Wetland restoration is widely promoted as a complementary nature-based climate solution, but its net carbon and GHG effects across wetland types and interventions remain poorly quantified at the global scale. We address this gap with a global meta-analysis spanning all major wetland types and restoration strategies. We conducted a global meta-analysis of 617 restored-altered pairs from 149 studies on five continents to assess how restoration influences major carbon stocks and greenhouse gas (GHG) fluxes relative to altered wetlands. Overall, across all wetland types studied, restoration significantly increased aboveground biomass, belowground biomass and soil carbon. Restored wetlands also exhibited significantly lower CO₂ fluxes, consistent with increased primary production and reduced aerobic decomposition following hydrological and vegetation recovery, but also higher CH₄ emissions particularly in peatlands where rewetting enhances anaerobic conditions. By contrast, neither N₂O flux (though close to) nor, particularly dissolved organic carbon concentration showed statistically significant overall changes. These global patterns were robust to sensitivity and leave-one-out analyses but varied strongly among wetland types and restoration approaches. Restored mangroves and peatlands more clearly exhibited significant biomass and soil carbon gains, whereas restored freshwater wetlands and peatlands significantly displayed strong belowground biomass and and decreases in both CO2 fluxes, though the later showed significant CH₄ flux increases. Other wetland types displayed more variable responses to restoration, if any. Hydrological restoration (mainly rewetting) produced the strongest improvements in aboveground biomass, soil carbon and N₂O flux reductions, though it significantly increased CH₄ flux. Vegetation recovery was significantly effective action increasing above- and belowground biomass, soil carbon, and decreasing CO2 fluxes. Data were dominated by studies from Asia, Europe and North America, by far made in the Northern hemisphere, highlighting major geographical gaps in Southern areas. Overall, our synthesis shows that wetland restoration reliably regenerates carbon stocks and reduces CO₂ emissions, supporting its inclusion in climate mitigation portfolios and nature-based solution frameworks. Short-term CH₄ emission increases and ecosystem-specific responses highlight the need for long-term monitoring, context-dependent restoration design and improved global coverage to optimise carbon benefits and inform on climate’s friendly restoration policies and actions.

Measurements of surface-atmosphere carbon dioxide (CO2) and methane (CH4) fluxes have been relatively sparse across the Arctic tundra and boreal biomes, causing significant uncertainties in carbon budget estimates from the region. While the availability of Arctic-boreal carbon flux data has increased substantially over the past decade, the data have remained spread across different repositories, scientific articles, and unpublished sources, making it difficult to leverage. Here we present a new dataset of monthly Arctic-boreal carbon fluxes (ABCFlux v2) across terrestrial (wetlands and uplands) and freshwater (lakes and rivers) ecosystems compiled from previous syntheses including the Arctic-boreal CO2 flux database (ABCFlux v1), the Boreal-Arctic Wetland and Lake Methane Dataset (BAWLD-CH4), and the Global River Methane Database (GRiMeDB). In addition, we consider data from general-purpose (e.g., Zenodo) and flux network repositories, literature, and site principal investigators. The dataset includes surface-atmosphere CO2 fluxes of gross primary production (GPP), ecosystem respiration (Reco), and net ecosystem exchange (NEE), alongside CH4 fluxes. For aquatic ecosystems, we split CH4 fluxes into diffusive and ebullitive flux pathways, and included potential emissions from transient storage in the water column (“storage fluxes”), alongside CO2 and CH4 concentrations dissolved in the surface water. Fluxes are measured through a variety of methods including chamber and eddy covariance techniques alongside bubble traps, ice-surveys, and concentration-based turbulence-driven modelling in aquatic ecosystems. The monthly flux data are reported together with supporting methodological and environmental metadata. The resulting ABCFlux v2 has 23 847 flux site-months, 8182 concentration site-months, and 199 seasonal observations from 1024 sites, and includes 56 139 reported fluxes (i.e. sum of GPP, Reco, NEE, and CH4 fluxes) from the years 1984 to 2024. The majority of monthly observations occurred after 1999. Wetlands had the highest number of site-month observations (8758), followed by boreal forest (6981), lotic ecosystems (6275), lentic ecosystems (3799) and upland tundra (3308). Measurements of CO2 dominated the dataset across most ecosystem types (25 222) except for lentic ecosystems, where CH4 flux site-months (3098) were more frequent than CO2 flux site-months (2915). Overall, ABCFlux v2 includes 160 % more site-months for terrestrial CO2 flux data compared to ABCFlux v1. Integrating and updating BAWLD-CH4 flux data from growing season averages to monthly fluxes resulted in 5671 site-months of chamber CH4 data compared to 762 site-years. This collaborative initiative, involving contributions from over 260 researchers, provides a comprehensive overview of the current state of the Arctic-boreal carbon flux network and its data, and serves as an important step in reducing uncertainties in Arctic-boreal carbon budgets and in enhancing our understanding of climate feedbacks. The data can be accessed at ORNL DAAC at https://doi.org/10.3334/ORNLDAAC/2448 (Virkkala et al., 2026).

