15 results on '"Davide Cicala"'
Search Results
2. Spatial analysis of demersal food webs through integration of eDNA metabarcoding with fishing activities
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Davide Cicala, Giulia Maiello, Fabio Fiorentino, Germana Garofalo, Daniela Massi, Alice Sbrana, Stefano Mariani, Simone D’Alessandro, Matteo Stefani, Lucie Perrodin, and Tommaso Russo
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Food Webs Analysis (FWA) ,environmental DNA (eDNA) ,marine communities ,abiotic factors ,fishing pressure ,Mediterranean Sea ,Science ,General. Including nature conservation, geographical distribution ,QH1-199.5 - Abstract
The evaluation of the status of marine communities, and especially the monitoring of those heavily exploited by fisheries, is a key, challenging task in marine sciences. Fishing activities are a major source of disruption to marine food webs, both directly, by selectively removing components at specific trophic levels (TL), and indirectly, by altering habitats and production cycles. Food web analysis can be very useful in the context of an Ecosystem Approach to Fisheries, but food web reconstructions demand large and expensive data sets, which are typically available only for a small fraction of marine ecosystems. Recently, new technologies have been developed to easily, quickly and cost-effectively collect environmental DNA (eDNA) during fishing activities. By generating large, multi-marker metabarcoding data from eDNA samples obtained from commercial trawlers, it is possible to produce exhaustive taxonomic inventories for the exploited ecosystems, which are suitable for food-web reconstructions. Here, we integrate and re-analyse the data of a recent study in which the α diversity was investigated using the eDNA opportunistically collected during fishing operations. Indeed, we collect highly resolved information on species feeding relationships to reconstruct the food webs at different sites in the Strait of Sicily (Mediterranean Sea) from eDNA and catch data. After observing that the trophic networks obtained from eDNA metabarcoding data are more consistent with the available knowledge, a set of food web indicators (species richness, number of links, direct connectance and generality) is computed and analysed to unravel differences in food webs structure through different areas (spatial variations). Species richness, number of links and generality (positively) and direct connectance (negatively) are correlated with increasing distance from the coast and fishing effort intensity. The combined effects of environmental gradients and fishing effort on food web structure at different study sites are then examined and modelled. Taken together, these findings indicate the suitability of eDNA metabarcoding to assist and food web analysis, obtain several food web-related ecological indicators, and tease out the effect of fishing intensity from the environmental gradients of marine ecosystems.
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- 2024
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3. Isotopic Overlap of Invasive and Native Consumers in the Food Web of Lake Trasimeno (Central Italy)
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Davide Cicala, Maria Teresa Guerra, Roberta Bardelli, Cristina Di Muri, Alessandro Ludovisi, Salvatrice Vizzini, and Giorgio Mancinelli
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invasive species ,non-indigenous species ,ecological impact ,δ13C and δ15N ,isotopic niche ,Procambarus clarkii ,Biology (General) ,QH301-705.5 - Abstract
An advanced characterization of the trophic niche of non-indigenous species (NIS) may provide useful information on their ecological impact on invaded communities. Here, we used carbon and nitrogen stable isotopes to estimate pairwise niche overlaps between non-indigenous and native consumers in the winter food web of Lake Trasimeno (central Italy). Overall, a relatively low pairwise overlap of isotopic niches was observed between NIS and native species. The only exception was the Louisiana crayfish Procambarus clarkii, which showed a relatively high and diffuse overlap with other native invertebrates. Our findings highlighted a high niche divergence between non-indigenous and native species in Lake Trasimeno, suggesting a potentially low degree of interspecific competition that may facilitate coexistence and, in turn, limit the strength of impacts. The divergent results obtained for the Louisiana crayfish indicate that additional control measures for this invasive species are needed to mitigate its impact on the Lake Trasimeno system.
