Journal Staff

Half of the world's forest is in boreal and sub-boreal ecozones, containing large carbon stores and fluxes. Carbon lost from headwater streams in these forests is underestimated. We apply a simple stable carbon isotope idea for quantifying the CO2 loss from these small streams; it is based only on in-stream samples and integrates over a significant distance upstream. We demonstrate that conventional methods of determining CO2 loss from streams necessarily underestimate the CO2 loss with results from two catchments. Dissolved carbon export from headwater catchments is similar to CO2 loss from stream surfaces. Most of the CO2 originating in high CO2 groundwaters has been lost before typical in-stream sampling occurs. In the Harp Lake catchment in Canada, headwater streams account for 10% of catchment net CO2 uptake. In the Krycklan catchment in Sweden, this more than doubles the CO2 loss from the catchment. Thus, even when corrected for aquatic CO2 loss measured by conventional methods, boreal and sub-boreal forest carbon budgets currently overestimate carbon sequestration on the landscape

Untersuchungen von Beugesehnennähten mittels Bildsequenzanalyse im Experiment

Im Rahmen dieser Arbeit werden die Ergebnisse aus Zugversuchen an Schweinesehnen, die mit verschiedenen Nahtmaterialien und den gängigen Nahttechniken für Beugesehnen der Hand genäht wurden, vorgestellt. Schwerpunkt der Untersuchungen ist die Ermittlung und Dokumentation der Reißfestigkeit der Naht und die Spaltbildung an der Kontaktstelle der genähten Sehnenstümpfe mittels biomechanischer Versuche. Das Eintreten der Spaltbildung und des Nahtrisses wird durch videotechnische Aufzeichnungen, die den eigentlichen Messvorgang an der Universalprüfmaschine begleiten, exakt dokumentiert (Bildsequenzanalyse). Die Bildsequenzanalyse stellt gegenüber den in der Literatur dokumentierten Methoden eine wesentliche Fort- bzw. Neuentwicklung zur Ermittlung der Spaltstabilität und der Reißfestigkeit von genähten Sehnen dar. Die Auswertung der Versuche mittels Bildsequenzanalyse wurde für 12 verschiedene Nahttechnik/Nahtmaterial-Kombinationen durchgeführt. Nach Entwicklung und Anfertigung einer neuen Einspannvorrichtung für die Sehnen, die eine optimale Festhaltung der Sehnenstümpfe gewährleistete, erfolgte die systematische Durchführung von Bildsequenzanalysen für gängige Sehnennaht-Techniken mit verschiedenen Fäden. Auf Grundlage der biomechanischen Versuche und der Weiterentwicklung bisheriger Kenntnisse zur Beugesehnennaht konnte im Rahmen dieser Arbeit eine optimierte bzw. eine neue Nahttechnik entwickelt werden (Marburger Sehnennaht I und II), die eine frühe postoperative Mobilisierung durch entsprechende Nahtfestigkeiten ermöglicht, eine gute Gleitfunktion aufweist sowie durch Erhaltung der Gefäßversorgung der Sehne einen sicheren Heilungsprozess gewährleistet. Die Ergebnisse der biomechanischen Versuche mit der Marburger Sehnennaht I und II sind in dieser Arbeit detailliert dokumentiert. Der Vergleich mit den gängigen Sehnennaht-Techniken zeigt, dass die Marburger Sehnennaht eine hohe Reißfestigkeit und die beste Spaltstabilität besitzt

Dissolved oxygen isotope modelling refines metabolic state estimates of stream ecosystems with different land use background

Dissolved oxygen (DO) is crucial for aerobic life in streams and rivers and mostly depends on photosynthesis (P), ecosystem respiration (R) and atmospheric gas exchange (G). However, climate and land use changes progressively disrupt metabolic balances in natural streams as sensitive reflectors of their catchments. Comprehensive methods for mapping fundamental ecosystem services become increasingly important in a rapidly changing environment. In this work we tested DO and its stable isotope ($^{18}$O$^{16}$O) ratios as novel tools for the status of stream ecosystems. For this purpose, six diel sampling campaigns were performed at three low-order and mid-latitude European streams with different land use patterns. Modelling of diel DO and its stable isotopes combined with land use analyses showed lowest P rates at forested sites, with a minimum of 17.9 mg m$^{-2}$ h$^{-1}$. Due to high R rates between 230 and 341 mg m$^{-2}$ h$^{-1}$ five out of six study sites showed a general heterotrophic state with P:R:G ratios between 0.1:1.1:1 and 1:1.9:1. Only one site with agricultural and urban influences showed a high P rate of 417 mg m$^{-2}$ h$^{-1}$ with a P:R:G ratio of 1.9:1.5:1. Between all sites gross G rates varied between 148 and 298 mg m$^{-2}$ h$^{-1}$. In general, metabolic rates depend on the distance of sampling locations to river sources, light availability, nutrient concentrations and possible exchanges with groundwater. The presented modelling approach introduces a new and powerful tool to study effects of land use on stream health. Such approaches should be integrated into future ecological monitoring

