Anthropic Effects Research Articles

The Late Holocene evolution of the Adra Delta subaqueous system (Northern Alboran Sea): Seismic-stratigraphic and geomorphic evidence of millennial scale climatic and anthropic effects

The formation and development of a small Mediterranean deltaic system are investigated through a primary seismic stratigraphic interpretation of a high-resolution seismic profile network, combined with multiple bathymetric data (including multibeam bathymetric imagery) and collated with shallow sediment cores collected with a vibro-corer device.The submarine delta of the Adra River is divided into a basal patchy seismic unit and five wedge-shaped younger seismic units that are related to the Holocene highstand stabilization. Limited age control indicates that the two uppermost seismic units are very recent, most likely related to a dearth of fluvial fluxes led by channel deviations and by sediment retention. The formation of the three older seismic units is correlated to three humid periods during the Middle Holocene, Late Holocene and Little Ice Age, under a general context of progressive aridification of southeastern Iberia.The stacking patterns and spatial distribution of individual seismic units document a history of episodic progradation of successive prodeltaic lobes, with a long-term evolution mediated by climatically-induced changes in the river basin and more recent anthropogenic interventions. Overall, the subaqueous deltaic system registers the complete modification of a deltaic system that evolves from a fluvial-dominated delta to recent wave-dominated wedges. In between, the deltaic system exhibits a progressive asymmetric character, due to the instauration of Atlantic waters on the shelf and their subsequent eastward redistribution. The Adra deltaic system is proposed as an outstanding example of a small deltaic system that reacts almost immediately to the complex interaction between natural changes in the system and anthropogenic interventions in the drainage basin.

Anthropogenic effect on the pedochemical variability of potentially toxic elements at the vicinity of an Antarctic research station.

Antarctica represents an isolated continent devoted to conservation and scientific research, although it accumulates records of increasing anthropic contamination. The historical continued use of fuel for power generation in Antarctic settlements is a potential source of toxic elements to the soil. We investigate Cd, Cr, Cu, Mn, Ni, Pb, V and Zn levels in surface soils in the vicinity of the Henryk Arctowski Antarctic Station, aiming to identify anthropic effects on their local pedochemical variability. Pollution indices were used and compared to evaluate possible cumulative anthropic impacts, whereas correlation analyzes were explored to identify potential sources of contamination. High concentrations of Pb and Zn were locally observed near fuel tanks and machinery facilities. Correlation and principal component analysis suggest that old fuel tanks, vehicle traffic and machinery disturbance are key, and contrasting, sources of contamination. Among the eight indices we compared, Enrichment Factor and Modified Degree of Contamination were chosen, showing very high enrichment for Pb and moderate for Zn. All other elements presented minimal or null enrichment. The evidence of potentially toxic elements enrichment on Antarctic soils associated with the long-term occupation of Antarctic research stations highlights the need for further monitoring and mitigation measures, especially in energy-generating systems.

Exploring biodiversity patterns in a marine and coastal protected area: Implications for management within and outside MCPAs

Identifying patterns and understanding the processes associated with Marine and Coastal Protected Areas (MCPAs) (local scale) are essential for developing specific hypotheses about trophic interactions and potential cascading effects of local and global changes. This can also serve as an initial step in the identification of biodiversity patterns and biological interactions on a regional scale. This study characterized a set of species/taxa composed of four subcommunities featuring macrobenthic infauna, epibenthic megafauna, birds, and mammals observed between 2019 and 2021 in the estuarine and marine system of the Pitipalena-Añihué MCPA in Chilean Patagonia. Biodiversity patterns were analyzed using multidimensional models and indices.A pool of 276 taxa were observed within the studied subcommunities, and reproduction was confirmed for several bird and mammal species (mostly on islets). The results indicate a system with several types of habitats, where the sea lion Otaria flavescens was dominant among the group of marine mammals. Notably, birds and epibenthic megafauna showed differences between the marine and estuarine environment. The observed biodiversity patterns can be attributed to environmental heterogeneity, as well as anthropic effects (including invasive species, fishing, and aquaculture). This work proposes a synthesized spatial distribution scheme of the main taxa, complemented by a matrix of hypothetical trophic interactions. Along with demonstrating the current lack of available information, this matrix offers an opportunity to assess the ecosystem's sensitivity, identify relevant information gaps, and develop hypotheses about specific trophic interactions (scalable to the region) and the potential cascading effects of ocean changes.