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- 2023
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4. Phthalate esters (PAEs) concentration pattern reflects dietary habitats (δ13C) in blood of Mediterranean loggerhead turtles (Caretta caretta)
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Monica Francesca Blasi, Pasquale Avino, Ivan Notardonato, Cristina Di Fiore, Daniela Mattei, Marco Friedrich Walter Gauger, Michelle Gelippi, Davide Cicala, Sandra Hochscheid, Andrea Camedda, Giuseppe Andrea de Lucia, and Gabriele Favero
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Phthalates ,Sea turtle ,Stable isotopes ,Mediterranean sea ,Acute exposure ,Marine pollution ,Environmental pollution ,TD172-193.5 ,Environmental sciences ,GE1-350 - Abstract
Phthalic acid esters (PAEs) are classified as endocrine disruptors, but it remains unclear if they can enter the marine food-web and result in severe health effects for organisms. Loggerhead turtles (Caretta caretta) can be chronically exposed to PAEs by ingesting plastic debris, but no information is available about PAEs levels in blood, and how these concentrations are related to diet during different life stages. This paper investigated, for the first time, six PAEs in blood of 18 wild-caught Mediterranean loggerhead turtles throughout solid-phase extraction coupled with gas chromatography-ion trap/mass spectrometry. Stable isotope analyses of carbon and nitrogen were also performed to assess the resource use pattern of loggerhead turtles. DEHP (12–63 ng mL-1) and DBP (6–57 ng mL-1) were the most frequently represented PAEs, followed by DiBP, DMP, DEP and DOP. The total PAEs concentration was highest in three turtles (124–260 ng mL-1) whereas three other turtles had concentrations below the detection limit. PAEs were clustered in three groups according to concentration in all samples: DEHP in the first group, DBP, DEP, and DiBP in the second group, and DOP and DMP in the third group. The total phthalates concentration did not differ between large-sized (96.3 ± 86.0 ng mL-1) and small-sized (67.1 ± 34.2 ng mL-1) turtles (p
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- 2022
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5. Trophic Niches, Trophic Positions, and Niche Overlaps between Non-Native and Native Fish Species in a Subalpine Lake
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Davide Cicala, Gianluca Polgar, Jordi René Mor, Roberta Piscia, Stefano Brignone, Silvia Zaupa, and Pietro Volta
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biological invasions ,invasive species ,stable isotopes ,isotopic niche ,food webs ,PASE electrofishing ,Hydraulic engineering ,TC1-978 ,Water supply for domestic and industrial purposes ,TD201-500 - Abstract
In the last century, Italian freshwater ecosystems have been invaded by several non-native fish species. In the subalpine Lake Mergozzo (northern Italy), several recently introduced non-native species dramatically expanded their populations. We used carbon and nitrogen stable isotopes to describe the isotopic niches and trophic positions of native and non-native fish species in Lake Mergozzo. We evaluated their trophic niches, trophic diversity, trophic redundancy and trophic evenness utilizing isotopic niche metrics, and estimated asymmetrical niche overlaps. The trophic traits of non-native fish species and Perca fluviatilis clearly define them as trophic generalists, in terms of among-individual variability of their isotopic niches. The historical increase in abundance of fish non-native species in this lake, their dominance by numbers and biomass within the assemblage, and their broad asymmetrical niche overlaps suggest that their higher degree of trophic generalism might have been one of the key factors that have promoted the invasion of the recipient community.
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- 2020
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6. Trophic Magnification of Legacy (PCB, DDT and Hg) and Emerging Pollutants (PFAS) in the Fish Community of a Small Protected Southern Alpine Lake (Lake Mergozzo, Northern Italy)
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Michela Mazzoni, Claudia Ferrario, Roberta Bettinetti, Roberta Piscia, Davide Cicala, Pietro Volta, Katrine Borgå, Sara Valsecchi, and Stefano Polesello
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trophic magnification factor ,bioaccumulation ,Hg ,PFAS ,organochlorine compounds ,lake fish ,Hydraulic engineering ,TC1-978 ,Water supply for domestic and industrial purposes ,TD201-500 - Abstract
The biomagnification of mercury, polychlorobiphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs) and perfluoroalkyl acids substances (PFASs) was evaluated in the trophic web of Lake Mergozzo, a small and deep Italian subalpine lake, which has been chosen because it is a protected environment, and discharges into the lake are mostly avoided. Carbon source and relative trophic levels were calculated by using 13C and 15N stable isotopes, respectively, and trophic magnification factors (TMFs) were derived. Zooplankton and thirteen species of fish were collected and analyzed, and the results showed the elevated level of biota contamination from both legacy and emerging pollutants, even if direct discharges were avoided. Concentrations in biota, expressed as sums of compounds, ranged from 0.4 to 60 µg kg−1 wet weight (ww) for PFASs, from 16 to 1.3 104 µg kg−1 lipid content (lw) for DDTs, from 17 to 1.5 104 µg kg−1 lw for PCBs and from 20.0 to 501 µg kg−1 ww for mercury (Hg). TMFs of this deep, cold lake, with a prevalent pelagic trophic chain, were high and clearly indicated fish biomagnification, except for PFAS. The biomagnification capability of PFAS in a fish-only food web was discussed by using the biomagnification of Hg as a benchmark for assessing their bioaccumulation potential.