Lakes, ponds, and reservoirs (hereafter: “lakes”) are important sources of the greenhouse gases carbon dioxide (CO2) and methane (CH4). Emissions of CO2 and CH4 from lakes are regulated in part by in-lake processes, including the production and storage of gases in the lower parts of the water column (bottom waters). However, while substantial efforts have been made to improve estimates of greenhouse gas emissions from lakes, limited data on gas concentrations along depth profiles have prevented the incorporation of bottom-water processes in global emission estimates. Here, we present GHG-depths: the largest existing dataset of depth-profile CO2 and CH4 measurements worldwide, including 522 lakes across 38 countries and all seven continents. These data include contributions from 45 research teams and 56 published studies, totaling 2558 discrete sampling events. As global change continues to alter biogeochemical cycling in lakes, these data can help improve mechanistic models to better predict greenhouse gas production and emission from lakes worldwide.

Coastal wetlands play a substantial role in regulating Earth’s climate through exchanges of greenhouse gases (GHGs). Current European policies promote widespread coastal wetland restoration to reverse historical losses and ongoing pressures. However, substantial uncertainty remains regarding how CO₂ and CH₄ fluxes respond to restoration across different coastal wetland types and whether these responses translate into net climate mitigation in terms of CO₂ equivalents (CO₂-eq). We measured simultaneous CO₂ and CH₄ fluxes using static chambers across four seasons at multiple locations spanning preserved, altered and restored sites within each of six European coastal wetlands of different ecological types. By comparing GHG exchanges and resulting CO₂-eq balances across wetlands, we identified the dominant biogeochemical drivers of CO₂ and CH₄ dynamics and assessed the climate mitigation potential of conservation and restoration actions. CO₂ fluxes were primarily controlled by landscape-scale vegetation cover and inundation, whereas CH₄ emissions responded to more subtle changes in water quality, salinity and wetland hydrodynamics. Comparisons of CO₂-eq balances between altered and restored sites revealed that seagrass replantation and eutrophication reversal generated significant mitigation benefits, driven by enhanced CO₂ uptake and reduced CH₄ emissions, respectively. In contrast, other restoration measures modified CO₂ and CH₄ fluxes in opposing directions, resulting in non-significant net climatic effects of CO2-eq balances. Overall, our results demonstrate that climate mitigation outcomes of coastal wetland restoration are both GHG-specific and wetland-type dependent, underscoring the need for tailored restoration strategies and robust, multi-GHG monitoring to detect and accurately quantify potential climatic benefits.

Microbial communities play a key role in organic matter (OM) decomposition and nutrient cycling in headwater streams. Macroinvertebrate shredders enhance these processes by producing large amounts of fine particles from microbe-colonized OM through shredding and egesta, yet how gut and faecal microbiota vary among shredder taxa remains largely unknown. Thus, we examined composition, diversity, and predicted functions of bacterial communities in leaves, guts, and faecal pellets of three Trichoptera shredders (Allogamus, Potamophylax, and Sericostoma) across two larval stages using 16S rRNA metabarcoding. Bacterial community composition differed significantly among the shredder taxa and between sample types, while ontogeny had only a minimal effect. Sericostoma showed the lowest diversity but the most distinct microbiota in their gut and faecal pellets, while Allogamus and Potamophylax hosted more diverse and overlapping bacterial communities. Carnobacterium and Tyzzerella were specialized bacteria in the shredder guts. Functional predictions showed clear metabolic transitions from aromatic compound degradation in leaves to amino acid and carbohydrate metabolism in guts and continued degradation of plant-derived substrates in faecal pellets, reflecting the shift from environmental to host-associated microbial processes during gut passage. Unique pathways in Sericostoma guts, such as palmitate and peptidoglycan biosynthesis, suggest host-specific adaptations. Overall, shredder identity rather than ontogenetic stage was the dominant factor structuring bacterial assemblages and functions, emphasizing the taxon-specific role of shredders as mediators of microbial dynamics, linking microbial structure with ecosystem-level processes in the stream detritus-food-web.

