The treatability of seven wastewater samples generated by a textile digital printing industry was... more The treatability of seven wastewater samples generated by a textile digital printing industry was evaluated by employing 1) anammox-based processes for nitrogen removal 2) microalgae (Chlorella vulgaris) for nutrient uptake and biomass production 3) white-rot fungi (Pleurotus ostreatus and Phanerochaete chrysosporium) for decolorization and laccase activity. The biodegradative potential of each type of organism was determined in batch tests and correlated with the main characteristics of the textile wastewaters through statistical analyses. The maximum specific anammox activity ranged between 0.1 and 0.2 g N g VSS-1 d-1 depending on the sample of wastewater; the photosynthetic efficiency of the microalgae decreased up to 50% during the first 24 hours of contact with the textile wastewaters, but it improved from then on; Pleurotus ostreatus synthetized laccases and removed between 20–62% of the colour after 14 days, while the enzymatic activity of Phanerochaete chrysosporium was inhi...
<p>Phytobenthos is the dominant primary producer in streams and sustains, w... more <p>Phytobenthos is the dominant primary producer in streams and sustains, with the allochthonous organic matter inputs, the higher trophic levels. Among the different groups that constitute the phytobenthos community some, especially diatoms, have been studied deeply while others remain quite overlooked. Hence, a characterisation of the overall phytobenthos community is needed, considering all the main taxonomic groups (diatoms, green algae, cyanobacteria and red algae), as related to the environmental conditions characterizing different alpine streams. Moreover, despite the ecological role played by the phytobenthos the knowledge about the factors that control the variations of the community among streams and throughout the different seasons is still poor. Among the different drivers that regulate the phytobenthos component, a pivotal factor is the occurrence of high-flow events that, controlling the stability of riverbed substrates, influences both the phyto and the zoobenthos composition and distribution. Thus, the frequency and the magnitude of flow disturbances are determinant in regulating the phytobenthos density and the recolonization patterns. The aim of this work was to characterize and compare the phytobenthos communities in different streams highlighting the role of the flow regulation due to hydropower reservoirs accounting for the influence of the lithology and the seasonality. The presented phytobenthos data derive from a one-year sampling campaign in four alpine streams representative of different flow conditions (natural vs regulated flow discharge) and lithology (silicate vs carbonate). The riverbed coverage has been estimated monthly in each stream and the biomass has been quantified. In lab, phytobenthos samples have been analysed to measure the photosynthetic activity and define their composition. The main groups (cyanobacteria, green algae, diatoms and algae with phycoerythrin) have been determined both by phyto-PAM deconvolution and by the quantification of the photosynthetic pigments. In order to estimate the bed disturbance, painted stones of different size classes were located in regular arrays along three transversal transects and the distance travelled was measured during every sampling. The preliminary results indicate that regulated streams seem characterized by a greater algae biomass possibly due to a more stable environment. Concerning the community composition, the percentage of diatoms is significatively higher in silicate substrates. Despite the few hours of light, winter promotes phytobenthos colonisation especially for the low frequency of relevant high-flow events but also for the absence of the shadow due to tree canopy on the riverbed.</p>
In the last decade, large scale biomonitoring programs have been implemented to obtain a robust u... more In the last decade, large scale biomonitoring programs have been implemented to obtain a robust understanding of freshwater in the name of helping to inform and develop effective restoration and management plans. A comprehensive biomonitoring dataset on the macroinvertebrate assemblages inhabiting the rivers of the Po Valley (northern Italy), comprised a total of 6762 sampling events (period 2007–2018), was analyzed in this study in order to examine coarse spatial and temporal trends displayed by biotic communities. Our results showed that macroinvertebrate compositions and derived structural and functional metrics were controlled by multiple environmental drivers, including altitude and climate (large scale), as well as habitat characteristics (local scale). Altitude proved to be the primary geographic driver, likely due to its association with thermal and precipitation regimes, thus explaining its overriding influence on macroinvertebrate assemblages. Significant temporal variatio...
