Karst aquifers have been globally exploited as a reliable source of drinking water but their intrinsic characteristics (concentrated recharge, high groundwater flow velocities, etc.) and the increase ...of anthropogenic pressures makes them highly vulnerable to pollution. Continuous monitoring of karst springs constitutes an effective approach for identifying episodic groundwater contamination and assuring safety conditions in drinking water supply systems. This study aims to improve groundwater protection insights through an integrated methodological approach based on real-time measurements of continuous water parameters coupled to bacterial analysis for the characterization of contamination events in a carbonate karst aquifer of a mountainous and rural area in S Spain. For this purpose, environmental, hydrodynamic and physico-chemical data in addition to bacterial activity (Escherichia coli) analysis were gathered from the analysis of eight flooding events at the two main outlets. In these karst springs, partially captured for drinking water supply, the recurrent turbid groundwater episodes suppose an important limitation for groundwater exploitation during several days, but also a concerning human health risk. The results revealed the different flow and sediment dynamics and mixing processes which determine the impact of faecal contamination derived from human activities on the karst groundwater drained by each spring. The described processes control the variable influence of allogenic recharge, which provokes notable differences regarding response times and maximum values of turbidity and associated bacterial activity in the investigated outlets. The outcomes of this work highlight the usefulness of the applied methodological framework to set the bases for an efficient implementation of early-warning strategies to prevent public health issues worldwide.
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•An approach for early detection of karst groundwater faecal contamination is presented.•Continuous monitoring of climate and water parameters was coupled to bacterial analysis.•Sediment source contribution to the karst springs was qualitatively assessed.•Human activities were responsible for the faecal bacteria detected at drinking water sources.•Site specific karst groundwater protection strategies are crucial to prevent public health issues.
This investigation deals with the application of a multi-technique approach combining data from turbidity, major ions, and trace elements to characterize the implications of allogenic recharge in a ...binary karst system and assess the relative hydrochemical contribution to karst springs captured for drinking use. Hydrodynamic and hydrochemical responses of the outlets to storm events were continuously monitored during four selected flooding events, and water samples were collected at the main sinking stream in the recharge area and discharge points (Cornicabra and Algarrobal springs) for chemical analysis. The obtained hydrogeochemical dataset was analyzed through mean of time-series and statistical analysis and allowed to describe the fate and origin of trace elements. Despite that most of analyzed components present a natural origin, the existence of a Wastewater Treatment Plant in the recharge area was determined to be the main source of P (phosphorus) concentrations measured in the karst springs. Sediment (particulate) transport constitutes the most important factor in the mobilization of Al, Mn, Ni, and Ba in both surface and groundwater, whilst Li, Sr, and P are mainly controlled by solute migration. The hydrochemical signature of allogenic water component was constrained by identifying characteristic correlations between Ba and Ca/Sr ratio in water samples. The combination of specific hydrogeological processes as ion solution and sorption processes onto solids between solutes and particles as well as water mixing processes (allogenic vs diffuse) result more evident in Algarrobal spring, which receives a higher contribution of allogenic component due to a greater feeding catchment.
