The load quantification of solutes and suspended materials in rivers provides meaningful ecologic... more The load quantification of solutes and suspended materials in rivers provides meaningful ecological information about watershed functionality. High-frequency measurements of flow are often available, whereas concentration data are commonly recorded at low frequencies. Different calculation methods have been developed by various authors to provide unbiased load estimation. We provide a new R package (RiverLoad) that implements several of the most widely used load estimation algorithms. The package provides an easy-to-use tool to rapidly calculate the load for various compounds and to compare different methods. The package also supplies additional functions to easily organize and analyze the data. A bootstrapping was performed on two example datasets to illustrate the reliability of the methods at different sampling frequencies. The RiverLoad package should make it easier to obtain load data and to compare different estimation algorithms. However, attention must be paid when selecting the method to avoid consistent error in the load estimation.
was mainly inhabited by ultramicrobacteria related to the LD12-lineage of Alphaproteobacteria and... more was mainly inhabited by ultramicrobacteria related to the LD12-lineage of Alphaproteobacteria and to Actinobacteria; the latter group preferred the shallow regions. Cytophaga-Flavobacteria, in particular a population related to Fluviicola sp., were more frequent in and below the layer of maximal P. rubescens abundances. Betaproteobacteria on the other hand were highly abundant in the epi-and hypolimnion, but not in the P. rubescens layer. Four betaproteobacterial subpopulations with contrasting longitudinal and/or vertical habitat preferences were distinguished: Putatively methylotrophic bacteria of the LD28 lineage (beta IV) preferentially inhabited the hypolimnion, Polynucleobacter acidiphobus was found throughout the epilimnion, Limnohabitans (R-BT065) more in the shallow regions of the lake, and Polynucleobacter necessarius ssp. asymbioticus only in hypoxic waters. Our results stress the potential importance of spatial niche differentiation in freshwater bacterioplankton. This variability should be taken into account, e.g., in studies of seasonal community changes derived from single sampling locations and depths.
The study area covers ∼1900 km of the Oglio River basin, between the outflow from Lake Iseo and t... more The study area covers ∼1900 km of the Oglio River basin, between the outflow from Lake Iseo and the confluence into Mella River. This area hosts a sandy mono-layer aquifer in its northern part (higher plain), that passes southwards into a multi-layer aquifer (lower plain) with increasing silt and clay contents. The transition between higher and lower plain is marked by a series of springs, the so called “spring belt". The area is crossed by hundreds of irrigation channels, fed by Oglio River water in its upstream stretch.
Recent studies have highlighted an increase of chloride in many lakes worldwide, with negative ef... more Recent studies have highlighted an increase of chloride in many lakes worldwide, with negative effects on chemical and physical properties of inland waters and freshwater biota. In this study, we assessed the long‐term trend (1993–2017) of chloride in Lake Iseo, located in the midlatitudes, and analyzed its relationship with discharge data of the inflows and hydrological and hydroclimatic changes. Additionally, we performed a specific annual survey, collecting water samples at a biweekly frequency in tributaries, calculating chloride load, and comparing the result with the chloride increase observed in lacustrine water. The combined use of Geographic Information System (GIS) and multivariate analyses allowed identification of possible sources of chloride and their seasonal dynamic within the mixed‐land‐use watershed: impervious surface and deicing salt, population and sewage effluents, livestock, and rainwater. Their potential contribution to total mass balance was assessed, cross‐c...
Surface irrigation in the Po Plain has altered the area's hydrologic balance. • Irrigation on unc... more Surface irrigation in the Po Plain has altered the area's hydrologic balance. • Irrigation on unconfined aquifers boosts aquifer recharge and dilutes groundwater NO 3. • Recharge from irrigation sustains present-day groundwater use by humans & ecosystems. • This should be considered in surface water conservation policies.
Limnological measurements and winter air temperatures recorded in a deep lake south of the Alps (... more Limnological measurements and winter air temperatures recorded in a deep lake south of the Alps (Lake Garda) have been analysed and related to temporal variations in 5 teleconnection patterns, i.e. the East Atlantic pattern (EA), the Eastern Mediterranean Pattern (EMP), the North Atlantic Oscillation (NAO), the Scandinavia pattern (SCAND) and the East Atlantic/West Russia Pattern (EA/WR). The EA and EMP played a significant role in winter in the large-scale atmospheric circulation over the Mediterranean region. Positive and negative EA, and negative and positive EMP phases were closely connected with the development of mild and harsh winters, respectively. In turn, harsh winters had a strong positive impact on the development of diatoms in spring and cyanobacteria in summer and autumn. These modifications were controlled through a linked chain of factors, which included lower winter lake water temperatures, deep lake circulation episodes, and higher replenishment of epilimnetic phosphorus at spring overturn. This work demonstrates the existence of a strong connection between large-scale climatic fluctuations over the Mediterranean area and the temporal variations in the limnological characteristics of the large lakes located between the Alps and the northern border of the Mediterranean region. Conversely, the NAO, SCAND and EA/WR did not show any relationship with the winter climate and the limnological characteristics of Lake Garda.
