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Oceanic red beds (ORBs) are present in Upper Cretaceous and Danian deep-marine deposits in the Basque–Cantabrian Basin of northern Spain. The presence and regularity of the succession of marl–limestone couplets is exceptional based on the macroscopic, microscopic and geochemical evidence collected. Five types of marl–limestone couplets are identified based on the colour, and a high maximum sedimentation rate (3.6 cm ka–1 ) is noted. The oxidizing activity of deep, cold-water masses is indicated by the oxygen isotope signal in the lower–upper Maastrichtian and Danian sections and the presence of the boreal inoceramidSpyridoceramus tegulatus.In theory, the variation in colour from grey to greenish-yellow, purple and pink up to red tones correlates with the Fe2+/(Fe2++Fe3+) ratio. It is interpreted as the possible palaeoenvironmental transit of particles that sediment out slowly in oxic environments when they circulate through cooler, oxidizing water masses. The colour is considered to be a depositional feature, and hematite, detected by X-ray diffraction, is the main staining agent, without discarding the possible redistribution of previous oxyhydroxides passing to hematite as a final product. The cell filling of the foraminifer shells does not incorporate appreciable amounts of Fe and Mg during diagenesis. Bacterial activity is detected using scanning electron microscopy images, both in the coccolith debris and in the detrital micas, although there is uncertainty as to its importance in the staining process.

[EN] The objective of this study was to analyse periodicities and the long-term variability of monthly Jucar River-Mancha Oriental Aquifer interactions (RAI) and regionally measured precipitation (PP) with special focus on the correlations between these local hydrological variables and the large climatic patterns governing the Iberian Peninsula, represented by their teleconnection indices - the North Atlantic Oscillation index (NAOi) and the Western Mediterranean Oscillation index (WeMOi). To that end, wavelet analysis has been applied since it not only provides insight into the time-series dynamics but also permits statistical interpretation and correlation analysis. As a result, several periodicities have been detected: intermittent semi-annual periodicity in PP and the NAOi and annual periodicity in the RAI, NAOi and WeMOi time series. Long cycles (approximately 14 years) are also observed in the PP and WeMOi time series. The cross-wavelet spectra show a correlation between the RAI and the rest of the variables on the semi-annual and the annual scales, while wavelet coherence detects common behaviour with longer cycles - 5-6 years between the NAOi and the RAI and cycles of both 1-5 years and 7-10 years between PP and the RAI. Furthermore, results show that the periodicities in the teleconnection indices and precipitation propagate into the RAI with certain lead times: 3 months between the RAI and PP and 6 months between the RAI and the NAOi. The results indicate that the detected periodicities and the coherence between the studied variables could have applications in strategic planning on a river basin scale, taking into account the propagation times and the frequency scale. This methodological approach can be applied into strategic water resource planning independently of the geographical location of the hydrogeological system, the basin size and the climate region., Special thanks go to the Júcar Water Authority (CHJ) and stakeholders (JCRMO) in the Mancha Oriental System for providing the necessary information. The content of this report does not represent the view of CHJ and JCRMO. This work has been funded by the research projects CGL2017-87216-C4-2-R from the National Research Program I + D + i (FEDER/Ministerio de Ciencia, Investigación y Universidades) and SBPLY/17/180501/000296 from the National Research Program I + D + i of the Junta of Communities of Castile-La Mancha. We would also like to thank Christine Laurin for the English copy editing and valued comments.

Nitrate (NO3-) removal from aquatic ecosystems involves several microbially mediated processes, including denitrification, dissimilatory nitrate reduction to ammonium (DNRA), and anaerobic ammonium oxidation (anammox), controlled by slight changes in environmental gradients. In addition, some of these processes (i.e. denitrification) may involve the production of undesirable compounds such as nitrous oxide (N2O), an important greenhouse gas. Saline lakes are prone to the accumulation of anthropogenic contaminants, making them highly vulnerable environments to NO3- pollution. The aim of this paper was to investigate the effect of light and oxygen on the different NO3- removal pathways under highly saline conditions. For this purpose, mesocosm experiments were performed using lacustrine, undisturbed, organic-rich sediments from the Petrola Lake (Spain), a highly saline waterbody subject to anthropogenic NO3- pollution. The revised 15N-isotope pairing technique (15N-IPT) was used to determine NO3- sink processes. Our results demonstrate for the first time the coexistence of denitrification, DNRA, and anammox processes in a highly saline lake, and how their contribution was determined by environmental conditions (oxygen and light). DNRA, and especially denitrification to N2O, were the dominant nitrogen (N) removal pathways when oxygen and/or light were present (up to 82%). In contrast, anoxia and darkness promoted NO3- reduction by DNRA (52%), combined with N loss by anammox (28%). Our results highlight the role of coupled DNRA-anammox, which has not yet been investigated in lacustrine sediments. We conclude that anoxia and darkness favored DNRA and anammox processes over denitrification and therefore to restrict N2O emissions to the atmosphere.

