Salinization of freshwater ecosystems represents a potential threat to biodiversity, but the distribution of salinity tolerance among freshwater organisms and its functional consequences are understudied. In this study, we reviewed global patterns of salinity tolerance across a broad range of freshwater organisms. Specifically, we compared published data on LC50 (a metric of salinity tolerance) across climatic regions, taxa, and functional feeding groups (FFGs). We found that microinvertebrates were more sensitive to salinity than vertebrates and macroinvertebrates. Within aquatic insects, there was considerable variability in tolerance across FFGs. Specifically, scrapers, gatherers, and filterers were more sensitive on average than omnivores, shredders, and predators. Thus, we predict that increasing salinization can negatively impact trophic diversity and in turn cause overall changes in the structure and function of freshwater ecosystems. We also identified both historical exposure and taxonomic affinity as potential drivers of contemporary salinity tolerance across freshwater organisms. Finally, we found important gaps in our understanding of the potential impacts of salinization on freshwater biodiversity, particularly in regions expected to be affected by increased salinization due to climate change and secondary salinization. Understanding the differential vulnerability of freshwater taxa is critical to predicting the ecosystem impacts of salinization, and informing conservation and management decisions.
... As regard of biodiversity, global analysis predict that consequences of freshwaters salinization would have great repercussion by reducing species richness, modifying species dominance patterns and altering population dynamics leading to modifications in the trophic webs structure (Castillo et al., 2018;Vidal et al., 2021). Biodiversity impacts are expected to occur not only at the taxonomic but also at the functional levels (Piscart et al., 2006;Suárez et al., 2017;Helenius et al., 2017;Gutierrez et al., 2018) which might impose serious risks for the entire ecosystem functioning and services provision (Iglesias, 2020). ...
... Biodiversity impacts are expected to occur not only at the taxonomic but also at the functional levels (Piscart et al., 2006;Suárez et al., 2017;Helenius et al., 2017;Gutierrez et al., 2018) which might impose serious risks for the entire ecosystem functioning and services provision (Iglesias, 2020). Even though researches show clear evidences of diversity changes due to salinity increase on different aquatic communities, experimental and modeling studies reveal that microinvertebrates would be more sensitive than other aquatic animals (Castillo et al., 2018). ...
Salinization of aquatic systems is predicted to increase due to climate and land use changes. Nevertheless, community responses may be different according to the ecosystem characteristics and contextual scenarios. Small flowing waters are particularly vulnerable to salinization, which may impact on the biodiversity and ecosystem processes, but this remains unclear. We conducted a study in 42 lowland streams characterized by overall high nutrient levels along a salinity gradient between 2 and 160 g L-1 to analyze changes in zooplankton structural and functional metrics, and the grazing effects of zooplankton on phytoplankton affecting the energy transfer. Generalized additive models revealed that the analyzed metrics were relatively influenced by salinity, with factors related to trophic conditions playing an important role as well. Total abundance and biomass decreased along the salinity gradient while increasing at intermediate soluble reactive phosphorous concentrations (SRP) in the former and with a linear increase in the SRP in the latter case. Taxonomic richness decreased with salinity and dissolved inorganic nitrogen, with species replacement toward saline-tolerant ones according to the compositional and optimums analyses. In opposite, functional richness did not display any specific trend within the environmental gradients. This explains why zooplankton compositional changes were not reflected into shifts in the grazing pattern on phytoplankton, which was in turn driven by SRP and dissolved oxygen concentrations. Further research is a critical requirement in these poorly studied ecosystems for planning mitigation actions to the co-occurrence of eutrophication and salinization in a fast changing world.
