Orals: Wed, 6 May, 14:00–17:55 | Room 2.23
Multiple stressors in aquatic systems interact across temporal and spatial scales, which complicates the evaluation of their individual and conjoint effects on water quality and ecosystem functioning. This is particularly complex when gradual changes (e.g. from multi-year droughts to decadal warming) add to the impact of short-termed extreme events (e.g. a heatwave or the sudden disruption of flow). At the same time, focusing on the individual dynamics of water quality/composition indicators as proxies of ecosystem functioning may lead to the underestimation of system-wide sensitivities. Here, we define the ‘biogeochemical space’ of a river system as the realized, two-dimensional configuration of water composition dynamics as captured by non-metric multidimensional scaling of spatially discrete and temporally-resolved monitoring data.
We applied this concept to explore the combined expression of hydrological, meteorological, and anthropic stress in the Lower Oder River, which flows along the German-Polish border, and where an unprecedented harmful algal bloom caused a major environmental disaster in the summer of 2022. Using 20 years of monthly physicochemical data over a 200-km river reach, and in combination with long-term temperature and discharge records, we reconstructed a progressive shift toward increasingly concentrated (ion-enriched) water composition states. This displacement was, on one side, strongly associated with multi-year anomalies in water temperature and in discharge (> 2°C and –40%) caused by drier conditions in the catchment since 2016. On another side, conservative ions showed monotonic increases that could not be explained by short- nor medium-term changes in discharge alone, which confirmed the increased pressure from industry and mining-related salt inputs that are significant in this region. Finally, we further illustrate how the biogeochemical space framework can be used to diagnose diverse responses in other river systems at regional and global scales, and characterize their sensitivities to multiple impacts.
How to cite: Goldhammer, T. and Torre Zaffaroni, P.: Disentangling multiple stressors in rivers using multivariate biogeochemical spaces, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18525, https://doi.org/10.5194/egusphere-egu26-18525, 2026.
Dissolved organic matter in estuarine sediments (SDOM) mediates carbon transformation and exchange across the sediment–water interface, yet its controls and fate remain poorly constrained. Here, we characterized SDOM along the Changjiang Estuary–East China Sea continuum using ultrahigh-resolution mass spectrometry, integrating prior stable and radiocarbon constraints to track SDOM provenance and age and to evaluate sediment–water exchange with co-located bottom-water DOM. SDOM was more biologically labile than bottom-water DOM, enriched in aliphatic, low-molecular-weight, nitrogen-containing compounds. We further examined chemically unassigned mass peaks (“dark matter”), which accounted for a substantial fraction of molecular richness but contributed a smaller share of bulk signal intensity. A sizable subset of these peaks was shared between sediments and the water column, indicating transferable sedimentary molecular fingerprints across the sediment–water interface. Spatial patterns identify the inner-shelf mobile mud zone as a hotspot where hydrodynamic disturbance and resuspension promote particle-mediated adsorption–desorption and rapid exchange, coupling the redistribution of fresh marine DOM with nearshore attenuation of terrestrial-derived signals. These results position SDOM as a reactive carbon pool in river-dominated margins and show that incorporating chemically dark matter yields a more complete molecular view of sediment–water DOM exchange.
How to cite: Zhang, Z., Yao, P., Zhao, B., Yi, Y., Chen, Z., Cai, R., Liang, W., and He, D.: Evolution of DOM molecular fingerprints from a river to ocean continuum: a comprehensive view of water columns, surface sediments, and chemically dark matter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7567, https://doi.org/10.5194/egusphere-egu26-7567, 2026.
The Menindee Lakes, situated on the lower Darling–Baaka River in central Australia, form a major regulated water-storage complex that supplies water to major agricultural and urban areas. As a shallow dryland lake–river complex, the system typically experiences prolonged low-flow periods punctuated by short pulse floods. However, the construction of the Menindee Lakes Scheme in the 1960s transformed the system into an artificial, low-energy lotic storage and sediment trap, fundamentally altering benthic sediment fluxes, residence times, and redox dynamics. With unexplained repeated mass fish mortality events over the past decade, it is essential to understand the biogeochemical mechanisms driving changes in oxygen availability.
Here, we combined seasonal sediment core incubations, stable isotope measurements, and field data-driven dissolved-oxygen modelling to identify and quantify the transformations and fate of nutrients and redox-active elements. Intact sediment cores were incubated in the field at eight sites spanning hydrologically distinct regions, capturing a gradient from fine, organic-rich sediments upstream to sandier sediments downstream. A two-step sequential oxic-to-anoxic incubation design, applied to the same cores, quantified fluxes of nutrients and redox metals, as well as nitrate isotope dynamics (δ¹⁵N–NO₃⁻, δ¹⁸O–NO₃⁻), resolving key redox-driven transformations.
Nutrient fluxes exhibited strong spatial and seasonal contrasts that aligned with flow regulation and associated fine-sediment accumulation. Fine-grained, organic-rich sediments associated with Lake Wetherell and the upper weir pool showed substantially higher biogeochemical reactivity than sandier downstream sites. In summer, weir-pool sediment oxygen demand nearly doubled, and Lake Wetherell consistently emerged as a biogeochemical hotspot, with NH₄⁺ and PO₄³⁻ release rates more than twice those elsewhere and PO₄³⁻ release increasing >20-fold. Under anoxic conditions, δ¹⁵N–NO₃ followed Rayleigh-type enrichment consistent with denitrification. However, δ¹⁸O–NO₃ showed decoupling from expected fractionation, indicating alternate redox-sensitive nitrogen cycling pathways (likely DNRA) that can recycle and retain N.
Anoxic fluxes of reduced nitrogen and redox-active species from the weir pool were stoichiometrically converted to sediment oxygen demand (SOD), upscaled to the weir-pool scale, and incorporated into a dissolved-oxygen box model to quantify sediment-mediated oxygen demand under no-flow conditions and the flow required for recovery following re-oxygenation. This demonstrated that during no-flow drought conditions, SOD can accumulate rapidly, while recovery following re-oxygenation is sensitive to both the magnitude and duration of managed flow releases. By integrating field, laboratory, and modelling approaches, we demonstrate how flow regulation and management-driven fine-sediment accumulation control redox-sensitive sediment biogeochemistry and amplify seasonal oxygen stress in regulated dryland rivers.
How to cite: Guyat, J., Tait, D., Johnson, S., Stewart, B., Ferguson, A., Padilla-Montalvo, J., Ralph, C., Taffs, K., Balzer, M., Mawhinney, W., Beresford, R., and Maher, D.: Intensive water management of dryland rivers drives fine-sediment accumulation, redox-sensitive internal loading, and flow-controlled oxygen dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6208, https://doi.org/10.5194/egusphere-egu26-6208, 2026.
Rivers form a crucial component of the global carbon (C) cycle. They not only link terrestrial and oceanic pools, but their floodplains and channels also act as C sources and sinks, and areas of C biogeochemical processing. Quantification of C fluxes is often challenging because estimates can be biased if measurements do not adequately capture the high spatial (upstream vs downstream, channel vs floodplain) and temporal (day vs night, dry vs wet seasons, year to year) variability. This study focuses on closing existing knowledge gaps on the influence of river geomorphology on biogeochemical C processes and lateral C exchanges across river reaches and seasons in tropical river systems by quantifying C processes, sources and storage in two tropical river floodplain systems. Rivers Sabaki and Tana both originate from Kenya’s central highlands and drain into the Indian Ocean, but they differ strongly in their geomorphology and the degree of impact by agriculture, reservoirs, industries and nutrient inputs. We characterized C pools and sources (using C and N stable isotope ratios as proxies) in river water and floodplain sediments during different field campaigns in 2024 and 2025 during the dry season (September - October), as well as regular sampling of river biogeochemistry throughout the year. Additionally, we measured in situ benthic and pelagic respiration rates and concentrations of dissolved greenhouse gases (GHG: CO2, N2O, CH4). Sediment organic carbon (OC) appeared to be mainly derived from riverine suspended matter, with localized contributions of floodplain vegetation in particular along the Tana River floodplains and in overbank floodplains of the Sabaki River. In the case of Sabaki, the sources of OC transported shows extreme contrasts between wet and dry periods, which are dominated by terrestrial runoff (mix of C4 and C3-derived C) and autochthonous production, respectively. The average sediment OC content showed a clear decline with depth (0.492% at <10 cm, 0.495% at 10-50 cm, 0.362% at 50-100 cm, 0.193% at 100-320 cm). Lower OC levels and preaged OC deposits within the top layer also supports the hypothesis that the floodplain OC is largely deposition from riverine particulate organic carbon (POC) during wet season. A strong correlation was observed between OC and clay content (r = 0.60, p < 0.001), and between OC and distance from the channel (r = 0.669 , p < 0.001). Clay provides reactive surface area for OC sorption, and lower flow energy and fine sediments settle furthest. During the dry season Sabaki system is strongly autotrophic, characterized by strong CO2 undersaturation and suspended matter dominated by photosynthetic biomass with a high OC content (on average 16.5%). Overall, our findings demonstrate that tropical river systems are highly dynamic component of the C cycle, in which geomorphology, seasonality, and land use strongly regulate C sources, storage and processing. Low land floodplains are primarily depositional sinks for in situ plant derived OC and allochthonous POC, with spatial patterns controlled by hydrodynamics and sediment texture, while temporal variability reflects shifts between terrestrial inputs during wet seasons and autochthonous production during dry periods.
