Microbial Community Ecology and Biotic Processes at the Aquatic/Terrestrial Interface

Rivers and their adjacent riparian zones are locations of high levels of biodiversity and are well known for their enhanced rates of important biogeochemical processes. Despite their small total area, rivers contribute disproportionally to regional carbon fluxes and riparian zones are hotspots of terrestrial denitrification. Microorganisms drive these biogeochemical processes as well as serve as the basis of brown food webs and contribute to physical processes such as sediment flocculation and soil aggregation. Despite the importance of microbial communities in rivers and riparian systems, they are relatively understudied in comparison to other riverine organisms. This doctoral work investigates microbial community structure and function at the aquatic/terrestrial interface. First, a theoretical work based on the newly proposed concept of microbial community coalescence explores the potential consequences of environmental mixing on lotic and riparian microbial community structure. This work takes a catchment-scale perspective of microbial community assembly across ecosystem boundaries. Next, results of a field study conducted across nine rivers in the UK are presented, providing insight about the influence of chemical, hydrological and spatial drivers on sediment fungal community structure. This provides a sub-catchment scale view of lotic fungal diversity. The final chapter details results of an experimental study investigating the influence of collembolans, ubiquitous soil organisms, on the production of the greenhouse gas N2O. This work explores the effects of biotic-scale processes on ecosystem functioning. We reviewed field studies investigating environmental mixing processes and found evidence that environmental mixing influences microbial community structure in some compartments, such as headwaters and estuaries. The application of the microbial community coalescence concept in rivers may increase the amount of variance explained between observed local communities. Despite a rich body of literature about lotic fungal decomposer communities inhabiting leaf litter, very few studies investigated general fungal diversity. Our investigation of sediment fungal communities revealed highly diverse communities that were differentiated by underlying geology. Hydrological and chemical variables explained some of the differences between microbial communities, while spatial variables were less important. Finally, we conducted an experimental study to investigate the microbial-driven process of denitrification – an anaerobic nitrogen cycling process that produces N2 and N2O, a greenhouse gas. We found the different species of the ubiquitous soil organism Collembola affect the proportion of N2O that is produced as an end-product of denitrification and that this is related to shifts in soil nitrate concentrations. Together, this work reports findings from several under-investigated areas of microbial structure and functioning in rivers, soils and across their interface at three different scales. Our results provide insight about patterns of riverine microbial biodiversity through application of a new conceptual framework that may improve explanatory power and through a field investigation that reveals the relative importance of spatial and environmental drivers. Our field investigation was one of the first studies in Europe to apply next-generation sequencing to general fungal communities in rivers. We also provide evidence that denitrification is impacted by the presence of soil microarthropods, organisms with highly diverse communities in riparian zones. As riverine systems are simultaneously vital for ecosystem function and highly threatened by anthropogenic activity, there is an urgent need for fundamental knowledge of lotic biodiversity patterns and their relationship with function to inform conservation and restoration efforts

Multispecies assemblages and multiple stressors: Synthesizing the state of experimental research in freshwaters

Recent decades have witnessed a sharp biodiversity decline in freshwaters due to multiple stressors. The presence of multiple stressors is expected to affect community structure and interactions in freshwater ecosystems, with subsequent functional consequences. We synthesized the state of experimental, manipulative multiple-stressor studies that focused on multispecies assemblages in freshwaters. Compared to rivers and lakes, wetland and groundwater ecosystems have received much less attention in identified multiple-stressor research. Most of the identified studies investigated combinations of abiotic stressors (e.g., nutrients, pesticides, heavy metals, warming, altered flow and sedimentation) on microbes and invertebrates while biotic stressors and vertebrates have been largely overlooked. The responses of community structure (e.g., alpha diversity, biomass, and abundance), some community/ecosystem functions (e.g., photosynthesis and autotrophic activity, leaf litter degradation), and morphological traits like body size and growth forms were frequently investigated. We observed a clear gap in biotic interactions under multiple-stressor conditions, which, although difficult to study, could impede a deeper mechanistic understanding of how multiple stressors affect freshwater assemblages and associated ecological processes. Although information on ecosystem recovery pathways following restoration is critical for freshwater management, few studies were designed to provide such information, signifying the disconnections between multiple-stressor research and environmental practice. To bridge these gaps, researchers and environmental practitioners need to work together to identify key stressors and interactions at different spatial and temporal scales and prioritize stressor management. Such collaborations will enhance the translation of multiple-stressor research into efficient management strategies to protect and restore freshwater ecosystems.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Deutscher Akademischer Austauschdienst http://dx.doi.org/10.13039/501100001655Leibniz‐GemeinschaftGerman Federal Ministry of Education and Research (BMBF)Peer Reviewe