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- 2020
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7. Stable Isotope Analysis and Persistent Organic Pollutants in Crustacean Zooplankton: The Role of Size and Seasonality
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Roberta Piscia, Michela Mazzoni, Roberta Bettinetti, Rossana Caroni, Davide Cicala, and Marina Marcella Manca
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stable isotope analysis ,persistent organic pollutants ,crustacean zooplankton ,freshwater ,size fractions ,seasonality ,Hydraulic engineering ,TC1-978 ,Water supply for domestic and industrial purposes ,TD201-500 - Abstract
Zooplankton is crucial for the transfer of matter, energy, and pollutants through aquatic food webs. Primary and secondary consumers contribute to the abundance and standing stock biomass, which both vary seasonally. By means of taxa- and size-specific carbon and nitrogen stable isotope analysis, the path of pollutants through zooplankton is traced and seasonal changes are addressed, in an effort to understand pollutant dynamics in the pelagic food web. We analyzed zooplankton plurennial changes in concentration of polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane and its relatives (DDTs) and in taxa-specific δ15N signatures in two size fractions, ≥450 µm and ≥850 µm, representative of the major part of zooplankton standing stock biomass and of the fraction to which fish predation is mainly directed, respectively. Our work is aimed at verifying: (1) A link between nitrogen isotopic signatures and pollutant concentrations; (2) the predominance of size versus seasonality for concentration of pollutants; and (3) the contribution of secondary versus primary consumers to carbon and nitrogen isotopic signatures. We found a prevalence of seasonality versus size in pollutant concentrations and isotopic signatures. The taxa-specific δ15N results correlated to pollutant concentrations, by means of taxa contribution to standing stock biomass and δ15N isotopic signatures. This is a step forward to understanding the taxa-specific role in pollutant transfer to planktivores and of zooplankton enrichment in PCBs and DDTs.
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- 2019
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8. Non-native fish assemblages display potential competitive advantages in two protected small and shallow lakes of northern Italy
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Vanessa, De Santis, primary, Davide, Cicala, additional, Ilaria, Baneschi, additional, Chiara, Boschi, additional, Stefano, Brignone, additional, Mattia, Iaia, additional, Silvia, Zaupa, additional, and Pietro, Volta, additional
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- 2022
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9. Ask the shark: Blackmouth catshark (Galeus melastomus) as a sentinel of plastic waste on the seabed
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Alice Sbrana, Alessandro Cau, Davide Cicala, Simone Franceschini, Tommaso Giarrizzo, Maria Flavia Gravina, Alessandro Ligas, Giulia Maiello, Marco Matiddi, Antonio Parisi, Paolo Sartor, Mario Sbrana, Umberto Scacco, Tommaso Valente, Claudio Viva, and Tommaso Russo
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Ecology ,Settore BIO/07 ,Plastic pollution ,plastic pollution ,Mediterranean Sea ,biomonitoring ,Galeus melastomus ,diet ,Biomonitoring ,Aquatic Science ,Ecology, Evolution, Behavior and Systematics ,Diet - Abstract
The presence of plastic waste in the marine environment has driven the scientific community to make significant efforts to study and mitigate its possible effects. One of the critical aspects is to determine if and how an increase in ingestion events may occur as a result of the accumulation of plastic waste on the seabed. In this study, G. melastomus is examined for its ability to indirectly provide information on the amount of macroplastics accumulating on the seafloor. Plastic ingestion is explored by describing the feeding habits of the species, which have the potential to provide very useful information regarding biological or ecological issues. The diet of G. melastomus mainly consisted of cephalopods, bathypelagic fishes, and decapod crustaceans, increasing in diversity during growth. The generalist-opportunistic feeding behaviour of this species leads to the incidental ingestion of plastic particles (N = 47, with a mean (± SD) of 1.47 ± 0.28 per specimen) which can be indirectly associated to the presence of macroplastics on the seafloor. Indeed, our results indicate a significant relationship between the amount of macroplastics present on the seabed and the frequency of ingestion of plastic particles by blackmouth catshark. We propose G. melastomus as an excellent candidate for developing a valid monitoring strategy for the presence of plastics on the seabed, as requested by the EU Marine Strategy Framework Directive.