How to cite: Cherono, S., Samarasinghe, S., Schwarz, C., Tamooh, F., Omengo, F., V. Borges, A., Adriaenssen, H., Drijvers, J., and Bouillon, S.: Carbon Sources, Transport and Sequestration in Tropical River Floodplains of Sabaki and Tana, Kenya, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5627, https://doi.org/10.5194/egusphere-egu26-5627, 2026.
Predicting the outcomes of redox processes in aquatic environments requires quantitative constraints on electron transfer reactions. Advances in electrochemical techniques have significantly improved our ability to quantify and constrain mineral-related biogeochemical redox processes that regulate carbon, nutrient, and contaminant cycling in aquatic environments. Manganese oxides are key redox-active minerals in these systems that influence organic matter transformation, nutrient availability, and contaminant fate. In particular, Mn(III)-oxides occupy a critical role due to their ability to act as both electron acceptors and donors in the redox landscape. However, their redox characteristics are poorly understood due to their intermediate and metastable nature. Here, we apply mediated electrochemical analysis (MEA) as an analytical laboratory technique to study the effect of changing redox conditions and solution chemistry on the redox-activity of two representative Mn(III)-oxides—manganite and hausmannite. We initially use MEA to benchmark the reactivity of these Mn(III)-oxides in “simple” pH-controlled aqueous solutions. To interpret the results from MEA, we use a process-based model that couples interfacial electron transfer kinetics with mass-transport dynamics to simulate how the current response changes as a function of electrochemical driving force. Using this approach, we extract redox parameters that dictate the reactivity of these Mn(III)-oxides as a function of shifting redox conditions. After benchmarking the redox behaviour in controlled conditions, we investigate the effect of solution chemistry by performing MEA experiments in aqueous matrices containing carbonate, organic matter, and environmentally relevant ligands to characterize their effects on mineral reactivity. By providing quantitative constraints on Mn redox reactivity, this work illustrates how advanced electrochemical techniques can potentially improve predictive understanding of coupled biogeochemical processes and inform models of water quality and ecosystem response under changing environmental conditions.
How to cite: Pothanamkandathil, V. and Aeppli, M.: Quantification of Mn(III)-Oxide Redox Activity: Integrating Mediated Electrochemistry with Kinetic and Mass-Transport Modelling., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7407, https://doi.org/10.5194/egusphere-egu26-7407, 2026.
Static models relying solely on land use are increasingly insufficient for predicting riverine dissolved organic matter (DOM) dynamics. Here, we address this limitation by proposing the Climate Pattern–Land Use Pathways (CPLUP) framework to disentangle the synergistic interactions between climatic drivers and land use. We developed this framework using a synoptic dataset from the Pearl River Basin (PRB, n=228) and validated it globally via a machine learning ensemble. In the Pearl River Basin, we observed that terrestrial signatures dominated the entire river network, whereas autochthonous signals significantly increased in the downstream reaches. Attribution analysis revealed that this spatial divergence was driven by climatic forces that activate static land-use sources. Specifically, high discharge provided the kinetic energy to mobilize terrestrial organic matter from land into rivers, representing a process limited by transport capacity. Conversely, solar radiation and temperature provided thermodynamic energy to catalyze biochemical transformations within the water column, representing a process limited by reaction kinetics. Building on these mechanistic insights, we established the CPLUP framework to explicitly map how distinct climatic drivers regulate specific land-use signals. By decoding these complex dynamics, our study provides a robust predictive tool (CPLUP) for forecasting riverine DOM under intensifying climate change and urbanization.
How to cite: Pang, Y., Zhang, Z.-X., Qi, H., Xing, C., Wang, H., Liu, Y., Ye, M., Zhang, Z., Gan, J., and He, D.: Climate pattern–land use pathways shape dissolved organic matter dynamics in the Pearl River Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8911, https://doi.org/10.5194/egusphere-egu26-8911, 2026.
Lateral export of organic carbon by rivers links terrestrial and aquatic carbon cycling, yet its magnitude, drivers, and variability remain poorly quantified at large spatial and temporal scales. Here we develop a physics-constrained multi-task machine learning model and use long-term in situ riverine total and dissolved organic carbon (TOC/DOC) observations to reconstruct daily TOC concentrations and fluxes at 0.25° resolution across the contiguous United States (CONUS) for the past four decades (1984–2023). The multi-task learning approach leverages DOC-rich records to inform TOC dynamics through their observed covariation, improving TOC estimates in regions with sparse measurements, particularly in the arid western United States. The reconstructed data reveal a widespread decoupling between TOC concentrations and fluxes, with concentration trends increasing over 47% of the domain while fluxes decline over 73%, indicating a dominant role of hydroclimatic control on transport efficiency rather than changes in carbon source availability alone. Analysis across dry and wet years shows that wetter hydroclimatic conditions, particularly following drought periods, are associated with pronounced TOC export, during which lateral carbon export can exceed 10% of concurrent terrestrial carbon uptake. These results demonstrate how hydroclimatic variability modulates organic carbon transport in river networks, with implications for estimating land carbon storage and land-water coupling under ongoing hydroclimatic change. We emphasize the importance of integrating large-sample, in situ riverine observations in improving understanding of coupled hydrological and biogeochemical processes from site to continental scales.
How to cite: Chen, S., Jiang, S., Blougouras, G., Zhang, H., Song, C., Lee, S.-C., Calamita, E., Lian, T., Huang, J., and Reichstein, M.: Observation-based reconstruction of riverine organic carbon fluxes reveals hydroclimatic controls on lateral carbon export, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12402, https://doi.org/10.5194/egusphere-egu26-12402, 2026.
Stream microbial communities play a vital role in ecosystem functioning, contributing to nutrient cycling, organic matter decomposition, and overall ecological health. Despite this, biogeochemical cycling is typically investigated independently to microbial communities, reducing our understanding of the drivers of microbially-mediated biogeochemical reactions, including those which produce and/or consume greenhouse gases. Given the connectivity of stream ecosystems, microbial communities and chemical substrates (e.g. DOM, nutrients) are also susceptible to influences from land-use changes that occur in the wider watershed. While many studies have examined stream microbial community structure and function along a land-use gradient, few have considered their connectivity with nearby riparian zones, nor conducted microbial diversity surveys in conjunction with biogeochemical measurements. Additionally, recent advancements in high-resolution organic matter characterisation have enabled investigation of the importance of organic matter quality and key metabolites in driving ecosystem function. Here, we examined microbial communities, DOM chemodiversity, and nutrient and DOC concentrations in the water column, streambed sediments, and adjacent riparian zone sediments in 16 headwater streams across a land-use gradient (categorised by percent agriculture, residential, industrial, and human development). We performed incubations with paired streambed and riparian sediments to quantify potential greenhouse gas production (carbon dioxide, methane, and nitrous oxide) and assess the relationship between microbial community structure, potential functional capacity, and greenhouse gas fluxes. We subsequently used high-resolution organic matter characterisation techniques (FTICR-MS and LC-MS) to investigate organic matter quality and key metabolites and how these changed with land-use to also affect microbial communities and greenhouse gas emissions. This work underscores the importance of combining microbial and biogeochemical measurements and how organic matter quality drives ecosystem function, especially in highly connected and complex systems that experience human-driven impacts across scales.
How to cite: Comer-Warner, S., Wolheim, W., and Bulseco, A.: Unravelling drivers of stream microbial-biogeochemical cycling along a land-use gradient: Effects of organic matter quality and chemodiversity on greenhouse gas fluxes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14219, https://doi.org/10.5194/egusphere-egu26-14219, 2026.
Dissolved organic matter (DOM) in sediments is pivotal in biogeochemical processes of aquatic ecosystems. Given the influence of reservoir operation on riverine ecosystems, the dynamics of DOM in reservoir sediments remain unclear. In this study, focusing on the Three Gorges Reservoir (TGR), one of the world’s largest reservoirs, we investigated the mechanisms underlying variations in sedimentary DOM using radiocarbon(Δ14C), optical, and molecular techniques. Furthermore, a DOM molecule–based numerical model was developed to assess the monthly and annual variations in sedimentary DOM from 2011 to 2080. Laboratory analysis demonstrated that there was more autochthonous DOM in sediments with a declining pattern from upstream to downstream in the wet season, and more allochthonous DOM in sediments with no spatial trend in the dry season. The findings suggested that variations of primary productivity and hydrological conditions influenced by reservoir operation likely modulated the dynamics of DOM in sediments of TGR. Moreover, based on the numerical simulation, from 2011 to 2080, July, April, and September hold major (>50%) of the year’s accumulation of allochthonous and autochthonous DOM in sediments. By 2080, the quantities of allochthonous and autochthonous DOM in sediments in TGR would reach 1166×104t and 129×104t, respectively. This study provides detailed insights into the dynamics of organic matter pools in reservoirs and enhances our understanding of the ecological impacts of reservoir construction on aquatic ecosystems.
How to cite: Wu, Y., Fang, H., Huang, L., He, C., Shi, Q., Yi, Y., He, D., and Wang, K.: Reservoir operation regulates the dynamics of dissolved organic matter in sediments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3015, https://doi.org/10.5194/egusphere-egu26-3015, 2026.