... It is well established that the photosynthetic activity (Silva, 2000), and community structure of diatoms (Dixit et al., 1999;Virtanen and Soininen, 2012;Schröder et al., 2015;Heikkinen et al., 2022) are both affected by prolonged exposure to salt. Yet, characterising salinity's specific influence on species composition and freshwater ecosystem functioning remains challenging (Castillo et al., 2018;Stenger-Kovács et al., 2023). In addition, increasing water temperature and reduced water flow velocity are both important factors that influence periphyton, though water chemistry is perceived to play a more crucial role in driving their community composition (Hering et al., 2006;Marcel et al., 2017). ...
OPEN ACCESS PAPER - Field observations form the basis of the majority of studies on microphytobenthic algal communities in freshwater ecosystems. Controlled mesocosm experiments data are comparatively uncommon. The few experimental mesocosm studies that have been conducted provide valuable insights into how multiple stressors affect the community structures and photosynthesis-related traits of benthic microalgae. The recovery process after the stressors have subsided, however, has received less attention in mesocosm studies. To close this gap, here we present the results of a riparian mesocosm experiment designed to investigate the effects of reduced flow velocity, increased salinity and increased temperature on microphytobenthic communities. We used a full factorial design with a semi-randomised distribution of treatments consisting of two levels of each stressor (2 × 2 × 2 treatments), with eight replicates making a total of 64 circular mesocosms, allowing a nuanced examination of their individual and combined influences. We aimed to elucidate the responses of microalgae communities seeded from stream water to the applied environmental stressors. Our results showed significant effects of reduced flow velocity and increased temperature on microphytobenthic communities. Recovery after stressor treatment led to a convergence in community composition, with priority effects (hypothesized to reflect competition for substrate between resident and newly arriving immigrant taxa) slowing down community shifts and biomass increase. Our study contributes to the growing body of literature on the ecological dynamics of microphytobenthos and emphasises the importance of rigorous experiments to validate hypotheses. These results encourage further investigation into the nuanced interactions between microphytobenthos and their environment and shed light on the complexity of ecological responses in benthic systems.
... Unfortunately, despite the fact that both stressors interact frequently in natural environments, there is very little information about the joint effects of glyphosate and salinity on cladocerans. This interaction could become even more frequent under the expected climate change scenarios, where increased salinization seems to be one of the consequences for freshwater biota (Castillo et al. 2018;Cañedo-Argüelles et al. 2019) that are typically more sensitive to climateinduced impacts than terrestrial organisms (Comte andGrenouillet 2013, López-Valcárcel et al. 2023). ...
Daphnia spinulata Birabén, 1917 is an endemic cladoceran species, frequent in the zooplankton communities of the shallow lakes of the Pampean region of Argentina. These lakes have varying salinity levels and, being located in agricultural areas, are frequently subject to pesticide pollution. This study aimed to determine the effects of the herbicide glyphosate (Panzer Gold®) in combination with different salinity levels on the biological parameters of D. spinulata and its recovery ability after a short exposure. Three types of assays were performed: an acute toxicity test, a chronic assessment to determine survival, growth and reproduction, and recovery assays under optimal salinity conditions (1 g L⁻¹). The LC50-48 h of glyphosate was 7.5 mg L⁻¹ (CL 3.15 to 11.72). Longevity and the number of offspring and clutches were significantly reduced due to the combined exposure of glyphosate and increased salinity. The timing of the first offspring did not recover after glyphosate exposure. Our results reveal that D. spinulata is sensitive to the herbicide Panzer Gold® at concentrations well below those indicated in the safety data sheet of this commercial formulation, which causes stronger negative effects in conditions of higher salinity. Further research is needed to shed light on the sensitivity of this cladoceran to glyphosate and its variability under other interactive stress factors.
... Over the last decades, the biodiversity of numerous aquatic ecosystems has been shown to be under direct and indirect increased salinity stress due to causes as diverse as the use of road deicing salts draining to lakes and rivers, saltwater intrusions in coastal areas due to rising sea levels, or increased evaporation accompanying global temperature changes (Cunillera-Montcusí et al., 2022). Salinization has been shown to impact ecological processes, trophic networks, functional trait diversity, and community composition in different ecosystems (e.g., Cañedo-Argüelles et al., 2013;Szöcs et al., 2014;Hintz and Relyea, 2019;Castillo et al., 2018;Tweedley et al., 2019;Röthig et al., 2023). Nevertheless such large scale variations are fundamentally rooted in the abil-ity of species to regulate their hydro-mineral balance and to minimize their osmoregulatory costs (Kinne, 1964;Kültz, 2015;Silver and Donini, 2021). ...
