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David GM, Pimentel IM, Rehsen PM, Vermiert AM, Leese F, Gessner MO. Multiple stressors affecting microbial decomposer and litter decomposition in restored urban streams: Assessing effects of salinization, increased temperature, and reduced flow velocity in a field mesocosm experiment. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 943:173669. [PMID: 38839005 DOI: 10.1016/j.scitotenv.2024.173669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Revised: 05/12/2024] [Accepted: 05/29/2024] [Indexed: 06/07/2024]
Abstract
A multitude of anthropogenic stressors impact biological communities and ecosystem processes in urban streams. Prominent among them are salinization, increased temperature, and altered flow regimes, all of which can affect microbial decomposer communities and litter decomposition, a fundamental ecosystem process in streams. Impairments caused by these stressors individually or in combination and recovery of communities and ecosystem processes after release from these stressors are not well understood. To improve our understanding of multiple stressors impacts we performed an outdoor stream mesocosm experiment with 64 experimental units to assess the response of microbial litter decomposers and decomposition. The three stressors we applied in a full-factorial design were increased salinity (NaCl addition, 0.53 mS cm-1 above ambient), elevated temperature (3.5 °C above ambient), and reduced flow velocity (3.5 vs 14.2 cm s-1). After two weeks of stressor exposure (first sampling) and two subsequent weeks of recovery (second sampling), we determined leaf-associated microbial respiration, fungal biomass, and the sporulation activity and community composition of aquatic hyphomycetes in addition to decomposition rates of black alder (Alnus glutinosa) leaves confined in fine-mesh litter bags. Microbial colonization of the litter was accompanied by significant mass loss in all mesocosms. However, there was little indication that mass loss, microbial respiration, fungal biomass, sporulation rate or community composition of aquatic hyphomycetes was strongly affected by either single stressors or their interactions. Two exceptions were temperature effects on sporulation and decomposition rate. Similarly, no notable differences among mesocosms were observed after the recovery phase. These results suggest that microbial decomposers and leaf litter decomposition are either barely impaired by exposure to the tested stressors at the levels applied in our experiment, or that communities in restored urban streams are well adapted to cope with these stressor levels.
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Affiliation(s)
- Gwendoline M David
- Department of Plankton and Microbial Ecology, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Stechlin, Germany.
| | - Iris Madge Pimentel
- Aquatic Ecosystem Research, Faculty of Biology, University of Duisburg-Essen, Essen, Germany
| | - Philipp M Rehsen
- Aquatic Ecosystem Research, Faculty of Biology, University of Duisburg-Essen, Essen, Germany; Centre for Water and Environmental Research (ZWU), University of Duisburg-Essen, Essen, Germany
| | - Anna-Maria Vermiert
- Department of Animal Ecology, Evolution and Biodiversity, Ruhr University Bochum, Bochum, Germany
| | - Florian Leese
- Aquatic Ecosystem Research, Faculty of Biology, University of Duisburg-Essen, Essen, Germany; Centre for Water and Environmental Research (ZWU), University of Duisburg-Essen, Essen, Germany
| | - Mark O Gessner
- Department of Plankton and Microbial Ecology, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Stechlin, Germany; Department of Ecology, Berlin Institute of Technology (TU Berlin), Berlin, Germany
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Aquatic Hyphomycete Taxonomic Relatedness Translates into Lower Genetic Divergence of the Nitrate Reductase Gene. J Fungi (Basel) 2021; 7:jof7121066. [PMID: 34947048 PMCID: PMC8708292 DOI: 10.3390/jof7121066] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 11/27/2021] [Accepted: 12/06/2021] [Indexed: 12/04/2022] Open
Abstract