East African Great Lakes are globally important waters that regulating carbon and nitrogen sources and sinks. Yet, microbial carbon and nitrogen cycling functions as well as their underlying environmental drivers in tropical deep lakes remain largely unexplored. Here, were collected vertical samples from typical large deep lakes in East African Rift Valley to assess environmental gradients and microbial metabolism functions of primary biogenic elements. We examined vertical distributions of nutrients, dissolved organic matter (DOM) properties, and quantified microbial carbon, nitrogen, and phosphorus cycling genes using high-throughput Quantitative Microbial Ecology Chip (QMEC) technique. Preliminary analyses indicate clear depth-dependent patterns in nutrient availability and microbial functional genes. Dissolved organic matter properties are likely important drivers of the depth patterns of these functional genes. The observed relationships between microbial functional genes and environmental variables provide insights into the vertical organization of microbial biogeochemical functions in deep tropical lakes.
How to cite: Yao, X., Zhao, Z., Kimirei, I. A., and Zhang, L.: Depth-dependent patterns of microbial carbon and nitrogen metabolism functions in deep East African Rift Valley Lakes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8649, https://doi.org/10.5194/egusphere-egu26-8649, 2026.
River systems in the UK are in poor condition, with sewage discharges and agricultural runoff identified as major contributors to declining river health. Effective assessment and management of river health requires real-time monitoring solutions; however, existing in-situ sensors are largely limited to physiochemical parameters and provide little information on organic pollution input or microbial contamination. This research demonstrates the implementation and deployment of novel multiparameter fluorescence-based sensors capable of measuring bacterial/algal contamination and organic pollution whilst simultaneously correcting for environmental optical interferences in real time. These portable multiparameter fluorometers were deployed as part of a sensing network along the River Dart catchment (UK) in October 2025. We present a dataset collected continuously in real-time over a 3-month period. As part of a managed water quality monitoring programme, continuous data on microbial contamination and organic pollution in the River Dart catchment collected using deployed novel multiparameter fluorescence-based sensors were compared alongside regular field spot sampling and standard laboratory water quality analysis. For the latter, biological oxygen demand, microbial counts and nutrient analysis were performed to contextualise and verify (ground truth) sensing data. Sensing system performance for the detection of organic pollution events and their subsequent impacts on river ecology was evaluated.
Our results demonstrate a strong correlation between tryptophan-like-fluorescence and biological oxygen demand, highlighting the ability of the sensor to monitor oxygen demand in real time. Using machine learning and artificial intelligence, we aim to produce a tool capable of detecting pollution events from sensor data and evaluating subsequent impacts on oxygen demand and phytoplankton growth. Our ultimate aim is to deliver a novel validated multiparameter fluorescence-based sensor, integrated within a real-time monitoring network, alongside a tool for interpreting water quality data regarding river health and pollution pressures. We anticipate these outputs combined will enhance potential for early detection of pollution events, facilitate agile decision making and river management and enhance understanding of biogeochemical processing in rivers.
How to cite: Perrett, R., Coombs, M., Tulloch, C., Thorn, R., Attridge, J., and Reynolds, D.: Development of an Innovative Multiparameter Fluorometer to Sense the Impact of Organic Pollution on River Health , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14997, https://doi.org/10.5194/egusphere-egu26-14997, 2026.
Biofilms (structured microbial communities), ubiquitous in a variety of aquatic and terrestrial ecosystems, strongly regulate arsenic (As) cycle. Dissolved organic matter (DOM), prevalent in natural environments, can stimulate the development and activity of microbial communities, thus enhancing microbially mediated arsenic biogeochemical processes. However how DOM regulate groundwater biofilms to drive the fate of As migration and transformation remains unclear. In this study, laboratory incubation experiments were integrated with extensive biofilm characterizations, 16S rRNA, qPCR, Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) to explore the behaviors and potential mechanisms of As under the mediation of biofilm and fluvic acid (FA), a representative of DOM in groundwater. The results showed that the regulation of FA induced more As incorporation and subsequent reduction of As(V) after the As(III) oxidation potentially mediated by aoxA/B. The interaction of protein and polysaccharide on the biofilms with As was the dominant adsorption mechanism. FA modification resulted in the secretion of more abundant EPS and provided more binding sites for the organic functional groups, which intensified the adsorption of protein and polysaccharide for As. In parallel, the addition of FA led to the secretion of larger amounts of α-configuration polysaccharide that produced greater steric hindrance promoting the As adsorption. The formation of FA-Ca-As ternary complexes still remained an important way for arsenic sequestration after biofilm-FA modification. The ultimately higher diversity and abundance of N and S cycling associated bacteria (e.g., Desulfitobacterium, Acinetobacter, Sphingobacterium), yielded by the addition of FA, likely contributed to the reduction of As(V) by enhancing arrA. Additionally, the electron shuttle effect of FA accelerated the electron transfer between As(V) and As (III), serving as another mechanism for As transformation. To the best of our knowledge, this study for the first time reveals the importance of DOM on the migration and transformation of As by biofilms. This study enriches the theoretical understanding of biosorption and biotransformation of As and provides new insight into environmental arsenic cycles.
How to cite: Li, H., Li, C., and Cavalca, L.: Biofilm Mediated Arsenic Migration and Transformation in Groundwater under the Influence of Dissolved Organic Matter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14816, https://doi.org/10.5194/egusphere-egu26-14816, 2026.
Proglacial floodplains are highly heterogeneous braided river systems in which glacier melt, groundwater, and snowmelt-fed tributaries interact over meter-to-tens-of-meters scales. This pronounced physicochemical heterogeneity among water sources generates contrasting hydrological regimes, benthic microbial communities, and water chemistry, resulting in strong spatial variability in biogeochemical processes. Confluences within these networks connect channels with distinct source signatures and microbial assemblages and may function as biogeochemical hotspots that disproportionately influence organic matter processing at the network scale. As rapid glacier retreat alters the relative contributions of meltwater, groundwater, and subglacial flows, proglacial floodplains offer valuable space-for-time analogues to investigate future shifts in carbon dynamics in alpine catchments.
Here, we investigated dissolved organic carbon (DOC) dynamics in a proglacial floodplain dominated by three contrasting water sources: a clean-ice glacier, a talus/rock glacier, and a groundwater spring. We hypothesized a transition from conservative transport or DOC consumption in glacier-fed streams to DOC production in streams influenced by talus/rock glacier and groundwater inputs, driven by differences in physicochemical conditions (e.g., turbidity, nutrients, temperature) and associated biological activity. Additionally, we aimed to quantify the net carbon balance of the floodplain at the system scale.
We sampled the three main water sources and 14 nodes across the braided network, with particular emphasis on major confluences. End-member mixing analysis (both EMMA/EEMMA) was applied to quantify source contributions, and differences between observed and expected DOC concentrations were evaluated. We used the percent differences between measured and predicted values to determine whether a stream segment functions as a DOC sink or source. Daily DOC loads were calculated at the floodplain outlet to assess net system functioning.
Our results revealed pronounced spatial variability in carbon dynamics associated with dominant water sources. Clean-ice glacier-dominated nodes were characterized by high discharge, elevated turbidity, and turbulent flow, and generally acted as DOC sinks. In contrast, nodes influenced by talus/rock glacier and groundwater inputs exhibited hydrological stability and functioned as DOC sources. Temporally, sink-source behavior shifted between early and late melt season conditions. Despite pronounced spatial and temporal variability, seasonal net DOC load at the outlet was close to zero, indicating that carbon behaved conservatively at the floodplain scale and reflecting the offsetting contributions of coexisting sink and source streams within the floodplain. Taken together, our results suggest that continued glacier retreat will promote a transition toward more hydrologically stable channels with enhanced carbon production. Such a shift is expected to reduce the prevalence of DOC sink behavior and increase the role of proglacial river networks as net carbon sources, with important implications for downstream carbon exports in future alpine catchments.
How to cite: Llanos-Paez, O. L., Deluigi, N., Grandi, G., Hallberg, L., Hou, J., and Tolosano, M.: Source-driven variability in dissolved organic carbon across a proglacial floodplain as a space- for time analogues of future carbon dynamics , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7488, https://doi.org/10.5194/egusphere-egu26-7488, 2026.
The relative supply of carbon (C), nitrogen (N), and phosphorus (P) to aquatic ecosystems is a key regulator of productivity, nutrient cycling, and food-web dynamics. Several environmental changes in high-altitude regions can directly or indirectly influence carbon (C), nitrogen (N), and phosphorus (P) cycling, retention, and availability through terrestrial, atmospheric, and in-situ aquatic processes, thereby regulating their export to lakes, rivers, and headwater streams.
While increasing concentrations of dissolved organic carbon (DOC) have been widely documented in high-latitude surface waters and increasingly reported for many high-elevation lakes and streams, concurrent long-term trends in nitrogen (N) and phosphorus (P) availability—and associated shifts in elemental stoichiometry—remain poorly constrained, particularly across heterogeneous high-mountain aquatic ecosystems. In these regions, declining atmospheric deposition can directly reduce external nutrient inputs but also indirectly alter soil chemistry and biogeochemical processes, for example by enhancing microbial mineralization of soil organic matter following reductions in soil acidity. At the same time, rapid climate warming and elevated atmospheric CO₂ are promoting increased alpine and subalpine plant productivity and upslope vegetation expansion, potentially enhancing nutrient sequestration in biomass and soils while increasing soil DOC production. Climate-driven shifts in seasonality, including earlier snowmelt, longer growing seasons, and warmer autumns and winters, further influence the timing and magnitude of nutrient uptake, transformation, and mobilization along terrestrial–aquatic flow paths. Finally, fundamental differences in hydrological residence times, internal processing, and network connectivity between lakes and rivers may drive divergent long-term trends in carbon and nutrient stoichiometry, but such cross-ecosystem assessments within high-mountain river networks remain scarce.