Phytoecological study of a Biosphere Reserve in arid climate in Tunisia

Anthropic effects and global change threaten biodiversity and genetic resources. Thus, their conservation becomes a primary necessity. This work aims to assess the conservation conditions for vegetation and causes that limit the progressive dynamics of the vegetation cover after a long period of defense. Using the quadrat point method, his work was conducted in two fenced zones and an unfenced zone of the Biosphere Reserve of BouHedma in a Tunisian arid climate. A total of 66 transects were investigated. In each transect species richness and, α and β indices were determined. The α and β diversity showed a low similarity in family and species composition in the studied zones. The Poaceae and Asteraceae families were the most representative in the studied zones and the most used for grazing. These results highlight that long-term conservation contributes to minimizing the reduction of biodiversity in the reserve. It is necessary to minimize razing and deforestation, especially in the unfenced zone. Thus, the setup of barriers and fences is highly recommended to retain the soil. In addition, finding an effective communication plan with the local population and visitors seems to be crucial.

Changes in submerged aquatic vegetation cover off the northern Yucatán Peninsula detected with Sentinel-2 imagery using a fuzzy classification system

Submerged aquatic vegetation (SAV) plays a major role in various coastal ecological processes, providing habitat and food to a marine community and environmental benefits to people. However, seagrass meadow extensions around the world are shrinking. The objective of this study was to analyze recent variation in SAV coverage along the northern coast of the Yucatán Peninsula. Using Sentinel-2 satellite imagery, acoustic echosounder field surveys, and a fuzzy classification system, we produced binary cartographic models of SAV coverage for 2016, 2018, and 2019. In a study area of approximately 16342 km2, we estimated SAV coverage of 5957.90 km2 in 2016, with a decline to 2873.55 km2 by 2019. Coverage in protected areas decreased from 2376.03 km2 to 1690.89 km2 over the same period. The Federal Protected Area for Flora and Fauna of Yum-Balam showed an estimated gain of 48.3 km2 (r = 11.63%), but that of Laguna de Términos an estimated reduction of 508.50 km2 (r = -29.77%), and coverage in the Los Petenes Biosphere Reserve decreased by 186.5 km2 (r = −5.35%). These changes are likely part of a complex dynamic in the study area, one that may include anthropic effects.

Spatial variation of summer microphytoplankton and zooplankton communities related to environmental parameters in the coastal area of Djerba Island (Tunisia, Eastern Mediterranean)

In the present study, we investigated the effects of pollution and anthropization on the summer distribution of phyto-zooplanktoncommunities in relation to environmental factors in the coastal zone of DjerbaIsland. On the basis of chemical factors, theDjerba coasts can be divided into two parts: the Western Area (WA), characterized by high values of nitrogen forms of nutrients,with higher N/P ratio, and the Eastern Area (EA), poorer in inorganic nitrogen with an N/P ratio lower than the Redfield ratio (16).Strong differences in terms of plankton communities were also observed between these two areas. Bacillariophyceae was the most important microphytoplankton group in the WA whereas the proportion of Cyanobacteria was higher in the EA. High Cyanobacteria abundance in the EA may be linked to high DIP concentration. In the WA, the Bacillariophyceae Chaetoceros, Coscinodiscus, Grammatophora, Navicula and Pinnularia reached high abundance in relation with their good adaptability to adverse conditions. Copepods were the most abundant zooplankton present in the WA (54–100% of total zooplankton abundance), whereas other zooplankton were always dominant (60–90%) in the EA. The small pollution-tolerant Calanoid copepod Paracalanus parvus was dominant in the WA, illustrating its affinity for highly eutrophic sites. Despite human pressure and industrial activities, the coastal waters of Djerba showed a wide diversity of microphytoplankton and zooplankton.

