Rivers impact the well-being of humans and the environment. As they increasingly face planetary-scale stressors, it is critically important to monitor and understand rivers at the global scale. As the only synoptic resource for global primary data on rivers, satellite remote sensing has recently begun to provide unprecedented opportunities for the monitoring, understanding, and prediction of global river behaviour. Despite these advances, the role of satellite remote sensing in global river science has still not been fully explored. New satellite systems and algorithms will enable substantial improvements in river measurements, provide new answers to long-standing or newly emerging scientific questions, and eventually update basic knowledge of rivers to advance global river science. In this Review we explore how remote sensing has been used to study the world’s rivers, examine challenges and opportunities for further advancing our understanding of rivers using existing and upcoming sensors, and identify possible solutions and future research directions. This Review synthesizes the transformative role of satellite remote sensing in reshaping global river science. It offers a strategic roadmap to overcome current challenges and update our fundamental understanding of Earth’s river systems.

Microorganisms inhabiting dynamic ecosystems are repeatedly exposed to environmental fluctuations and disturbances which require physiological adaptations, often associated with fitness trade-offs. In glacier-fed streams, benthic biofilms, the dominant microbial lifeform, frequently experience environmental fluctuations, including drying and rewetting. However, the diversity of responses of glacier-fed stream biofilm to drought stress is not well understood. For instance, stress priming, where prior exposure to a stressor enhances performance during subsequent events, has not been documented in glacier-fed stream bacteria. Here, we investigated how bacterial strains from glacier-fed stream biofilm respond to recurrent drying and whether they exhibit stress priming. To test this, we exposed 22 bacterial strains to repeated short (6 h) drying-rewetting cycles to assess whether their growth improves after repeated exposures. We further tested stress priming by assessing their survival to longer droughts (24 h and 96 h), quantified their biofilm formation, and explored their genomic traits to evaluate whether these features explain the various drought responses. Most strains survived a single short drought, but often at the cost of prolonged lag phases and reduced growth rates. Repeated drought exposure led to divergent stress responses: several strains exhibited signs of stress priming by improving growth traits and/or gaining the ability to withstand prolonged drought only after prior exposure. These responses were largely independent of taxonomy or genomic potential, suggesting that regulatory mechanisms dominate drought adaptation in glacier-fed stream bacteria. Overall, our findings highlight the response diversity among glacier-fed stream biofilm bacteria and show that adaptation often comes at the cost of altered growth dynamics, a potential strategy to cope with the natural hydrological fluctuations in glacier-fed streams.

The retreat of glaciers opens up large proglacial areas which become available for colonization and primary succession. Yet, factors that contribute to habitability during early succession in proglacial areas remain poorly understood. In proglacial streams, biofilms, which are matrix-enclosed microbial communities, colonize the streambed and grow into millimeter thick mats. Particularly in proglacial streams draining relatively flat and stable lateral terraces, these biofilms may augment habitability by reducing water scarcity through clogging of the streambed. To quantitatively address this phenomenon, we performed streamside flume experiments and conceived the idealized terrace model, which models stream length elongation as a function of microbially induced clogging, sediment hydraulic properties, stream roughness, slope, width and inflow. Significant stream elongation, and hence habitabilization, occurs when clogging suffices to induce unsaturated conditions below the streambed. Considering multiple terrace configurations with educated parameter bounds, we found a wide range of possible elongation, ranging from none to 100-fold. Sensitivity analysis suggests that sediment hydraulic properties mostly contribute to variability in stream elongation due to biofilm induced clogging. Taken together, we here show that microbial communities can significantly extend the habitability of proglacial stream ecosystems by inducing streambed clogging and retaining water. This is relevant in light of the rapid glacier retreat.