Here, we review the state-of-the-art of limnological investigations in the large and deep lakes s... more Here, we review the state-of-the-art of limnological investigations in the large and deep lakes south of the Alps (DSLs), lakes Garda, Maggiore, Como, Iseo and Lugano. In the pre-industrial age, these lakes were ultra-or oligotrophic. Increasing anthropogenic pressure and the impact of global warming has led to an acceleration of eutrophication and a decrease in the frequency of full mixing episodes, which have induced a state of meromixis in lakes Lugano and Iseo. In the last two decades, other changes have been identified, including fundamental variations in the long-term dynamics and structure of phytoplankton communities, identification of new toxigenic cyanobacteria and cyanotoxins, increases in the introduction and establishment of allochthonous species, and continuous detection of new, emerging chemical pollutants. Overall, these fundamental changes are quickly transforming the features of the DSLs. The ability to document and reconstruct changes in lake aquatic biota and micropollutants was strongly dependent on both research efforts and the availability of technologies to appraise these changes. In this context, the ongoing adoption of new technological tools, such as high-frequency monitoring and high throughput sequencing, is opening the way to a new level of comprehension of physical, chemical and biological processes, and aquatic biodiversity. New outlooks and new conceptual frameworks are necessary to cope with the huge dimensions of high-throughput data and analysis of big data.
Dataset and R script for the article "Microalgae colonization of different microplastic poly... more Dataset and R script for the article "Microalgae colonization of different microplastic polymers in experimental mesocosms across an environmental gradient" by Nava V., Matias M., Castillo-Escrivà A., Messyasz B. and Leoni B. accepted by Global Change Biology.
A variety of organisms can colonize microplastic surfaces through biofouling processes. Heterotro... more A variety of organisms can colonize microplastic surfaces through biofouling processes. Heterotrophic bacteria tend to be the focus of plastisphere research; however, the presence of epiplastic microalgae within the biofilm has been repeatedly documented. Despite the relevance of biofouling in determining the fate and effects of microplastics in aquatic systems, data about this process are still scarce, especially for freshwater ecosystems. Here, our goal was to evaluate the biomass development and species composition of biofilms on different plastic polymers and to investigate whether plastic substrates exert a strong enough selection to drive species sorting, overcoming other niche‐defining factors. We added microplastic pellets of high‐density polyethylene (HDPE), polyethylene terephthalate (PET), and a mix of the two polymers in 15 lentic mesocosms in five different locations of the Iberian Peninsula, and after one month, we evaluated species composition and biomass of microalgae developed on plastic surfaces. Our results, based on 45 samples, showed that colonization of plastic surfaces occurred in a range of lentic ecosystems covering a wide geographical gradient and different environmental conditions (e.g., nutrient concentration, conductivity, macrophyte coverage). We highlighted that total biomass differed based on the polymer considered, with higher biomass developed on PET substrate compared to HDPE. Microplastics supported the growth of a rich and diversified community of microalgae (242 species), with some cosmopolite species. However, we did not observe species‐specificity in the colonization of the different plastic polymers. Local species pool and nutrient concentration rather than polymeric composition seemed to be the determinant factor defying the community diversity. Regardless of specific environmental conditions, we showed that many species could coexist on the surface of relatively small plastic items, highlighting how microplastics may have considerable carrying capacity, with possible consequences on the wider ecological context.
Climate change and other anthropogenic stressors have led to long-term changes in the thermal str... more Climate change and other anthropogenic stressors have led to long-term changes in the thermal structure, including surface temperatures, deepwater temperatures, and vertical thermal gradients, in many lakes around the world. Though many studies highlight warming of surface water temperatures in lakes worldwide, less is known about long-term trends in full vertical thermal structure and deepwater temperatures, which have been changing less consistently in both direction and magnitude. Here, we present a globally-expansive data set of summertime in-situ vertical temperature profiles from 153 lakes, with one time series beginning as early as 1894. We also compiled lake geographic, morphometric, and water quality variables that can influence vertical thermal structure through a variety of potential mechanisms in these lakes. These long-term time series of vertical temperature profiles and corresponding lake characteristics serve as valuable data to help understand changes and drivers of...