Sarcosaprophagous Muscid Fly (Diptera: Muscidae) Assemblages Along an Anthropized Gradient in the Humid Chaco Ecoregion, Chaco Province, Argentina.

Deforestation, agriculture, farmyard animal husbandry, and urbanization are known to be the main causes of biodiversity loss and habitat fragmentation. The present study evaluated the role of anthropization in modulating Muscidae (Diptera) assemblages in the Humid Chaco ecoregion of Argentina, by testing the biotic homogenization and intermediate disturbance hypotheses. The study focused on natural, rural, and urban habitats in San Lorenzo Department, Chaco Province, where sarcosaprophagous muscid flies were surveyed. A total of 1,343 muscid flies were captured and identified to 7 genera and 24 species and morphospecies. We observed the effect of anthropization on the structuring of the assemblages and the presence of exotic species associated with human activity resulting from biotic homogenization. The highest abundance was recorded in the urban habitat, while the highest species richness and diversity (Shannon-Wienner and Hill's numbers) were found in the rural habitat, supporting the intermediate disturbance hypothesis. Several species are classified as indicators of habitat as well as according to their index of synanthropy. Our results provide valuable information about the use of sarcosaprophagous muscids as indicators of disturbance of natural habitats and about possible health risks related to this family of Calyptratae flies previously unsurveyed in northeastern Argentina. This information could be used in the ecological, agronomy, sanitary, and forensic fields.

Tara (Caesalpinia spinosa) in Natural and Agroforestry Systems under an Altitudinal Gradient in the Peruvian Andes: Responses to Soil and Climate Variation

This research examined how edaphoclimatic variations are related to dendrometric variables of the Tara tree in natural and agroforestry systems in Cajamarca, Peru. Evaluations followed three approaches: (a) principal components analysis (PCA) with environmental factors and altitude classes with 1 °C of temperature variation for edaphic and dendrometric variables; (b) evaluation of possible differences by the bootstrap method for the different variables in the PCAs; and (c) correlation analysis between plant density, plant and crown height, stem and crown diameter, and the number of stem branches with the physical and chemical attributes of the soil and with air temperature. In the altitudinal gradient from 2021 to 3007 ± 7 m, the temperature ranged from 19.8 to 13.4 ± 0.4 °C; the soils possessed alkaline pH, high organic matter (OM), K and CEC, lower contents of CaCO3, N, P, K, B, Cu, Fe, Mn, and Zn. The soil properties with the most significant contribution to PCAs were OM, CEC, N content, and sand, with no variation among environments but among altitudes. None of the dendrometric variables varied as a function of altitude and temperature in PCAs run in the natural environment. However, in the agroforestry environment, there was a greater crown diameter, and tree and crown height in the 2185 m altitude class associated with Medicago sativa. In contrast, the opposite behavior was found in these variables and in the altitude class 2798 m associated with low Fe content, and already in the altitude class at 3007 m, a larger stem diameter is associated with higher levels of CaCO3. The anthropic effect on the agroforestry environment did not significantly alter the soil’s CEC, OM, N, and sand. Tara’s crown diameter and tree height appeared higher in agroforestry environments. The variations of Fe and CaCO3 in the soil might have influence on the development of Tara individuals in natural and agroforestry environments. It is important to carry out further studies for a better understanding of the relationship between the production of Tara pods and soil fertility in altitudinal variation, aiming to improve the income and employment of family farmers who exploit Tara in the Peruvian Andes.

