Women in limnology: From a historical perspective to a present-day evaluation

Research in limnology is nurtured by the work of many fascinating and passionate women, who have contributed enormously to our understanding of inland waters. Female limnologists have promoted and established the bases of our knowledge about inland waters and fostered the need of protecting the values of those ecosystems. However, on numerous occasions, their contribution to the advancement of limnology has not been duly recognized. Here, we review the presence of women in limnology through the history of the discipline: from the pioneers who contributed to the origins to present day' developments. We aim at visibilizing those scientists and establish them as role models. We also analyze in a simple and illustrative way the current situation of women in limnology, the scientific barriers they must deal with, and their future prospects. Multiple aspects fostering the visibility of a scientist, such as their presence in conferences, awards, or representation in societal or editorial boards show a significant gap, with none of those aspects showing a similar visibility of women and men in limnology. This article raises awareness of the obstacles that women in limnology faced and still face, and encourages to embrace models of leadership, scientific management, and assessment of research performance far from those commonly established.info:eu-repo/semantics/publishedVersio

3. Water Physicochemistry in IRES

Peer reviewe

Organizational Principles of Hyporheic Exchange Flow and Biogeochemical Cycling in River Networks Across Scales

Hyporheic zones increase freshwater ecosystem resilience to hydrological extremes and global environmental change. However, current conceptualizations of hyporheic exchange, residence time distributions, and the associated biogeochemical cycling in streambed sediments do not always accurately explain the hydrological and biogeochemical complexity observed in streams and rivers. Specifically, existing conceptual models insufficiently represent the coupled transport and reactivity along groundwater and surface water flow paths, the role of autochthonous organic matter in streambed biogeochemical functioning, and the feedbacks between surface-subsurface ecological processes, both within and across spatial and temporal scales. While simplified approaches to these issues are justifiable and necessary for transferability, the exclusion of important hyporheic processes from our conceptualizations can lead to erroneous conclusions and inadequate understanding and management of interconnected surface water and groundwater environments. This is particularly true at the landscape scale, where the organizational principles of spatio-temporal dynamics of hyporheic exchange flow (HEF) and biogeochemical processes remain largely uncharacterized. This article seeks to identify the most important drivers and controls of HEF and biogeochemical cycling based on a comprehensive synthesis of findings from a wide range of river systems. We use these observations to test current paradigms and conceptual models, discussing the interactions of local-to-regional hydrological, geomorphological, and ecological controls of hyporheic zone functioning. This improved conceptualization of the landscape organizational principles of drivers of HEF and biogeochemical processes from reach to catchment scales will inform future river research directions and watershed management strategies

Simulating rewetting events in intermittent rivers and ephemeral streams: a global analysis of leached nutrients and organic matter

Climate change and human pressures are changing the global distribution and extent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico‐chemical changes (preconditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experimentally simulated, under standard laboratory conditions, rewetting of leaves, riverbed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative characteristics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dissolved substances during rewetting events (56‐98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contributed most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached organic matter. The opposite pattern was found in the arid zone. Environmental variables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached substances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying events

Simulating rewetting events in intermittent rivers and ephemeral streams: A global analysis of leached nutrients and organic matter

Climate change and human pressures are changing the global distribution and the ex‐ tent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico‐chemical changes (precon‐ ditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experi‐ mentally simulated, under standard laboratory conditions, rewetting of leaves, river‐ bed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative character‐ istics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dis‐ solved substances during rewetting events (56%–98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contrib‐ uted most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached OM. The opposite pattern was found in the arid zone. Environmental vari‐ ables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached sub‐ stances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying event

Wechselwirkende Einflüsse von mikrobieller Gemeinschaft und Hydrogeomorphologie in sandigen Bachbetten