Aquatic hyphomycetes are key microbial decomposers in freshwater that are capable of producing extracellular enzymes targeting complex molecules of leaf litter, thus, being crucial to nutrient cycling in these ecosystems. These fungi are also able to assimilate nutrients (e.g., nitrogen) from stream water, immobilizing these nutrients in the decomposing leaf litter and increasing its nutritional value for higher trophic levels. Evaluating the aquatic hyphomycete functional genetic diversity is, thus, pivotal to understanding the potential impacts of biodiversity loss on nutrient cycling in freshwater. In this work, the inter- and intraspecific taxonomic (ITS1-5.8S-ITS2 region) and functional (nitrate reductase gene) diversity of 40 aquatic hyphomycete strains, belonging to 23 species, was evaluated. A positive correlation was found between the taxonomic and nitrate reductase gene divergences. Interestingly, some cases challenged this trend: Dactylella cylindrospora (Orbiliomycetes) and Thelonectria rubi (Sordariomycetes), which were phylogenetically identical but highly divergent regarding the nitrate reductase gene; and Collembolispora barbata (incertae sedis) and Tetracladium apiense (Leotiomycetes), which exhibited moderate taxonomic divergence but no divergence in the nitrate reductase gene. Additionally, Tricladium chaetocladium (Leotiomycetes) strains were phylogenetically identical but displayed a degree of nitrate reductase gene divergence above the average for the interspecific level. Overall, both inter- and intraspecific functional diversity were observed among aquatic hyphomycetes.
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Venâncio C, Ribeiro R, Lopes I. Seawater intrusion: an appraisal of taxa at most risk and safe salinity levels. Biol Rev Camb Philos Soc 2021; 97:361-382. [PMID: 34626061 DOI: 10.1111/brv.12803] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 09/23/2021] [Accepted: 09/27/2021] [Indexed: 11/30/2022]
Abstract
Seawater intrusion into low-lying coastal ecosystems carries environmental risks. Salinity levels at these coastal ecosystems may vary substantially, causing ecological effects from mortality to several sublethal endpoints, such as depression of rates of feeding, somatic growth, or reproduction. This review attempts to establish safe salinity levels for both terrestrial and freshwater temperate ecosystems by integrating data available in the literature. We have four specific objectives: (i) to identify the most sensitive ecological taxa to seawater intrusion; (ii) to establish maximum acceptable concentrations-environmental quality standards (MAC-EQSs) for sea water (SW) from species sensitivity distributions (SSDs); (iii) to compile from the literature examples of saline intrusion [to be used as predicted environmental concentrations (PECs)] and to compute risk quotients for the temperate zone; and (iv) to assess whether sodium chloride (NaCl) is an appropriate surrogate for SW in ecological risk assessments by comparing SSD-derived values for NaCl and SW and by comparing these with field data. Zooplankton, early life stages of amphibians and freshwater mussels were the most sensitive ecological receptors for the freshwater compartment, while soil invertebrates were the most sensitive ecological receptors for the terrestrial compartment. Hazard concentration 5% (HC5 ) values, defined as the concentration (herein measured as conductivity) that affects (causes lethal or sublethal effects) 5% of the species in a distribution, computed for SW were over 22 and 40 times lower than the conductivity of natural SW (≈ 52 mS/cm) for the freshwater and soil compartment, respectively. This sensitivity of both compartments means that small increments in salinity levels or small SW intrusions might represent severe risks for low-lying coastal ecosystems. Furthermore, the proximity between HC5 values for the soil and freshwater compartments suggests that salinized soils might represent an additional risk for nearby freshwater systems. This sensitivity was corroborated by the derivation of risk quotients using real saline intrusion examples (PECs) collected from the literature: risk was >1 in 34 out of 37 examples. By contrast, comparisons of HC5 values obtained from SSDs in field surveys or mesocosm studies suggest that natural communities are more resilient to salinization than expected. Finally, NaCl was found to be slightly more toxic than SW, at both lethal and sublethal levels, and, thus, is suggested to be an acceptable surrogate for use in risk assessment.