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- 2022
10. Phthalate esters (PAEs) concentration pattern reflects dietary habitats (δ
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Monica Francesca, Blasi, Pasquale, Avino, Ivan, Notardonato, Cristina, Di Fiore, Daniela, Mattei, Marco Friedrich Walter, Gauger, Michelle, Gelippi, Davide, Cicala, Sandra, Hochscheid, Andrea, Camedda, Giuseppe Andrea, de Lucia, and Gabriele, Favero
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Diethylhexyl Phthalate ,Phthalic Acids ,Animals ,Esters ,Ecosystem ,Gas Chromatography-Mass Spectrometry ,Diet ,Turtles - Abstract
Phthalic acid esters (PAEs) are classified as endocrine disruptors, but it remains unclear if they can enter the marine food-web and result in severe health effects for organisms. Loggerhead turtles (Caretta caretta) can be chronically exposed to PAEs by ingesting plastic debris, but no information is available about PAEs levels in blood, and how these concentrations are related to diet during different life stages. This paper investigated, for the first time, six PAEs in blood of 18 wild-caught Mediterranean loggerhead turtles throughout solid-phase extraction coupled with gas chromatography-ion trap/mass spectrometry. Stable isotope analyses of carbon and nitrogen were also performed to assess the resource use pattern of loggerhead turtles. DEHP (12-63 ng mL
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- 2021
11. Spatial variation in the feeding strategies of Mediterranean fish. Flatfish and mullet in the Gulf of Gaeta (Italy)
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Giulio Careddu, Davide Cicala, Loreto Rossi, Simona Sporta Caputi, Federico Fiorentino, Maria Letizia Costantini, and Edoardo Calizza
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0106 biological sciences ,Ecological niche ,biology ,Ecology ,010604 marine biology & hydrobiology ,estuarine and coastal waters ,Pegusa lascaris ,stable isotopes ,Interspecific competition ,Aquatic Science ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Food web ,Mullet ,Liza ramada ,trophic niche ,Demersal fish ,Citharus linguatula ,Ecology, Evolution, Behavior and Systematics ,Isotope analysis ,Trophic level - Abstract
Marine coastal areas are highly productive due to the presence of various inputs of organic matter, including terrestrial material, which fuels food webs. However, the ecological mechanisms underlying the productivity of benthic and demersal fish species in estuarine areas are poorly understood. By means of C and N stable isotope analysis and Bayesian mixing models, we investigated the trophic niches of three common fish species: Citharus linguatula, Pegusa lascaris (flatfish) and Liza ramada (mullet) in the Gulf of Gaeta (Italy). Fish were collected from the north-western area and the south-eastern area of the Gulf of Gaeta, the latter affected by organic inputs from the Garigliano River. The results highlighted the riverine terrestrial origin of the organic matter at the base of the food web in the south-eastern area and marine autochthonous input in the north-western area. All fish species increased their trophic specialisation in proximity to the river mouth. L. ramada specialised on seston of terrestrial origin, reducing its niche overlap with C. linguatula and P. lascaris. Away from the river mouth, all species were characterised by longer individuals, increased intraspecific diet variability and higher interspecific similarity in resource use. Organic input from the river represented a complementary trophic niche axis that enabled lower interspecific niche overlap in the south-eastern area, where fish populations were found at higher densities. In conclusion, this study provided information about the effects of the flow of material from the basal compartment up to abundant fish species in areas enriched by organic matter of varying origin.