Glacier-fed streams (GFSs) are harsh environments hosting unique, highly specialized communities. Interestingly, glaciers and their GFSs are also present in Earth's tropical regions, where environmental characteristics contrast with GFS conditions elsewhere. Yet, despite the unique and isolated nature of tropical GFSs, little is known about their inhabitants, even though they may disappear later this century with ongoing climate change. Here, we examined diatom communities from one of the last tropical African GFSs in the Rwenzori Mountains, Uganda, to characterize the composition and diversity of this unique system. Six sediment-associated biofilm samples were collected from two reaches of a stream draining the Mt. Stanley Glacier, and the resident diatom communities were studied morphologically using light and scanning electron microscopy, as well as through the sequencing of amplicons from extracted DNA (18S and rbcL). In general, morphological results agree well with barcoding results, but each individually provides irreplaceable insights. In total, we identify 24 morphotypes utilizing light microscopy, 101 diatom Amplicon Sequence Variants (ASVs) using 18S sequences, and 65 ASVs with rbcL. Across approaches, common genera include Achnanthidium, Psammothidium, Neidium, Cymbopleura, Eunotia, and Pinnularia. However, only about half of the diversity could be assigned to the species level across methodologies, including several of the most common taxa, indicating a high level of uniqueness. Accordingly, one of the most common taxa encountered is described here as a new species, Neidium rwenzoriense sp. nov. Our results emphasize the Rwenzori Mountains as a global hotspot for endemism, and the novelty of disappearing tropical GFSs as diatom habitats.

Atmospheric deposition delivers carbon to glacier surfaces, including from fossil fuel and biomass combustion. Nonetheless, spatial variation in the sources of organic and black carbon deposited on glaciers is poorly understood, along with their role in driving glacier outflow dissolved organic matter (DOM) composition and fate. Here, we used bulk and compound‐specific carbon isotopic analyses to constrain the sources of dissolved organic carbon (DOC) and dissolved black carbon (DBC) in 10 glacier outflows across four regions. To understand the relationships between glacier DOM composition and sources of DOC and DBC, isotopic data were used in conjunction with ultrahigh resolution molecular‐level analyses. Globally, a substantial yet variable component of DOC was sourced from anthropogenic aerosols (12%–91%; median 50%), influencing regional DOM composition (aliphatics 26.9%–58.4% relative abundance; RA). Relatively older radiocarbon ages (i.e., larger fossil‐derived component) of glacier DOC were correlated with more 13 C depleted DOC and DBC signatures, where DOM had higher aromaticity, elevated RA of condensed aromatics, and a lower RA of aliphatic compounds. This study highlights that anthropogenic deposition is pervasive, but its extent varies spatially with ramifications for DOM composition, and thus reactivity and fate.

The shrinkage of glaciers and the vanishing of glacier-fed streams (GFSs) are emblematic of climate change. However, forecasts of how GFS microbiome structure and function will change under projected climate change scenarios are lacking. Combining 2,333 prokaryotic metagenome-assembled genomes with climatic, glaciological, and environmental data collected by the Vanishing Glaciers project from 164 GFSs draining Earth's major mountain ranges, we here predict the future of the GFS microbiome until the end of the century under various climate change scenarios. Our model framework is rooted in a space-for-time substitution design and leverages statistical learning approaches. We predict that declining environmental selection promotes primary production in GFSs, stimulating both bacterial biomass and biodiversity. Concomitantly, predictions suggest that the phylogenetic structure of the GFS microbiome will change and entire bacterial clades are at risk. Furthermore, genomic projections reveal that microbiome functions will shift, with intensified solar energy acquisition pathways, heterotrophy and algal-bacterial interactions. Altogether, we project a 'greener' future of the world's GFSs accompanied by a loss of clades that have adapted to environmental harshness, with consequences for ecosystem functioning.

In high-mountain landscapes, biological resources such as organic carbon (OC) are often limited and heterogeneously stored in poorly developed soils, snow, ground ice and glaciers. Climate change influences the dynamics of OC mobilization to- and processing into- the recipient streams. These patterns can vary from seasonal (e.g., snow melt in spring) to daily (e.g., ice melt in summer) depending on the location of the streams within the catchment. Capturing the temporal richness of stream biogeochemical signals is now a reality with the advent of high-resolution sensors. In this study, we used wavelet analysis on high-frequency discharge (Q) and dissolved organic carbon (DOC) measurements from nine streams in the Swiss Alps to investigate whether synchrony (S) of Q (SQ) and DOC (SDOC) persisted or collapsed among streams, and its response to the spatial position, climate, and land cover gradients across different time scales. Our findings reveal that short-term (0-10 days) SQ and SDOC were strongly influenced by distance between streams and network connectivity. In contrast, catchment-related properties (i.e., altitude or land cover) were more important in driving SQ and SDOC dynamics at longer time scales (>50 days). However, the degree to which local catchment properties controlled S patterns at the longest timescales depended both on the response variable (i.e., Q vs. DOC) as well on the main land cover (i.e., vegetation vs. glacier). Elucidating the most prominent timescales of SDOC is relevant given the hydrological alterations projected for high-mountain regions. We show that glaciers impose a unique seasonal regime on DOC concentration, potentially overriding the effects of other local hydrological or biogeochemical processes during downstream transport. Consequently, SDOC dynamics in high-mountain streams may change as glaciers shrink, thereby altering downstream opportunities for biogeochemical transformations.