The Gulf of Mexico coastal plain contains one of the largest dune systems in Mexico. These dunes and particularly their paleosols contain valuable paleoenvironmental information, however this aspect ...has been poorly studied. Here, we present the preliminary results obtained from buried paleosols of coastal dune ridges in Veracruz with the aim to reconstruct the environmental conditions during their formation as well as the phases of stability (pedogenesis) and instability (sedimentation) of the landscape. Three profiles were studied in the areas of Punta Delgada, PD (in the north), Palma Sola, PS, and La Mancha, LM (in the south). The chronological frame was constructed by radiocarbon dating of paleosols organic matter and pedogenic carbonates, and by Optical Stimulated Luminiscence (OSL) dating for the dune sediments. For each section several paleosols levels were identified whose properties permitted the differentiation of pedogenetic trends as well as their periods of formation. Nevertheless, the three sections did not provide for a continuous record of pedogenesis and sedimentation, as most of the paleosols are truncated by erosion. PS is the most complete profile which is formed from Marine Isotope Stage (MIS) 5c to MIS 1, with especially well-developed Holocene paleosols. LM includes only paleosols developed during MIS 4 and MIS 3, and PD shows only one paleosol originated during MIS 2. Although, the chronology is not complete as it has been constructed with a few dates, we consider each section contains information from different chronological windows. The results demonstrate that the oldest paleosols formed under more humid conditions during MIS 5c to 5a and probably MIS 4. As the MIS 4 to MIS 2 paleosols contain pedogenic carbonates, we interpret drier climates or with higher evapotranspiration rates. Paleosols from the early Holocene exhibit vertic properties probably formed by seasonal climates. Soils from the Middle-Late Holocene are less developed, due to the activation of the dune sedimentation. The results found here are compared at a regional scale with the dune system in the northern Gulf of Mexico and Yucatan peninsula, revealing both synchronous and asynchronous systems of eolian dynamics. The major asynchrony relates to the Wisconsinian stage (MIS 4 to MIS 2) for which high intensity of dune development is documented in the Veracruz and northern coasts whereas no dunes of that age are found in the Yucatan peninsula.
Karst groundwater-dependent ecosystems (KGDEs) in the Mediterranean region are important in terms of ecosystem services and biodiversity but are increasingly under anthropogenic pressures and ...climate-change constraints. For this study, the ecohydrological characteristics, threats, and protection status of 112 selected KGDEs around the Mediterranean Sea, including caves, springs, rivers and wetlands, were evaluated, based on local expert knowledge and scientific literature. Results demonstrate that KGDEs contribute considerably to regional biodiversity. The diversity of karst landscapes, combined with the groundwater emergence at springs, leads to exceptional habitat diversity, particularly in arid climates, where KGDEs serve as a refuge for species that could not thrive in the surrounding environment. The most common threats identified among the selected sites are direct human disturbances, such as mass tourism or overfishing, water-quality deterioration and water shortage from aquifer overdraft and/or climate change. Although most of the selected sites are under protection, conservation measures are frequently insufficient. Such shortcomings are often caused by poor data availability, little knowledge on conservation needs of invertebrate species, and conflicts of interest with the local population. For this purpose, it is necessary to raise environmental awareness and promote interdisciplinary research, in order to monitor water quality and quantity in addition to the status of the biocenoses.
Groundwater vulnerability mapping is one of the tools most often applied to analyse the sensitivity of karst aquifers to pollution. These maps aim to support stakeholders in decision-making and to ...promote land-use management compatible with water protection; however, the validation of these maps is still a challenge in many cases, triggering high uncertainty. For karst media, due to the strong heterogeneity in recharge mechanisms and hydraulic characteristics, validation is a significant stage and it must be inherent within the groundwater vulnerability assessment process. This work aims to assess the implementation of tools used for protecting the quality of water discharging or extracted from the Ubrique karst system in southern Spain, which supplies drinking water that is threatened by periodical pollution/turbidity episodes. A groundwater vulnerability map, attained by application of the COP method and validated by multiple in-situ observations, shows an extremely vulnerable system due to the absence of protective overlayers and the significant development of exokarst landforms, including shallow holes. This map could constitute the basis for defining protection zones for the Ubrique springs; however, their comprehensive protection requires the implementation of monitoring tools and an effective management strategy, through an early warning system that assures stable environmental and hydrogeological conditions and improves operational procedures associated with the drinking water service. This research establishes the strong relationship of the different methods applied to protect the source from contamination events, ranging from classical hydrodynamic and hydrochemical approaches to the implementation of protection zones and early warning groundwater quality monitoring networks.