Coastal wetlands play a substantial role in regulating Earth's climate through exchanges of greenhouse gases (GHGs). Current European policies promote widespread coastal wetland restoration to reverse historical losses and ongoing pressures. However, substantial uncertainty remains regarding how carbon dioxide (CO2) and methane (CH4) fluxes respond to restoration across different coastal wetland types and whether these responses translate into net climate mitigation in terms of CO2 equivalents (CO2-eq). We measured simultaneous CO2 and CH4 fluxes using static chambers across four seasons at multiple locations spanning preserved, altered and restored sites within six European coastal wetlands of different ecological types. By comparing GHG exchanges and resulting CO2-eq balances across wetlands, we identified dominant biogeochemical drivers of CO2 and CH4 dynamics and assessed the climate mitigation potential of conservation and restoration actions. CO2 fluxes were primarily controlled by landscape-scale vegetation cover and inundation, whereas CH4 emissions responded to less evident changes in water quality, salinity and wetland hydrodynamics. Comparisons of CO2-eq balances between altered and restored sites showed that seagrass replantation was associated with significant mitigation potential under both 100-year and 20-year CH4 warming scenarios, while eutrophication reversal through improved water treatment was only significant under the 20-year scenario. In contrast, other restoration measures modified CO2 and CH4 fluxes in opposing directions, resulting in no significant net change in combined CO2-eq balances. Overall, our results demonstrate that climatic responses to coastal wetland restoration are both GHG-specific and wetland-type dependent, underscoring the need for tailored restoration strategies and robust, multi-GHG monitoring to detect and accurately quantify potential climatic benefits.

Biofilms developing on plastic surfaces (the plastisphere) are increasingly recognized for their ecological significance, yet the drivers of community biomass and biodiversity remain poorly understood. Moreover, plastisphere research has focused on a narrow range of polymers, leaving widely distributed substrates such as textiles understudied. Here, we assessed the relative importance of temporal succession and substrate properties (polymeric composition and color) in shaping microalgal and bacterial community composition and photosynthetic abundances, and evaluated whether substrate-specific selection results in long-term community divergence or is restricted to early colonization. We conducted a mesocosm experiment simulating a lotic system to examine biofilm development on polyester textiles and non-synthetic analogue (cotton), each in two colors (black, white). Prokaryotic and microalgal eukaryotic community composition (16S, 18S rRNA), together with pico-photosynthetic abundances assessed by flow cytometry, were monitored over five time points spanning 7 to 35 days. Microbial diversity, community composition, and inferred prokaryotic functions did not differ significantly among polymer types or colors, indicating that substrate characteristics played a limited role in overall community assembly and the predominance of opportunistic colonization, despite the presence of indicator species. In contrast, microalgal abundances differed among substrates, with higher abundances observed on cotton, suggesting that substrate properties may still influence specific aspects of biofilm development. Temporal succession emerged as the primary driver of community change, with significant effects observed for prokaryotic communities even over short timescales. These findings emphasize that temporal dynamics must be explicitly considered in plastisphere studies, as differences in colonization time may confound interpretations of substrate effects.

Leaf litter decomposition is a vital ecosystem process in which macroinvertebrate-shredders produce substantial amounts of fine particulate organic matter (FPOM) via sloppy feeding and defecation, creating a substratum and substrate for microbial assemblages. However, microbial communities colonizing the shredder-produced FPOM are understudied compared to those in streams and on original leaves. Here, we investigated the bacterial community composition on shredder-produced FPOM in a laboratory experiment. We fed alder, beech, and maple leaves conditioned under oxic or anoxic conditions to Sericostoma (Insecta: Trichoptera) larvae. We collected shredded leaf particles and faecal pellets as shredder-produced FPOM at different times and examined their microbial communities using 16S rRNA amplicon sequencing. We hypothesized that shredder-produced FPOM types harbor diverse, distinct, and specialized microbial taxa in response to leaf species and conditioning. We found significantly higher alpha diversity on shredded leaves compared to faecal pellets. Microbial communities on faecal pellets differed from initial leaf communities and with anoxic and oxic conditioning. Bacterial communities developing on leaves were dominated by common leaf decomposers including Flavobacterium and Pseudomonas whereas faecal pellets harbored gut bacterial taxa including Acinetobacter and Carnobacterium. These results underline the importance of conditioning and shredder activity in shaping FPOM-attached bacterial communities, increasing bacterial diversity in stream ecosystems.