Microbial diversity and proxy species for human impact in Italian karst caves

To date, the highly adapted cave microbial communities are challenged by the expanding anthropization of these subterranean habitats. Although recent advances in characterizing show-caves microbiome composition and functionality, the anthropic effect on promoting the establishment, or reducing the presence of specific microbial guilds has never been studied in detail. This work aims to investigate the whole microbiome (Fungi, Algae, Bacteria and Archaea) of four Italian show-caves, displaying different environmental and geo-morphological conditions and one recently discovered natural cave to highlight potential human-induced microbial traits alterations. Results indicate how show-caves share common microbial traits in contrast to the natural one; the first are characterized by microorganisms related to outdoor environment and/or capable of exploiting extra inputs of organic matter eventually supplied by tourist flows (i.e. Chaetomium and Phoma for fungi and Pseudomonas for bacteria). Yet, variation in microalgae assemblage composition was reported in show-caves, probably related to the effect of the artificial lighting. This study provides insights into the potential microbiome cave contamination by human-related bacteria (e.g. Lactobacillus and Staphylococcus) and commensal/opportunistic human associated fungi (e.g. Candida) and dermatophytes. This work is critical to untangle caves microbiome towards management and conservation of these fragile ecosystems.

Ecology and “bird-habitat” relationship in the cedar forest of Aurès mountain (Eastern Algeria)

Abstract This work aims to compile the birds breeding in the cedar forest of Aurès and to study the “Bird – Habitat” relationships. The data was collected using the progressive frequency sampling method that served as the basis for the diagnosis build on an analytical approach designed around three tools (mutual information, ecological profiles, modelling). Information theory tools allowed us to identify the indicator values of species as well as the most important descriptors. Habitat modelling has been prepared for species with a high indicator value. The logistic models are shown to be well adapted to the nature of the ornithological data. They related the occurrences of the species with the dendro-ecological descriptors. The 70 surveys carried out enabled us to identify 32 bird species. The ecological analysis revealed the most active descriptors and the species with high indicator value. The best-fitting models are those of Short-toed Treecreeper with positive effect of dead wood, density of trees and variability of distances between trees, and European Robin with negative effect of anthropization and general coverage, and positive effect of crown parametres. We conclude that promoting forest structural complexity by diversifying management regimes will be key to maintain avian biodiversity in cedar forests.

Worldwide impacts of landscape anthropization on mosquito abundance and diversity: A meta-analysis.

In recent decades, the emergence and resurgence of vector-borne diseases have been well documented worldwide, especially in tropical regions where protection and defense tools for human populations are still very limited. In this context, the dynamics of pathogens are influenced by landscape anthropization (i.e., urbanization, deforestation, and agricultural development), and one of the mechanisms through which this occurs is a change in the abundance and/or diversity of the vectors. An increasing number of empirical studies have described heterogeneous effects of landscape anthropization on vector communities; therefore, it is difficult to have an overall picture of these effects on a global scale. Here, we performed a meta-analysis to quantify the impacts of landscape anthropization on a global scale on the presence/abundance and diversity of mosquitoes, the most important arthropods affecting human health. We obtained 338 effect sizes on 132 mosquito species, compiled from 107 studies in 52 countries that covered almost every part of the world. The results of the meta-analysis showed an overall decline of mosquito presence/abundance and diversity in response to urbanization, deforestation, and agricultural development, except for a few mosquito species that have been able to exploit landscape anthropization well. Our results highlighted that these few favored mosquito species are those of global concern. They, thus, provide a better understanding of the overall effect of landscape anthropization on vector communities and, more importantly, suggest a greater risk of emergence and transmission of vector-borne diseases in human-modified landscapes.