The rapid melting of mountain glaciers and the vanishing of their streams is emblematic of climate change1,2. Glacier-fed streams (GFSs) are cold, oligotrophic and unstable ecosystems in which life is dominated by microbial biofilms2,3. However, current knowledge on the GFS microbiome is scarce4,5, precluding an understanding of its response to glacier shrinkage. Here, by leveraging metabarcoding and metagenomics, we provide a comprehensive survey of bacteria in the benthic microbiome across 152 GFSs draining the Earth’s major mountain ranges. We find that the GFS bacterial microbiome is taxonomically and functionally distinct from other cryospheric microbiomes. GFS bacteria are diverse, with more than half being specific to a given mountain range, some unique to single GFSs and a few cosmopolitan and abundant. We show how geographic isolation and environmental selection shape their biogeography, which is characterized by distinct compositional patterns between mountain ranges and hemispheres. Phylogenetic analyses furthermore uncovered microdiverse clades resulting from environmental selection, probably promoting functional resilience and contributing to GFS bacterial biodiversity and biogeography. Climate-induced glacier shrinkage puts this unique microbiome at risk. Our study provides a global reference for future climate-change microbiology studies on the vanishing GFS ecosystem. Leveraging metabarcoding and metagenomics, a survey of bacteria in the benthic microbiome across 152 glacier-fed streams (GFSs) provides a global reference for future climate-change microbiology studies on the vanishing GFS ecosystem.

Glacier-fed streams (GFS) feature among Earth’s most extreme aquatic ecosystems marked by pronounced oligotrophy and environmental fluctuations. Microorganisms mainly organize in biofilms within them, but how they cope with such conditions is unknown. Here, leveraging 156 metagenomes from the Vanishing Glaciers project obtained from sediment samples in GFS from 9 mountains ranges, we report thousands of metagenome-assembled genomes (MAGs) encompassing prokaryotes, algae, fungi and viruses, that shed light on biotic interactions within glacier-fed stream biofilms. A total of 2,855 bacterial MAGs were characterized by diverse strategies to exploit inorganic and organic energy sources, in part via functional redundancy and mixotrophy. We show that biofilms probably become more complex and switch from chemoautotrophy to heterotrophy as algal biomass increases in GFS owing to glacier shrinkage. Our MAG compendium sheds light on the success of microbial life in GFS and provides a resource for future research on a microbiome potentially impacted by climate change. Thousands of metagenome-assembled genomes from the Vanishing Glaciers project showcase the interactions between prokaryotes, algae, fungi and viruses in glacier-fed stream environments.

Inland waters (streams, rivers, lakes, and reservoirs) are important sources of greenhouse gases (GHGs), including carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), to the atmosphere. Their importance has been acknowledged in the IPCC assessment reports and in the regional and global greenhouse budgets coordinated by the Global Carbon Project (GCP). In the framework of the 2nd phase of the REgional Carbon Cycle Assessment and Processes (RECCAP-2) initiative of the GCP, a comprehensive synthesis of existing estimates of regional to global inland water GHG emissions was conducted (Lauerwald et al., 2023a, 2023b) to support the inclusion of these emissions in (sub-)continental GHG budgets. Although that synthesis was published only two years ago, a number of new global estimates have been published since. Here, we present an updated synthesis of recent, global inland water GHG emissions estimates. Moreover, we go beyond the scope of the RECCAP2 synthesis by analyzing regional patterns in more detail, and summarizing the state of knowledge about long-term trends of inland water GHG emissions in response to changes in climate, land use, wastewater management and river damming. Based on that, we discuss how contemporary inland water GHG emissions are impacted by anthropogenic activities and how they may evolve over the 21st century.We estimate that global inland water GHG emissions have a combined warming potential of 8 (5–13) Pg CO2-eq. yr⁻¹ for a 100-year time horizon (GWP100). CO2 emissions, primarily from tropical river systems, contribute approximately three-quarters of this total, while CH4, largely from lakes and reservoirs, accounts for most of the remainder. Notably, boreal and Arctic lakes are important emitters due to their large total area, while nutrient-rich lakes and reservoirs with warmer temperatures in the mid to low latitudes exhibit the highest per-area CH4 emission rates. Contributions from N2O emissions are relatively minor.About one third of CH4 emissions and about three quarters of N2O emissions from global inland waters can be attributed to anthropogenic perturbations, primarily through eutrophication. For inland water CO2 emissions, quantification of the anthropogenic component is more complex. Empirical and modelling studies suggest that global greening also increases terrestrial carbon deliveries to inland waters, and through that, emissions of CO2 from inland waters. Moreover, changes in streamflow are an uncertain, but very important driver. Most dramatic increases are expected for inland water CH4 and N2O emissions, which are projected to strongly increase in response to global warming, while changes in nutrient loads from agricultural runoff may offset or enhance that trend.ReferencesLauerwald et al. 2023a, GBC, https://doi.org/10.1029/2022GB007657Lauerwald et al. 2023b, GBC, https://doi.org/10.1029/2022GB007658