Raman spectroscopy is gaining ground in the analysis of microplastics, especially due to its high... more Raman spectroscopy is gaining ground in the analysis of microplastics, especially due to its high spatial resolution that allows the investigation of small plastic particles, whose numeric abundance is argued to be particularly relevant in aquatic systems. Here, we aimed at outlining the status of Raman analysis of microplastics from aquatic systems, highlighting the advantages and the drawbacks of this technique and critically presenting tools and ways to effectively employ this instrument and to improve the spectra obtained and their interpretation. In particular, we summarized procedural information for the use of Raman spectroscopy, and we discussed issues linked to fluorescence interference and the analysis of weathered polymers, which may complicate the interpretation of Raman signatures. In this context, a deep understanding of the different plastic polymers and their Raman peaks and chemical fingerprints is fundamental to avoid misidentification. Therefore, we provided a cat...
Abstract Freshwaters constitute a fundamental and extremely limited resource for atoll islands’ p... more Abstract Freshwaters constitute a fundamental and extremely limited resource for atoll islands’ population. The interplay of climatic and human-driven processes, which affect both the quantity and the quality of freshwater resources, may exacerbate the problem of water security and availability. This work evaluated the effects of good spectrum of anthropic impacts on groundwater quality in a typical and representative native inhabited island (c.a. 850 people) of Maldives, analyzing and interpreting hydrological and hydrochemical data, collected during a specific field survey on 51 sampling points after a rainy season. The island groundwater is constituted by a thin asymmetric lens, periodically recharged by rain. The lifestyle of people and water exploitation seem to be sustainable, even if groundwater resources are already experiencing moderate contamination and, limited to some areas, heavy pollution. The sources of impacts have been identified in diffuse organic matter contamination due to a poor domestic wastewater treatment, farming (poultry) and gardening activities. To face these impacts, it is essential to build a sewer system paired with a possibility to recycle wastewater reducing water over-exploitation. The collaborative and educational initiatives organization, at different levels, can increase the capacity for planning a sustainable development. Our results provide useful information for sustainable management plans to preserve freshwater resources of the island, which conservation is especially important considering the context of the future lifestyle changes and climatic scenarios for the Maldives. These findings can be extended by analogy to others atoll islands.
With the widespread occurrence of microplastics in aquatic ecosystems having been firmly establis... more With the widespread occurrence of microplastics in aquatic ecosystems having been firmly established, the focus of research has shifted towards the assessments of their influence on ecosystem functions and food webs. This includes interactions between microplastics and microalgae, as fundamental components at the base of aquatic food webs and pivotal organisms in a wide range of ecosystem functions. In this review, we present the current state of knowledge on microalgae-microplastic interactions and summarize the potential effect on their respective fate. Microplastics can and do interact with microalgae and the available literature has suggested that the epiplastic community of microalgae differs consistently from the surrounding aquatic communities; however, it is still not clear whether this different colonization is linked to the composition of the surface or more to the availability of a "hard" substrate on which organisms can attach and grow. Further studies are needed to understand to what extent the properties of different plastic materials and different environmental factors may affect the growth of microalgae on plastic debris. Biofouling may alter microplastic properties, especially increasing their density, consequently affecting the vertical fluxes of plastics. Moreover, microplastics may have toxic effects on microalgae, which could be physical or related to chemical interactions with plasticizers or other chemicals associated with plastics, with consequences for algal growth, photosynthetic activity, and morphology. Microplastics seems to have the potential to affect not only the quality (e.g., fatty acids and lipids composition, food dilution effect) but also the quantity of algal production, both positively and negatively. This may have consequences for energy fluxes, which may propagate throughout the whole food web and alter aquatic productivity. Even though experimental results have indicated reciprocal impacts between plastics and microalgae, it is currently difficult to predict how these impacts may manifest themselves at the ecosystem level. Therefore, further studies are needed to address this important topic.
Groundwater level forecasting is a useful tool for a more efficient and sustainable groundwater r... more Groundwater level forecasting is a useful tool for a more efficient and sustainable groundwater resource management. Developing models that can accurately reproduce groundwater level response to meteorological conditions can lead to a better understanding of the groundwater resource availability. Here an autoregressive neural network (NNARx) approach is proposed and compared with autoregressive linear models with exogenous input (ARx) in order to forecast groundwater level in an aquifer system where a linear groundwater level response to recharge by rainfall is observed. A well known problem regarding neural networks consists in the high risk of overfitting. Here, three NNARx model were trained using different methods to avoid overfitting: Early stopping, Bayesian regularization and a combination of both. The results show that on the short term forecasting (up to 15 days) the performance of NNARx and ARx are comparable but the ARx model generalizes better, while the NNARx trained with Bayesian regularization outperforms the linear models and the other NNARx models on longer scenarios on the test set. As linear models are less time demanding and do not require high computational power, they can be considered as suitable tools for short term groundwater level forecasting in linear systems while when longer scenarios are needed neural networks can be considered more reliable, and training them with Bayesian regularization allows to minimize the risk of overfitting.