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- 2019
12. Trophic Magnification of Legacy (PCB, DDT and Hg) and Emerging Pollutants (PFAS) in the Fish Community of a Small Protected Southern Alpine Lake (Lake Mergozzo, Northern Italy)
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Roberta Piscia, Roberta Bettinetti, Katrine Borgå, Michela Mazzoni, Sara Valsecchi, Pietro Volta, Davide Cicala, Stefano Polesello, and Claudia Ferrario
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lcsh:Hydraulic engineering ,010504 meteorology & atmospheric sciences ,Biomagnification ,PFAS ,Geography, Planning and Development ,chemistry.chemical_element ,lake fish ,010501 environmental sciences ,Aquatic Science ,01 natural sciences ,Biochemistry ,Zooplankton ,lcsh:Water supply for domestic and industrial purposes ,lcsh:TC1-978 ,trophic magnification factor ,0105 earth and related environmental sciences ,Water Science and Technology ,Trophic level ,lcsh:TD201-500 ,Pelagic zone ,Biota ,Hg ,Food web ,Mercury (element) ,bioaccumulation ,chemistry ,Bioaccumulation ,Environmental chemistry ,Environmental science ,organochlorine compounds ,Lake fish ,Organochlorine compounds ,Trophic magnification factor - Abstract
The biomagnification of mercury, polychlorobiphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs) and perfluoroalkyl acids substances (PFASs) was evaluated in the trophic web of Lake Mergozzo, a small and deep Italian subalpine lake, which has been chosen because it is a protected environment, and discharges into the lake are mostly avoided. Carbon source and relative trophic levels were calculated by using 13C and 15N stable isotopes, respectively, and trophic magnification factors (TMFs) were derived. Zooplankton and thirteen species of fish were collected and analyzed, and the results showed the elevated level of biota contamination from both legacy and emerging pollutants, even if direct discharges were avoided. Concentrations in biota, expressed as sums of compounds, ranged from 0.4 to 60 µ, g kg&minus, 1 wet weight (ww) for PFASs, from 16 to 1.3 104 µ, 1 lipid content (lw) for DDTs, from 17 to 1.5 104 µ, 1 lw for PCBs and from 20.0 to 501 µ, 1 ww for mercury (Hg). TMFs of this deep, cold lake, with a prevalent pelagic trophic chain, were high and clearly indicated fish biomagnification, except for PFAS. The biomagnification capability of PFAS in a fish-only food web was discussed by using the biomagnification of Hg as a benchmark for assessing their bioaccumulation potential.
- Published
- 2020
13. The role of alien fish (the centrarchid Micropterus salmoides) in lake food webs highlighted by stable isotope analysis
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Loreto Rossi, Pasquale Carlino, Maria Letizia Costantini, Giulio Careddu, Davide Cicala, Simona Sporta Caputi, Edoardo Calizza, and Federico Fiorentino
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0106 biological sciences ,fish ,food web ,invasive species ,predation ,stable isotopes ,aquatic science ,biology ,Ecology ,010604 marine biology & hydrobiology ,Micropterus ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Food web ,Predation ,Habitat ,Freshwater fish ,Trophic level ,Isotope analysis ,Apex predator - Abstract
Non‐native freshwater fish species can have adverse ecological impacts on native populations. However, the mechanisms determining the success or otherwise of their invasion and their role in invaded communities remain largely unknown. This is particularly true for the Mediterranean region, where endemic species characterised by restricted natural ranges may be at high risk of extinction. The largemouth bass (Micropterus salmoides) is native to North America but is invasive in the Italian Peninsula. The aim of this study was to explore the trophic position of M. salmoides, its diet and niche overlap with native fish species in the littoral areas of a Mediterranean lake. Our study was supported by analysis of stable C and N isotopes in the tissues of fish and their potential food sources, twenty years after the introduction of the largemouth bass to Lake Bracciano (Italy). Samples were collected in locations varying in terms of physical structure and resource availability at lower trophic levels in the food web, which was greater in the southern (hereafter: South) than in the northern (hereafter: North) area of the lake. These differences made it possible to explore the mechanisms linking environmental conditions and the role of alien predators in the invaded food web. The abundance of M. salmoides was higher, and the diversity of native fish species was lower, in North than South. In North, M. salmoides had a piscivorous diet and occupied a higher trophic position in the food web than in South, where invertebrates constituted an important part of its diet. As a consequence, trophic niche interference with other fish species at intermediate trophic levels was higher in South. In contrast, in North, M. salmoides showed stronger trophic interference with the percid Perca fluviatilis, a native top predator in the food web, but weaker interference with remaining fish species. Our results help to understand the role of alien species in the food webs of Lake Bracciano, which primarily depends on the habitat and the availability of prey across trophic levels. Physical and ecological variations in the habitat were associated with differences in predatory interactions among native and alien fish species. This suggests that a reduction in productivity and biodiversity at lower trophic levels in lake food webs may favour the success of opportunistic invasive fish species, given the ability of the invaders to maintain some of their characteristics silent, and to fully express their genotype under favourable environmental conditions.