PLASMA CALCIUM AND PHOSPHORUS LEVELS IN Chelonia mydas JUVENILES OBTAINED FROM THREE FEEDING AREAS ON THE BRAZILIAN COAST

The contamination of the marine environment by industrial, agricultural, and domestic effluents is extremely harmful, influencing, in many cases, the abundance and diversity of food resources. In addition to changes in diet, impacted environments provide a favorable scenario for the occurrence of diseases in aquatic organisms. Little is known about the effect of anthropization on the health of Chelonia mydas populations in Brazil. This work aimed to evaluate biochemical parameters of juvenile green turtles in three feeding areas in Brazil with distinct degrees of anthropization. From October 2012 to May 2014, 123 specimens of C. mydas were captured at three feeding sites along the coast of Brazil, with obvious differences between degrees of anthropization. Of these, 21 specimens were captured at the Vitória Bay, ES, 42 specimens at the Abrolhos Marine National Park, BA, and 60 specimens at the Atol das Rocas Biological Reserve, RN. The biochemical parameters evaluated were calcium (Ca), phosphorus (P) and their ratio (Ca:P). Plasma concentrations of P showed a significant difference between the feeding areas, decreasing according to the distance from the coastal region. The work recommends the study of plasma phosphorus levels as an indicator of the environmental quality of feeding sites in Brazil. For this, studies that correlate the P levels of food components of green turtles with plasma levels should be carried out.

The Use of Envi-Met for the Assessment of Nature-Based Solutions’ Potential Benefits in Industrial Parks—A Case Study of Argales Industrial Park (Valladolid, Spain)

Urbanization causes major changes in environmental systems, including those related with radiation balances and other meteorological conditions because of changes in surfaces and the physical environment. In addition, cities generate specific microclimates as a consequence of the diverse conditions within the urban fabric. Industrial parks represent vast urban areas, often neglected, contributing to the degradation of the urban environment, including poor thermal comfort as a result of soil sealing and low albedo surfaces. Nature-Based Solutions (NBS) can promote the mitigation of the anthropic effects of urbanization using nature as an inspiration. The present study, aimed at estimating the microclimate conditions in a fraction of the Argales industrial park in the city of Valladolid (Spain), with the use of the ENVI-Met software, assesses the current situation and a planned NBS scenario. Base scenario simulation results demonstrate different conditions across the simulations, with higher temperatures on sun-exposed surfaces with low albedo, and lower temperature spots, mostly associated with shadowed areas near existent buildings. After the simulation of the NBS scenario, the results show that, when compared with the base scenario, the projected air temperature changes reach reductions of up to 4.30 °C for the locations where changes are projected from impervious low albedo surfaces to shaded areas in the vicinity of trees and a water body.

Low level of anthropization linked to harsh vertebrate biodiversity declines in Amazonia

Assessing the impact of human activity on ecosystems often links local biodiversity to disturbances measured within the same locality. However, remote disturbances may also affect local biodiversity. Here, we used environmental DNA metabarcoding to evaluate the relationships between vertebrate biodiversity (fish and mammals) and disturbance intensity in two Amazonian rivers. Measurements of anthropic disturbance -here forest cover losses- were made from the immediate vicinity of the biodiversity sampling sites to up to 90 km upstream. The findings suggest that anthropization had a spatially extended impact on biodiversity. Forest cover losses of <11% in areas up to 30 km upstream from the biodiversity sampling sites were linked to reductions of >22% in taxonomic and functional richness of both terrestrial and aquatic fauna. This underscores the vulnerability of Amazonian biodiversity even to low anthropization levels. The similar responses of aquatic and terrestrial fauna to remote disturbances indicate the need for cross-ecosystem conservation plans that consider the spatially extended effects of anthropization.