Saline lakes are subject to numerous environmental impacts closely related to human activities, including mining, desiccation and pollution. These lakes are mostly located in arid and semi-arid regions located in endorheic basins, which combined with the low precipitation and high evaporation rates typical for these regions, may lead to the accumulation of pollutants. Saline lakes are polluted mainly through inputs of agricultural wastewater along with organic and inorganic wastes from domestic and industrial sources. The excessive anthropogenic loading of nutrients, especially nitrogen (N), can result in eutrophication of these ecosystems. Here, the importance of pollution in saline lakes was assessed, placing special emphasis on N pollution and its attenuation in aquatic interfaces. Two main interfaces are present in saline lakes: (1) the sediment-water interface; (2) the freshwater-saltwater interface. While the former is the most important one for microbial turnover, the latter plays also a key role in pollution attenuation based on solute transport by density-driven flows. The study of how saline lakes can attenuate N pollutants (e.g. nitrate) is a step forward in preserving the good ecological status of these ecosystems. This work highlights the need of integrating a wide range of techniques from different disciplines such as limnology, hydrogeology, geochemistry or microbial ecology for such studies. The effective application of conservation policies by managers will depend on the degree of knowledge of these systems.

Lake Alboraj, located in southeast Spain, was declared natural Microreserve and included into European Natura-2000 Network due to its contribution to environmental heritage. Unfortunately, the ecological status of the lake has changed dramatically, mainly due to the lowering of water table caused by groundwater abstractions for irrigation. It is a permanent small karstic lake whose surface has reduced in the last decades to nearly the third part of its historical water level. The water column shows a marked seasonal oxycline, that splits an aerobic upper layer (epilimnion) from an anaerobic layer below (hypolimnion). Sequencing 16S rRNA gene amplicons and applying chemical tools at epilimnion, hypolimnion and sediment, showed a clear gradient in the bacterial community structure, which support the co-existence of assimilatory and dissimilatory microbial mediated reactions. Results allows to infer that microbial stratification could provide various physical and chemical environments at different depths in the water column related to biogeochemical reactions providing N-S-C- recycling processes.

Monitoring dissolved nitrate (NO3−) concentrations is essential for conservation efforts in aquatic ecosystems. Spectrophotometric methods are a widely accepted approach for NO3− analysis. They detect NO3− as a colored diazo complex after reduction to nitrite (NO2−) and its consequent reaction with the so-called Griess reagent. This method is commonly used for freshwater and saline water samples, even though it requires applying a heavy metal in powder form (cadmium) or high concentrations of heavy metal salts (vanadium-III), as a reductant. There has been little discussion about applying these methods for hypersaline samples. This study optimizes an existing method for use in high saline conditions based on the Griess reaction. Five factors were studied: incubation temperature, reaction time, concentration of EDTA, concentration of trisodium citrate, and concentration of reductant (VCl3). Optimal conditions were obtained by using the Box-Behnken design and included using VCl3 17.5 mM, trisodium citrate 70 mM, and an incubation temperature of 60 °C for 40 min. These conditions provided a linear range from 0.55 μM to 50 μM NO3−. The method showed a moderate precision (ranging from 4.3% to 15.4%). The proposed protocol was tested with hypersaline natural samples and showed recovery rates between 92.6% and 100.1%. This protocol for NO3− determination is the first specifically described for hypersaline samples.

Nitrate (NO3−) removal from aquatic ecosystems involves several microbially mediated processes including denitrification, dissimilatory nitrate reduction to ammonium (DNRA), and anaerobic ammonium oxidation (anammox) regulated by slight changes in environmental gradients. Saline lakes are prone to the accumulation of anthropogenic contaminants, making them highly vulnerable environments to NO3− pollution. We investigated nitrate removal pathways in mesocosm experiments using lacustrine, undisturbed, organic-rich sediments from Pétrola Lake (Spain), a highly saline waterbody subject to anthropogenic NO3− pollution. We used the revised 15N-isotope pairing technique (15N-IPT) to determine NO3− sink processes. Our results demonstrate the coexistence of denitrification, DNRA, and anammox processes, and their contribution was determined by environmental conditions (oxygen and light). DNRA and N2O-denitrification were the dominant nitrogen (N) removal pathways when oxygen and/or light were present (up to 82 %). In contrast, anoxia and darkness promoted NO3− reduction by DNRA (52 %) and N loss by anammox (28 %). Our results highlight the role of coupled DNRA-anammox, as yet has never been investigated in hypersaline lake ecosystems. We conclude that anoxia and darkness favored DNRA and anammox processes over denitrification and therefore reduce N2O emissions to the atmosphere.