Here, we analyzed decadal-scale changes (from 2005 to 2025) in dissolved organic carbon (DOC), dissolved inorganic nitrogen (DIN), and soluble reactive phosphorus (SRP) across 35 sites spanning lakes (n = 14) and rivers and streams (n = 21) within the Pyrenees mountain range. Dissolved organic carbon (DOC) increased consistently across sites, while dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (SRP) showed widespread declines, largely independent of catchment type or aquatic system. Declines in dissolved inorganic nitrogen (DIN) were most pronounced during the growing season and, together with increasing dissolved organic carbon (DOC) at several sites, suggest enhanced retention of nitrogen by alpine vegetation and soil microbial communities, potentially reinforced by long-term reductions in atmospheric nitrogen deposition. In contrast, declines in soluble reactive phosphorus (SRP) occurred primarily during late autumn and winter, indicating that key biogeochemical controls operate during the non-growing season, potentially linked to reduced physical weathering inputs, altered hydrological pathways, increased sediment retention, and changes in atmospheric deposition
Linking nutrient trends with rising DOC concentrations revealed a consistent shift in elemental ratios across the majority of sites, characterized by increasing carbon availability relative to limiting nutrients. Collectively, these patterns indicate a co-ocurrance of increased DOC (or browning) and oligotrophication of high-mountain lakes and running waters, with likely consequences for primary production, microbial metabolism, and food-web structure in alpine and subalpine aquatic ecosystems under continued climate change.
How to cite: Gómez-Gener, L., Palacín, C., and Camarero, L.: Multi-decadal ecosystem stoichiometric changes across high-mountain Pyrenean aquatic ecosystems driven by reduced acid deposition and climate change, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21235, https://doi.org/10.5194/egusphere-egu26-21235, 2026.
Glacier-fed streams across the world’s major mountain ranges are consistently energy limited, contributing low concentrations of bio-reactive organic carbon (C) to downstream recipients. Yet, climate-driven glacial retreat is expected to alter both C and nutrient supply in glacial-fed streams with consequences for downstream elemental fluxes and ecosystem functioning. As sources shift from glacier melt to groundwater and snowmelt, reductions in stream power and turbidity promote primary production, giving rise to a “greening effect” that favours autochthonous supply of organic C. In conjunction, lower flow turbulence may also reduce phosphorus (P) inputs from erosion-driven rock weathering. Yet, the impacts of altered energy and nutrient stoichiometry on microbial energetics and C cycling remain unknown across high-mountain catchments.
In this study, we established chamber bioassays to measure metabolic rates and changes in dissolved organic carbon (DOC), nitrate, and phosphate concentrations over 24 h in, using sediments and stream water from clean ice glacier, rock glacier, and groundwater-fed headwaters, as well as from downstream recipients. Bioassays included three nutrient treatments (C+N, P+N, and C+N+P) together with an ambient stream water control, incubated at 8 °C under dark (12 h) and light (12 h) conditions. Gross primary production and ecosystem respiration metabolism rates were quantified with high resolution optical oxygen monitoring.
We found that both microbial degradation and production of DOC increased in headwaters without clean ice glacier inputs, with the highest metabolic rates and greatest reductions in DOC concentrations observed in sediments receiving rock glacier inputs. The sediments from rock glacier and groundwater-fed headwaters were also C limited, whereas the clean ice glacier showed no response to C additions. Interestingly, we found no evidence for microbial P limitation in any site, despite low ambient P concentrations.
These results demonstrate that microbial C cycling and energy demand in proglacial headwaters can be expected to increase with glacial retreat, imposed by a switch in the microbial communities from chemolithotrophic to heterotrophic and photoautotrophic dominance. Although microbial biomass growth increased and stream water stoichiometry predicted C and P co-limitation, the unexpected absence of P limitation in bioassays suggests flexibility in stoichiometric strategies, allowing for a wide range in C:P ratios of microbial biomass present in proglacial streams. To resolve the impacts of glacial retreat on stream ecosystem functioning, we thus stress the need for complementing indirectly inferred nutrient limitation with direct nutrient manipulation experiments.
How to cite: Hallberg, L., Deluigi, N., Grandi, G., Hou, J., Llanos-Paez, O., and Tolosano, M.: Demand of carbon prevails over nutrients in proglacial streams subjected to glacier retreat: a nutrient manipulation bioassay, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16798, https://doi.org/10.5194/egusphere-egu26-16798, 2026.
Glacial rivers play an important role in transporting dissolved and particulate nutrients from glaciers to downstream ecosystems where they influence ocean primary productivity. Abiotic and biotic processes in glacial environments enrich meltwaters with various nutrients. These may undergo changes in concentration and speciation along the river catchments due to lateral inputs or in-channel processes. However, the temporal and spatial variabilities of such nutrient fluxes are poorly constrained.
We monitored diurnal and seasonal changes in nutrient concentrations along a ~120-km long glacier river in Western Iceland. We combined time-resolved in situ chemical analysis using microfluidic sensors for dissolved nitrate (NO3–aq) and phosphate (PO43-aq) with in situ temperature, pH, conductivity, and turbidity measurements. We also carried out seasonal sampling along glacier-to-ocean transects of the river catchment and characterized both aqueous and particulate fractions of macro- and micronutrients, dissolved organic matter composition, and DNA.
The in situ sensor data revealed diurnal fluctuations in NO3–aq concentrations of up to 1 µM, with a decrease during the day and an increase at night. These diurnal trends were consistent across seasons. In contrast, PO43-aq exhibited seasonal variability, with significant changes related to glacial discharge.
The glacier-to-ocean transect showed enrichment in dissolved organic carbon (DOC) and iron (Feaq) with increasing distance from the glacier, likely reflecting soil-derived lateral inputs and a variation in DSiaq due to geothermal inputs. Downstream, a link between decreasing PO43-aq and increasing Feaq concentrations may suggest adsorption or coprecipitation processes. Changes in dissolved inorganic nitrogen (DIN) hint at a potential increase in channel microbial uptake along the river path.
Overall, our findings highlight the spatial and temporal variability in nutrient export from glacial rivers to the ocean, showing relative contributions of different nutrient sources across seasons and distance from the glacier.
How to cite: Ajmar, M., Perez, J. P. H., Feord, H. K., Eberle, A., Bahl, C., Antony, R., Majumder, A., Gislason, S. R., O'Flaherty, C., Beaton, A., Sigurðsson, G., Tranter, M., and Benning, L. G.: Spatial and seasonal variability of nutrient export from a subarctic glacial river to the ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20745, https://doi.org/10.5194/egusphere-egu26-20745, 2026.
Climate-induced permafrost thaw unlocks large organic carbon stores. Permafrost rivers receive substantial terrestrial inputs of thawing organic carbon (OC) that is mostly degraded to photochemical and microbial respiratory carbon dioxide (CO2). Yet, there is little information on how photochemical and microbial processes combine to alter fluvial carbon dynamics, and ultimately, carbon budget in permafrost areas. Our results from permafrost rivers on the Qinghai-Tibet Plateau mechanistically describe that photodegradation, as a rate limiting and priming step, initiates ring cleavage reactions, rapidly reducing dissolved OC (DOC) molecular weight from aromatic to aliphatic compounds. This in turn resulted in alteration of riverine microbial communities, further converting photo-altered DOC to CO2. Strikingly, the combination of photochemical and microbial processes forms a synergistic interplay, expediting CO2 delivery to the atmosphere, of which 33 ± 10% is derived from millennial-aged permafrost carbon. Our findings highlight that strong solar radiation at high-altitude accelerates microbial CO2 production, and emission, from photo-altered permafrost DOC, contributing to the permafrost carbon feedback that intensifies warming.
How to cite: Zhang, L., Battin, T., and Karlsson, J.: Synergistic photochemical and microbial degradation of DOC enhance CO2 emissions from permafrost river on the Qinghai-Tibet Plateau, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2275, https://doi.org/10.5194/egusphere-egu26-2275, 2026.
Ocean acidification and warming modify iron (Fe) redox cycling by altering reaction kinetics, speciation, and complexation processes that control Fe bioavailability in coastal waters. These drivers arise from both anthropogenic CO₂ emissions and natural volcanic inputs, which coexist in the ocean and allow the investigation of Fe(II) oxidation under contrasting chemical regimes.
Within the FeRIA project (PID2021-123997NB-I00), Fe(II) oxidation dynamics were investigated at coastal sites influenced by volcanic CO₂ emissions (Fuencaliente and Tazacorte, La Palma) and at sites mainly affected by anthropogenic CO₂ (El Hierro and Gran Canaria). Although both systems experience reduced pH, volcanic environments introduce additional chemical species that influence Fe complexation and redox reactivity.