Climate Change and Overuse: Water Resource Challenges during Economic Growth in Coquimbo, Chile

The arid Coquimbo region of Chile has experienced a significant economic growth in recent decades, fueled in large part by water-intensive activities such as mining and agriculture. Under this context, a monthly and annual trend analysis of precipitation, streamflow, and piezometric levels was carried out. Thus, 43 pluviometric stations, 11 fluviometric stations, and 11 wells were selected. These stations were evaluated for their temporal trends using the Mann–Kendall test. Results revealed a significant decrease in river flows, with negative and significant trends concentrated in the mean and maximum flows, both at annual and monthly levels. Likewise, positive trends were found in the depth to water table on wells, with significant trends in 81.8% of the monthly cases, and in 72.7% of the annual cases. While also decreasing over the same period, rainfall trends exhibit high variability and lacked significance. Although the amounts of precipitation have decreased, this does not seem to be the main factor responsible for the scarcity of water in the region, but rather an excessive consumption of this resource. This is endorsed by the increase in GDP (Gross Domestic Product), which is explained by activities that consume water (mining and agriculture). Similarly, an increase in the granting of underground water rights was verified, which speaks of the high demands for the resource. However, future modeling is advised to better understand the regional hydrology of the area and quantify the anthropic effects on water resources more precisely.

Spatio-temporal dynamics of the commercial seabob shrimp Xiphopenaeus kroyeri (Heller, 1862) and physico-chemical parameters in a marine protected area: Changes in abundance and distribution after 20 years

Studies comparing parameters before and after the establishment of protected areas in coastal environments allow improvements of management plans and recognition of alterations due to natural or anthropic effects. This study compared spatio-temporal variation in abundance of Xiphopenaeus kroyeri in two equivalent periods. The first period was 12 years before the establishment of the Marine Protected Area and the second was 8 years after. The influence of environmental factors in relation to abundance was also analyzed. Samples were conducted monthly at Ubatuba Bay, Southeast Brazilian coast in period 1 (1995–1996) and 2 (2016–2017). Five transects were sampled using the same methodology, encompassing depths from 5 to 15 meters and areas sheltered or exposed to tidal waves and currents. Abundance varied seasonally. Higher values were obtained in December, March, and June of period 1 and in April and July of period 2. These months correspond to autumn and the beginning of winter. Seasonal fluctuations in abundance seems to be a response to higher and more stable salinity and the efficacy of the closed season (March–May), favoring a higher abundance in the autumn. There was no significant difference of X. kroyeri abundance between periods. Results indicate stability of population density through time in the region, suggesting conservation measurements are aiding species’ protection is spite of a larger fishing fleet. Our study reinforces the importance of measurements to mitigate fishery resources along with other non-commercial species important to preserve local biodiversity.

Effect of woody plant removal in herb-subshrub communities in preserved and disturbed Brazilian Chaco areas

The impacts caused on Chaco plant communities by the removal of woody species, together with the effects on the composition and functional structure of herbaceous plants, are still unknown. Therefore, this study aimed to assess the effects of anthropization on herb-subshrub communities in preserved and disturbed Chaco areas. Specifically, we examined differences and similarities in species diversity, composition and proportion of life forms in eight areas of Brazilian Chaco. Samples were taken from herb-subshrub communities using 800 1x1m² plots located in disturbed and preserved areas. Among 130 recorded species, 46 were exclusive to disturbed areas. The composition of species differed between preserved and disturbed areas (PERMANOVA; p = 0.001). PCoA ordination analysis showed greater aggregation of the plots in disturbed areas than in preserved areas. In preserved areas, an analysis of indicator species showed Hemicryptophytes species as the most representative life form. In disturbed areas, the proportion of life forms among indicator species was Hemicryptophytes, followed by Therophytes and Chamaephytes. Our study shows evidence that alterations in species composition, structure, and diversity, as well as sets of indicator species, occur in herb-subshrub communities. The removal of trees and bushes leads to a new configuration of this component in Chaco environments.