Multispecies assemblages and multiple stressors: Synthesizing the state of experimental research in freshwaters

Recent decades have witnessed a sharp biodiversity decline in freshwaters due to multiple stressors. The presence of multiple stressors is expected to affect community structure and interactions in freshwater ecosystems, with subsequent functional consequences. We synthesized the state of experimental, manipulative multiple-stressor studies that focused on multispecies assemblages in freshwaters. Compared to rivers and lakes, wetland and groundwater ecosystems have received much less attention in identified multiple-stressor research. Most of the identified studies investigated combinations of abiotic stressors (e.g., nutrients, pesticides, heavy metals, warming, altered flow and sedimentation) on microbes and invertebrates while biotic stressors and vertebrates have been largely overlooked. The responses of community structure (e.g., alpha diversity, biomass, and abundance), some community/ecosystem functions (e.g., photosynthesis and autotrophic activity, leaf litter degradation), and morphological traits like body size and growth forms were frequently investigated. We observed a clear gap in biotic interactions under multiple-stressor conditions, which, although difficult to study, could impede a deeper mechanistic understanding of how multiple stressors affect freshwater assemblages and associated ecological processes. Although information on ecosystem recovery pathways following restoration is critical for freshwater management, few studies were designed to provide such information, signifying the disconnections between multiple-stressor research and environmental practice. To bridge these gaps, researchers and environmental practitioners need to work together to identify key stressors and interactions at different spatial and temporal scales and prioritize stressor management. Such collaborations will enhance the translation of multiple-stressor research into efficient management strategies to protect and restore freshwater ecosystems

Rate of environmental change across scales in ecology

The rate of change (RoC) of environmental drivers matters: biotic and abiotic components respond differently when faced with a fast or slow change in their environment. This phenomenon occurs across spatial scales and thus levels of ecological organization. We investigated the RoC of environmental drivers in the ecological literature and examined publication trends across ecological levels, including prevalent types of evidence and drivers. Research interest in environmental driver RoC has increased over time (particularly in the last decade), however, the amount of research and type of studies were not equally distributed across levels of organization and different subfields of ecology use temporal terminology (e.g. 'abrupt' and 'gradual') differently, making it difficult to compare studies. At the level of individual organisms, evidence indicates that responses and underlying mechanisms are different when environmental driver treatments are applied at different rates, thus we propose including a time dimension into reaction norms. There is much less experimental evidence at higher levels of ecological organization (i.e. population, community, ecosystem), although theoretical work at the population level indicates the importance of RoC for evolutionary responses. We identified very few studies at the community and ecosystem levels, although existing evidence indicates that driver RoC is important at these scales and potentially could be particularly important for some processes, such as community stability and cascade effects. We recommend shifting from a categorical (e.g. abruptversusgradual) to a quantitative and continuous (e.g. degrees C/h) RoC framework and explicit reporting of RoC parameters, including magnitude, duration and start and end points to ease cross-scale synthesis and alleviate ambiguity. Understanding how driver RoC affects individuals, populations, communities and ecosystems, and furthermore how these effects can feed back between levels is critical to making improved predictions about ecological responses to global change drivers. The application of a unified quantitative RoC framework for ecological studies investigating environmental driver RoC will both allow cross-scale synthesis to be accomplished more easily and has the potential for the generation of novel hypotheses

How widespread use of generative AI for images and video can affect the environment and the science of ecology