High evaporation rates in semi-arid to arid regions result in an increase in salinity that can exacerbate the effect of pollutants in water bodies.This study examines how groundwater drives pollution removal in wetlands, wells and springs within the Chaotic Subbetic Complexes (southern Spain). This evaporitic system, localy with a clear karstic functioning, is characterized by groundwater with a wide range of mineralization. Hydrochemical and multi-isotopic (δ34S, δ18O, δ15N, δ13C and δ2H) techniques were used to understand the geochemical processes leading to pollutant attenuation within the complexes. There, regional groundwater evolve from recharge/transition areas, with low salinity, to the discharge zone. Mineralization of groundwater depends on the dissolution of evaporitic deposits (gypsum, halite) of Keuper age, which increases salinity of the water drained by the outlet springs. δ15N and δ18O values of dissolved nitrate (NO3−) were used to estimate the relative contribution of N sources. NO3− is mainly derived from agricultural inputs (nitrate and urea fertilizers). Long-residence groundwater plays an important role in the biogeochemical evolution. Denitrification is responsible for NO3− removal in transitional zones and discharge springs. This process is promoted by the oxidation of organic carbon, derived from recharge areas and further transported to deeper zones of the aquifer. The findings of this study provide a new understanding of how hydrogeological functioning is connected to pollutant removal in an evaporitic karst system, where the scale of groundwater flows plays a key role in biogeochemical processes.

Management of water resources in hyper-arid areas faces vital challenges in a global climate change context. Consequently, understanding the effects on groundwater sources can help mitigating the problem of water scarcity and the negative impact of human intervention on the environment. A case study area in the hyper-arid climate of the United Arab Emirates, was tackled here with the focus on applying stable isotopes as tools for evaluating groundwater sources and quality assessment. The results of major ions indicate variable increase in groundwater salinity moving away from Al Hajar Mountains recharge areas to the discharge areas (Arabian Gulf coast). The data of stable isotopes (δ18OH2O, δ2HH2O, δ18ONO3, δ15NNO3, δ18OSO4, δ34SSO4, δ11B) suggest impact of paleo-groundwater in the abstractions of the wells nearest to the coast. Nitrate isotopes indicate farming activities sources that can be masked due to the contribution from the nitrate-poor paleo-groundwater. Nitrate reduction processes are expected near to the recharge front. Sulphate and boron isotopes further suggest that influence of ancient evaporite dissolution in salinization. Management efforts should be focused on the diffuse sources of quality mitigations that can be vital in fingerprinting local and regional (transboundary) effects.

Chittur block represents a mid-land region of Palakkad district, Kerala and the block differs from the rest of the blocks in its climate and availability of groundwater. About 75% of the people depend on agriculture for their livelihood. Results showed that groundwater salinity levels (up to 1,963 mg/L TDS),fluoride (up to 6.3 mg/L) and nitrate (up to 141 mg/L) contents have increased significantly in tandem with the increase in groundwater abstraction. Before human intervention the chemical weathering of gneisses and granites was the main process impinging on the chemical signature of groundwater. The initial chemical equilibrium conditions change with increasing groundwater withdrawal rates and fertilizer input, in a milieu of lower natural groundwater recharge. The appearance of higher levels of bicarbonate, linked to denitrification processes, and the decrease in calcium, due to calcite precipitation, can lead to increased content of sodium and fluoride in groundwater. In this scenario the use of groundwater resources for human consumption and agriculture represents a public health risk if water management actions do not change the trend in water use in the near future. The potential loss of fertile soil by groundwater salinization must also be considered when planning sustainable policies in a region with over dependence on groundwater resources.

