1,721,067 research outputs found
Hypolimnetic oxygen depletion in a deep oligomictic lake under climate change
Get PDFDissolved oxygen (DO) concentration is a fundamental metric to describe climate-related alterations in deep lakes. Increasing water temperatures enhance thermal stratification, leading in temperate basins to a growing isolation of deep waters. This leads to the depletion of hypolimnetic DO, which adds up to limited nutrient circulation and restricted replenishment of the trophogenic layers. With vanishing convective mixing, it is commonly believed that the only source of hypolimnetic DO replenishment will be represented by deep intrusions of cold oxygenated waters from the tributaries. In this study, we first analyse the 1993-2020 long-term observed trends of DO concentrations in the subalpine deep oligomictic Lake Maggiore (Italy/Switzerland). Then, through an algorithm calculating daily intrusion depths and mass discharges of DO for the major tributaries, we show that deep insertions are suppressed for increasing winter water temperatures and residual thermal stratification. Turbulent entrainment is proved fundamental for DO replenishment, leading to mass discharges of DO released into the deep hypolimnion up to more than two orders of magnitude larger than the original ones from the tributaries. Last, we discuss the results of simulations made through a one-dimensional coupled ecological-hydrodynamic model about the possible effects of a full turnover on DO concentrations in the deep hypolimnion. Two cases are displayed, with the turnover taking place either now or with an anoxic hypolimnion deriving from decades of isolation due to severe climate warming. Through this study, climate warming is shown to be a fundamental driver of DO in Lake Maggiore, its depletion harming both water quality and the ecosystem
Model simulations of the ecological dynamics induced by climate and nutrient load changes for deep subalpine Lake Maggiore (Italy/Switzerland)
Get PDFClimate warming affects lake ecosystems both through its direct effect on the phenology of species and through the alteration of the physical and chemical environments, which in turn affect community composition. In deep lakes, stratification enhancement and mixing reduction have already been observed, leading to hypolimnetic anoxia and to the rise of cyanophytes. The increase in stability depends on the rise of air temperature due to global emissions of greenhouse gases (GHG). Primary production could then either increase with rising epilimnetic temperature and buoyancy or decrease as fewer nutrients are upwelled from deep layers. The prevailing outcome, as well as the quantitative and temporal dynamics of all climate-induced modifications, depend on the specific lake characteristics. Individual analyses are then needed, one-dimensional coupled hydrodynamic-ecological numerical models being suitable tools for such predictions. Here, we simulated with GLM-AED2 (General Lake Model – Aquatic EcoDynamics) the 2020-2085 dynamics of the oligomictic and oligotrophic deep subalpine Lake Maggiore (Italy/Switzerland), according to the Swiss Climate Change Scenarios CH2011. Multiple realisations were performed for each scenario with random meteorological series obtained from the Vector-Autoregressive Weather Generator (VG), highlighting the uncertainties related to meteorology. Increase and decrease of nutrient loads were also tested. Results show that anoxia would occur in the hypolimnion regardless of nutrient input reduction, unless global GHG emissions were immediately reduced. Total phytoplankton biomass would be weakly affected by climate change, strongly depending on nutrient input, yet water warming would cause cyanophytes to compete with diatoms. Therefore, the fate of Lake Maggiore would be tied to both global and local environmental policies
Relevance of inflows on the thermodynamic structure and on themodeling of a deep subalpine lake (Lake Maggiore, NorthernItaly/Southern Switzerland)
No full texttAtmospheric exchanges largely dominate the heat budget of deep lakes in temperate regions. Heat importand export by through-flows is of much lower entity and has been neglected or simplified in many numer-ical thermodynamic models of lakes. This is often due either to the unavailability of data for inflows andoutflows, or to the difficulties in forecasting the evolution of their discharge and temperature in cli-mate change studies. While disregarding through-flows may seem correct, riverine intrusions can bringwarmer water than the deep hypolimnetic one to the lower metalimnion and upper hypolimnion, wheresunlight does not penetrate and mixing is poor. For holomictic lakes with significant inflow contribu-tions, this can affect the thermal structure at