Dissolved oxygen (DO) sustains river ecosystems, but the effects of hydrological extremes remain poorly understood. While high river discharge (Q) enhances aeration, floods also deliver oxygen-consuming pollutants, making net impacts uncertain. Here, we analyze daily DO and its percent saturation (DO%sat), and Q in 1156 Chinese rivers over three years. We show that DO and DO%sat decrease with rising Q in 69.1% and 55.7% of rivers, respectively. Floods (Q > 95th percentile) cause abrupt declines in both DO (19.7%) and DO%sat (16.2%) in 80.1% and 69.4% of the rivers, respectively, with the sharpest declines in agricultural and urban areas. These abrupt deoxygenation events link to increased ammonium and land-use intensity, causing more frequent hypoxia in developed regions. Contrary to initial expectations, floods often reduce oxygen levels, with faster recovery in urbanized regions. As climate change intensifies flooding, such sudden deoxygenation shocks may degrade aquatic ecosystems particularly in human-altered landscapes.

Climate change is predicted to alter the hydrological and thermal regimes of high-mountain streams, particularly glacier-fed streams. However, relatively little is known about how these environmental changes impact the microbial communities in glacier-fed streams. Here, we operated streamside flume mesocosms in the Swiss Alps, where benthic biofilms were grown under treatments simulating climate change. Treatments comprised four flow (natural, intermittent, stochastic, and constant) and two temperature (ambient streamwater and warming of +2°C) regimes. We monitored microbial biomass, diversity, community composition, and metabolic diversity in biofilms over 3 months. We found that community composition was largely influenced by successional dynamics independent of the treatments. While stochastic and constant flow regimes did not significantly affect community composition, droughts altered their composition in the intermittent regime, favouring drought-adapted bacteria and decreasing algal biomass. Concomitantly, warming decreased algal biomass and the abundance of some typical glacier-fed stream bacteria and eukaryotes, and stimulated heterotrophic metabolism overall. Our study provides experimental evidence towards potential and hitherto poorly considered impacts of climate change on benthic biofilms in glacier-fed streams.

In glacierized high mountain catchments, streamflow generation is strongly influenced by snow and glacier melt, processes especially sensitive to rising temperatures and ongoing climate change. These vulnerabilities make mountain headwater catchments a research priority; However, limited observational data and complex glacier-snow interactions often challenge conventional hydrological modeling in high-mountainous areas. Although several models have been developed to simulate streamflow dynamics in glacierized settings, many either lack comprehensive glacier representations or oversimplify them, failing to incorporate critical processes such as glacier evolution over time (e.g., glacier retreat).To address these limitations, we employed the recently developed SWAT-GL model, which integrates a mass balance module and a glacier evolution parameterization to more accurately track changes in glacier volume and extent. Using a degree-day approach and ∆h-parameterization for glacier adjustment, SWAT-GL provides a robust framework for simulating spatiotemporal streamflow dynamics in glacierized catchments.We applied SWAT-GL to the Valsorey catchment in the canton of Valais, Western Swiss Alps, calibrating the model with in-situ meteorological and streamflow data collected over the past decade. Our analyses revealed pronounced interannual variability in flow intermittency between climatically contrasting years, underscoring the distinct influences of glacier-fed and non-glacier-fed sub-catchments on overall runoff patterns. In particular, we identified notable differences in no-flow occurrences and seasonal streamflow recessions. Glacier-fed streams exhibited prolonged baseflow during warmer periods, while non-glacier-fed streams experienced an earlier onset and more frequent episodes of low or no-flow conditions.Ongoing work applies future climate change scenarios to explore how continued glacier retreat will reshape these flow regimes and flow intermittency patterns. These findings will provide valuable insights into the resilience and adaptability of alpine hydrological systems.