The main goal of this dissertation was to explore the interactions between the hydrogeomorphology of the streambed in sandy lowland low-order streams and the microbial community inhabiting it. In particular, (i) the influence of the vertical water exchange across the streambed and (ii) of the sediment transport on the function and structure of the streambed microbial community, (iii) and the potential of the microbial community to influence these physical factors were explored. The influences were studied with a model system approach (micro- and mesocosms). Firstly, I examined the significance of vertical water exchange across the streambed for the microbial community. I determined the differences in the microbial community structure and function associated with sediments of differing grain sizes. The grain sizes differed in surface-to-volume ratio and hydraulic conductivity. The results revealed vertical water exchange as the major factor for the structure and function of the microbial community. Secondly, I studied the ability of the microbial community to influence the vertical water exchange across two sandy streambeds: leveled and rippled. My results showed that the microbial community can reduce and even block the vertical water exchange by reducing pore space with gas bubbles formed due to high primary production. Thirdly, I determined the effect of short-term sediment transport events on the function of the microbial community and on the influence of the microbial community on vertical water exchange. The results show that the mechanical stress associated with short-term sediment transport events does not influence the microbial community function. However, a single short-term sediment transport event increased vertical water exchange by (i) releasing the gas bubbles produced by the microbial community and (ii) creating irregularities in the flume bed. Lastly, I ascertained the potential of benthic algal mats to transport sediment by means of buoyancy-mediated detachment from the bed. The results revealed the detachment of algal mats as a novel mechanism of sediment transport during low-flow periods. Overall, the interactions studied show that in sandy streambeds (i) the pattern of vertical water exchange is the primary physical template for the microbial community, and (ii) the activity of the microbial community and sediment transport are stochastic sources of spatiotemporal heterogeneity in vertical water exchange. These results contribute to the understanding and prediction of stream ecosystem functions in sandy streams, which is of special significance in light of the increase in fine sediment load in streams worldwide.Das Ziel dieser Dissertation war es, die Wechselwirkungen zwischen der Hydrogeomorphologie von sandigen Bachbetten (Bäche geringerer Ordnung - nach Strahler) und der darin lebenden mikrobiellen Gemeinschaft zu untersuchen. Im Speziellen galt es dabei, (i) den Einfluss des vertikalen Wasseraustausches zwischen Porenwasser und Bachwasser, als auch (ii) den Sedimenttransport bezogen auf die Struktur und die Funktion der mikrobiellen Gemeinschaft zu untersuchen. Zusätzlich wurde in diesem Zusammenhang (iii) das Potential der mikrobiellen Gemeinschaft genauer betrachtet, diese physikalischen Faktoren zu beeinflussen. Diese Interaktionen wurden in Modellökosystemen analysiert (Mikro- und Mesokosmos). Als erstes habe ich geprüft, ob der vertikale Wasseraustausch zwischen Porenwasser und Bachwasser für die mikrobielle Gemeinschaft von Bedeutung ist. Die Struktur und Funktion der mikrobiellen Gemeinschaft wurde in Sedimenten unterschiedlicher Korngröße erfasst. Die Korngröße der Sedimente wurden so gewählt, dass sich das Verhältnis der besiedelbaren Oberfläche zum Nährstofftransport im Porenvolumen unterschieden hat. Die Ergebnisse zeigen, dass der vertikale Wasseraustausch der Haupteinflussfaktor für die Struktur und die Funktion der mikrobiellen Gemeinschaft ist. Als zweites untersuchte ich die Fragestellung, in wie weit die mikrobielle Gemeinschaft den vertikalen Wasseraustausch sandiger Bachbette, die sich in ihrer Rauigkeit unterscheiden (eben und geriffelt), zu beeinflussen. Meine Ergebnisse zeigen, dass die mikrobielle Gemeinschaft den vertikalen Wasseraustausch einschränken und sogar blockieren kann. Der Porenraum wurde signifikant durch die Einlagerung von Gasblasen, die bei der Primärproduktion entstehen, reduziert. Als drittes untersuchte ich den Effekt von kurzzeitigen Ereignissen des Sedimenttransports auf die Funktion der mikrobiellen Gemeinschaft und den damit verbundenen Einfluss auf den vertikalen Wasseraustausch. Der mechanisch wirkende Stress, verursacht durch den Sedimenttransport, hatte keinen Einfluss auf die Funktion der mikrobiellen Gemeinschaft. Dennoch erhöht ein einmaliger, kurzzeitiger Sedimenttransport den vertikalen Wasseraustausch durch (i) herauslösen der durch die mikrobiellen Gemeinschaft produzierten Gasblasen und (ii) Schaffung von Unregelmäßigkeiten im Rinnenbett. Zuletzt ermittelte ich das Potential von auftreibenden, benthischen Algenmatten, Sediment vom Gewässerbett zu lösen und flussabwärts zu transportieren. In Fließrinnenexperimenten konnte ich zeigen, dass das Ablösen von Algenmatten ein wichtiger und bislang unberücksichtigter Mechanismus von Sedimenttransport während Perioden mit geringem Wasserabfluss darstellen kann. Zusammenfassend zeigen die betrachteten Wechselwirkungen in sandigen Bachbetten, dass (i) das Modell des vertikalen Wasseraustausches der primäre physikalische Faktor ist, der die Struktur und die Funktion der mikrobiellen Gemeinschaft im Bachbett prägt. Des Weiteren sind (ii) die Aktivität der mikrobiellen Gemeinschaft sowie der Sedimenttransport stochastische Quellen raum-zeitlicher Heterogenität des vertikalen Wasseraustauschs. Vor allem im Hinblick auf die zunehmenden Ablagerung von Feinsedimenten in Bächen weltweit tragen diese Ergebnisse wesentlich zum Verständnis und der Prognose von Ökosystemfunktionen in sandigen Bachläufen bei

Editorial: Watershed and Stream: The Inseparable Functional/Biogeochemical Unit

International audienc

Amount of DOC measured in Bti solution and 5x Bti solution as well as DOC concentration and Absorbance specific ultraviolet absorbance (SUVA254) of filtered Bti solution and 5x Bti solution