Generative artificial intelligence (AI) models will have broad impacts on society including the scientific enterprise; ecology and environmental science will be no exception. Here, we discuss the potential opportunities and risks of advanced generative AI for visual material (images and video) for the science of ecology and the environment itself. There are clearly opportunities for positive impacts, related to improved communication, for example; we also see possibilities for ecological research to benefit from generative AI (e.g., image gap filling, biodiversity surveys, and improved citizen science). However, there are also risks, threatening to undermine the credibility of our science, mostly related to actions of bad actors, for example in terms of spreading fake information or committing fraud. Risks need to be mitigated at the level of government regulatory measures, but we also highlight what can be done right now, including discussing issues with the next generation of ecologists and transforming towards radically open science workflows

Multiple-stressor effects on leaf litter decomposition in freshwater ecosystems: A meta-analysis

1. Recent years have witnessed a surge in research on the effects of multiple stressors in freshwater ecosystems. While studies have increased, the synthesis of their findings into a broader understanding of ecosystem-level effects remains an ongoing endeavour. Leaf litter decomposition, a frequently investigated and pivotal ecosystem function in freshwaters, is sensitive to changes in abiotic conditions and biotic communities, and therefore susceptible to multiple-stressor effects. 2. Here, we synthesize findings from 27 manipulative experimental studies encompassing 61 responses of litter decomposition to paired stressors such as warming, nutrient enrichment and emerging pollutants in freshwater ecosystems. We calculated the individual and overall interaction effect sizes resulting from two stressors occurring simultaneously. Furthermore, we analysed the effect of moderator variables in the size and direction of interaction effect sizes using a meta-analytical approach. 3. Although the vote-counting method showed additive interactions to dominate individual observations (91.8%), weighted random-effects meta-analysis revealed an overall antagonistic interaction between stressors (i.e. the cumulative effect of paired stressors on litter decomposition was less than the sum of their single effects). Our results emphasized the influence of experimental characteristics such as macroinvertebrate involvement, habitat type (lentic vs. lotic) and litter quality (assumed from plant mycorrhizal association) in shaping the responses of litter decomposition to multiple stressors. 4. Our meta-analysis highlights the need to incorporate local ecological complexities in manipulative experiments to improve predictions of multiple-stressor effects on biodiversity and ecosystem functions. The present study underscores the importance of considering biotic interactions and adopting the metacommunity framework in conservation and restoration actions to support the management of freshwater ecosystems in an era of rapid global change

Ten simple rules for hosting artists in a scientific lab

Hosting an artist in a scientific lab is likely a new experience for many scientists in the natural and engineering sciences, and perhaps also for many artists, yet it can be a very beneficial experience for both parties [1]. “Art and science are in a tension that is most fruitful when these disciplines observe and penetrate each other and experience how much of the other they themselves still contain” [2]. During our science and art collaborations in the last years, we have learned what connects and what separates our disciplines, how different yet common our worlds of working and thinking are, and how stimulating such collaborations can be. Although scientists and artists belong to two different cultural worlds, many share research as a congruent method to explore and understand the world around us. Often, scientific and artistic work spaces are indistinguishable as they are full of equipment, materials, tools, and computers to run experiments and analyze data [3,4]. Science and art are fundamentally connected through their focus on creativity [5]. Also, both scientists and artists deliberately venture into the public realm in the spirit of Hannah Arendt: “Humanity is never won in loneliness and never by handing one’s work over to the public. Only if you take your life and person[ality] into the venture of the public realm, will you reach [humanity]” [6]. At the most fundamental level, science and art both try to understand the world around us and to guide society to recognize and solve problems. Artistic and scientific research may also have much more in common than one expects at first sight: They both involve years of schools and personal development, they both involve trial and error, and the sharing of results with different communities. However, transdisciplinary cooperation requires openness, a willingness to take risks, the ability for self-reflection, respect, and esteem for the other culture as well as a lot of appreciative listening from both parties [7,8]. Our paper thus intends to serve as a practical guide for both, artists-in-residence and the hosting scientific lab to easier cross borders, to better collaborate, to better learn from each other, and to sustainably bridge the different cultures of science and the arts. Our discussion starts at the point where a decision for such an interaction has already taken place. Still wondering if this is for you? There is much to gain for both sides. For the scientists, for example, this interaction can be a source of new ideas and questions, offering new points of view. Some of us also felt that this interaction offered training in explaining research in clear, simple language, and provided opportunities for interfacing with the science-curious public in a curated context. For the artists, this can be about learning new tools, methods, and approaches and about the specific topics on which a lab works