Riassunto Le ricerche condotte nei grandi laghi a sud delle Alpi hanno dimostrato una stretta dip... more Riassunto Le ricerche condotte nei grandi laghi a sud delle Alpi hanno dimostrato una stretta dipendenza dei processi di mescolamento da modi di circolazione atmosferica rilevanti per l'area mediterranea (East Atlantic pattern, EA e Eastern Mediterranean Pattern, EMP). In inverno, EA e EMP sono associati a una situazione di alta pressione nell'Oceano Atlantico settentrionale, e a un forte afflusso di aria fredda dall'Europa settentrionale e centrale verso il Mediterraneo. Il raffreddamento dell'aria, causando una diminuzione delle temperature lacustri, favorisce una maggiore estensione della circolazione primaverile, e un maggiore rifornimento di nutrienti verso la superficie e di ossigeno verso l'ipolimnio. L'impatto sulle comunità biologiche è stato studiato nel Garda e, in parte, nel lago Maggiore e nel lago d'Iseo. Nel Garda, a seguito di inverni più freddi e all'aumentare della disponibilità primaverile di nutrienti, sono stati osservati significativi aumenti nella crescita delle diatomee in primavera e dei cianobatteri in estate e autunno. Nel Garda e nel lago Maggiore, mentre la temperatura ambientale è risultata influenzare la tempistica del picco primaverile in densità di Daphnia, l'entità dello stesso è apparsa mediata dal mescolamento e dalle disponibilità alimentari. Risultati simili sono stati verificati nel lago d'Iseo. Un aumento delle temperature invernali potrebbe determinare una diminuzione nella frequenza degli episodi di mescolamento completo. Nel breve periodo ciò porterebbe ad un miglioramento della qualità delle acque superficiali, diminuendo la fertilizzazione primaverile e, come finora dimostrato nel Garda, lo sviluppo di cianobatteri. Nel lungo periodo aumenterebbe invece il rischio di innesco di condizioni meromittiche. PAROLE CHIAVE: laghi sudalpini / eutrofizzazione / cambiamenti climatici / East Atlantic pattern / Eastern Mediterranean Pattern Influence of climatic fluctuations on the large lakes south of the Alps: implications in the context of global warming Synoptic analyses carried out in the largest lakes south of the Alps demonstrated a tight coupling between deep mixing dynamics and winter climatic fluctuations strictly controlled by atmospheric modes of variability relevant for the Mediterranean region, namely the East Atlantic pattern and the Eastern Mediterranean Pattern. In winter, the EA and EMP modes are associated with an intense northeasterly airûow bringing cold air from continental Europe over the Mediterranean basin. In turn, harsh winters had a strong impact on the lake water temperatures, deep lake circulation episodes, higher replenishment of epilimnetic phosphorus and hypolimnetic oxygen at spring overturn. Fertilisation was greatly enhanced in the meromictic and more eutrophic lakes. The effects of such a linked chain of events on phytoplankton were studied in Lake Garda where harsh winters and higher P-replenishment had a positive impact on the development of diatoms in spring and cyanobacteria in summer and autumn. Timing of Daphnia population density peak in lakes Garda, Maggiore and Iseo was directly correlated with water temperatures, while the level of peak density was mediated by the extent of spring mixing and food availability. It was hypothesized that an increase in the winter temperatures could cause a decrease in the occurrence of complete overturn episodes. In the short period, this should improve water quality, decreasing the replenishment of phosphorus andas demonstrated in Lake Garda-the development of cyanobacteria. On the long-term, the lake warming could increase the risk of triggering meromictic conditions. KEY WORDS: deep perialpine lakes / eutrophication / climatic change / East Atlantic pattern / Eastern Mediterranean Pattern § Inserto speciale Stato attuale e tendenze evolutive negli ecosistemi di acque interne e di transizione in Italia, a cura di Pierluigi Viaroli CORE Metadata, citation and similar papers at core.ac.uk Provided by Archivio istituzionale della ricerca-Fondazione Edmund Mach
The load quantification of solutes and suspended materials in rivers provides meaningful ecologic... more The load quantification of solutes and suspended materials in rivers provides meaningful ecological information about watershed functionality. High-frequency measurements of flow are often available, whereas concentration data are commonly recorded at low frequencies. Different calculation methods have been developed by various authors to provide unbiased load estimation. We provide a new R package (RiverLoad) that implements several of the most widely used load estimation algorithms. The package provides an easy-to-use tool to rapidly calculate the load for various compounds and to compare different methods. The package also supplies additional functions to easily organize and analyze the data. A bootstrapping was performed on two example datasets to illustrate the reliability of the methods at different sampling frequencies. The RiverLoad package should make it easier to obtain load data and to compare different estimation algorithms. However, attention must be paid when selecting the method to avoid consistent error in the load estimation.