Coastal wetland restoration is widely promoted as a tool for climate change mitigation, but its effect on the carbon cycle is not well constrained. We conducted a systematic review and meta-analysis of peer-reviewed field studies that directly contrasted restored with altered sites, covering carbon stocks and greenhouse gas fluxes across mangroves, saltmarshes, seagrass meadows, brackish systems, and coastal freshwater wetlands. Literature searches yielded 66 studies and 257 pairwise restored versus altered site comparisons. Multilevel random-effects models with nested study effects showed significant increases after restoration in soil carbon, aboveground biomass, and belowground biomass. Mean greenhouse gas flux changes after restoration were non-significant for CO₂, CH₄, and N₂O. Meta-regressions detected no significant differences among wetland types, though this result is constrained by unbalanced evidence across systems and studied parameters. The available data are geographically biased toward tropical and subtropical Asia, with minimal coverage in Africa and limited data from temperate and cold coastal regions. Among the covered variables dissolved organic carbon is critically underrepresented, constraining whole-system impact estimates. Overall, the data examined in this study show that restoration consistently rebuilds biomass and soil carbon without a detectable systematic “cost” from methane or nitrous oxide, indicating positive outcomes for greenhouse gas fluxes. To translate these findings into policy-ready estimates, monitoring of greenhouse gases and dissolved organic carbon should be expanded, altered versus restored designs should be prioritized, and underrepresented regions and wetland types should be targeted.

(Sub)tropical inland waters are important greenhouse gas (GHG) sources, yet limited observations have long hindered broad analyses of GHG variability across this diverse region. Here, through a meta-analysis, we have examined the rates and drivers of GHG emissions from flowing and standing (sub)tropical inland waters. We find considerable spatial variation in fluxes, largely related to differences in hydroclimate, geomorphology, land cover and human disturbance. Flowing waters emit more carbon dioxide (3,3872,1215,702 TgCO2 yr-1, expressing medianfirst quartilethird quartile), methane (10.60.128.8 TgCH4 yr-1) and nitrous oxide (0.620.351.10 TgN2O yr-1) than standing waters (11473219 TgCO2 yr-1, 5.42.19.1 TgCH4 yr-1 and 0.030.020.05 TgN2O yr-1, respectively). (Sub)tropical inland waters release 4,23824737375 TgCO2-equivalents annually, with first- to third-order streams contributing 75% of riverine emissions and lakes larger than 100 km2 contributing 59% of standing water emissions. Our results suggest emissions from (sub)tropical waters are 29-72% lower than earlier estimates, a downward revision with important implications for global GHG budgets.

Leaf litter decomposition (LLD) is a key ecosystem function where invertebrate shredders produce large amounts of fine particulate organic matter (FPOM) that serves as a substrate for microbial assemblages. Here, we explore the shredder-produced FPOM composition and activity of FPOM-associated microbial communities in response to different leaf species and their conditioning. In a laboratory experiment, we fed leaves of different elemental compositions (alder, beech and maple), conditioned under oxic or anoxic conditions, to caddisfly larvae (Sericostoma sp.). We hypothesized differences in FPOM elemental and fatty acid composition and FPOM-associated microbial activity among the leaf species, conditioning, and two types of shredder-produced FPOM, i.e. shredded leaves and faecal pellets. Our results suggest that leaf conditioning and shredder activity play pivotal roles in shaping FPOM composition and FPOM-associated microbial activity. We observed lower C/N ratios with high-C/N litter (beech and maple leaves) after conditioning and no change in the elemental composition of the faecal pellets compared to the leaves. However, we observed differences in microbial fatty acid proportions and composition on leaves and faecal pellets with significantly higher fractions of bacterial fatty acids on faecal pellets than on leaves. We also noted a significant impact of leaf conditioning on the microbial activity of shredded leaves and faecal pellets, with a higher microbial growth efficiency observed on faecal pellets compared to ingested leaves. These findings highlight the crucial influence of leaf species and conditioning on the activity of shredder-produced FPOM, emphasizing the complex interplay between leaf properties and fate and microbial processes in streams.