intermediate depths, hampering any numerical modelwhich neglects through-flows. This study focuses on a relevant basin under such aspect, Lake Maggiore(Northern Italy/Southern Switzerland), which drains the rainiest watershed of the Southern Alps. First, wequantify to what extent a one-dimensional fixed-level model ignoring through-flows is able to predict theobserved evolution of the thermal structure of the lake and the improvements resulting from reproducingthe main inflows and outflows. Then, we directly discuss the influence of through-flows on the thermo-dynamic structure of Lake Maggiore. The General Lake Model (GLM) was here adopted, reproducing the1998–2014 period, spanning years with different meteorological and hydrological features. Results showthat a calibrated enclosed-lake model can give satisfactory results only if it employs an unrealisticallylow light extinction coefficient to allow heating of the deep metalimnion and hypolimnion, whose realwarming strongly depends on interflows
Rainfall increases the abundance of antibiotic resistance genes within a riverine microbial community
No full textInfections with antibiotic resistant bacteria are among the major threats for human health. Studies elucidating the role of the environment in their spread are still in their infancy, it, however, seems that different environments might function as a long-term reservoir of antibiotic resistance genes (ARGs) that reside within their microbial communities. An increasing number of studies target the presence and the persistence of ARGs in waters and soils that are exposed to human activities; they, however, rarely consider the spatial/temporal variability that predominate in these environments. Here we evaluated the effect of a moderate rain event (4 mm rain hâ1) on the abundance and distribution of ARGs (tetA, ermB, blaCTXM, sulII, and qnrS), by comparing measurements of gene abundances during the rainfall to the yearly average, in the waters of a large subalpine river. ARG abundances, which all increased during the rain event, were then correlated to several microbiological, physical and chemical variables, in order to establish their potential origin. Increments in ARG abundances during rainfall (total ARGs: 24 fold) was concomitant to an increase in total phosphorous, N-NH4, and microbial aggregates. Our results show a strong influence of a moderate rainfall on the abundances of ARGs, and suggest the catchment as their source. The impact of moderate rainfalls in areas exposed to anthropic activities should then be considered in modelling and management of ARG dynamics
Forecasting the evolution in the mixing regime of a deep subalpine lake under climate change scenarios through numerical modelling (Lake Maggiore, Northern Italy/Southern Switzerland)
Get PDFThe impact of air temperature rise is eminent for the large deep lakes in the Italian subalpine district, climate change being caused there by both natural phenomena and anthropogenic greenhouse-gases (GHG) emissions. These oligomictic lakes are experiencing a decrease in the frequency of winter full turnover and an intensification of stability. As a result, hypolimnetic oxygen concentrations are decreasing and nutrients are accumulating in bottom water, with effects on the whole ecosystem functioning. Forecasting the future evolution of the mixing pattern is relevant to assess if a reduction in GHG releases would be able to revert such processes. The study focuses on Lake Maggiore, for which the thermal structure evolution under climate change in the 2016–2085 period was assessed through numerical simulations, performed with the General Lake Model (GLM). Different prospects of regional air temperature rise were considered, given by the Swiss Climate Change Scenarios CH2011. Multiple realisations were performed for each scenario to obtain robust statistical predictions, adopting random series of meteorological data produced with the Vector-Autoregressive Weather Generator (VG). Results show that a reversion in the increasing thermal stability would be possible only if global GHG emissions started to be reduced by ~ 2020, allowing an equilibrium mixing regime to be restored by the end of the twenty-first century. Otherwise, persistent lack of complete-mixing, severe water warming and extensive effects on water quality are to be expected for the centuries to come. These projections can be extended to the other lakes in the subalpine district
Satellite Monitoring system of Subalpine lakes with open source software: the case of SIMILE Project
No full textSIMILE Project has the aim of supporting the definition of management policies and the
operational decisions for the insubric Lakes through an innovative information system based on
data from an integrated monitoring system, consisting of remote sensing of water quality