Why farmers should manage the arbuscular mycorrhizal symbiosis

The Tansley review by Ryan & Graham (2018) provided a welcome critical perspective on the role of arbuscular mycorrhizal (AM) fungi in large‐scale industrial agriculture, with a focus on cereals (wheat, Triticum aestivum). They conclude that there is little evidence that farmers should consider the abundance or diversity of AM fungi when managing crops. We welcome many of the points made in the paper, as they give an opportunity for self‐reflection, considering that the importance of AM fungi in agroecosystems is often taken for granted. However, we suggest that it is too early to draw the overall conclusion that the management of AM fungi by farmers is currently not warranted. We offer the following points to contribute to the discussion. The first point pertains to the overall focus of Ryan & Graham (2018), which strongly determines the recommendations at which the authors arrive. This scope is limited to yield, at the expense of neglecting aspects of sustainability. We then argue that AM fungal communities do respond negatively to aspects of agricultural management, and list evidence for their positive effects to agronomically important traits, including yield in cereals. In our final argument, we advocate for transitioning to agroecosystems that are more AM compatible in order to increasingly take advantage of all the potential services these ancient symbionts, and other soil biota, can provide

Myristate and the ecology of AM fungi : significance, opportunities, applications and challenges

A recent study by Sugiura and coworkers reported the nonsymbiotic growth and spore production of an arbuscular mycorrhizal (AM) fungus, Rhizophagus irregularis, when the fungus received an external supply of certain fatty acids, myristates (C:14). This discovery follows the insight that AM fungi receive fatty acids from their hosts when in symbiosis. If this result holds up and can be repeated under nonsterile conditions and with a broader range of fungi, it has numerous consequences for our understanding of AM fungal ecology, from the level of the fungus, at the plant community level, and to functional consequences in ecosystems. In addition, myristate may open up several avenues from a more applied perspective, including improved fungal culture and supplementation of AM fungi or inoculum in the field. We here map these potential opportunities, and additionally offer thoughts on potential risks of this potentially new technology. Lastly, we discuss the specific research challenges that need to be overcome to come to an understanding of the potential role of myristate in AM ecology

Multispecies assemblages and multiple stressors: Synthesizing the state of experimental research in freshwaters

AbstractRecent decades have witnessed a sharp biodiversity decline in freshwaters due to multiple stressors. The presence of multiple stressors is expected to affect community structure and interactions in freshwater ecosystems, with subsequent functional consequences. We synthesized the state of experimental, manipulative multiple‐stressor studies that focused on multispecies assemblages in freshwaters. Compared to rivers and lakes, wetland and groundwater ecosystems have received much less attention in identified multiple‐stressor research. Most of the identified studies investigated combinations of abiotic stressors (e.g., nutrients, pesticides, heavy metals, warming, altered flow and sedimentation) on microbes and invertebrates while biotic stressors and vertebrates have been largely overlooked. The responses of community structure (e.g., alpha diversity, biomass, and abundance), some community/ecosystem functions (e.g., photosynthesis and autotrophic activity, leaf litter degradation), and morphological traits like body size and growth forms were frequently investigated. We observed a clear gap in biotic interactions under multiple‐stressor conditions, which, although difficult to study, could impede a deeper mechanistic understanding of how multiple stressors affect freshwater assemblages and associated ecological processes. Although information on ecosystem recovery pathways following restoration is critical for freshwater management, few studies were designed to provide such information, signifying the disconnections between multiple‐stressor research and environmental practice. To bridge these gaps, researchers and environmental practitioners need to work together to identify key stressors and interactions at different spatial and temporal scales and prioritize stressor management. Such collaborations will enhance the translation of multiple‐stressor research into efficient management strategies to protect and restore freshwater ecosystems.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Deutscher Akademischer Austauschdienst http://dx.doi.org/10.13039/501100001655Leibniz‐GemeinschaftGerman Federal Ministry of Education and Research (BMBF