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Affiliation(s)
- Cátia Venâncio
- Department of Life Sciences, Centre for Functional Ecology, University of Coimbra, Calçada Martim de Freitas, Coimbra, 3000-456, Portugal
| | - Rui Ribeiro
- Department of Life Sciences, Centre for Functional Ecology, University of Coimbra, Calçada Martim de Freitas, Coimbra, 3000-456, Portugal
| | - Isabel Lopes
- CESAM & Department of Biology, University of Aveiro, Aveiro, 3810-193, Portugal
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Simões S, Canhoto C, Bärlocher F, Gonçalves AL. Hydrological contraction patterns and duration of drying period shape microbial-mediated litter decomposition. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 785:147312. [PMID: 33957592 DOI: 10.1016/j.scitotenv.2021.147312] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 04/19/2021] [Accepted: 04/19/2021] [Indexed: 06/12/2023]
Abstract
The length and number of streams experiencing intermittency is expected to increase in response to human population growth, associated water use, and climate change. In these streams, habitat contraction may occur at distinct rates giving rise to drying periods of distinct duration. To date, the impact of drought installation rate and duration have been mostly overlooked. In this microcosm study, stream conditioned oak leaf litter was subjected to either a short (5 weeks) or a long (8 weeks) drying period, originating from a very slow, slow, or abrupt contraction. The effects of these treatments were compared at the end of the drying period in terms of microbial-mediated litter mass loss, fungal biomass, respiration, and sporulation rates. A very slow contraction pattern led to 1.3 times higher mass loss than both slow or abrupt contraction. Fungal biomass, respiration and sporulation rates were up to 2.3 times lower under slow than abrupt contraction. Both drying period durations inhibited leaf decomposition, suggesting an early, critical effect of drying on microbial-mediated processing, regardless of contraction pattern. This seems to be related to an impoverishment of leaf associated fungal communities and resultant lower functional efficacy - species richness decreased by up to 75% in response to a long (vs. short) drying period, despite the maintenance of mycelial biomass. Our results show the relevance of aquatic hyphomycetes to litter decomposition in dry streambeds, particularly following slower habitat contraction patterns. Faster wet-to-dry transitions and longer drying periods strongly impaired microbial functioning, with potential impacts on global processing rates and cascading effects through changes of detritus quality. If confirmed in field tests, such impacts on stream functioning may be mitigated by preserving riparian forests, which may protect against extreme drying events by buffering temperature changes.
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Affiliation(s)
- S Simões
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal.
| | - C Canhoto
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal.
| | - F Bärlocher
- Department of Biology, Mt. Allison University, Sackville E4L1G7, New Brunswick, Canada.
| | - A L Gonçalves
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal.
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Oliveira R, Martínez A, Gonçalves AL, Almeida Júnior ES, Canhoto C. Salt pulses effects on in-stream litter processing and recovery capacity depend on substrata quality. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 783:147013. [PMID: 33872895 DOI: 10.1016/j.scitotenv.2021.147013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 03/29/2021] [Accepted: 04/04/2021] [Indexed: 06/12/2023]
Abstract
Human activities have greatly extended and intensified freshwater salinization, which threatens the structure and functioning of streams and rivers. Research on salt effects on in-stream processes has been strongly biased towards chronic salinization at constant levels. The aim of this study was to assess microbial mediated decomposition of two leaf species contrasting in quality (alder and oak) and associated descriptors, during salt-pulsed contamination (salinization period) and after cessation of salt additions (recovery period). Leaves were incubated in a mountain stream (central Portugal) longitudinally divided over 22 m. Half of the stream (salinized half) was subjected to daily short-term sharp salinity increases (conductivity up to ~48 mS cm-1) during 7 days while the other half (control half) was used as control. During the salinization period, salt exposure negatively affected mass loss and microbial respiration rate of alder (high-quality resource) while effects on fungal sporulation rate were independent of leaf quality. Fungal biomass was not impacted. After the recovery period, mass loss and respiration rate in both leaf species were similar between experimental stream halves. Fungal biomass associated with oak was enhanced and sporulation rate of alder, maintained in the previously salinized half, remained depressed. These results point out that the effects of salt pulses may be more deleterious in streams exclusively lined by high (vs. low) quality riparian trees as a result of a less efficient microbial-mediated leaf processing, and a reduced contribution to the conidial pool, even beyond the salinization period.