Fe(II) oxidation rates exhibited strong spatial variability and were controlled by the combined effects of physi-cochemical parameters (pH, temperature, salinity, dissolved oxygen) and organic ligands. Lower pH consistently decreased Fe(II) oxidation kinetics, favouring longer Fe(II) lifetimes, while increasing temperature enhanced oxidation rates. Dissolved and particulate organic matter exerted a key control through complexation, either stabilising Fe(II) and inhibiting oxidation or promoting electron transfer depending on ligand composition and functional groups.
These results highlight the kinetic balance between acidification, warming, and organic complexation in regulating Fe(II) persistence. They also assess whether volcanic CO₂–impacted marine systems capture the dominant kinetic and complexation processes controlling Fe(II) oxidation under future anthropogenic ocean acidification.
How to cite: Santana-Casiano, J. M., González-Dávila, M., González, A. G., Bullón-Téllez, A., Coussy, V., Sánchez-Mendoza, I., and González-Santana, D.: Fe(II) Biogeochemistry in Coastal Waters, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4433, https://doi.org/10.5194/egusphere-egu26-4433, 2026.
Antarctica and the Southern Ocean are central to the Earth’s climate and oceanic circulation systems. Microbial communities inhabiting the Southern Ocean drive biogeochemical cycles, underpin trophodynamics, and affect atmospheric chemistry. The ongoing climate crisis is affecting these processes, with possible cascading effects on the structure and functioning of phytoplankton communities in the surface waters of the Southern Ocean. The CLAW hypothesis, which describes a feedback mechanism between phytoplankton, the dimethylsulphide (DMS) production, the cloud condensation nuclei (CCN) formation, and albedo, represents a prominent link between the changing marine microbial dynamics and climate. Additionally, marine DMS production appears to be influenced by the availability of microbially-derived vitamin B12, involved in the methionine biosynthesis, and is already regarded as a limiting factor for the phytoplankton growth, thus playing a role in shaping microbial community structure. Understanding the role of the ocean microbiome in these processes is therefore essential to evaluate how marine microbial communities impact climate regulation, and vice versa.
Previous studies on the surface waters of the west Antarctic Peninsula and in the Southern Ocean have described taxonomic profiles of marine microorganisms and identified metabolic functions related to degradation of phytoplankton-derived organic matter. However, the role of the functional diversity in the interplay between climate change, microbial communities, and DMS-cycling pathway remains poorly understood. Here, we present an integrated analysis of the microbial functional diversity of surface waters along the Drake Passage and the west Antarctic Peninsula, sampled during the 2023/24 Austral Summer. Shotgun metagenomic sequencing and 16S rRNA amplicon analysis were performed, and enabled the description of spatial distribution of genes involved in DMS and cobalamin biosynthesis pathways along the transect. We coupled this data with chlorophyll chemotaxonomy and geochemical analyses. This integrated approach holds the potential to advance our understanding of microbial responses to the impacts of climate change, and the identification of specific microbial pathways that could enhance climate change in the Southern Ocean, ultimately helping to fill gaps in climate change modeling.
How to cite: Gallo, G., Brusca, J., Campoli, L. M., Di Iorio, L., Bolinesi, F., Bradley, J. A., Mangoni, O., Cordone, A., and Giovannelli, D.: Microbial taxonomic and functional diversity across the Drake Passage and the west Antarctic Peninsula, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13871, https://doi.org/10.5194/egusphere-egu26-13871, 2026.
Quantifying biogeochemical processes in coastal sediments requires analytical approaches capable of resolving microscale variability in redox-sensitive solutes. Conventional porewater sampling techniques provide limited spatial resolution and often disturb in situ equilibria, obscuring fine-scale heterogeneity associated with bioturbation, root activity, and microbial processes. These limitations are particularly critical in mangrove sediments, where organic matter remineralization and redox dynamics are highly heterogeneous. In addition, small-scale geomorphological contrasts between erosional and depositional settings can influence sediment structure, permeability, and diagenetic pathways. Here, we applied two-dimensional Diffusive Equilibration in Thin Films (2D-DET) coupled with colorimetric detection to map porewater solutes associated with early diagenesis in mangrove sediments from two sites (MAR1 and MAR2) in the Marapanim River Estuary (Pará State, Brazil). The sites, sampled in winter 2025, represent erosional and depositional zones on opposite sides of a tidal channel. Two-dimensional distributions of dissolved Fe and Mn (Fed and Mnd), PO₄³⁻, H₂S, NO₂⁻, NO₃⁻, and NH₄⁺ were quantified. Hyperspectral imaging enabled the discrimination of Fed and PO₄³⁻ distributions within a single gel. In general, Fed was broadly distributed throughout the imaged porewaters (to ~17 cm depth) at both sites, with patchy concentrations reaching up to ~500 µmol L-1. Dissolved H₂S, measured at MAR1, was largely absent across most of the profile, allowing Fed to remain mobile. In contrast, PO₄³⁻ was preferentially enriched at greater depths, indicating partial Fe-P decoupling likely related to efficient phosphate retention in shallow sediments and accumulation under more reducing conditions at depth. Mnd distributions were comparatively more homogeneous than Fed, consistent with slower redox kinetics. Near-zero NO₂⁻ and NO₃⁻ concentrations combined with elevated NH₄⁺ indicate dominant ammonification and nitrification that is inhibited or masked by nitrate consumption processes. Clear contrasts emerged between geomorphological settings. At the erosional site (MAR1), Fed and Mnd concentrations were higher, more laterally variable, and NH₄⁺ maxima occurred deeper in the sediment, consistent with enhanced porewater flushing and advective transport. In contrast, the depositional site (MAR2) exhibited more persistent Fe-P decoupling and shallower NH₄⁺ accumulation. Such differences could be attributed to differences in grain size, permeability and mudflat slope and therefore porewater residence time. Two-dimensional imaging further revealed pronounced lateral heterogeneity associated with biogenic structures. At MAR1, a microzone showed elevated sulfide and Fed depletion, consistent with localized pyritization and associated phosphate release. In another Fed/PO₄³⁻ gel from MAR1, microzones linked to sediment coloration and young Rhizophora plants reflected alternating Fed release and removal under contrasting redox conditions. At MAR2, a near-surface zone exhibited Mnd enrichment coupled with Fed depletion beneath a Rhizophora seedling, consistent with a root-influenced redox microenvironment. Overall, results demonstrate the capacity of 2D-DET to resolve geomorphology and biota-driven microscale diagenetic organization in macrotidal Amazonian mangrove sediments that is not accessible using conventional porewater techniques.
How to cite: Cavalcante-Silva, M., Barreira, J., Trevisan, C. L., Matos, C., do Nascimento Monte, C., Berredo, J., Machado, W., Abril, G., Mouret, A., and Metzger, E.: Two-dimensional imaging of porewater chemistry to investigate the heterogeneity of diagenetic processes in Amazonian mangrove sediments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11589, https://doi.org/10.5194/egusphere-egu26-11589, 2026.
Posters on site: Thu, 7 May, 08:30–10:15 | Hall X1
Water chemistry can change dramatically during a flood event. While variations in the concentration of inorganic ions, nutrients and bulk DOC as function of discharge have been intensively investigated, changes in dissolved organic matter (DOM) quality were considered less detailed with respect to high resolution techniques. DOM is a highly complex mixture consisting of thousands of different elemental compositions. Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is the analytical tool with the up to date highest DOM quality resolution. Here we present a novel data evaluation strategy for time series applied to a flood event in a small river catchment. As sampling area the Ammer River near Tübingen, southern Germany was selected. During a flood event with 900% MQ in 2021, six water samples were collected within five hours period at the Pfäffingen monitoring station while discharge changed by a factor of five. Water samples were filtered (Whatman GF/F), acidified and passed through PPL cartridges. Methanolic eluates were analyzed by FTICR-MS in negative ionization mode (ESI-). Molecular formulas (MFs) were calculated for the mass range between 150–1000 Da using in-house software, considering the elements: carbon 12C1–80, hydrogen 1H1–198, oxygen 16O0–40, nitrogen14N0–2, and sulphur 32S0–1. A total of 3500 formulas were shared among all six samples. Inter sample ranks were calculated for each molecular formula based on relative signal intensity, with rank 1 representing the highest and rank 6 the lowest abundance. (1,2). From the inter sample ranks the rank sequences were derived (for example 3-6-1-5-4-2) and used as input tor hierarchical cluster analysis (HCH). Five superordinate clusters were selected for further evaluation. Rank distribution of formulas within each cluster were visualized via bar graph and molecular formulas were plotted in van Krevelen diagrams (H/C versus O/C). This visualization revealed flood-specific compositional dynamics in DOM. Sulfur-containing compounds (CHOS) exhibited their highest relative abundance at peak discharge (fourth sample), whereas aliphatic CHO compounds (H/C > 1.5) were most abundant at low discharge (first and last samples). In contrast, aliphatic CHO (H/C > 1.5) showed highest abundance at lowest discharge (first sample and last sample). Nitrogen-containing components (CHNO) showed different ranking distribution and revealed highest abundance in the second and third sample (before discharge peak).
In conclusion, DOM exhibits highly divers and dynamic behavior during flood events due to its complex composition and information received from bulk DOC concentrations alone seems to be insufficient to capture these compositional changes.