• Current biomonitoring approaches are widely used but have some limitations. • DNA metabarcoding... more • Current biomonitoring approaches are widely used but have some limitations. • DNA metabarcoding provides a new complementary tool for biomonitoring. • Metabarcoding allows extending the range of taxa used as bioindicators. • Metabarcoding data could be used to establish molecular metrics and indices. • Future work should standardise procedures and improve data analysis. The bioassessment of aquatic ecosystems is currently based on various biotic indices that use the occurrence and/ or abundance of selected taxonomic groups to define ecological status. These conventional indices have some limitations, often related to difficulties in morphological identification of bioindicator taxa. Recent development of DNA barcoding and metabarcoding could potentially alleviate some of these limitations, by using DNA sequences instead of morphology to identify organisms and to characterize a given ecosystem. In this paper, we review the structure of conventional biotic indices, and we present the results of pilot metabarcoding studies using environmental DNA to infer biotic indices. We discuss the main advantages and pitfalls of metabarcoding approaches to assess parameters such as richness, abundance, taxonomic composition and species ecological values, to be used for calculation of biotic indices. We present some future developments to fully exploit the potential of metabarcoding data and improve the accuracy and precision of their analysis. We also propose some recommendations for the future integration of DNA metabarcoding to routine biomonitoring programs.
The Water Framework Directive introduced in Europe major changes to improve the management of wat... more The Water Framework Directive introduced in Europe major changes to improve the management of water resources. This study aims to highlight some of the potential implications of its implementation for lake water monitoring in Italy. A Life+ project was launched to plan the first monitoring of lake macroinvertebrates standardized at the national level. Quantile regression analysis was used to explain different metrics of diversity describing macroin-vertebrate communities in response to twenty-one variables representing chemical, physical and morphological characteristics of the environment. Nine lakes located in two Italian regions (Piedmont and Sardinia) were analyzed covering a wide trophic spectrum, from oligotrophy to hyper-eutrophy. The lakes were sampled following the national standardized protocol with samples covering the three recognized lake zones: littoral, sublittoral, profundal. The studied lakes had high chemical variability with conductivity ranging between 53 and 561 S/cm, pH between 6.5 and 9.1, and alkalinity between 14 and 398 mg/l. The bottom sediments were characterized by fine sand (range 51–99%), followed by silt (1–35%) and clay (0–28%). When the Lake Habitat Survey was also applied to these lakes, its synthetic indices (LHMS, Lake Habitat Modification Score and LHQA, Lake Habitat Quality Assessment) produced higher values in natural lakes (mean values ± SD: LHMS = 26 ± 7, LHQA = 57 ± 3) than in the reservoirs (LHMS = 22 ± 4, LHQA = 52 ± 6). In all lakes, macroin-vertebrates mainly consisted of chironomids and oligochaetes characterized by relative abundances up to 80% and >90%, respectively. Using quantile regression to evaluate limiting responses, only two variables, namely sampling depth and oxygen percent saturation (oxygen content), resulted the ones that best explained all the analyzed metrics of diversity of the macroinvertebrate communities. Depth and oxygen were then used to suggest synthetic models describing the various metrics of potential community diversity. These models can help the environmental agencies responsible for monitoring at the national level in distinguishing entire lakes or part of them with high biodiversity from those in altered conditions and then address remediation efforts toward the water bodies with the most critical conditions. Such approach could also be used to optimize the sampling procedures for the application of the Benthic Quality Index for lakes currently adopted at national level.
Various factors, such as habitat availability , competition for space, predation, temperature, nu... more Various factors, such as habitat availability , competition for space, predation, temperature, nutrient supplies, presence of waterfalls, flow variability and water quality, control the abundance, distribution and productivity of stream-dwelling organisms. Each of these factors can influence the response of the density of organisms to a specific environmental gradient, inflating variability and making difficult to understand the possible causal relationship. In our study, we used quantile regression mixed models and Akaike's information criterion as an indicator of goodness to examine two different datasets, one belonging to Italy and one belonging to Finland, and to detect the limiting action of selected environmental variables. In the Italian dataset, we studied the relationships among five macroinvertebrate families and three physical habitat characteristics (water velocity, depth and substratum size); in the Finnish dataset the relationships between taxa richness and 16 environmental characteristics (chemical and physical). We found limiting relationships in both datasets and validated all of them on different datasets. These relationships are quantitative and can be used to predict the range of macroinvertebrate densities or taxa richness as a function of environmental characteristics. They can be a tool for management purposes, providing the basis for habitat-based models and for the development of ecological indices.