was mainly inhabited by ultramicrobacteria related to the LD12-lineage of Alphaproteobacteria and... more was mainly inhabited by ultramicrobacteria related to the LD12-lineage of Alphaproteobacteria and to Actinobacteria; the latter group preferred the shallow regions. Cytophaga-Flavobacteria, in particular a population related to Fluviicola sp., were more frequent in and below the layer of maximal P. rubescens abundances. Betaproteobacteria on the other hand were highly abundant in the epi-and hypolimnion, but not in the P. rubescens layer. Four betaproteobacterial subpopulations with contrasting longitudinal and/or vertical habitat preferences were distinguished: Putatively methylotrophic bacteria of the LD28 lineage (beta IV) preferentially inhabited the hypolimnion, Polynucleobacter acidiphobus was found throughout the epilimnion, Limnohabitans (R-BT065) more in the shallow regions of the lake, and Polynucleobacter necessarius ssp. asymbioticus only in hypoxic waters. Our results stress the potential importance of spatial niche differentiation in freshwater bacterioplankton. This variability should be taken into account, e.g., in studies of seasonal community changes derived from single sampling locations and depths.
The study area covers ∼1900 km of the Oglio River basin, between the outflow from Lake Iseo and t... more The study area covers ∼1900 km of the Oglio River basin, between the outflow from Lake Iseo and the confluence into Mella River. This area hosts a sandy mono-layer aquifer in its northern part (higher plain), that passes southwards into a multi-layer aquifer (lower plain) with increasing silt and clay contents. The transition between higher and lower plain is marked by a series of springs, the so called “spring belt". The area is crossed by hundreds of irrigation channels, fed by Oglio River water in its upstream stretch.
Recent studies have highlighted an increase of chloride in many lakes worldwide, with negative ef... more Recent studies have highlighted an increase of chloride in many lakes worldwide, with negative effects on chemical and physical properties of inland waters and freshwater biota. In this study, we assessed the long‐term trend (1993–2017) of chloride in Lake Iseo, located in the midlatitudes, and analyzed its relationship with discharge data of the inflows and hydrological and hydroclimatic changes. Additionally, we performed a specific annual survey, collecting water samples at a biweekly frequency in tributaries, calculating chloride load, and comparing the result with the chloride increase observed in lacustrine water. The combined use of Geographic Information System (GIS) and multivariate analyses allowed identification of possible sources of chloride and their seasonal dynamic within the mixed‐land‐use watershed: impervious surface and deicing salt, population and sewage effluents, livestock, and rainwater. Their potential contribution to total mass balance was assessed, cross‐c...
Surface irrigation in the Po Plain has altered the area's hydrologic balance. • Irrigation on unc... more Surface irrigation in the Po Plain has altered the area's hydrologic balance. • Irrigation on unconfined aquifers boosts aquifer recharge and dilutes groundwater NO 3. • Recharge from irrigation sustains present-day groundwater use by humans & ecosystems. • This should be considered in surface water conservation policies.
Limnological measurements and winter air temperatures recorded in a deep lake south of the Alps (... more Limnological measurements and winter air temperatures recorded in a deep lake south of the Alps (Lake Garda) have been analysed and related to temporal variations in 5 teleconnection patterns, i.e. the East Atlantic pattern (EA), the Eastern Mediterranean Pattern (EMP), the North Atlantic Oscillation (NAO), the Scandinavia pattern (SCAND) and the East Atlantic/West Russia Pattern (EA/WR). The EA and EMP played a significant role in winter in the large-scale atmospheric circulation over the Mediterranean region. Positive and negative EA, and negative and positive EMP phases were closely connected with the development of mild and harsh winters, respectively. In turn, harsh winters had a strong positive impact on the development of diatoms in spring and cyanobacteria in summer and autumn. These modifications were controlled through a linked chain of factors, which included lower winter lake water temperatures, deep lake circulation episodes, and higher replenishment of epilimnetic phosphorus at spring overturn. This work demonstrates the existence of a strong connection between large-scale climatic fluctuations over the Mediterranean area and the temporal variations in the limnological characteristics of the large lakes located between the Alps and the northern border of the Mediterranean region. Conversely, the NAO, SCAND and EA/WR did not show any relationship with the winter climate and the limnological characteristics of Lake Garda.