Differences in atmospheric phosphorus deposition amongst rural and urban land use locations in Missouri

Atmospheric phosphorus (AP) produced by both anthropogenic and natural processes influences phytoplankton productivity and alters carbon processing in water bodies, resulting in potential impairment and toxic phytoplankton blooms. The production of AP, which is oftentimes transported vast distances by wind dispersal in the form of enriched mineral dust, can be re-deposited by wet (precipitation based) or dry (continual) deposition. Both rural and urban locations in Missouri experience varying anthropogenic activities; therefore, distinguishing between varying land use locations at these sites provides insight as to why AP may differ. The objective of this study is to determine if AP deposition differs among rural and urban land use locations in Missouri. When soil has been recently agitated and readily exposed, we hypothesize this additional P in the atmosphere will result in higher bulk deposition flux totals (BD) in rural locations. AP was collected from three rural locations and three urban locations, using a standard sized utility bucket, altered to reduce debris. After each two-week sampling period, a total sample water volume for each site is collected, total P is analyzed (TP), which determines the BD flux of each site by factoring the time it took to collect each sample (4 samples over approximately 70 days). Rural locations had the highest BD. Rural locations were not significantly different than urban locations (F5,18 = 1.667, p = 0.194). Further analysis of AP and the implication on water bodies is needed, as AP analysis is exceedingly rare. A multitude of differing land use practices results in variables that contribute significantly to the production of AP.Crystal Rein, Sarahi Viscarra Arellano, Karl Friesen-Hughes, Ashley King, Alexia Marten, Corey Sanderson, Jason J Venkiteswaran, Helen Baulch, Nora Jessie Casson, Colin J Whitfield, and Rebecca North (University of Missouri, University of Saskatchewan, Wilfrid Laurier University, University of Winnipeg

LakeEnsemblR: an R package that facilitates ensemble modelling of lakes

Model ensembles have several benefits compared to single-model applications but are not frequently used within the lake modelling community. Setting up and running multiple lake models can be challenging and time consuming, despite the many similarities between the existing models (forcing data, hypsograph, etc.). Here we present an R package, LakeEnsemblR, that facilitates running ensembles of five different vertical one-dimensional hydrodynamic lake models (FLake, GLM, GOTM, Simstrat, MyLake). The package requires input in a standardised format and a single configuration file. LakeEnsemblR formats these files to the input required by each model, and provides functions to run and calibrate the models. The outputs of the different models are compiled into a single file, and several post-processing operations are supported. LakeEnsemblR's workflow standardisation can simplify model benchmarking and uncertainty quantification, and improve collaborations between scientists. We showcase the successful application of LakeEnsemblR for two different lakes

Global patterns of nitrate isotope composition in rivers and adjacent aquifers reveal reactive nitrogen cascading

Remediation of nitrate pollution of Earth’s rivers and aquifers is hampered by cumulative biogeochemical processes and nitrogen sources. Isotopes (δ15N, δ18O) help unravel spatiotemporal nitrogen(N)-cycling of aquatic nitrate (NO3−). We synthesized nitrate isotope data (n = ~5200) for global rivers and shallow aquifers for common patterns and processes. Rivers had lower median NO3− (0.3 ± 0.2 mg L−1, n = 2902) compared to aquifers (5.5 ± 5.1 mg L−1, n = 2291) and slightly lower δ15N values (+7.1 ± 3.8‰, n = 2902 vs +7.7 ± 4.5‰, n = 2291), but were indistinguishable in δ18O (+2.3 ± 6.2‰, n = 2790 vs +2.3 ± 5.4‰, n = 2235). The isotope composition of NO3− was correlated with water temperature revealing enhanced N-cascading in warmer climates. Seasonal analyses revealed higher δ15N and δ18O values in wintertime, suggesting waste-related N-source signals are better preserved in the cold seasons. Isotopic assays of nitrate biogeochemical transformations are key to understanding nitrate pollution and to inform beneficial agricultural and land management strategies