parameters of the lakes with latest generation satellite images, buoys equipped with sensors for the
continuous detection of limnological and meteorological parameters within the lakes and in the use
of additional data on water quality that will be collected through citizen science. Maggiore,
Lugano and Como are the lakes involved in the project. This paper presents the satellite
monitoring system implemented for the project, based on open data and GIS tools, together with
the results obtained in the first 18 months of activitie
Patagonian ostracods as indicators of climate-related hydrological variables: Implications for paleoenvironmental reconstructions in Southern South America
Get PDFDifferent precipitation regimes across Patagonia generate an environmental gradient that is expected to reflect upon the solute composition and concentration of lake water through the ensuing differences in water balance. In turn, this hydrochemical gradient could influence the occurrence and distribution of ostracods in the area. A cluster analysis on hydrochemical data of 36 Southern Patagonian waterbodies shows that low salinity, bicarbonate-dominated waters characterize Andean and ecotonal lakes, located in the wetter part of the precipitation gradient, while their steppe counterparts, which receive a much lower precipitation input, are more saline, enriched in all major anions and sodium-dominated. Kruskal-Wallis tests followed by Mann-Whitney pairwise comparisons show statistically significant differences in the ostracod species each water type hosts, with L. patagonica, E. cecryphalium, P. smaragdina and P. incae being found in the more dilute waters characteristic of Andean and ecotonal lakes and Limnocythere rionegroensis in the mesohaline, evaporatively evolved waters typical of steppe lakes. Other species studied do not appear to have such distinct distributions, having been found throughout the range of conditions studied. These findings promote the use of the aforementioned ostracods as semi-quantitative paleohydrological indicators, which could improve paleoclimatic reconstructions in Patagonia.Fil: Ramón Mercau, María Josefina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Laprida, Cecilia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Massaferro, Julieta. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Administración de Parques Nacionales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rogora, Michela. Consiglio Nazionale delle Ricerche; ItaliaFil: Tartari, Gabriele. Consiglio Nazionale delle Ricerche; ItaliaFil: Maidana, Nora Irene. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
PET particles raise microbiological concerns for human health while tyre wear microplastic particles potentially affect ecosystem services in waters
Get PDFAlthough abundant and chemically peculiar, tyre wear microplastic particles (TWP) and their impact on the microbial communities in water are largely understudied. We tested in laboratory based semi-continuous cultures the impact of TWP and of polyethylene terephthalate (PET) derived particles (following a gradient of relative abundance) on the pathobiome (the group of potential human pathogenic bacteria) of a freshwater microbial community exposed to contamination by the effluent of a urban wastewater treatment plant, for a period of 28 days. We could define the modulated impact of the two types of microplastic particles: while PET does not favour bacterial growth, it offers a refuge to several potential pathogens of allochthonous origin (from the treated sewage effluent), TWP act as an additional carbon source, promoting the development and the massive growth of a biofilm composed by fast-growing bacterial genera including species potentially harmful and competitive in abating biodiversity in surface waters. Our results demonstrate the different ecological role and impact on freshwater environments of TWP and PET particles, and the need to approach the study of this pollutant not as a whole, but considering the origin and the chemical composition of the different particles.Fil: Sathicq, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Limnología "Dr. Raúl A. Ringuelet". Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología; ArgentinaFil: Sabatino, Raffaella. Consiglio Nazionale delle Ricerche; ItaliaFil: Di Cesare, Andrea. Consiglio Nazionale delle Ricerche; ItaliaFil: Eckert, Ester M.. Consiglio Nazionale delle Ricerche; ItaliaFil: Fontaneto, Diego. Consiglio Nazionale delle Ricerche; ItaliaFil: Rogora, Michela. Consiglio Nazionale delle Ricerche; ItaliaFil: Corno, Gianluca. Consiglio Nazionale delle Ricerche; Itali
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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