1) Herzsprung P. et al., Environ. Sci. Technol. (2012), 46, 5511-5518
2) Dadi. et al., Environ. Sci. Technol. (2017), 51, 13705-13713
How to cite: Herzsprung, P., Kamjunke, N., Lechtenfeld, O. J., Rode, M., Friese, K., Glaser, C., Spahr, S., and von Tümpling, W.: An advanced data evaluation strategy for assessing temporal changes in dissolved organic matter quality during flood events based on ultrahigh-resolution mass spectrometry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7984, https://doi.org/10.5194/egusphere-egu26-7984, 2026.
Rising water temperatures and increasingly frequent low-flow conditions are expected to intensify under climate change, yet their combined effects on internal nutrient loading in streams remain poorly understood. During summer, higher temperatures can enhance biological activity and organic matter mineralisation at the sediment–water interface, while reduced discharge limits oxygen supply, potentially stimulating nutrient release from sediments.
In this study, we investigate the mechanisms and drivers of nutrient remobilisation from stream sediments using controlled laboratory experiments under different temperature and low-flow scenarios. We specifically assess how temperature effects interact with sediment characteristics to determine the magnitude of internal nutrient release.
Our results show that nutrient remobilisation responds significantly to temperature changes; however, the response is non-linear and strongly dependent on the initial trophic state of the stream and sediment biomass. These findings suggest that stream warming may substantially enhance internal nutrient loading in some systems but not in others. This context-dependent response highlights the need to account for sediment legacy effects when assessing climate change impacts on stream water quality and when designing management strategies under prolonged low-flow conditions.
How to cite: Liao, Z.: Can stream warming trigger internal nutrient remobilisation from sediments?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5605, https://doi.org/10.5194/egusphere-egu26-5605, 2026.
Phytoplankton are a key driver of global marine biogeochemical cycles, but the response to ocean warming remains difficult to predict, partly because the temperature-dependence of physiological processes is not well understood. This study extends an optimality-based phytoplankton growth model to include metabolic responses to temperature. Using microcosm data, we identify two key parameters showing roughly consistent temperature responses: maximum uptake rate (V0) and chlorophyll synthesis cost (ζC). We assess the accuracy of temperature-dependent species-specific (SS) and non-species-specific (nSS) model configurations in reproducing microcosm experimental data, relative to a non-temperature-dependent, species-specific control model (noTemp). Our results demonstrate that explicitly accounting for temperature-dependence can significantly improve predictions of phytoplankton biomass production, nitrogen uptake, and stoichiometry. The SS configuration consistently outperforms other setups in predicting particulate organic carbon, chlorophyll-a, and nutrients (DIN, DIP), while the nSS configuration still performs substantially better than the (species-specific) noTemp configuration. These findings underscore the importance of accounting for temperature-dependence in ecological models for future projections of phytoplankton responses to environmental change.
How to cite: Moncayo, D., Schartau, M., Ryabov, A., Moorthi, S., and Pahlow, M.: Temperature effects on optimality-based phytoplankton growth model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6786, https://doi.org/10.5194/egusphere-egu26-6786, 2026.
Amaranth (AM) is a typical anionic azo dye, which has been applied in cosmetics, wood, paper, synthetic fiber, food additives, leather, and artificial dyeing, poses significant risks to both human health and the environment. Therefore, its removal from water is essential to safeguard public health and ensure a sustainable ecosystem. In this work, a novel magnetic Fe3O4@LPP was successfully synthesized via a co-precipitation method and applied for the removal of AM dye from an aqueous environment. Several characterization techniques, including point of zero charge (pHPZC), N2 adsorption/desorption, Energy dispersive X-ray spectroscopy (EDS), Field emission scanning electron microscopy (FE-SEM), Vibrating sample magnetometer (VSM), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM) and X-ray diffractometer (XRD), were analyzed to reveal the functional and structural properties of the as-synthesized Fe3O4@LPP composite. AM dye adsorption performances were tested as a function of the operational conditions, such as stirring speed (50-300 rpm), temperature (25-55 oC), initial pH solution (2-10), Fe3O4@LPP dosage (0.01 to 0.08 g/30 mL), contact duration (0-180 minutes), and initial AM dye concentration (50-500 mg/L) in a batch mode of operation. Kinetic analysis revealed that the sorption process followed the pseudo-1st-order kinetic model across all initial concentrations, showing strong correlation between the experimental data and the model predications. Furthermore, the equilibrium sorption data were best fitted by the Langmuir isotherm model, suggesting monolayer sorption on a homogeneous surface, with a maximal adsorption uptake of 445.5±19.6 mg g-1. The thermodynamic analysis of AM dye adsorption indicated that the process was endothermic, feasible, and spontaneous. Various eluting agents were evaluated in the desorption studies, and 0.1 M NaOH exhibited the greater desorption efficiency of 89.4%. Overall, the outcomes of this study confirm that Fe3O4@LPP composite is a promising and effective adsorbent for the remove of dyestuff from wastewater.
Keywords: Removal, Amaranth, Iron oxide, Lychee peel, Desorption.
How to cite: Hsu, J.-Y., Munagapati, V. S., and Wen, J.-C.: Adsorptive removal of an anionic Amaranth dye from aqueous solution using magnetic iron oxide-loaded lychee peel powder (Fe3O4@LPP): Isotherm, kinetic, thermodynamic and desorption studies, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9232, https://doi.org/10.5194/egusphere-egu26-9232, 2026.
Estuaries act as biogeochemical filters for organic matter and nutrients transported from rivers into coastal waters, with the balance of turnover processes such as remineralization and nitrification determining whether these are retained, transformed or exported into the coastal ocean. In the German Bight, three main river systems (Ems, Weser and Elbe) provide water and matter inputs. These rivers and their estuaries are heavily impacted by human activities, including dredging, damming and intensive nutrient inputs causing eutrophication, which may substantially alter their biogeochemical filter function. We aim to assess how differing anthropogenic pressures may influence nitrogen transformation processes and, consequently, the efficiency of estuaries as biogeochemical filters.
During an early autumn 2024 cruise on the RV Heincke (HE647), we measured parameters such as salinity, turbidity, oxygen and chlorophyll-a-fluorescence in all three estuaries and sampled nutrients focusing on dissolved inorganic nitrogen (ammonium, nitrite and nitrate) and dual stable isotopes of nitrate. Additionally, nitrification and ammonium uptake rates were determined in the Elbe and Ems estuaries.
All three estuaries were characterized by high nitrate input to coastal waters. However, ammonium uptake and nitrification rates differed substantially among the systems, with the highest uptake observed during a phytoplankton bloom in the coastal outer waters of the Ems Estuary. Our results indicate that suspended matter concentration, oxygen availability and chlorophyll-a-fluorescence are the main factors driving the remineralization and retention of reactive nitrogen in estuarine and coastal waters.
How to cite: Sanders, T., Schulz, G., Rewrie, L., Neumann, A., Macovei, V.-A., Voynova, Y., and Dähnke, K.: Controls of inputs of reactive nitrogen into the German Bight in the main Estuaries: No two are alike, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17969, https://doi.org/10.5194/egusphere-egu26-17969, 2026.
The expansion of land-use activities severely threatens primary forests in the Congo Basin. As the dominant mode of deforestation in this region, it is expected to affect soil nutrient stocks and availability and, consequently, forest productivity. To assess how shifting cultivation affects carbon species transformation and export to rivers, four catchments, of which two draining forested landscapes and two draining agricultural landscapes were selected in the Yangambi region, Democratic Republic of the Congo. The catchments were equipped with sensors to continuously quantify discharge, water temperature, oxygen concentrations and sediment loads, amongst other parameters, while periodic water sampling was conducted to quantify chemical water composition. Based on these samples, concentrations and yields of the full spectrum of carbon species (DOC, DIC, CO₂, CH₄) were calculated. We found that baseflow dissolved organic carbon (DOC) concentrations were nearly identical in both groups of streams. However, significantly higher carbon dioxide(CO₂) and methane(CH₄) concentrations were observed in streams draining agricultural landscapes compared to forested streams. This apparent paradox can be explained by much higher carbon turnover rates in agricultural streams, driven by enhanced microbial metabolism resulting from environmental changes such as increased light and temperature, greater erosion, and higher nutrient availability (N and P). Thus, agricultural streams rapidly mineralize organic carbon to CO₂ and CH₄, preventing its persistence in the dissolved organic pool.
How to cite: Bondongwe Wombe, M., Drake William, T., Landuyt, D., Barthel, M., Ewango, C., Boeckx, P., and Bauters, M.: Land use change effects on carbon yield in lowland streams of the Congo Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15334, https://doi.org/10.5194/egusphere-egu26-15334, 2026.
Pharmaceutical compounds are widespread in anoxic environments, yet their direct utilization by methanogens has not been demonstrated. We show that the antidiabetic drug metformin can serve as a substrate for methane production by the obligate methylotroph Methermicoccus shengliensis, representing the first reported case of methanogenesis from pharmaceuticals. Long-term incubations revealed methane production concomitant with 30% metformin consumption over 71 days, accompanied by 7% incorporation of ¹³C-labeled CO₂ into methane, which is lower than the ~30% reported for M. shengliensis during growth on methoxylated coal compounds (1). No methane production or degradation was observed for naproxen, an anti-inflammatory drug, despite its O-methoxy group being structurally similar to methoxylated coal compounds.
Proteomic analyses revealed substrate-specific differences between metformin- and methanol-grown cultures (reference substrate), including overexpression of dimethylamine-methyltransferases and changes in the expression of energy metabolism proteins. A strong stress response was observed, characterized by overexpression of proteins involved in metabolic maintenance and stress mitigation. Several upregulated proteins, along with those associated with potential substrate degradation or transport, were located within predicted horizontally transferred genomic regions.