- Published
- 2018
14. Epilithon δ15N signatures indicate the origins of nitrogen loading and its seasonal dynamics in a volcanic lake
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Loreto Rossi, Edoardo Calizza, Giulio Careddu, Maria Letizia Costantini, Giovanna Jona-Lasinio, Davide Cicala, and Federico Fiorentino
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0106 biological sciences ,decision sciences (all) ,bioindicator ,environmental monitoring ,freshwater ,stable isotopes ,tourism ,water pollution ,ecology evolution ,behavior and systematics ,ecology ,General Decision Sciences ,010501 environmental sciences ,01 natural sciences ,Algal bloom ,Ecosystem ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences ,Ecology ,010604 marine biology & hydrobiology ,Aquatic ecosystem ,Lake ecosystem ,Plankton ,Oceanography ,Environmental science ,Spatial variability ,Eutrophication ,Bioindicator - Abstract
The intensification of agricultural land use and urbanisation has increased nutrient loads in aquatic ecosystems. Nitrogen loads can alter ecosystem structure and functioning, resulting in increased algal productivity, algal blooms and eutrophication. The principal aim of the present paper is to extend the use of epilithic δ 15 N signatures to a lake ecosystem in order to evaluate the potential impact of anthropogenic nitrogen discharges (organic and inorganic) that can also reach coastal waters. Epilithic associations were collected from volcanic rocks in different seasons in shallow water along the entire perimeter of Lake Bracciano and analysed for their nitrogen stable isotope signatures. Furthermore, some stones were moved from an unpolluted site to a polluted one in order to verify the effect on the nitrogen signature of the epilithic association. The epilithon’s δ 15 N signatures provided strong evidence of the space-time variability of N inputs. The differing quality of nitrogen loads was reflected in high isotopic variation within the lake, especially at the beginning of summer (1.7‰ ≤ δ 15 N ≤ 13.3‰), while in winter, when anthropogenic pressure was lowest, the δ 15 N signature variation was less accentuated (3.1‰ ≤ δ 15 N ≤ 7.6‰). At all sampling times, spatial variability was found to be related to the various human activities along the lake shore (especially tourism and agriculture), while seasonal variation at all sampling sites was related to the intensity of anthropogenic pressures (higher in summer and lower in winter). Our results showed that epilithic algal associations and the physicochemical properties of the water did not influence the δ 15 N signature, which in contrast was strongly related to the site-specific effect of human activities around the lake. Thus, the distribution of δ 15 N across space and time can be used to direct nutrient reduction strategies in the region and can assist in monitoring the effectiveness of environmental protection measures.
- Published
- 2017
15. Epilithon δ15N signatures indicate the origins of nitrogen loading and its seasonal dynamics in a volcanic Lake.
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Federico, Fiorentino, Davide, Cicala, Giulio, Careddu, Edoardo, Calizza, Giovanna, Jona-Lasinio, Loreto, Rossi, and Letizia, Costantini Maria
- Subjects
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CRATER lakes , *NITROGEN isotopes , *WATER pollution , *EUTROPHICATION , *ENVIRONMENTAL protection - Abstract
The intensification of agricultural land use and urbanisation has increased nutrient loads in aquatic ecosystems. Nitrogen loads can alter ecosystem structure and functioning, resulting in increased algal productivity, algal blooms and eutrophication. The principal aim of the present paper is to extend the use of epilithic δ 15 N signatures to a lake ecosystem in order to evaluate the potential impact of anthropogenic nitrogen discharges (organic and inorganic) that can also reach coastal waters. Epilithic associations were collected from volcanic rocks in different seasons in shallow water along the entire perimeter of Lake Bracciano and analysed for their nitrogen stable isotope signatures. Furthermore, some stones were moved from an unpolluted site to a polluted one in order to verify the effect on the nitrogen signature of the epilithic association. The epilithon’s δ 15 N signatures provided strong evidence of the space-time variability of N inputs. The differing quality of nitrogen loads was reflected in high isotopic variation within the lake, especially at the beginning of summer (1.7‰ ≤ δ 15 N ≤ 13.3‰), while in winter, when anthropogenic pressure was lowest, the δ 15 N signature variation was less accentuated (3.1‰ ≤ δ 15 N ≤ 7.6‰). At all sampling times, spatial variability was found to be related to the various human activities along the lake shore (especially tourism and agriculture), while seasonal variation at all sampling sites was related to the intensity of anthropogenic pressures (higher in summer and lower in winter). Our results showed that epilithic algal associations and the physicochemical properties of the water did not influence the δ 15 N signature, which in contrast was strongly related to the site-specific effect of human activities around the lake. Thus, the distribution of δ 15 N across space and time can be used to direct nutrient reduction strategies in the region and can assist in monitoring the effectiveness of environmental protection measures. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
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