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Affiliation(s)
- Ricardo Oliveira
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
| | - Aingeru Martínez
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal.
| | - Ana Lúcia Gonçalves
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
| | - Edivan S Almeida Júnior
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
| | - Cristina Canhoto
- Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
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Niedrist GH, Cañedo-Argüelles M, Cauvy-Fraunié S. Salinization of Alpine rivers during winter months. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2021; 28:7295-7306. [PMID: 33029775 PMCID: PMC7840655 DOI: 10.1007/s11356-020-11077-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 09/30/2020] [Indexed: 05/27/2023]
Abstract
Human-induced (i.e., secondary) salinization affects aquatic biodiversity and ecosystem functioning worldwide. While agriculture or resource extraction are the main drivers of secondary salinization in arid and semi-arid regions of the world, the application of deicing road salt in winter can be an important source of salts entering freshwaters in cold regions. Alpine rivers are probably affected by salinization, especially in highly populated mountain regions, although this remains to be explored. In this study, we analyzed multi-year conductance time series from four rivers in the European Alps and demonstrated that the application of deicing road salt is linked to peaking rivers' salinity levels during late winter/early spring. Especially in small catchments with more urban surfaces close to the rivers, conductance increased during constant low-flow periods in late winter and was less correlated with discharge than in summer. Thus, our results suggest that small rivers highly connected to urban infrastructures are prone to considerable salinity peaks during late winter/early spring. Given the low natural level of salinities in Alpine rivers, the aquatic biodiversity might be significantly affected by the recorded changes in conductance, with potential consequences on ecosystem functioning. Thereby, we urge the research community to assess the impact of secondary salinization in Alpine rivers and call for an implementation of management practices to prevent the degradation of these pristine and valuable ecosystems.
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Affiliation(s)
- Georg H Niedrist
- Department of Ecology, River and Conservation Research, University of Innsbruck, Innsbruck, Austria.
| | - Miguel Cañedo-Argüelles
- Freshwater Ecology, Hydrology and Management group (FEHM), Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals, Institut de Recerca de l'Aigua (IdRA), Universitat de Barcelona, Barcelona, Spain
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Cañedo-Argüelles M, Kefford B, Schäfer R. Salt in freshwaters: causes, effects and prospects - introduction to the theme issue. Philos Trans R Soc Lond B Biol Sci 2018; 374:rstb.2018.0002. [PMID: 30509904 DOI: 10.1098/rstb.2018.0002] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/25/2018] [Indexed: 01/07/2023] Open
Abstract
Humans are globally increasing the salt concentration of freshwaters (i.e. freshwater salinization), leading to significant effects at the population, community and ecosystem level. The present theme issue focuses on priority research questions and delivers results that contribute to shaping the future research agenda on freshwater salinization as well as fostering our capacity to manage salinization. The issue is structured along five topics: (i) the estimation of future salinity and evaluation of the relative contribution of the different drivers; (ii) the physiological responses of organisms to alterations in ion concentrations with a specific focus on the osmophysiology of freshwater insects and the responses of different organisims to seawater intrusion; (iii) the impact of salinization on ecosystem functioning, also considering the connections between riparian and stream ecosystems; (iv) the role of context in moderating the response to salinization. The contributions scrutinise the role of additional stressors, biotic interactions, the identify of the ions and their ratios, as well as of the biogeographic and evolutionary context; and (v) the public discourse on salinization and recommendations for management and regulation. In this paper we introduce the general background of salinization, outline research gaps and report key findings from the contributions to this theme issue.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.