Here, we review the state-of-the-art of limnological investigations in the large and deep lakes s... more Here, we review the state-of-the-art of limnological investigations in the large and deep lakes south of the Alps (DSLs), lakes Garda, Maggiore, Como, Iseo and Lugano. In the pre-industrial age, these lakes were ultra-or oligotrophic. Increasing anthropogenic pressure and the impact of global warming has led to an acceleration of eutrophication and a decrease in the frequency of full mixing episodes, which have induced a state of meromixis in lakes Lugano and Iseo. In the last two decades, other changes have been identified, including fundamental variations in the long-term dynamics and structure of phytoplankton communities, identification of new toxigenic cyanobacteria and cyanotoxins, increases in the introduction and establishment of allochthonous species, and continuous detection of new, emerging chemical pollutants. Overall, these fundamental changes are quickly transforming the features of the DSLs. The ability to document and reconstruct changes in lake aquatic biota and micropollutants was strongly dependent on both research efforts and the availability of technologies to appraise these changes. In this context, the ongoing adoption of new technological tools, such as high-frequency monitoring and high throughput sequencing, is opening the way to a new level of comprehension of physical, chemical and biological processes, and aquatic biodiversity. New outlooks and new conceptual frameworks are necessary to cope with the huge dimensions of high-throughput data and analysis of big data.
Dataset and R script for the article "Microalgae colonization of different microplastic poly... more Dataset and R script for the article "Microalgae colonization of different microplastic polymers in experimental mesocosms across an environmental gradient" by Nava V., Matias M., Castillo-Escrivà A., Messyasz B. and Leoni B. accepted by Global Change Biology.
A variety of organisms can colonize microplastic surfaces through biofouling processes. Heterotro... more A variety of organisms can colonize microplastic surfaces through biofouling processes. Heterotrophic bacteria tend to be the focus of plastisphere research; however, the presence of epiplastic microalgae within the biofilm has been repeatedly documented. Despite the relevance of biofouling in determining the fate and effects of microplastics in aquatic systems, data about this process are still scarce, especially for freshwater ecosystems. Here, our goal was to evaluate the biomass development and species composition of biofilms on different plastic polymers and to investigate whether plastic substrates exert a strong enough selection to drive species sorting, overcoming other niche‐defining factors. We added microplastic pellets of high‐density polyethylene (HDPE), polyethylene terephthalate (PET), and a mix of the two polymers in 15 lentic mesocosms in five different locations of the Iberian Peninsula, and after one month, we evaluated species composition and biomass of microalgae developed on plastic surfaces. Our results, based on 45 samples, showed that colonization of plastic surfaces occurred in a range of lentic ecosystems covering a wide geographical gradient and different environmental conditions (e.g., nutrient concentration, conductivity, macrophyte coverage). We highlighted that total biomass differed based on the polymer considered, with higher biomass developed on PET substrate compared to HDPE. Microplastics supported the growth of a rich and diversified community of microalgae (242 species), with some cosmopolite species. However, we did not observe species‐specificity in the colonization of the different plastic polymers. Local species pool and nutrient concentration rather than polymeric composition seemed to be the determinant factor defying the community diversity. Regardless of specific environmental conditions, we showed that many species could coexist on the surface of relatively small plastic items, highlighting how microplastics may have considerable carrying capacity, with possible consequences on the wider ecological context.
Climate change and other anthropogenic stressors have led to long-term changes in the thermal str... more Climate change and other anthropogenic stressors have led to long-term changes in the thermal structure, including surface temperatures, deepwater temperatures, and vertical thermal gradients, in many lakes around the world. Though many studies highlight warming of surface water temperatures in lakes worldwide, less is known about long-term trends in full vertical thermal structure and deepwater temperatures, which have been changing less consistently in both direction and magnitude. Here, we present a globally-expansive data set of summertime in-situ vertical temperature profiles from 153 lakes, with one time series beginning as early as 1894. We also compiled lake geographic, morphometric, and water quality variables that can influence vertical thermal structure through a variety of potential mechanisms in these lakes. These long-term time series of vertical temperature profiles and corresponding lake characteristics serve as valuable data to help understand changes and drivers of...