The impact of prospective climate change on the hydrological and ecological status of the mountai... more The impact of prospective climate change on the hydrological and ecological status of the mountain stretch of the Serio river (ca. 300 km 2) in the Northern Italian Alps was investigated. A hydrological model was used to mimic theflow regime, and experimental suitability curves were used to assess weighted usable area (WUA) for brown trout (Salmo trutta) in different stages (adult, young, and spawning), and four macroinvertebrates families (Leuctridae, Heptageniidae, Limnephilidae, and Limoniidae). Discharge-WUA curves were obtained using instream flow incremental methodology/physical habitat simulation system (IFIM-PHABSIM), and a seasonal WUA assessment was carried out. The future (until 2100) hydrological cycle was projected using outputs from two general circulation models from Assessment Report 5 of the Intergovernmental Panel on Climate Change (IPCC). The results display a potential for a large flow decrease yearly, until −60% at 2050 and −56% at 2090. Spring melt peaks will be largely dampened, with the largest projected decrease of −60% in 2050 and −66% in 2090. Also fall flows will be largely smoothed, down to −70% for 2050 and −56% for 2090. To quantify habitat quality, a specific quantile WUA 20% , was used and exceeded presently for 292 days in a year, and the percentage of critical days n c% when WUA < WUA 20%. Adult trouts will have decreasing n c% yearly (from 20% now to down to 13% in 2090), increasing in winter and spring and decreasing in fall. Young trouts will have decreasing n c% yearly (from 20% now to down to 2% in 2040 and 2090), but increasing in winter. Spawning, occurring in winter, will have lower n c% (from 16% now, to down to 8% in 2090). Macroinvertebrate families will have constant n c% yearly, unless for Leuctridae (from 20% now to up to 38% in 2050), and noticeable decrease of n c% in winter for Leuctridae until 2090, increase in spring and summer, and decrease in fall for all families until 2090. Correlation analysis of the WUA against weather and hydrological variables displayed that temperature is the most influencing variable, decreasing habitat suitability for all species in fall, and increasing suitability in spring, unless for young trouts.
The presence of different kinds of leaf packs (native or alien) and environmental gradients can a... more The presence of different kinds of leaf packs (native or alien) and environmental gradients can affect the composition and abundance of macroinvertebrate assemblages in freshwater ecosystems, but little is known about the interactive effects. Here, we investigated (1) how environmental gradients could influence leaf packs macroinvertebrates and (2) which was the chief factor (among water quality, mass loss of leaf packs, and flow regime) affecting macroinvertebrate assemblages in impaired streams. We analyzed leaf packs in six sites in impaired streams, characterized by wastewater discharges and dominated by pollution-tolerant macroinvertebrate species. Using principal component analysis, we defined two environmental gradients as follows: a water quality gradient, related to anthropogenic alteration, and a hydro-morphological gradient, mostly related to the catchment features. Our results pointed out that, in the tested conditions , biological metrics, such as functional groups and taxa richness, were chiefly influenced by the water quality gradient, while different leaf types in packs influenced the total taxa richness, but did not cause significant variation in the distribution and abundance of macroinverte-brate functional groups. On the contrary, the mass loss differed for different leaf types and was related to the stream and catchment features (mainly flow). This work showed that, in impaired streams, macroinvertebrate assemblages colonizing leaf packs are more influenced by water quality than by leaf types. Thus, the improvement of water quality should be the priority in restoration programs and should be achieved before any effort to restore native riparian vegetation.
