT3a-d, and PsMT4) were identified and classified into MT2, MT3, and MT4 subfamilies based on conserved cysteine motifs and domain architecture. Quantitative real-time PCR showed differential and tissue-specific expression of MT genes in roots and leaves following exposure to copper for up to 4 h. These findings provide the first comprehensive characterisation of the MT gene family in P. stratiotes and demonstrate their potential role in copper tolerance, supporting the application of this species in the phytoremediation of metal-contaminated aquatic systems.

This paper presents a comparative analysis of the floristic composition and site characteristics of four peat bogs in Bucovina, Romania: Poiana Stampei, Romanesti, Saru Dornei, and Gaina-Lucina. The research was based on phytosociological releves on 25 msq plots and direct field phenological observations, on six field visits from May to August 2026. Vegetation was characterised using the Braun Blanquet method, and floristic similarity between sites was assessed with the Sorensen and Bray Curtis indices. All four plots shared a common core of taxa characteristic of peatland vegetation: Sphagnum spp., Carex rostrata, Drosera rotundifolia, Eriophorum vaginatum, and Vaccinium species. Species richness was 13 taxa at Poiana Stampei, Romanesti, and Saru Dornei, and 12 at Gaina-Lucina. Romanesti and Saru Dornei showed the highest floristic similarity (descriptive values, not statistically tested, given a single releve per site), while Gaina-Lucina differed most markedly, not through species richness, which was similar across sites, but through species identity and through the presence of Betula nana, a glacial relict absent from the other sites. The results provide a descriptive basis for future research on the floristic composition and conservation of these habitats.