... Such negative effects of a wide range of salinization values, possibly being invertebrate species specific (Castillo et al. 2018), suggests that alterations in ion concentrations may have important implications for aquatic ecosystem functioning through reduction of shredder biomass. Here, we reinforce the need to evaluate long-term effects of freshwater salinization (Canhoto et al. 2023) particularly on key leaf consumers with distinct tolerance to salinity; our results were obtained with S. festiva, a case-building shredder, described as potentially presenting higher tolerance to salinity and other pollutants than non-case forming species (Castillo et al. 2018). ...
Secondary salinization is a growing concern for freshwaters worldwide. The lethal and sub-lethal effects on shredders are known, but not whether these result from direct exposure to contaminated aquatic medium and/or from indirect effects of distinct substrate quality through fungal conditioning in salinized media. Here, chestnut and oak leaves were conditioned for 4 weeks in reference (Cond0, 0 g/l NaCl) or salinized (Cond3, 3 g/l NaCl) media before being offered to the shredder Schizopelex festiva maintained in reference (Inv0) or salinized (Inv3) media. Fungal biomasses associated with leaf litter and consumption, respiration rates, growth, survival, and feeding preference of S. festiva were assessed. We found lower fungal biomass in both leaf species conditioned in Cond3 medium. Consumption rates were higher for oak than chestnut, and in Inv0 than Inv3, but were not affected by conditioning media. Growth was also affected by invertebrate media (Inv0 > Inv3), while Inv3 led to the lowest survival. Schizopelex festiva preferred Cond0 over Cond3 oak leaves only in Inv0. Results strongly suggest that direct exposure to salinized media is a main pathway of salt toxicity to shredders through a generalized reduction in invertebrates’ metabolic rates when facing salt stress. Salt addition to the media may result in an energetic investment in osmotic regulation at the expense of consumption and growth, with consequences for invertebrate survival. Potential negative effects of salt contamination on shredders’ ability to select more nutritious food items may contribute to cascading effects throughout the stream food webs, particularly in streams lined with more recalcitrant leaf litter.
... Salt is introduced to freshwater ecosystems by various routes including the mobilization of natural salts (Herczeg et al. 2001;Cañedo-Argüelles et al. 2013) and anthropogenic salinization including e.g., humanaccelerated weathering, mining, vegetation removal and application of fertilizers, irrigation practices, and road de-icing salts (Cañedo-Argüelles et al. 2013;Dugan et al. 2017). Eukaryotic microbial community shifts caused by salinity are well documented (von Alvensleben et al. 2016;Castillo et al. 2018;Li et al. 2018;Nuy et al. 2018). Similarly, effects on the growth rates of individual taxa are well documented. ...