One of the primary goals of biological assessment of streams is to identify which of a suite of c... more One of the primary goals of biological assessment of streams is to identify which of a suite of chemical stressors is limiting their ecological potential. Elevated metal concentrations in streams are often associated with low pH, yet the effects of these two potentially limiting factors of freshwater biodiversity are rarely considered to interact beyond the effects of pH on metal speciation. Using a dataset from two continents, a biogeochemical model of the toxicity of metal mixtures (Al, Cd, Cu, Pb, Zn) and quantile regression, we addressed the relative importance of both pH and metals as limiting factors for macro-invertebrate communities. Current environmental quality standards for metals proved to be protective of stream macroinvertebrate communities and were used as a starting point to assess metal mixture toxicity. A model of metal mixture toxicity accounting for metal interactions was a better predictor of macroinvertebrate responses than a model considering individual metal toxicity. We showed that the direct limiting effect of pH on richness was of the same magnitude as that of chronic metal toxicity, independent of its influence on the availability and toxicity of metals. By accounting for the direct effect of pH on macroinvertebrate communities, we were able to determine that acidic streams supported less diverse communities than neutral streams even when metals were below no-effect thresholds. Through a multivariate quantile model, we untangled the limiting effect of both pH and metals and predicted the maximum diversity that could be expected at other sites as a function of these variables. This model can be used to identify which of the two stressors is more limiting to the ecological potential of running waters.
Agricultural insecticides constitute a major driver of animal biodiversity loss in freshwater eco... more Agricultural insecticides constitute a major driver of animal biodiversity loss in freshwater ecosystems. However, the global extent of their effects and the spatial extent of exposure remain largely unknown. We applied a spatially explicit model to estimate the potential for agricultural insecticide runoff into streams. Water bodies within 40% of the global land surface were at risk of insecticide runoff. We separated the influence of natural factors and variables under human control determining insecticide runoff. In the northern hemisphere, insecticide runoff presented a latitudinal gradient mainly driven by insecticide application rate; in the southern hemisphere, a combination of daily rainfall intensity, terrain slope, agricultural intensity and insecticide application rate determined the process. The model predicted the upper limit of observed insecticide exposure measured in water bodies (n ¼ 82) in five different countries reasonably well. The study provides a global map of hotspots for insecticide contamination guiding future freshwater management and conservation efforts.
The treatability of seven wastewater samples generated by a textile digital printing industry was... more The treatability of seven wastewater samples generated by a textile digital printing industry was evaluated by employing 1) anammox-based processes for nitrogen removal 2) microalgae (Chlorella vulgaris) for nutrient uptake and biomass production 3) white-rot fungi (Pleurotus ostreatus and Phanerochaete chrysosporium) for decolorization and laccase activity. The biodegradative potential of each type of organism was determined in batch tests and correlated with the main characteristics of the textile wastewaters through statistical analyses. The maximum specific anammox activity ranged between 0.1 and 0.2 g N g VSS-1 d-1 depending on the sample of wastewater; the photosynthetic efficiency of the microalgae decreased up to 50% during the first 24 hours of contact with the textile wastewaters, but it improved from then on; Pleurotus ostreatus synthetized laccases and removed between 20–62% of the colour after 14 days, while the enzymatic activity of Phanerochaete chrysosporium was inhi...