These data were collected from different treatments. Once we added the larvae and Bti, we gas-tight sealed all microcosms, and the experiment started. We vigorously shook the three additional control microcosms to ensure equilibration of gas between pore water, surface water, and headspace, and gas samples were collected for determining the initial amount of CO2 and CH4. At 24 h, 72 h, and 120 h after the start of the experiment, dissolved O2 concentration, and the CO2 and CH4 mixing ratios in the headspace were measured to determine O2 consumption and CO2 and CH4 emission rates of the sediment. We ended the experiment after 120 h when the first adult was observed. The dissolved O2 concentration in the overlying water was 81 ± 8 % saturation at the end of the experiment. After sampling the headspace at 120 h, we vigorously shook the microcosms to ensure full equilibration between porewater, surface water, and headspace, and collected gas samples from the headspace to determine the total net production of CO2 and CH4 during the experimental period, which includes gas that has accumulated in the pore water. We collected 100 µL of headspace gas from each microcosm at 24 h, 72 h, and 120 h after the start of the experiment using a gastight syringe (Hamilton, USA). The mixing ratios (ppmv) of CO2 and CH4 were measured by injecting the samples into a gas analyzer (Ultra-portable Greenhouse Gas Analyzer; UGGA, Los Gatos Research Inc., Mountain View, CA, USA) in closed-loop operation (Wilkinson et al. 2018). By assuming full equilibration between the headspace and the overlying water, we determined the amount of CH4 and CO2 (µmol) in the headspace and overlying water at each sampling time (gas-specific Henry coefficients at incubation temperature were estimated following (International Hydropower Association 2010)). We then calculated the emissions rates of CH4 and CO2 as the difference in mass between two subsequent samplings divided by the elapsed time. The emission rates include fluxes across the sediment-water interface and potential oxidation of CH4 and CO2 production by respiration in the surface water. After each headspace sampling, we measured dissolved O2 concentration in the overlying water. We calculated the amount of O2, assuming equilibrium between the water and the headspace, as the sum of O2 gas in the headspace and dissolved O2 in the overlying water (µmol). We calculated O2 consumption rates (i.e. respiration) from the difference between two subsequent samplings divided by the elapsed time. We estimated the total net production rate of CH4 and CO2, including gas that has accumulated in the sediment porewater and bubbles during the five-day experiment, from the difference in the amounts estimated from measurements after shaking of the additional control microcosms at the beginning of the experiment, and those estimated after the final shaking of each experimental microcosm at the end of the experiment. The net CH4 and CO2 production rates include gas that was produced in the sediment but not emitted to the water and headspace during the incubation period

Total amounts of CH4 and CO2 measured at the end of the experiment after vigorously shaking each microcosm

These data were collected from different treatments. Once we added the larvae and Bti, we gas-tight sealed all microcosms, and the experiment started. We vigorously shook the three additional control microcosms to ensure equilibration of gas between pore water, surface water, and headspace, and gas samples were collected for determining the initial amount of CO2 and CH4. At 24 h, 72 h, and 120 h after the start of the experiment, dissolved O2 concentration, and the CO2 and CH4 mixing ratios in the headspace were measured to determine O2 consumption and CO2 and CH4 emission rates of the sediment. We ended the experiment after 120 h when the first adult was observed. The dissolved O2 concentration in the overlying water was 81 ± 8 % saturation at the end of the experiment. After sampling the headspace at 120 h, we vigorously shook the microcosms to ensure full equilibration between porewater, surface water, and headspace, and collected gas samples from the headspace to determine the total net production of CO2 and CH4 during the experimental period, which includes gas that has accumulated in the pore water. We collected 100 µL of headspace gas from each microcosm at 24 h, 72 h, and 120 h after the start of the experiment using a gastight syringe (Hamilton, USA). The mixing ratios (ppmv) of CO2 and CH4 were measured by injecting the samples into a gas analyzer (Ultra-portable Greenhouse Gas Analyzer; UGGA, Los Gatos Research Inc., Mountain View, CA, USA) in closed-loop operation (Wilkinson et al. 2018). By assuming full equilibration between the headspace and the overlying water, we determined the amount of CH4 and CO2 (µmol) in the headspace and overlying water at each sampling time (gas-specific Henry coefficients at incubation temperature were estimated following (International Hydropower Association 2010)). We then calculated the emissions rates of CH4 and CO2 as the difference in mass between two subsequent samplings divided by the elapsed time. The emission rates include fluxes across the sediment-water interface and potential oxidation of CH4 and CO2 production by respiration in the surface water. After each headspace sampling, we measured dissolved O2 concentration in the overlying water. We calculated the amount of O2, assuming equilibrium between the water and the headspace, as the sum of O2 gas in the headspace and dissolved O2 in the overlying water (µmol). We calculated O2 consumption rates (i.e. respiration) from the difference between two subsequent samplings divided by the elapsed time. We estimated the total net production rate of CH4 and CO2, including gas that has accumulated in the sediment porewater and bubbles during the five-day experiment, from the difference in the amounts estimated from measurements after shaking of the additional control microcosms at the beginning of the experiment, and those estimated after the final shaking of each experimental microcosm at the end of the experiment. The net CH4 and CO2 production rates include gas that was produced in the sediment but not emitted to the water and headspace during the incubation period