ABSTRACT Glacier-fed streams are permanently cold, ultra-oligotrophic, and physically unstable environments, yet microbial life thrives in benthic biofilm communities. Within biofilms, microorganisms rely on secondary metabolites for communication and competition. However, the diversity and genetic potential of secondary metabolites in glacier-fed stream biofilms remain poorly understood. In this study, we present the first large-scale exploration of biosynthetic gene clusters (BGCs) from benthic glacier-fed stream biofilms sampled by the Vanishing Glaciers project from the world’s major mountain ranges. We found a remarkable diversity of BGCs, with more than 8,000 of them identified within 2,868 prokaryotic metagenome-assembled genomes, some of them potentially conferring ecological advantages, such as UV protection and quorum sensing. The BGCs were distinct from those sourced from other aquatic microbiomes, with over 40% of them being novel. The glacier-fed stream BGCs exhibited the highest similarity to BGCs from glacier microbiomes. BGC composition displayed geographic patterns and correlated with prokaryotic alpha diversity. We also found that BGC diversity was positively associated with benthic chlorophyll a and prokaryotic diversity, indicative of more biotic interactions in more extensive biofilms. Our study provides new insights into a hitherto poorly explored microbial ecosystem, which is now changing at a rapid pace as glaciers are shrinking due to climate change.IMPORTANCEGlacier-fed streams are characterized by low temperatures, high turbidity, and high flow. They host a unique microbiome within biofilms, which form the foundation of the food web and contribute significantly to biogeochemical cycles. Our investigation into secondary metabolites, which likely play an important role in these complex ecosystems, found a unique genetic potential distinct from other aquatic environments. We found the potential to synthesize several secondary metabolites, which may confer ecological advantages, such as UV protection and quorum sensing. This biosynthetic diversity was positively associated with the abundance and complexity of the microbial community, as well as concentrations of chlorophyll a. In the face of climate change, our study offers new insights into a vanishing ecosystem.

Runoff from rapidly melting mountain glaciers is a dominant source of riverine organic carbon in many high-latitude and high-elevation regions. Glacier dissolved organic carbon is highly bioavailable, and its composition likely reflects internal (e.g., autotrophic production) and external (i.e., atmospheric deposition) sources. However, the balance of these sources across Earth's glaciers is poorly understood, despite implications for the mineralization and assimilation of glacier organic carbon within recipient ecosystems. We assessed the molecular-level composition of dissolved organic matter from 136 mountain glacier outflows from 11 regions covering six continents using ultrahigh resolution 21 T mass spectrometry. We found substantial diversity in organic matter composition with coherent and predictable (80% accuracy) regional patterns. Employing stable and radiocarbon isotopic analyses, we demonstrate that these patterns are inherently linked to atmospheric deposition and in situ production. In remote regions like Greenland and New Zealand, the glacier organic matter pool appears to be dominated by in situ production. However, downwind of industrial centers (e.g., Alaska and Nepal), fossil fuel combustion byproducts likely underpin organic matter composition, resulting in older and more aromatic material being exported downstream. These findings highlight that the glacier carbon cycle is spatially distinct, with ramifications for predicting the dynamics and fate of glacier organic carbon concurrent with continued retreat and anthropogenic perturbation.

Cross-domain interactions are an integral part of the success of biofilms in natural environments but remain poorly understood. Here, we describe cross-domain interactions in stream biofilms draining proglacial floodplains in the Swiss Alps. These streams, as a consequence of the retreat of glaciers, are characterised by multiple environmental gradients and perturbations (e.g., changes in channel geomorphology, discharge) that depend on the time since deglaciation. We evaluate co-occurrence of bacteria and eukaryotic communities along streams and show that key community members have disproportionate effects on the stability of community networks. The topology of the networks, here quantified as the arrangement of the constituent nodes formed by specific taxa, was independent of stream type and their apparent environmental stability. However, network stability against fragmentation was higher in the streams draining proglacial terrain that was more recently deglaciated. We find that bacteria, eukaryotic photoautotrophs, and fungi are central to the stability of these networks, which fragment upon the removal of both pro- and eukaryotic taxa. Key taxa are not always abundant, suggesting an underlying functional component to their contributions. Thus, we show that there is a key role played by individual taxa in determining microbial community stability of glacier-fed streams.