&amp;lt;p&amp;gt;Phytobenthos is the dominant primary producer in streams and sustains, w... more &amp;lt;p&amp;gt;Phytobenthos is the dominant primary producer in streams and sustains, with the allochthonous organic matter inputs, the higher trophic levels. Among the different groups that constitute the phytobenthos community some, especially diatoms, have been studied deeply while others remain quite overlooked. Hence, a characterisation of the overall phytobenthos community is needed, considering all the main taxonomic groups (diatoms, green algae, cyanobacteria and red algae), as related to the environmental conditions characterizing different alpine streams. Moreover, despite the ecological role played by the phytobenthos the knowledge about the factors that control the variations of the community among streams and throughout the different seasons is still poor. Among the different drivers that regulate the phytobenthos component, a pivotal factor is the occurrence of high-flow events that, controlling the stability of riverbed substrates, influences both the phyto and the zoobenthos composition and distribution. Thus, the frequency and the magnitude of flow disturbances are determinant in regulating the phytobenthos density and the recolonization patterns. The aim of this work was to characterize and compare the phytobenthos communities in different streams highlighting the role of the flow regulation due to hydropower reservoirs accounting for the influence of the lithology and the seasonality. The presented phytobenthos data derive from a one-year sampling campaign in four alpine streams representative of different flow conditions (natural vs regulated flow discharge) and lithology (silicate vs carbonate). The riverbed coverage has been estimated monthly in each stream and the biomass has been quantified. In lab, phytobenthos samples have been analysed to measure the photosynthetic activity and define their composition. The main groups (cyanobacteria, green algae, diatoms and algae with phycoerythrin) have been determined both by phyto-PAM deconvolution and by the quantification of the photosynthetic pigments. In order to estimate the bed disturbance, painted stones of different size classes were located in regular arrays along three transversal transects and the distance travelled was measured during every sampling. The preliminary results indicate that regulated streams seem characterized by a greater algae biomass possibly due to a more stable environment. Concerning the community composition, the percentage of diatoms is significatively higher in silicate substrates. Despite the few hours of light, winter promotes phytobenthos colonisation especially for the low frequency of relevant high-flow events but also for the absence of the shadow due to tree canopy on the riverbed.&amp;lt;/p&amp;gt;
In the last decade, large scale biomonitoring programs have been implemented to obtain a robust u... more In the last decade, large scale biomonitoring programs have been implemented to obtain a robust understanding of freshwater in the name of helping to inform and develop effective restoration and management plans. A comprehensive biomonitoring dataset on the macroinvertebrate assemblages inhabiting the rivers of the Po Valley (northern Italy), comprised a total of 6762 sampling events (period 2007–2018), was analyzed in this study in order to examine coarse spatial and temporal trends displayed by biotic communities. Our results showed that macroinvertebrate compositions and derived structural and functional metrics were controlled by multiple environmental drivers, including altitude and climate (large scale), as well as habitat characteristics (local scale). Altitude proved to be the primary geographic driver, likely due to its association with thermal and precipitation regimes, thus explaining its overriding influence on macroinvertebrate assemblages. Significant temporal variatio...
• Current biomonitoring approaches are widely used but have some limitations. • DNA metabarcoding... more • Current biomonitoring approaches are widely used but have some limitations. • DNA metabarcoding provides a new complementary tool for biomonitoring. • Metabarcoding allows extending the range of taxa used as bioindicators. • Metabarcoding data could be used to establish molecular metrics and indices. • Future work should standardise procedures and improve data analysis. The bioassessment of aquatic ecosystems is currently based on various biotic indices that use the occurrence and/ or abundance of selected taxonomic groups to define ecological status. These conventional indices have some limitations, often related to difficulties in morphological identification of bioindicator taxa. Recent development of DNA barcoding and metabarcoding could potentially alleviate some of these limitations, by using DNA sequences instead of morphology to identify organisms and to characterize a given ecosystem. In this paper, we review the structure of conventional biotic indices, and we present the results of pilot metabarcoding studies using environmental DNA to infer biotic indices. We discuss the main advantages and pitfalls of metabarcoding approaches to assess parameters such as richness, abundance, taxonomic composition and species ecological values, to be used for calculation of biotic indices. We present some future developments to fully exploit the potential of metabarcoding data and improve the accuracy and precision of their analysis. We also propose some recommendations for the future integration of DNA metabarcoding to routine biomonitoring programs.