Measuring reliable greenhouse gases (GHGs) fluxes at the interface between water bodies and the atmosphere in inland waters is crucial in the context of climate change but remains highly challenging. GHG fluxes can be measured directly in-situ with chambers placed at the water-atmosphere interface and connected to portable gas analysers providing high-frequency timeseries of GHGs partial pressures inside the chamber. Fluxes are usually assumed constant over the time of incubation, but varying GHG sources and changing environmental conditions and/or ebullition from the sediment produce non-linear patterns and breakpoints in the timeseries, not mentioning the possibility for poor manipulation of the device, disturbance of the sampling site by the operator, or malfunctioning sensors. Accordingly, it is common procedure to visualize and select part of the measurements manually for each incubation before proceeding with fluxes computation. In the ongoing Horizon Europe project RESTORE4Cs, we have performed CO2 and CH4 chamber measurements in 36 different sites located in 6 major coastal wetlands across Europe, including intertidal saltmarshes and seagrass beds, freshwater and brackish ponds and marshes, and coastal lagoons. Between October 2023 and August 2024, we have gathered a database of 822 floating chamber incubations, collected by multiple operators and with 3 different gas analysers. Here we focus on the data processing part and assess to what extent we need expert evaluation of the time series to produce reliable flux estimates. We have developed an automated data processing script able to compute fluxes estimates for all incubations. Timeseries are fitted with both a linear and non-linear models. The script identifies potential bubbling in CH4 measurements and estimates the diffusive versus ebullitive components based on the statistical characteristics of the first derivative of pCH4. All incubations were manually inspected by 16 members of our team, all experts in GHG chamber measurements with various levels of experience. About half of these timeseries were inspected independently by at least 3 experts, enabling to compare if and why experts disagree. For both CO2 and CH4, non-linear fitting performed better than linear models for 69% incubations, indicating a substantial number of non-linear patterns in the dataset; however, the difference between the two models was less than 10% for 86% of the incubations. The ebullition pathway was the dominant CH4 flux in less than 10% of the incubations. Experts disagreed substantially on the data selection in 34% of the incubations, which produced uncertainties in flux estimates larger than 10% of the inter-expert flux average. The highest discrepancies were related to suspicious or non-linear features in the time series. To avoid subjectivity and ensure robustness and repeatability of flux estimates, we present guidelines on how CO2 and CH4 incubation time series should be processed, regardless of whether they are processed automatically or after an expert manual inspection.

Coastal wetlands are crucial for biodiversity and act as critical buffers for carbon sequestration and atmospheric greenhouse gases (GHG) concentrations, yet their degradation often turns them into GHG sources. Restoration is widely implemented to recover these services, but it remains unclear whether interventions successfully re-establish the microbial functional diversity underpinning biogeochemical cycles. We tested the hypothesis that restoration aligns prokaryotic community structure with natural references, analyzing, a European gradient of coastal wetlands, comparing well-preserved, altered, and restored sites in water and sediment. Using 16SrRNA-metabarcoding and IndVal-Analysis, we characterized community assembly identifying diagnostic functional consortia. Results revealed a marked difference in water and sediment recovery after restoration. Bacterioplankton communities rapidly converge to natural references, while sediment microbiome displayed significant "ecological memory". Restored wetlands show sediment communities structurally distinct from well-preserved, retaining alteration-associated guilds decades. Results support the initial hypothesis: restoration processes in coastal wetlands can re-establish communities and metabolisms resembling well-preserved conditions in the water in the short term, while sediments retain microbial communities and metabolisms inherited from altered conditions for a long time. Future strategies must integrate active sediment interventions using molecular bioindicators to validate not only the landscape appearance, but the effective reactivation of ecosystem processes and microbiota-related services. ### Competing Interest Statement The authors have declared no competing interest. project RESTORE4Cs - Modelling RESTORation of wEtlands for Carbon pathways, Climate Change mitigation and adaptation, ecosystem services, and biodiversity, Co-benefits (DOI: 10.3030/101056782), co-funded by the European Union under the Horizon Europe research and innovation programme, 101056782 CLIMAWET-CONS (PID2019-104742RB-I00), funded by the Agencia Estatal de Investigation of the Spanish Government project ECCAEL (PROMETEO CIPROM-2023-031), funded by the Generalitat Valenciana