The soil mantle of the tropical karst landscapes of southern Mexico was a key resource for ancient Maya agriculture and experienced deep transformation due to long-term human impacts under changing ...environmental conditions. We conducted a comparative analysis of three compound soil toposequences in mountainous (Sierra de Chiapas/Middle Usumacinta Valley, Busiljá, and Chinikihá archaeological sites) and platform (NE Yucatán Peninsula, Yalahau region) karst landscapes to reconstruct general tendencies and regional variations in pedodiversity development and soil–human interactions since the Early Preclassic Period. Toposequence characterization is based on macro- and micromorphological observations, accompanied by a suite of laboratory data. Calcareous upland geoforms of all toposequences have similar soil combinations consisting of shallow Rendzina and deep red clayey Terra Rossa types of profiles. We argue that Rendzinas, now dominant in the upland soil cover, in most cases, are not a product of incipient pedogenesis on limestone; they have developed from the residues of Terra Rossa soils after their advanced erosion. Pedosediments generated by ancient soil erosion have been found in the piedmont and depression positions in the mountainous landscapes of Chiapas, as a result of lateral downslope soil removal, and in the subsurface karstic cavities in the platform of NE Yucatán, indicating vertical “soil piping.” The soils of the lowland domains show contrasting differences between the toposequences: gleyic clay–rich soils and humic alluvial soils prevail in Chinikihá and Busiljá, whereas hydromorphic carbonate soils have formed in Yalahau karstic depressions. These differences in the lowland soil properties led to divergent ancient Maya land use strategies; in Chinikihá and Busiljá, the major agricultural domain was developed in the lowlands, implying largescale artificial drainage. On the contrary, in Yalahau, mostly upland Rendzinas were cultivated, implying “precision agriculture” and “container gardening.”
El modelado de escenarios de cambios climáticos utilizando sistemas de información geográfica para estimar la resiliencia de la cobertura vegetal es una herramienta útil para proyectar impactos ...futuros e implementar estrategias de conservación o manejo. En el presente trabajo asociamos espacialmente la biodiversidad de la cobertura vegetal del Suroeste de México con su capacidad para adaptarse a los efectos del cambio climático. Para analizar esta asociación se estimaron índices de riqueza y diversidad de especies, y su relación con escenarios de clima futuro. Se utilizaron los registros geográficos del Inventario Nacional Forestal y de Suelos para ocho comunidades vegetales (arbórea, arbustiva, herbácea, palma, cactus, bejucos, helechos y xerófita) distribuidas entre Guerrero, Oaxaca y Chiapas. La proyección climática fue al 2050, con modelos de circulación global A2 (promedio CCCMA, HADCM3 y CSIRO), 19 variables bioclimáticas y una resolución de 2.5 minutos. Los escenarios de cambio climático se modelaron con el algoritmo MaxEnt y la riqueza de especies, índice de diversidad y regresiones espaciales con el software Diva-GIS v7.5. Los modelos de regresión espacial estimaron que a mayor riqueza y diversidad de especies mayor seria la resiliencia que mostraría el ecosistema. Las comunidades vegetales cactus, palma y xerófita mostraron mayor vulnerabilidad al cambio climático. Las variaciones en la estacionalidad de la temperatura resultó ser el factor que condicionaría su distribución futura. Por lo que, las estrategias de conservación o manejo deberían considerar a la diversidad como un agente del ecosistema que amortiguaría a los efectos negativos del clima futuro.
Lipid A is the bioactive component of lipopolysaccharide, and presents a dynamic structure that undergoes modifications in response to environmental signals. Many of these structural modifications ...influence
virulence. This is the case of lipid A hydroxylation, a modification catalyzed by the dioxygenase LpxO. Although it has been established that oxygen is required for lipid A hydroxylation acting as substrate of LpxO in
, an additional regulatory role for oxygen in
expression has not been described. The existence of this regulation could be relevant considering that
faces low oxygen tension during infection. This condition leads to an adaptive response by changing the expression of numerous genes, and transcription factors Fnr and ArcA are major regulators of this process. In this work, we describe for the first time that lipid A hydroxylation and
expression are modulated by oxygen availability in
serovar Enteritidis (
. Enteritidis). Biochemical and genetic analyses indicate that this process is regulated by Fnr and ArcA controlling the expression of
. In addition, according to our results, this regulation occurs by direct binding of both transcription factors to specific elements present in the
promoter region. Altogether, our observations revealed a novel role for oxygen acting as an environment signal controlling lipid A hydroxylation in
. Enteritidis.
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