Most cryospheric ecosystems are energy limited. How their energetics will respond to climate change remains largely unknown. This is particularly true for glacier-fed streams, which interface with the cryosphere and initiate some of Earth’s largest river systems. Here, by studying resource stoichiometry and microbial energetics in 154 glacier-fed streams sampled by the Vanishing Glaciers project across Earth’s major mountain ranges, we show that these ecosystems and their benthic microbiome are overall carbon and phosphorus limited. Threshold elemental ratios and low carbon use efficiencies (median: 0.15) modelled from extracellular enzymatic activities corroborate resource limitation in agreement with maintenance metabolism of benthic microorganisms. Space-for-time substitution analyses suggest that glacier shrinkage will stimulate benthic primary production in glacier-fed streams, thereby relieving microbial metabolism from carbon limitation. Concomitantly, we find that increasing streamwater temperature will probably stimulate microbial growth (temperature sensitivity: 0.62 eV). Consequently, elevated microbial demands for phosphorus, but diminishing inputs from subglacial sources, may intensify phosphorus limitation as glaciers shrink. Our study thus unveils a ‘green transition’ towards autotrophy in the world’s glacier-fed streams, entailing shifts in the energetics of their microorganisms.

Viruses modulate the diversity and activity of microbial communities. However, little is known about their role for the structure of stream bacterial biofilm communities. Here, we present insights into the diversity and composition of viral communities in various streams draining three proglacial floodplains in Switzerland. Proglacial streams are characterized by extreme environmental conditions, including near-freezing temperatures and ultra-oligotrophy. These conditions select for few but well-adapted bacterial clades, which dominate biofilm communities and occupy niches via microdiversification. We used metagenomic sequencing to reveal a diverse biofilm viral assemblage in these streams. Across the different floodplains and streams, viral community composition was tightly coupled to that of the bacterial hosts, which was underscored by generally high host specificity. Combining predictions of phage-host interactions with auxiliary metabolic genes (AMGs), we identify specific AMGs shared by phages infecting microdiverse clade members. Our work provides a step towards a better understanding of the complex interactions among bacteria and phages in stream biofilm communities in general and streams influenced by glacier meltwaters and characterized by microdiversity in particular.

Stream periphytons are candidate ecosystem engineers in proglacial margins. Here, we quantify the extent to which they are engineers for the case of hillslope-fed tributaries in the terrace zones of proglacial margin alluvial plains. Candidate ecosystem engineering effects relate to periphyton-driven changes in (1) vertical infiltration of water, which in turn could aid plant colonization and hence local surface stabilization, and (2) near-bed hydraulics, notably near-bed turbulence properties. We ran two flume experiments in parallel in the proglacial margin of the Otemma glacier (Switzerland), reproducing the environmental conditions found in terrace streams. In both experiments, we followed periphyton development on initially bare sediments for 28 days. Then, whilst the experiment continued undisturbed in one flume, in the second and over a further 26 days, we introduced disturbances in the form of desiccation events. Throughout the entire experiment length, we collected imagery for close-range SfM-MVS photogrammetry, data on vertical infiltration, and near-bed hydraulics. The experiments showed that periphyton development significantly changed the streambed properties. First, periphyton development over the timescale of a few days reduced bed roughness and clogged the benthic interstitial space, reducing water infiltration. These effects were insensitive to the disturbance regime. Second, the changes in streambed roughness modified the near-bed turbulent structures, and this resulted in a reduction of bursting events and in the modification of the turbulent kinetic energy at the near-bed layer. The latter, however, appeared to be less important in these environments as compared with the impacts on infiltration. Given the low water retaining capacity of glacial sediments, the observation that periphyton can reduce vertical infiltration explains wider observations of their importance in glacial floodplains where vegetation succession is critically constrained by water availability. The relatively reduced impacts on near-bed turbulence also contribute to explaining why disturbance in proglacial margin streams remains a key limit on ecological succession. Stream periphytons are candidate ecosystem engineers in proglacial margins. We demonstrate that the development of periphyton reduces bed roughness and clogs the benthic interstice space, reducing vertical water infiltration. The changes in streambed roughness modify the near-bed turbulent structures, and this results in a reduction of adverse bursting events and in the modification of the turbulent kinetic energy at the near-bed layer.image