Photochemical degradation of dissolved organic matter (DOM) has been the subject of numerous studies; however, its regulation along the inland water continuum is still unclear. We aimed to unravel the DOM photoreactivity and concurrent DOM compositional changes across 30 boreal aquatic ecosystems including peat waters, streams, rivers, and lakes distributed along a water residence time (WRT) gradient. Samples were subjected to a standardized exposure of simulated sunlight. We measured the apparent quantum yield (AQY), which corresponds to DOM photomineralization per photon absorbed, and the compositional change in DOM at bulk and individual compound levels in the original samples and after irradiation. AQY increased with the abundance of terrestrially derived DOM and decreased at higher WRT. Additionally, the photochemical changes in both DOM optical properties and molecular composition resembled changes along the natural boreal WRT gradient at low WRT (<3 years). Accordingly, mass spectrometry revealed that the abundance of photolabile and photoproduced molecules decreased with WRT along the boreal aquatic continuum. Our study highlights the tight link between DOM composition and DOM photodegradation. We suggest that photodegradation is an important driver of DOM composition change in waters with low WRT, where DOM is highly photoreactive.

AbstractStreams are significant emitters of carbon dioxide (CO2) to the atmosphere that are influenced by diel CO2 dynamics. However, we know little about diel CO2 variability within streams, the diel dynamics of CO2 in the air above streams, and the consequences for emission calculations. We studied five pre‐alpine streams by equipping three sites per stream in close proximity (~ 1 km apart) with automatic logging stations that continuously recorded water and air CO2 partial pressures (pCO2) for 2–4 d. All streams and sites showed increased pCO2 at night and decreased pCO2 during the day, however, with fourfold higher diel amplitudes for atmospheric pCO2 compared to the water. Calculating diffusive CO2 fluxes with fixed compared to dynamic measured atmospheric CO2 resulted in negligible to 431% lower estimates. We might thus currently overestimate fluvial CO2 emissions and should include diel water and air CO2 variability to more accurately assess stream CO2 emissions.

IntroductionWoodchips as a source of particulate organic carbon (POC) are proposed as a nature-based solution to enhance nutrient uptake and retention in agricultural streams. However, the effective implementation of woodchips for nutrient removal in streams requires an advanced understanding of their potential and limits, considering their performance under various environmental conditions. This study tested the efficiency of woodchips on the uptake of soluble reactive phosphorus (SRP) and ammonium (N-NH4) across different experimental scales and complexity. We investigated whether the presence of woodchips can increase SRP and N-NH4 uptake in laboratory flumes under controlled conditions, outdoor flumes under semi-controlled conditions, and agricultural streams. Additionally, we examined how the effects of woodchips will change over time via a 6-week incubation in the outdoor flumes.MethodsThe woodchips were pre-colonized for four weeks to allow the growth of biofilms. We performed short-term nutrient additions without (control) and with (treatment) woodchips in all three experimental setups. Uptake parameters were determined via concentration changes over time in the laboratory flumes and concentration changes over travel distance in the outdoor flumes and the stream channels. The effects of woodchips on SRP and N-NH4 uptake rates were analyzed using an effect size model.ResultsWe found positive effects of woodchips on nutrient uptake only in the laboratory flumes but no or even negative effects in the outdoor flumes and the agricultural streams. Over the 6-week incubation in the outdoor flumes, we did not observe significant changes in the effects of woodchips on nutrient uptake.DiscussionThese findings highlight that considering experimental scales and influencing environmental conditions is crucial when testing the application of woodchips as nature-based solutions to mitigate nutrient loads in agricultural streams.