The Water Framework Directive introduced in Europe major changes to improve the management of wat... more The Water Framework Directive introduced in Europe major changes to improve the management of water resources. This study aims to highlight some of the potential implications of its implementation for lake water monitoring in Italy. A Life+ project was launched to plan the first monitoring of lake macroinvertebrates standardized at the national level. Quantile regression analysis was used to explain different metrics of diversity describing macroin-vertebrate communities in response to twenty-one variables representing chemical, physical and morphological characteristics of the environment. Nine lakes located in two Italian regions (Piedmont and Sardinia) were analyzed covering a wide trophic spectrum, from oligotrophy to hyper-eutrophy. The lakes were sampled following the national standardized protocol with samples covering the three recognized lake zones: littoral, sublittoral, profundal. The studied lakes had high chemical variability with conductivity ranging between 53 and 561 S/cm, pH between 6.5 and 9.1, and alkalinity between 14 and 398 mg/l. The bottom sediments were characterized by fine sand (range 51–99%), followed by silt (1–35%) and clay (0–28%). When the Lake Habitat Survey was also applied to these lakes, its synthetic indices (LHMS, Lake Habitat Modification Score and LHQA, Lake Habitat Quality Assessment) produced higher values in natural lakes (mean values ± SD: LHMS = 26 ± 7, LHQA = 57 ± 3) than in the reservoirs (LHMS = 22 ± 4, LHQA = 52 ± 6). In all lakes, macroin-vertebrates mainly consisted of chironomids and oligochaetes characterized by relative abundances up to 80% and >90%, respectively. Using quantile regression to evaluate limiting responses, only two variables, namely sampling depth and oxygen percent saturation (oxygen content), resulted the ones that best explained all the analyzed metrics of diversity of the macroinvertebrate communities. Depth and oxygen were then used to suggest synthetic models describing the various metrics of potential community diversity. These models can help the environmental agencies responsible for monitoring at the national level in distinguishing entire lakes or part of them with high biodiversity from those in altered conditions and then address remediation efforts toward the water bodies with the most critical conditions. Such approach could also be used to optimize the sampling procedures for the application of the Benthic Quality Index for lakes currently adopted at national level.
Various factors, such as habitat availability , competition for space, predation, temperature, nu... more Various factors, such as habitat availability , competition for space, predation, temperature, nutrient supplies, presence of waterfalls, flow variability and water quality, control the abundance, distribution and productivity of stream-dwelling organisms. Each of these factors can influence the response of the density of organisms to a specific environmental gradient, inflating variability and making difficult to understand the possible causal relationship. In our study, we used quantile regression mixed models and Akaike's information criterion as an indicator of goodness to examine two different datasets, one belonging to Italy and one belonging to Finland, and to detect the limiting action of selected environmental variables. In the Italian dataset, we studied the relationships among five macroinvertebrate families and three physical habitat characteristics (water velocity, depth and substratum size); in the Finnish dataset the relationships between taxa richness and 16 environmental characteristics (chemical and physical). We found limiting relationships in both datasets and validated all of them on different datasets. These relationships are quantitative and can be used to predict the range of macroinvertebrate densities or taxa richness as a function of environmental characteristics. They can be a tool for management purposes, providing the basis for habitat-based models and for the development of ecological indices.
The impact of prospective climate change on the hydrological and ecological status of the mountai... more The impact of prospective climate change on the hydrological and ecological status of the mountain stretch of the Serio river (ca. 300 km 2) in the Northern Italian Alps was investigated. A hydrological model was used to mimic theflow regime, and experimental suitability curves were used to assess weighted usable area (WUA) for brown trout (Salmo trutta) in different stages (adult, young, and spawning), and four macroinvertebrates families (Leuctridae, Heptageniidae, Limnephilidae, and Limoniidae). Discharge-WUA curves were obtained using instream flow incremental methodology/physical habitat simulation system (IFIM-PHABSIM), and a seasonal WUA assessment was carried out. The future (until 2100) hydrological cycle was projected using outputs from two general circulation models from Assessment Report 5 of the Intergovernmental Panel on Climate Change (IPCC). The results display a potential for a large flow decrease yearly, until −60% at 2050 and −56% at 2090. Spring melt peaks will be largely dampened, with the largest projected decrease of −60% in 2050 and −66% in 2090. Also fall flows will be largely smoothed, down to −70% for 2050 and −56% for 2090. To quantify habitat quality, a specific quantile WUA 20% , was used and exceeded presently for 292 days in a year, and the percentage of critical days n c% when WUA < WUA 20%. Adult trouts will have decreasing n c% yearly (from 20% now to down to 13% in 2090), increasing in winter and spring and decreasing in fall. Young trouts will have decreasing n c% yearly (from 20% now to down to 2% in 2040 and 2090), but increasing in winter. Spawning, occurring in winter, will have lower n c% (from 16% now, to down to 8% in 2090). Macroinvertebrate families will have constant n c% yearly, unless for Leuctridae (from 20% now to up to 38% in 2050), and noticeable decrease of n c% in winter for Leuctridae until 2090, increase in spring and summer, and decrease in fall for all families until 2090. Correlation analysis of the WUA against weather and hydrological variables displayed that temperature is the most influencing variable, decreasing habitat suitability for all species in fall, and increasing suitability in spring, unless for young trouts.