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Affiliation(s)
- Miguel Cañedo-Argüelles
- Grup de recerca FEHM (Freshwater Ecology, Hydrology and Management), Departament de Biologia Evolutiva, Ecologia i Ciència Ambientals, Universitat de Barcelona, Avda Diagonal 643, 08028 Barcelona, Spain
| | - Ben Kefford
- Institute for Applied Ecology, University of Canberra, Australian Capital Territory 2601, Australia
| | - Ralf Schäfer
- Department of Quantitative Landscape Ecology, University Koblenz-Landau, Fortstr. 7, 76829 Landau, Germany
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Berger E, Frör O, Schäfer RB. Salinity impacts on river ecosystem processes: a critical mini-review. Philos Trans R Soc Lond B Biol Sci 2018; 374:rstb.2018.0010. [PMID: 30509912 DOI: 10.1098/rstb.2018.0010] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/15/2018] [Indexed: 11/12/2022] Open
Abstract
In many dry parts of the world, salinization of water resources threatens freshwater biodiversity and the livelihood of people. However, ecological impact studies remain scarce. Here, we review field-observations of salinity impacts on ecosystem processes such as leaf decomposition, metabolism, biomass production and nutrient cycling, with a special emphasis on dryland ecosystems. In addition, we discuss the potential linkages of these processes to ecosystem service delivery-the benefits that humans derive from ecosystems-as additional nature conservation arguments and the challenges associated with this endeavour.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.
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Affiliation(s)
- Elisabeth Berger
- Department of Quantitative Landscape Ecology, University Koblenz-Landau, Fortstr. 7, 76829 Landau, Germany
| | - Oliver Frör
- Department of Environmental Economics, University Koblenz-Landau, Fortstr. 7, 76829 Landau, Germany
| | - Ralf B Schäfer
- Department of Quantitative Landscape Ecology, University Koblenz-Landau, Fortstr. 7, 76829 Landau, Germany
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Entrekin SA, Clay NA, Mogilevski A, Howard-Parker B, Evans-White MA. Multiple riparian-stream connections are predicted to change in response to salinization. Philos Trans R Soc Lond B Biol Sci 2018; 374:20180042. [PMID: 30509922 PMCID: PMC6283969 DOI: 10.1098/rstb.2018.0042] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/10/2018] [Indexed: 12/20/2022] Open
Abstract
Secondary freshwater salinization, a common anthropogenic alteration, has detrimental, lethal and sub-lethal effects on aquatic biota. Ions from secondary salinization can become toxic to terrestrial and aquatic organisms when exposed to salinized runoff that causes periodic high-concentration pulses. Gradual, low-level (less than 1000 ppm salinity) increases in salt concentrations are also commonly documented in regions with urbanization, agriculture, drilling and mining. Despite widespread low-level salt increases, little is known about the biological and ecological consequences in coupled riparian-stream systems. Recent research indicates lethal and even sub-lethal levels of ions can subsidize or stress microbial decomposer and macroinvertebrate detritivores that could lead to alterations of three riparian-stream pathways: (i) salinized runoff that changes microbial decomposer and macroinvertebrate detritivore and algae performance leading to changes in composition and processing of detrital pools; (ii) riparian plant salt uptake and altered litter chemistry, and litterfall for riparian and aquatic detritivores and their subsequent enrichment, stimulating decomposition rates and production of dissolved and fine organic matter; and (iii) salt consumption in salinized soils could increase riparian detritivore growth, decomposition and dissolved organic matter production. Subsidy-stress and reciprocal flows in coupled riparian-stream connections provide frameworks to identify the extent and magnitude of changes in detrital processing from salinization.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.
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Affiliation(s)
- Sally A Entrekin
- Department of Biology, University of Central Arkansas, Conway, AR 72035, USA
- Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Natalie A Clay
- School of Biological Sciences, Louisiana Tech University, Ruston, LA 71272, USA
| | | | - Brooke Howard-Parker
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA
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