Raman spectroscopy is gaining ground in the analysis of microplastics, especially due to its high... more Raman spectroscopy is gaining ground in the analysis of microplastics, especially due to its high spatial resolution that allows the investigation of small plastic particles, whose numeric abundance is argued to be particularly relevant in aquatic systems. Here, we aimed at outlining the status of Raman analysis of microplastics from aquatic systems, highlighting the advantages and the drawbacks of this technique and critically presenting tools and ways to effectively employ this instrument and to improve the spectra obtained and their interpretation. In particular, we summarized procedural information for the use of Raman spectroscopy, and we discussed issues linked to fluorescence interference and the analysis of weathered polymers, which may complicate the interpretation of Raman signatures. In this context, a deep understanding of the different plastic polymers and their Raman peaks and chemical fingerprints is fundamental to avoid misidentification. Therefore, we provided a cat...
Abstract Freshwaters constitute a fundamental and extremely limited resource for atoll islands’ p... more Abstract Freshwaters constitute a fundamental and extremely limited resource for atoll islands’ population. The interplay of climatic and human-driven processes, which affect both the quantity and the quality of freshwater resources, may exacerbate the problem of water security and availability. This work evaluated the effects of good spectrum of anthropic impacts on groundwater quality in a typical and representative native inhabited island (c.a. 850 people) of Maldives, analyzing and interpreting hydrological and hydrochemical data, collected during a specific field survey on 51 sampling points after a rainy season. The island groundwater is constituted by a thin asymmetric lens, periodically recharged by rain. The lifestyle of people and water exploitation seem to be sustainable, even if groundwater resources are already experiencing moderate contamination and, limited to some areas, heavy pollution. The sources of impacts have been identified in diffuse organic matter contamination due to a poor domestic wastewater treatment, farming (poultry) and gardening activities. To face these impacts, it is essential to build a sewer system paired with a possibility to recycle wastewater reducing water over-exploitation. The collaborative and educational initiatives organization, at different levels, can increase the capacity for planning a sustainable development. Our results provide useful information for sustainable management plans to preserve freshwater resources of the island, which conservation is especially important considering the context of the future lifestyle changes and climatic scenarios for the Maldives. These findings can be extended by analogy to others atoll islands.
With the widespread occurrence of microplastics in aquatic ecosystems having been firmly establis... more With the widespread occurrence of microplastics in aquatic ecosystems having been firmly established, the focus of research has shifted towards the assessments of their influence on ecosystem functions and food webs. This includes interactions between microplastics and microalgae, as fundamental components at the base of aquatic food webs and pivotal organisms in a wide range of ecosystem functions. In this review, we present the current state of knowledge on microalgae-microplastic interactions and summarize the potential effect on their respective fate. Microplastics can and do interact with microalgae and the available literature has suggested that the epiplastic community of microalgae differs consistently from the surrounding aquatic communities; however, it is still not clear whether this different colonization is linked to the composition of the surface or more to the availability of a "hard" substrate on which organisms can attach and grow. Further studies are needed to understand to what extent the properties of different plastic materials and different environmental factors may affect the growth of microalgae on plastic debris. Biofouling may alter microplastic properties, especially increasing their density, consequently affecting the vertical fluxes of plastics. Moreover, microplastics may have toxic effects on microalgae, which could be physical or related to chemical interactions with plasticizers or other chemicals associated with plastics, with consequences for algal growth, photosynthetic activity, and morphology. Microplastics seems to have the potential to affect not only the quality (e.g., fatty acids and lipids composition, food dilution effect) but also the quantity of algal production, both positively and negatively. This may have consequences for energy fluxes, which may propagate throughout the whole food web and alter aquatic productivity. Even though experimental results have indicated reciprocal impacts between plastics and microalgae, it is currently difficult to predict how these impacts may manifest themselves at the ecosystem level. Therefore, further studies are needed to address this important topic.
Groundwater level forecasting is a useful tool for a more efficient and sustainable groundwater r... more Groundwater level forecasting is a useful tool for a more efficient and sustainable groundwater resource management. Developing models that can accurately reproduce groundwater level response to meteorological conditions can lead to a better understanding of the groundwater resource availability. Here an autoregressive neural network (NNARx) approach is proposed and compared with autoregressive linear models with exogenous input (ARx) in order to forecast groundwater level in an aquifer system where a linear groundwater level response to recharge by rainfall is observed. A well known problem regarding neural networks consists in the high risk of overfitting. Here, three NNARx model were trained using different methods to avoid overfitting: Early stopping, Bayesian regularization and a combination of both. The results show that on the short term forecasting (up to 15 days) the performance of NNARx and ARx are comparable but the ARx model generalizes better, while the NNARx trained with Bayesian regularization outperforms the linear models and the other NNARx models on longer scenarios on the test set. As linear models are less time demanding and do not require high computational power, they can be considered as suitable tools for short term groundwater level forecasting in linear systems while when longer scenarios are needed neural networks can be considered more reliable, and training them with Bayesian regularization allows to minimize the risk of overfitting.