The presence of different kinds of leaf packs (native or alien) and environmental gradients can a... more The presence of different kinds of leaf packs (native or alien) and environmental gradients can affect the composition and abundance of macroinvertebrate assemblages in freshwater ecosystems, but little is known about the interactive effects. Here, we investigated (1) how environmental gradients could influence leaf packs macroinvertebrates and (2) which was the chief factor (among water quality, mass loss of leaf packs, and flow regime) affecting macroinvertebrate assemblages in impaired streams. We analyzed leaf packs in six sites in impaired streams, characterized by wastewater discharges and dominated by pollution-tolerant macroinvertebrate species. Using principal component analysis, we defined two environmental gradients as follows: a water quality gradient, related to anthropogenic alteration, and a hydro-morphological gradient, mostly related to the catchment features. Our results pointed out that, in the tested conditions , biological metrics, such as functional groups and taxa richness, were chiefly influenced by the water quality gradient, while different leaf types in packs influenced the total taxa richness, but did not cause significant variation in the distribution and abundance of macroinverte-brate functional groups. On the contrary, the mass loss differed for different leaf types and was related to the stream and catchment features (mainly flow). This work showed that, in impaired streams, macroinvertebrate assemblages colonizing leaf packs are more influenced by water quality than by leaf types. Thus, the improvement of water quality should be the priority in restoration programs and should be achieved before any effort to restore native riparian vegetation.
One of the primary goals of biological assessment of streams is to identify which of a suite of c... more One of the primary goals of biological assessment of streams is to identify which of a suite of chemical stressors is limiting their ecological potential. Elevated metal concentrations in streams are often associated with low pH, yet the effects of these two potentially limiting factors of freshwater biodiversity are rarely considered to interact beyond the effects of pH on metal speciation. Using a dataset from two continents, a biogeochemical model of the toxicity of metal mixtures (Al, Cd, Cu, Pb, Zn) and quantile regression, we addressed the relative importance of both pH and metals as limiting factors for macro-invertebrate communities. Current environmental quality standards for metals proved to be protective of stream macroinvertebrate communities and were used as a starting point to assess metal mixture toxicity. A model of metal mixture toxicity accounting for metal interactions was a better predictor of macroinvertebrate responses than a model considering individual metal toxicity. We showed that the direct limiting effect of pH on richness was of the same magnitude as that of chronic metal toxicity, independent of its influence on the availability and toxicity of metals. By accounting for the direct effect of pH on macroinvertebrate communities, we were able to determine that acidic streams supported less diverse communities than neutral streams even when metals were below no-effect thresholds. Through a multivariate quantile model, we untangled the limiting effect of both pH and metals and predicted the maximum diversity that could be expected at other sites as a function of these variables. This model can be used to identify which of the two stressors is more limiting to the ecological potential of running waters.
Agricultural insecticides constitute a major driver of animal biodiversity loss in freshwater eco... more Agricultural insecticides constitute a major driver of animal biodiversity loss in freshwater ecosystems. However, the global extent of their effects and the spatial extent of exposure remain largely unknown. We applied a spatially explicit model to estimate the potential for agricultural insecticide runoff into streams. Water bodies within 40% of the global land surface were at risk of insecticide runoff. We separated the influence of natural factors and variables under human control determining insecticide runoff. In the northern hemisphere, insecticide runoff presented a latitudinal gradient mainly driven by insecticide application rate; in the southern hemisphere, a combination of daily rainfall intensity, terrain slope, agricultural intensity and insecticide application rate determined the process. The model predicted the upper limit of observed insecticide exposure measured in water bodies (n ¼ 82) in five different countries reasonably well. The study provides a global map of hotspots for insecticide contamination guiding future freshwater management and conservation efforts.
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