This study expands the known substrate range of methylotrophic methanogens and identifies pharmaceuticals as a previously unrecognized contributor to anaerobic methane production, with potential implications for subsurface carbon cycling in contaminated environments.
(1) D. Mayumi et al., Methane production from coal by a single methanogen. Science 354, 222-225 (2016).
How to cite: Gilevska, T., Bonaglia, S., and Rotaru, A.-E.: Methanogenesis from the antidiabetic drug metformin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20720, https://doi.org/10.5194/egusphere-egu26-20720, 2026.
Despite its central role in marine food webs, nutrient cycling, and carbon export, mixotrophy remains difficult to quantify, largely because robust tools for resolving the relative contributions of autotrophic and heterotrophic metabolism in plankton are still lacking. Mixotrophic strategies blur traditional functional classifications and could hypothetically confer ecological advantages under variable environmental regimes. Yet current approaches often rely on bulk physiological rates or grazing experiments that provide only partial or indirect insights into trophic behaviour. As highlighted by Millette et al.(2024), these methodological limitations hinder the integration of mixotrophy into ecosystem and biogeochemical models, underscoring the need for novel, process-based tracers capable of resolving trophic behaviour at the level of cellular metabolism.
Hydrogen isotope ratios (δ²H) in lipids and carbohydrates from aquatic and terrestrial organisms, as well as from sedimentary archives, are widely employed to reconstruct past hydroclimatic conditions. Emerging evidence, however, indicates that δ²H values in these biomolecules also encode metabolic signals in addition to climatic ones (Holloway-Phillips et al., 2025). Such influences complicate straightforward climatic reconstructions and highlight the need to better identify the processes that determine δ²H variability in organic matter. Yet, once these contributions are disentangled, the metabolic information embedded in δ²H values may itself become a valuable tracer for unresolved ecophysiological processes—among them, marine mixotrophy
Previous experimental work has revealed that lipid δ²H values in bacteria (Zhang et al., 2009) and green algae (Cormier et al., 2022) respond specifically to their trophic metabolism. Building on these findings, we present initial experiments with protists designed to test whether δ²H & δ13C values of different biomolecules (including fatty acids, phytols and sterols) similarly reflect shifts in central metabolic pathways. Two complementary experimental systems are compared: continuous cultures of Chlorella under osmo-heterotrophic conditions, and batch cultures of mixoplankton feeding on prey.
These new compound-specific isotope measurements were obtained using gas chromatography–isotope ratio mass spectrometry on the aforementioned compounds from these systems alongside RNA-sec, pigment and physiological data. Our data suggest that lipid δ²H values are indeed sensitive to the degree of heterotrophic growth in diverse protist lineages, pointing to their potential as indicators of metabolic flexibility.
If these relationships can be confirmed and quantitatively calibrated, compound-specific hydrogen isotope analysis could provide a powerful new tool for investigating the prevalence and dynamics of mixotrophy.
References:
Zhang, X. et al. (2009). PNAS. doi:10.1073/pnas.0903030106
Cormier, M.-A. et al. (2022). New Phytologist. doi:10.1111/nph.18023
Millette, N. C. et al. (2024). Journal of Plankton Research. doi:10.1093/plankt/fbad020
Holloway-Phillips, M. et al. (2026). New Phytologist. doi:10.1111/nph.70845
How to cite: Cormier, M.-A., Berard, J.-B., Salik, M. A., Flynn, K., and Bougaran, G.: Exploring Metabolic Signals of Mixotrophy in Marine Protists Using Compound-Specific Hydrogen Isotopes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21744, https://doi.org/10.5194/egusphere-egu26-21744, 2026.
“REE-rich mud” has attracted attention as an unconventional resource for critical rare-earth elements (REE) used in green and high-tech industries [1]. It is a type of pelagic clay characterized by high REE (especially heavy REE) concentrations. In REE-rich mud, biogenic calcium phosphate (BCP; fish-bone apatite) plays a key role as a major host phase of REE, linking sedimentary REE enrichment to marine phosphorus (P) cycling and biological productivity [2]. Preliminary Nd–P one-box mass-balance analyses [3] suggested that fish-derived P burial may constitute an important component of total P burial in pelagic realms and that variability in P cycling may therefore be a major control on the conditions favorable for REE-rich mud formation. This motivates a reassessment that explicitly accounts for oceanographic processes which regulates nutrient supply and redistribution.
In this study, we develop a Nd–P mass-balance model that represents the ocean in a subdivided, coupled-reservoir framework to account for internal transport and redistribution. The framework tracks major P cycling and burial pathways, including burial associated with organic matter, authigenic phases (Ca-phosphate and Fe-bound P), and fish debris (BCP), together with neodymium (Nd) as a representative REE.
Using this framework, we aim to examine how redistribution of nutrients and Nd influences inferred BCP burial contributions and, by extension, the conditions favorable for REE-rich mud formation. We will conduct sensitivity and scenario experiments on internal transport and biological productivity within the ocean, and discuss implications for linking Earth-system processes to REE-rich mud genesis.
[1] Kato et al. (2011) Nat. Geosci. 4, 535–539. [2] Ohta et al. (2020) Sci. Rep. 10, 9896. [3] Matsunami et al. (2025) AGU Annual Meeting 2025, PP24B-08.
1: School of Engineering, Univ. of Tokyo, 2: ORCeNG, Chiba Institute of Technology
How to cite: Matsunami, R., Yasukawa, K., Nakamura, K., and Kato, Y.: Phosphorus cycling and REE enrichment in pelagic clay: Insights from a coupled Nd–P mass-balance approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3776, https://doi.org/10.5194/egusphere-egu26-3776, 2026.
The 2021 eruption of Tajogaite volcano (La Palma, Canary Island) significantly altered the nearby coastal environment and chemistry through the formation of lava delta. Despite the importance of metal speciation for the ecosystems, our knowledge of Fe-organic speciation and the input of lava associated with the lava deltas formation in its biogeochemical cycle remains limited. This study explores the impact of the Tajogaite eruption on the Fe speciation by measuring the labile Fe-binding ligands (LFe) and their conditional stability constants (log KcondFe’L).
Before, during and after the volcano eruption, 10 stations were monitored and analyzed by competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV) method, using TAC as a competitive ligand. To determine the optimal experimental conditions for comparing the different environments along the sampling years, different detection windows were employed (2, 5 and 10 µM TAC). The LFe concentrations ranged between 2.32 and 12.38 nM, with a maximum recorded in February 2023 near the southern lava delta (station 5, 28.616ºN, 12.38 nM). Other high concentrations were found from April to September 2024 at northern stations near to the other lava delta (28.624ºN, 11.20 nM). The minimum LFe concentration was observed at offshore station (station 10, 17.932ºW, 28.599ºN, 2.32 nM).
The observed log KcondFe’L were between 9.33 and 10.73 under the studied conditions and correspond to weak ligands (L2-type) such as humic substances or polyphenols. The results show clear spatial and temporal variability, with significantly higher ligand concentration near lava deltas, suggesting a lasting volcanic influence on ligand production with a clear impact on the Fe speciation. Thus, the arriving of lava and the lava deltas formation act as a local source of Fe-biding ligands for several years after the eruption, keeping Fe in solution. However, the impact is locally limited, highlighting the importance of sampling site selection for accessing volcanic effects on coastal trace metal cycling.
How to cite: Coussy, V., G. González, A., González-Santana, D., Gonzalez-Davila, M., and Santana-Casiano, J. M.: Iron-binding ligands in the coastal waters of La Palma affected by the Tajogaite volcanic eruption, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4469, https://doi.org/10.5194/egusphere-egu26-4469, 2026.
On continental margins, the vertical flux of particulate organic carbon (POC) attenuates rapidly. However, the role of lateral transport in redistributing and preserving older carbon is a major unresolved question. To quantify these carbon pathways, we integrate data from three complementary sources in the SW Iberian margin, a key mid-latitude region for (paleo)climate studies: a year-long (December 2023-November 2024) sediment trap time-series (four traps intercepting subsurface and deep layers on the mid- and lower slope), discrete-depth in-situ pump sampling (>1000 L per depth) at six stations, and surface sediment samples.
Complementary CTD and hydrographic data revealed distinct water masses: the Eastern North Atlantic Central Water (ENACW; ~50–500 m), underlain by the warm, saline Mediterranean Outflow Water (MOW; 500–1600 m), characterized by elevated turbidity, and the Northeast Atlantic Deep Water (NEADW; >1700 m).
The annual sediment trap record reveals subsurface Δ¹⁴C-POC ranges between -20 and -75‰ (i.e., 100-550 14C yr BP), while deep-water POC shows highly variable, older signatures, varying between -50 and -130‰ (i.e., 350-1070 14C yr BP). A pronounced Δ¹⁴C depletion in May at both moorings, coincident with MOW intensification onshore, signals a major lateral injection of aged carbon.