Riassunto Le ricerche condotte nei grandi laghi a sud delle Alpi hanno dimostrato una stretta dip... more Riassunto Le ricerche condotte nei grandi laghi a sud delle Alpi hanno dimostrato una stretta dipendenza dei processi di mescolamento da modi di circolazione atmosferica rilevanti per l'area mediterranea (East Atlantic pattern, EA e Eastern Mediterranean Pattern, EMP). In inverno, EA e EMP sono associati a una situazione di alta pressione nell'Oceano Atlantico settentrionale, e a un forte afflusso di aria fredda dall'Europa settentrionale e centrale verso il Mediterraneo. Il raffreddamento dell'aria, causando una diminuzione delle temperature lacustri, favorisce una maggiore estensione della circolazione primaverile, e un maggiore rifornimento di nutrienti verso la superficie e di ossigeno verso l'ipolimnio. L'impatto sulle comunità biologiche è stato studiato nel Garda e, in parte, nel lago Maggiore e nel lago d'Iseo. Nel Garda, a seguito di inverni più freddi e all'aumentare della disponibilità primaverile di nutrienti, sono stati osservati significativi aumenti nella crescita delle diatomee in primavera e dei cianobatteri in estate e autunno. Nel Garda e nel lago Maggiore, mentre la temperatura ambientale è risultata influenzare la tempistica del picco primaverile in densità di Daphnia, l'entità dello stesso è apparsa mediata dal mescolamento e dalle disponibilità alimentari. Risultati simili sono stati verificati nel lago d'Iseo. Un aumento delle temperature invernali potrebbe determinare una diminuzione nella frequenza degli episodi di mescolamento completo. Nel breve periodo ciò porterebbe ad un miglioramento della qualità delle acque superficiali, diminuendo la fertilizzazione primaverile e, come finora dimostrato nel Garda, lo sviluppo di cianobatteri. Nel lungo periodo aumenterebbe invece il rischio di innesco di condizioni meromittiche. PAROLE CHIAVE: laghi sudalpini / eutrofizzazione / cambiamenti climatici / East Atlantic pattern / Eastern Mediterranean Pattern Influence of climatic fluctuations on the large lakes south of the Alps: implications in the context of global warming Synoptic analyses carried out in the largest lakes south of the Alps demonstrated a tight coupling between deep mixing dynamics and winter climatic fluctuations strictly controlled by atmospheric modes of variability relevant for the Mediterranean region, namely the East Atlantic pattern and the Eastern Mediterranean Pattern. In winter, the EA and EMP modes are associated with an intense northeasterly airûow bringing cold air from continental Europe over the Mediterranean basin. In turn, harsh winters had a strong impact on the lake water temperatures, deep lake circulation episodes, higher replenishment of epilimnetic phosphorus and hypolimnetic oxygen at spring overturn. Fertilisation was greatly enhanced in the meromictic and more eutrophic lakes. The effects of such a linked chain of events on phytoplankton were studied in Lake Garda where harsh winters and higher P-replenishment had a positive impact on the development of diatoms in spring and cyanobacteria in summer and autumn. Timing of Daphnia population density peak in lakes Garda, Maggiore and Iseo was directly correlated with water temperatures, while the level of peak density was mediated by the extent of spring mixing and food availability. It was hypothesized that an increase in the winter temperatures could cause a decrease in the occurrence of complete overturn episodes. In the short period, this should improve water quality, decreasing the replenishment of phosphorus andas demonstrated in Lake Garda-the development of cyanobacteria. On the long-term, the lake warming could increase the risk of triggering meromictic conditions. KEY WORDS: deep perialpine lakes / eutrophication / climatic change / East Atlantic pattern / Eastern Mediterranean Pattern § Inserto speciale Stato attuale e tendenze evolutive negli ecosistemi di acque interne e di transizione in Italia, a cura di Pierluigi Viaroli CORE Metadata, citation and similar papers at core.ac.uk Provided by Archivio istituzionale della ricerca-Fondazione Edmund Mach
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