Population decline at distribution margins: Assessing extinction risk in the last glacial relictual but still functional metapopulation of a European butterfly

AbstractAimTo determine the interplay between climate and land use changes in driving population dynamics in a butterfly species, Coenonympha hero, at the southern limit of its distribution.LocationFrench Jura massif and Europe.MethodsWe analysed patterns of genetic diversity distribution at 817 loci in 136 butterflies from 31 sites using NGS to infer the genetic structure and population size changes over time, using two methods of demographic inference (SNP frequency spectrum analyses and coalescent ABC inferences). We then characterized the climate and land use descriptors of C. hero geographic distribution using species distribution modelling (SDM) and ordination method and compared demographic changes to changes in climatically suitable areas.ResultsCoenonympha hero persists in the Jura massif as three core populations that share a common history of decline in two steps: an old decline and a more recent decline that resulted in population fragmentation, the southernmost sites being the most threatened (lowest genetic diversity). Climate change during the Würm glaciation is presumably the main factor explaining the first demographic decline. The second decline started 2000 years ago possibly under increased human pressure as suggested by recent extinctions in several sites nowadays characterized by urban and agricultural surfaces. Both climate and land use variables are important descriptors of C. hero distribution, as SDM predictions were improved by adding aridity index, altitude and land use to bioclimatic predictors. Its habitats include forests in north‐eastern Europe and grasslands in the Jura massif.Main conclusionsUsing SDM and genetic demographic inferences, we identified a persistent glacial refuge for the species in Europe. We show that although this relictual population has declined and fragmented under the combined effects of climate warming and anthropization, the metapopulation is still functional but requires particular conservation attention to maintain its connectivity, and to favour the local persistence of this highly endangered butterfly species.

Assessment of the metal contamination index in groundwater of the quaternary of the Middle Kert Basin, north‐eastern Morocco

AbstractThe purpose of this study is to highlight the quality of groundwater, with a special focus on the level of heavy metal contamination. To know the extent of this contamination, the protection and proper management of the groundwater resource is indispensable. The present work is in line with the metallic assessment of the water quality of the Oued Kert basin (Mediterranean area, Driouch province, eastern Morocco) by collecting 46 samples following ISO 5665 standard and tested pH, TDS, EC. Samples were analyzed for Heavy Metals with ICP‐MS and Flame Atomic Absorption Spectrometry (Pb, Cu, Hg, Al, Fe, Zn, Cr, Cd, and Ni) to detect heavy metal content. The interpretation of the analytical data, about the phenomena responsible for mineralization, was done using the hydro‐chemical classification, resulting from the integrated HPI approach, in addition to the statistical analysis of the data by the analysis of the main PCA components. The majority of the samples were found to be within limits, except for Fe, at some sampling locations, which is above the desirable limit, that is, 300 μg/L according to the Moroccan Drinking Water Standard. This indicates natural and anthropic effects. It shows that the groundwater to the northwest of the study area is probably affected by the leaching of heavy metals from the previous Mhajer mine.

Diversity and dynamics in larval digenean assemblages parasitizing Heleobia parchappii in a freshwater shallow lake from the Southeastern Pampa plain, Argentina.

Digeneans have important roles within ecosystems; however, it is estimated that only 14% of the species have been described. Therefore, before being able to detail their role, digenean species’ identification and the diversity present in the ecosystems must be known. In this study, the diversity and the temporal-spatial dynamics of larval digeneans in the freshwater snail Heleobia parchappii were analysed in a shallow lake. Specimens of H. parchappii were collected seasonally at three points during one year and a total of 2871 molluscs were analysed. A total of 23 species of digenea were registered and both the overall prevalence and the composition of the assemblages presented temporal and spatial variations, responding to the differential environmental conditions characteristics (anthropic effect, presence of native forests, and differential use of the habitat by the definitive hosts) of three sampled sites. The assemblages of larval digenean in their first intermediate host support the idea that this area is of great importance in biodiversity, and could be endemic areas of some species of digenean that use reptiles, amphibians and bats as hosts, groups that are at risk of conservation. Protection of these environments is a fundamental pillar in the policies for the conservation of wild flora and fauna.