Human activities and climate change cause abiotic factors to fluctuate through time, sometimes passing thresholds for organismal reproduction and survival. Multiple stressors can independently or interactively impact organisms; however, few studies have examined how they interact when they overlap spatially but occur asynchronously. Fluctuations in salinity have been found in freshwater habitats worldwide. Meanwhile, heatwaves have become more frequent and extreme. High salinity pulses and heatwaves are often decoupled in time but can still collectively impact freshwater zooplankton. The time intervals between them, during which population growth and community recovery could happen, can influence combined effects, but no one has examined these effects. We conducted a mesocosm experiment to examine how different recovery times (0‐, 3‐, 6‐week) between salt treatment and heatwave exposure influence their combined effects. We hypothesized that antagonistic effects would appear when having short recovery time, because previous study found that similar species were affected by the two stressors, but effects would become additive with longer recovery time since fully recovered communities would respond to heatwave similar to undisturbed communities. Our findings showed that, when combined, the two‐stressor joint impacts changed from antagonistic to additive with increased recovery time between stressors. Surprisingly, full compositional recovery was not achieved despite a recovery period that was long enough for population growth, suggesting legacy effects from earlier treatment. The recovery was mainly driven by small organisms, such as rotifers and small cladocerans. As a result, communities recovering from previous salt exposure responded differently to heatwaves than undisturbed communities, leading to similar zooplankton communities regardless of the recovery time between stressors. Our research bolsters the understanding and management of multiple‐stressor issues by revealing that prior exposure to one stressor has long‐lasting impacts on community recovery that can lead to unexpected joint effects of multiple stressors.
Stream ecosystem functioning is often impaired by warming and salinization, but the joint effect of both environmental stressors on key processes such as leaf litter decomposition is virtually unknown, particularly in the tropics. We experimentally explored how increased water temperature (26, 29 and 32°C) and salinity (no salt addition, 0.1, 1.0 and 10 g l⁻¹ NaCl added) affected the rates of total, microbial and detritivore-mediated decomposition, in stream microcosms containing leaf litter of Ficus insipida and larvae of Chironomus sp. collected from tropical streams. Effects of temperature were strong and consistent with previous findings: it promoted microbial decomposition and reduced decomposition mediated by detritivores, which showed greater feeding activity at 26°C. Salinity was negatively correlated with microbial decomposition at 32°C; it also had a negative influence on detritivore-mediated decomposition, which was nevertheless non-significant due to the high detritivore mortality at higher salinities. Notably, total decomposition was reduced with the joint presence of both factors (32°C and salt addition treatments, compared to 26°C and no salt addition), indicating the existence of additive effects and highlighting the relevance of multiple-stressor contexts when assessing the consequences of global change on stream ecosystems.
Urban waterbodies provide important services to humans and play a considerable role in biodiversity conservation. Yet, we still know very little about how urban pond ecosystems may respond to ongoing and future stresses operating at multiple spatial scales. Here we examined the littoral macroinvertebrates in 20 urban waterbodies as an indicator community to assess how local waterbody condition and urban land use affected their taxonomic and functional composition. Although macroinvertebrates were diverse (total richness of 60 taxa ranging from 10 to 41), they were dominated by two major taxonomic groups, the Diptera Chironomidae (36%) and the Annelida Oligochaeta (22%), which largely represented the dominant functional group of the Collectors-Gatherers (63%). Fuzzy clustering identified four different types of communities based on taxonomic and functional groups. These reflected inversed gradients in the dominance of Collectors-Gatherers versus ponds with higher abundances of Herbivores (Gastropoda Pulmonata, Hemiptera, Trichoptera), Collectors-Filterers (Gastropoda Prosobranchia, Crustacea Ostracoda), Predators (Odonata), and Parasites (Nematoda, Hydracarina). Distance-based redundancy analysis identified macrophyte cover and green landscape (parks and buildings with yards) within a 100 m radius as the best drivers of macroinvertebrate taxonomic and functional composition. We also noted a comparable variance explained by models that included parks within a 500 m radius or buildings with yards within a 2000 m radius. Our results have implications for urban landscape management as it suggests that human alteration in the urban landscape can be transmitted at least up to 2000 m from ponds.