Along the water column during the oligotrophic season, discrete-depth samples show that POC concentrations peak at the fluorescence maximum (above 100 m depth) before declining sharply. Δ¹⁴C values above 100 m indicate POC that has incorporated bomb-¹⁴C. Below ~100 m, Δ¹⁴C decreases markedly, especially within local turbidity maxima across all water masses. Notably, Δ¹⁴C depletion within the MOW-intermediate nepheloid layer (INL) was not distinct from other INLs, suggesting that lateral transport operates broadly along the margin. Preliminary data indicate higher aluminum (Al) at depth at all stations, suggesting the lateral supply of resuspended sediments. Ongoing Al and δ¹³C-POC analyses will clarify the origin of this and sediment trap material.
In surface sediments, Δ¹⁴C and δ¹³C of sedimentary OC indicate the increase of more recalcitrant (older, potentially terrestrial) OC offshore. Critically, sedimentary OC (¹⁴C age: 875-4800 14C yr BP) is consistently older than coeval, bomb-¹⁴C–bearing planktic foraminifera. This decoupling demonstrates that laterally advected, mineral-protected organic matter is preferentially sequestered, while vertically exported labile carbon is degraded.
Our findings establish lateral transport as a major control on the age and redistribution of OC in this dynamic margin. We conclude that accurate carbon cycling models must explicitly account for lateral supply (particularly via nepheloid layers) as a key mechanism for delivering and preserving aged carbon in deep-sea sediments, challenging the traditional paradigm of vertical export as the principal sequestration pathway.
How to cite: Ausin, B., Merchán Gómez, C., Lakrani Hewage, P., Haghipour, N., Magill, C. R., Sanchez-Vidal, A., Eglinton, T., Mollenhauer, G., Grotheer, H., Achterberg, E., Saavedra-Pellitero, M., Dunlop, J., Kim, M., Fernández Bremer, Á., Hodell, D., and Sierro, F. J.: Lateral transport as a major control for old organic carbon ages in the SW Iberian margin , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17944, https://doi.org/10.5194/egusphere-egu26-17944, 2026.
The recalcitrant dissolved organic carbon (RDOC) pool in the deep ocean is crucial for long-term carbon sequestration, yet the mechanisms sustaining its stability below 1,000 m remain unclear. While high hydrostatic pressure (HHP) is traditionally viewed as inhibiting microbial activity, its role in regulating DOC transformation is poorly resolved. Here, we isolated the effect of pressure by incubating natural deep-sea DOC with a hadal microbial consortium across a gradient of 20–115 MPa at 4 °C, simulating depths from 2,000 to 11,000 m.
Over 25-day incubations, bulk DOC concentrations remained stable, yet microbial biomass exhibited a non-linear pressure response, peaking at intermediate pressures (20–60 MPa) and declining under higher pressures. Molecular-level analysis via FT-ICR MS revealed that increasing pressure systematically shifted the DOC pool toward higher oxidation states and O/C ratios, lower H/C ratios, and enrichment of carboxyl-rich, heteroatom-poor compounds. These changes were potentially driven by pressure-stimulated formation and persistence of thermodynamically stable DOC, rather than preferential removal of labile substrates. Metagenomic and metatranscriptomic analyses further indicated that HHP enhances oxidative stress responses and upregulates high-energy carbon oxidation pathways, suggesting microbial metabolic reprogramming toward energy maximization under extreme conditions.
Our findings demonstrate that HHP actively reprograms deep-sea microbial metabolism to accelerate DOC recalcitrance, transforming the deep biosphere into an active driver of long-term carbon storage. This challenges the paradigm of the deep sea as a passive carbon reservoir and underscores the need to incorporate pressure-dependent microbial metabolic flexibility into carbon cycle models to better predict oceanic carbon responses under global change.
How to cite: Lin, H. and Zhang, Y.: High Hydrostatic Pressure Activates Microbes to Accelerate Deep-Sea Carbon Recalcitrance, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21516, https://doi.org/10.5194/egusphere-egu26-21516, 2026.
The fate of hydrophobic organic pollutants in the marine environment is largely controlled by organic carbon (OC) cycling processes. The Arctic is warming three times as fast as the global average, resulting in a profound alteration in OC fluxes to the Arctic Ocean. Consequently, remote Arctic shelf sediments serve as an ideal receptor for assessments of the impact of OC quantity and quality on pollutant fate.
Here, we compiled a database of congener-specific polychlorinated biphenyl (PCB) concentrations (510 entries, 84 sites) in surface sediment of four Eurasian Arctic shelves via integration of new measurements and literature data. Total organic carbon content and isotopic data were retrevied from CASCADE (The Circum-Arctic Sediment CArbon DatabasE) to examine the PCB storage in sediment as a function of OC source (marine versus terrestrial). In order to reduce the impact of variability in water-phase concentrations caused by region, latitude and depositional year, we controlled for these factors. The adjusted concentrations (in ng-PCB/g-OC) in sediment with high fractions of marine OC are 0.82-1.22 log units higher in Barents and Kara Seas and 0.092-1.49 log units higher in Laptev and East Siberian Seas, compared to those with high fractions of terrestrial OC. Albeit uncertainties in current estimations due to wide geographical coverage and correction assumptions, these values are comparable to previously reported differences of partition coefficients between marine and terrestrial OC in other regions (e.g., 0.2-1 log units higher in marine OC sites in Baltic Sea, compared to terrestral OC sites).
Based on these results, PCB accumulation in Arctic shelf sediment was predicted for future climate change scenarios using an observational dataset of terrestrial inputs and marine OC fluxes derived from the global state-of-the-art ocean- and sea ice biogeochemistry model FESOM2.1-REcoM3. The accumulated amount of PCBs in marine OC in Arctic shelf sediments from 2000-2100 is estimated to be about 26 tonnes, which is more than 8 times higher than the accumulated amount in terrestral OC from both coastal erosion and riverine inputs. These results demonstrate that shifts in OC fluxes as a consequence of climate change can impact storage capacity of hydrophobic organic pollutants in aquatic systems.
How to cite: Shi, X., Oziel, L., Benskin, J. P., Gustafsson, Ö., and Sobek, A.: The origin of sediment organic carbon influences hydrophobic organic pollutant dynamics in Arctic shelf sediments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14283, https://doi.org/10.5194/egusphere-egu26-14283, 2026.
Posters virtual: Thu, 7 May, 14:00–18:00 | vPoster spot 2
EGU26-5322 | ECS | Posters virtual | VPS6
Selective pressure of atrazine on bacterial pattern in a hypersaline lake environmentThu, 07 May, 14:06–14:09 (CEST) vPoster spot 2
The attenuation of atrazine in the saline water of the hypersaline Pétrola lake from a natural reserve (SE Spain) was studied to get more insight into the processes governing the fate of the contaminant in highly saline environments. In microcosms, the water column was spiked with 15.4 mg/L of atrazine for 24 days. Before atrazine amendment, the initial distribution of bacterial community was mostly composed of Proteobacteria (25.5 %), Cyanobacteria (25.2 %), Actinobacteriota (18.5 %), Verrucomicrobiota (11.5 %) and Bacteroidota (10.1 %). Within the mayor phyla, the most abundant families were identified as Cyanobiaceae (25 %), Rhodobacteraceae (10 %), Alcaligenaceae (9.9 %), Microbacteriaceae (7.3 %) and a poorly described PeM15 (6.2 %).
The reduction of atrazine concentration in the water column reaches 86.9 %, which means a reduction of dissolved atrazine mass of 98.1 %. Parallel to the decrease in atrazine, the amount of its intermediate degradation metabolite, desethylatrazine, increased. Desethylatrazine was the major short-term metabolite within the first 8-12 days, indicating the potential activity by atrazine-degrading bacteria. No deisopropylatrazine was detected in the saline water above detection limit. Microbiology results showed that atrazine can be removed from the saline lake environment. After atrazine amendment, the taxonomic bacterial composition at phylum level shifted to Proteobacteria (60.8 %), Patescibacteria (9.7 %), Bacteroidota (7.3 %), Campylobacterota (6.4 %) and Actinobacteriota (2.1 %). Atrazine supplementation suggested a selective pressure on bacterial structure morphology through the emergence of different dominant groups (i.e., Campylobacterota) or even the eradication of those phyla of bacteria capable of photosynthesis (i.e., Cyanobacteria). At family level, Rhodobacteraceae (16.7 %), Burkholderiaceae (11.7 %), Thiomicrospiraceae (7.9 %), Methylophagaceae (6.7 %), Sulfurimonadaceae (4.4 %) and Solimonadaceae (3.3 %) were the most abundant in the water column at the end of the experiment.
Related atrazine-degrading families established at the end of the experiment were Rhodobacteraceae, Solimonadaceae, Pseudomonadaceae, Rhizobiaceae, Chromatiaceae, Bacillaceae, Xanthomonadaceae, Caulobacteraceae, Moraxellaceae, Streptomycetaceae, Microbacteriaceae and Nannocystaceae. Related candidates such as Pseudomonas paralactis, Microbacterium sp., or Arthrobacter sp., among others, were isolated in water samples from previous studies. The bacterial candidates for atrazine degradation identified in the water column indicate that the herbicide acted as a selective pressure factor, altering the composition of the bacterial pattern. The water column would constitute a reactive environment which may govern the fate of pesticides in saline surface water bodies.
How to cite: Espín Montoro, Y., Martínez Couque, G., Fernández Pérez, J. A., Álvarez Ortí, M., and Gómez Alday, J. J.: Selective pressure of atrazine on bacterial pattern in a hypersaline lake environment , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5322, https://doi.org/10.5194/egusphere-egu26-5322, 2026.