Meandering rivers are characterized by geomorphic units like cut banks, point bars, and thalwegs. These units arise from interactions between hydrological and geomorphological forces. However, the individual contributions of geomorphic units to whole-river metabolism or nutrient processing are unclear because these quantifications are often done at larger spatial scales. We used closed recirculating chambers to measure benthic gross primary production (GPP), respiration (R), N uptake or release, and P uptake or release at bimonthly intervals over 1 y at different geomorphic units in the Mulde River, Germany. We compared GPP, R, and nutrient processing among a cut bank, a point bar, and the thalweg at a natural meander. We also compared the cut bank of this natural meander with a cut bank fixed by riprap at a human-altered meander. In the natural meander, GPP, R, and nutrient processing rates were higher at the point bar than the cut bank or thalweg. These differences are likely related to larger sediment grain sizes that provide a more stable substrate for microbial communities. A strong interaction between geomorphic units and time for GPP and NH4+ fluxes suggested that differences in nutrient processing rates among geomorphic units were restricted to specific times during the year. Specifically, we found that the nutrient processing rates differed among geomorphic units during the summer, but not winter. Furthermore, in June and August 2017, R was 2 to 3× lower at the cut bank stabilized by riprap than at the natural cut bank. Our results demonstrate that rivers are composed of functionally distinct geomorphic units susceptible to human-induced hydromorphological degradation. However, strong interactions between space and time and large within-geomorphic unit variability propose that local drivers influence ecosystem function, suggesting that we need additional research to resolve these drivers at the scales of geomorphic units.

Plastic debris is thought to be widespread in freshwater ecosystems globally 1 . However, a lack of comprehensive and comparable data makes rigorous assessment of its distribution challenging 2 , 3 . Here we present a standardized cross-national survey that assesses the abundance and type of plastic debris (>250 μm) in freshwater ecosystems. We sample surface waters of 38 lakes and reservoirs, distributed across gradients of geographical position and limnological attributes, with the aim to identify factors associated with an increased observation of plastics. We find plastic debris in all studied lakes and reservoirs, suggesting that these ecosystems play a key role in the plastic-pollution cycle. Our results indicate that two types of lakes are particularly vulnerable to plastic contamination: lakes and reservoirs in densely populated and urbanized areas and large lakes and reservoirs with elevated deposition areas, long water-retention times and high levels of anthropogenic influence. Plastic concentrations vary widely among lakes; in the most polluted, concentrations reach or even exceed those reported in the subtropical oceanic gyres, marine areas collecting large amounts of debris 4 . Our findings highlight the importance of including lakes and reservoirs when addressing plastic pollution, in the context of pollution management and for the continued provision of lake ecosystem services.

Textile fibre evidence can provide important activity level information in criminal cases. To date, very few studies have investigated fibre persistence on fabrics exposed to aquatic conditions, even though items of evidence and victim's bodies can regularly be found in aquatic environments. This lack of research on whether fibres (and other trace evidence) persist on evidence submerged in water, has shown to impact practice as it is reported that crime scene examiners do not attempt to recover this evidence, due to the belief that it would not be present. The dynamic nature of aquatic environments mean that the studies are difficult to conduct in situ and variables, such as water flow rate are not possible to control and thought to be difficult to monitor. To address these challenges, artificial streams (also known as mesocosms) were employed in this study to investigate the persistence rate of polyester fibres on different fabric types (Woollen/nylon mix carpet, 100% polyester fleece, and 95% polyester/5% elastane sports vest) for a four week exposure time (1, 8, 24, 48, 120, 168, 264, 336, 504 and 672 hrs). The effect of water flow rate on the persistence of fibres was investigated by conducting the experiment with two flow velocities; 'high' (∼2.75 L/s) or 'low' (∼0.7 L/s). Significant differences between textile type were seen at 504 hrs under low flow conditions and 8, 24, 168 and 264 hrs under high flow conditions. When comparing flow velocities, a significant difference was seen at 1 hr exposure for the fleece textile only, indicating that the two flow rates used in this study do not significantly affect fibre persistence. Initial loss rates were highest for the first hour of submergence for the carpet, fleece and sports vest. Fibre persistence rates were highest on the carpet, followed by fleece and then sports vest. Persistence rates remained mostly constant after 24 hrs for all textiles but with redistribution of fibres between textiles being seen after this exposure time. The use of artificial flumes in this study provided a balance between realistic experimentation and a controlled study; key experimental variables could be continously and safely monitored. This study provides the first fibre persistence data in river type environments and proposes a new method for testing persistence in aquatic environments. This approach is not limited to fibres evidence and could be employed for other evidence such as glass, pollen, fingerprints and DNA.