Daphnia spinulata Birabén, 1917 is an endemic cladoceran species, frequent in the zooplankton communities of the shallow lakes of the Pampean region of Argentina. These lakes have varying salinity levels and, being located in agricultural areas, are frequently subject to pesticide pollution. This study aimed to determine the effects of the herbicide glyphosate (Panzer Gold®) in combination with different salinity levels on the biological parameters of D. spinulata and its recovery ability after a short exposure. Three types of assays were performed: an acute toxicity test, a chronic assessment to determine survival, growth and reproduction, and recovery assays under optimal salinity conditions (1 g L − 1 ). The LC 50 -48h of glyphosate was 7.5 mg L − 1 (3.15–11.72). Longevity and the number of offspring and clutches were significantly reduced by glyphosate and high salinity exposure, whether in isolation or combined. The timing of the first offspring did not recover after glyphosate exposure. Our results reveal that D. spinulata is sensitive to the herbicide, which causes stronger negative effects in conditions of higher salinity. Further research is needed to shed further light on the sensitivity of this cladoceran to glyphosate and its variability under other interactive stress factors.
Megaprojects pose a major global environmental challenge. For instance, the forthcoming construction of the Nicaraguan Canal has generated controversy regarding its social and environmental consequences. To some, it will represent an unparalleled environmental catastrophe; to others, it will lead to net environmental and social benefits. In both cases, the Panama Canal emerges as an analogy to inform the environmental and social fate of Nicaragua. In our view, this comparison is incomplete and does not accurately represent the social and environmental realities of the two countries, and therefore, it might be of limited use for predicting the future of Nicaragua. Our analysis—based on evidence from the literature—revealed three emerging themes. First, our current understanding of the long-term environmental consequences of the two Canals in Central America is rather limited, even after 100 years of experience in Panama. Second, the historical, environmental and political differences between the two countries make the Panama Canal a poor predictor for the environmental and social fate of Nicaragua. Finally, previous assessments of the consequences of both megaprojects might be biased by a focus on forest conservation alone. This suggests that the apparent environmental and social benefits provided by such megaprojects might be more marginal than expected. This calls for a deeper analysis of costs and benefits of the construction and management of the two Canals in the Central American region, and their impacts on the natural world. These uncertainties might be a common consequence of many large-scale megaprojects around the world.
Anthropogenic salinization of rivers is an emerging issue of global concern, with significant adverse effects on biodiversity and ecosystem functioning. Impacts of freshwater salinization on biota are strongly mediated by evolutionary history, as this is a major factor determining species physiological salinity tolerance. Freshwater insects dominate most flowing waters, and the common lotic insect orders Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies) are particularly salt-sensitive. Tolerances of existing taxa, rapid adaption, colonization by novel taxa (from naturally saline environments) and interactions between species will be key drivers of assemblages in saline lotic systems. Here we outline a conceptual framework predicting how communities may change in salinizing rivers. We envision that a relatively small number of taxa will be saline-tolerant and able to colonize salinized rivers (e.g. most naturally saline habitats are lentic; thus potential colonizers would n
Freshwater macroinvertebrates provide a useful and reliable indicator of the health of our rivers, streams, ponds and wetlands. As environmental awareness within the community increases, there is an increasing interest in the need to assess the health of our local waterways and school curriculums are changing to reflect this important ecological trend. The Waterbug Book provides a comprehensive and accurate identification guide for both professionals and non-professionals. It contains an easy-to-use key to all the macroinvertebrate groups and, for the first time, high quality colour photographs of live specimens. It provides a wealth of basic information on the biology of macroinvertebrates, and describes the SIGNAL method for assessing river health. The Waterbug Book is full of practical tips about where to find various animals, and what their presence can tell about their environment. Winner of the 2003 Eureka Science Book Prize and the 2003 Whitley Medal.
The Field Guide to Freshwater Invertebrates of North America focuses on freshwater invertebrates that can be identified using at most an inexpensive magnifying glass. This Guide will be useful for experienced nature enthusiasts, students doing aquatic field projects, and anglers looking for the best fish bait, lure, or fly. Color photographs and art, as well as the broad geographic coverage, set this guide apart. 362 color photographs and detailed descriptions aid in the identification of speciesIntroductory chapters instruct reader on how to use book, different inland water habitats and basic ecological relationships of freshwater invertebratesBroad taxonomic coverage is more comprehensive than any guide currently available.