Blooms and flows: Effects of variable hydrology and management on reservoir water quality

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2023 The Authors. Ecosphere published by Wiley Periodicals LLC on behalf of The Ecological Society of America.Canada First Research Excellence Fund; Canada Foundation for Innovation; Mitacs; Buffalo Pound Water Treatment PlantPeer ReviewedFlow management has the potential to significantly affect ecosystem condition. Shallow lakes in arid regions are especially susceptible to flow management changes, which can have important implications for the formation of cyanobacterial blooms. Here, we reveal water quality shifts associated with changing source water inflow management. Using in situ monitoring data, we studied a seven-year time span during which inflows to a shallow, eutrophic drinking water reservoir transitioned from primarily natural landscape runoff (2014–2015) to managed flows from a larger upstream reservoir (Lake Diefenbaker; 2016–2020) and identified significant changes in cyanobacteria (as phycocyanin) using generalized additive models to classify cyanobacterial bloom formation. We then connected changes in water source with shifts in chemistry and the occurrence of cyanobacterial blooms using principal components analysis. Phycocyanin was greater in years with managed reservoir inflow from a mesotrophic upstream reservoir (2016–2020), but dissolved organic matter (DOM) and specific conductivity, important determinants of drinking water quality, were greatest in years when landscape runoff dominated lake water source (2014–2015). Most notably, despite changing rapidly, it took multiple years for lake water to return to a consistent and reduced level of DOM after managed inflows from the upstream reservoir were resumed, an observation that underscores how resilience may be hindered by weak resistance to change and slow recovery. Environmental flows for water quality are rarely defined, yet we show that trade-offs exist between poor water quality via elevated conductivity and DOM and higher bloom risk, depending on water source. Our work highlights the importance of source water quality, not just quantity, to water security, and our findings have important implications for water managers who must protect ecosystem services while adapting to projected hydroclimatic change

Proper interpretation of dissolved nitrous oxide isotopes, production pathways, and emissions requires a modelling approach.

Stable isotopes ([Formula: see text]15N and [Formula: see text]18O) of the greenhouse gas N2O provide information about the sources and processes leading to N2O production and emission from aquatic ecosystems to the atmosphere. In turn, this describes the fate of nitrogen in the aquatic environment since N2O is an obligate intermediate of denitrification and can be a by-product of nitrification. However, due to exchange with the atmosphere, the [Formula: see text] values at typical concentrations in aquatic ecosystems differ significantly from both the source of N2O and the N2O emitted to the atmosphere. A dynamic model, SIDNO, was developed to explore the relationship between the isotopic ratios of N2O, N2O source, and the emitted N2O. If the N2O production rate or isotopic ratios vary, then the N2O concentration and isotopic ratios may vary or be constant, not necessarily concomitantly, depending on the synchronicity of production rate and source isotopic ratios. Thus prima facie interpretation of patterns in dissolved N2O concentrations and isotopic ratios is difficult. The dynamic model may be used to correctly interpret diel field data and allows for the estimation of the gas exchange coefficient, N2O production rate, and the production-weighted [Formula: see text] values of the N2O source in aquatic ecosystems. Combining field data with these modelling efforts allows this critical piece of nitrogen cycling and N2O flux to the atmosphere to be assessed

Large carbon dioxide fluxes from headwater boreal and sub-boreal streams

Half of the world's forest is in boreal and sub-boreal ecozones, containing large carbon stores and fluxes. Carbon lost from headwater streams in these forests is underestimated. We apply a simple stable carbon isotope idea for quantifying the CO2 loss from these small streams; it is based only on in-stream samples and integrates over a significant distance upstream. We demonstrate that conventional methods of determining CO2 loss from streams necessarily underestimate the CO2 loss with results from two catchments. Dissolved carbon export from headwater catchments is similar to CO2 loss from stream surfaces. Most of the CO2 originating in high CO2 groundwaters has been lost before typical in-stream sampling occurs. In the Harp Lake catchment in Canada, headwater streams account for 10% of catchment net CO2 uptake. In the Krycklan catchment in Sweden, this more than doubles the CO2 loss from the catchment. Thus, even when corrected for aquatic CO2 loss measured by conventional methods, boreal and sub-boreal forest carbon budgets currently overestimate carbon sequestration on the landscape

Model scenario #5 – Isotopic composition of dissolved and emitted N₂O with a variable production rate and variable isotopic composition of the source.

<p>Maximum production rate is in sync with the greatest ¹⁵N and ¹⁸O values of the source.</p