Agricultural pollution and wastewater effluents from the village of Petrola cause a high pressure over Petrola Lake-aquifer system (Central Spain). The lake is rich in sulfate (SO42−), with concentrations up to 1,280 mmol/L. Petrola lake is considered one of the most symbolic saline wetlands in Castilla-La Mancha Region, due to its geomorphology, hydrology and salinity (up to 109.4 mS/cm). At the water-sediment interface anaerobic conditions and high dissolved organic carbon (up to 21.5 mmol/L) and sulfide production (up to 5 nmol/L) suggest the development of bacterial sulfate reduction processes (BSR). Hydrochemical and isotopic results confirm a mixing trend between high density brine water from the lake and freshwater from the regional groundwater flow. The sulfur origin in the system seems to be linked to sulfide oxidation of Lower Cretaceous sediments (Utrillas Facies) that are rich in sulfide and organic matter. Sulfur and oxygen isotope data show the sulfate-bearing mineral dissolution as the main source of SO42− in surface water. The study concludes that the regulation of the amount of sulfur depends on the relationship between the kinetics of BSR and the hydrodynamic instability driven by the different density of groundwater flow.

El humedal salino de Pétrola, situado en un ambiente semiárido en el sureste de la provincia de Albacete (España), constituye la zona de descarga de una cuenca endorreica de alrededor de 42 km2. La laguna está sometida a múltiples entradas de contaminación derivadas de actuaciones antrópicas, originando que las condiciones biológicas y físico-químicas de partida de la masa de agua hayan sido gravemente modificadas. La elevada salinidad del sistema (123.000 μS/cm, noviembre 2010) da lugar a un ambiente extremo que propicia condiciones exclusivas capaces de albergar ciertos procesos redox mediados por extremófilos adaptados. Estos microorganismos pueden ejercer un papel fundamental en la atenuación de la contaminación de origen urbano y agrícola existente. Entre las entradas de contaminantes destacan el nitrato, y la atrazina, un herbicida usado ampliamente en las prácticas agrícolas, y sus metabolitos desetilatrazina y deisopropilatrazina. Las concentraciones de atrazina y sus productos de transformación pueden superan los 100 ng/L. Por ello, el objetivo de este trabajo es la búsqueda de microrganismos extremófilos implicados en la atenuación de contaminantes en la laguna de Pétrola, con especial atención en aquellos que puedan estar biodegradar la atrazina. El primer enfoque para la detección de microorganismos extremófilos, que puedan participar en procesos de biorremediación, ha consistido en un análisis metagenómico. Para ello, se recogieron sedimentos de la laguna en 7 puntos cuyas aguas presentan diferentes características físico-químicas. Se extrajo el ADN genómico bacteriano del sedimento y se sometió al análisis metagenómico mediante secuenciación del gen 16S rRNA, lo que permitió caracterizar las poblaciones bacterianas presentes en la laguna. Como resultado, se ha detectado una gran diversidad de microorganismos extremófilos. Entre ellos, destaca el grupo relacionado con procesos de desnitrificación fototrófica y nitrato-sulfato-reducción. Dentro de este grupo, se ha buscado la presencia de microorganismos relacionados con procesos de degradación de contaminantes, aunque, debido al gran número de datos generados, los resultados todavía se encuentran en proceso de análisis. El segundo enfoque ha consistido en la búsqueda de bacterias degradadoras de atrazina, mediante la amplificación por PCR con cebadores diseñados para la amplificación de los genes involucrados en la ruta de degradación de este contaminante organoclorado (Figura). En este punto, se ha conseguido la amplificación de fragmentos, con un patrón diferente en los distintos sedimentos evaluados, lo cual da idea de los diferentes procesos que se están produciendo en puntos de la laguna sometidos a distintas condiciones ambientales. Los resultados ofrecen información acerca de la presencia de microorganismos extremófilos que pueden participar en procesos de atenuación de contaminantes. Se vislumbra la formación de un complejo sistema simbiótico de degradación en cadena que debe seguir estudiándose en mayor profundidad en futuros trabajos orientados a la biorremediación.

Saline lakes are subject to numerous environmental impacts related to human activities. Pollution is one of the major threats to water bodies, since it produces the increase of nitrogen and sulfur contents, changing the chemical and biological conditions of the ecosystem. Microbially mediated redox processes exert a fundamental control on nutrient and contaminant turnover. Therefore, the aim of this study was to determine the influence of land use on the microbial communities responsible for N and S turnover in the lacustrine sediments from Pétrola Lake (SE Spain) disturbed by anthropogenic activities (agriculture, farming, mining, and wastewaters). To reach this goal, chemical and molecular tools (sequencing of 16S rDNA gene) were applied. The results showed the influence of land use on the chemistry and microbial community structure of the sediments from the saline lake. Compared to natural conditions, wastewater and mining showed the largest differences in terms of microbial structure as a result of salinity. These findings provide better understanding of how land use affects the water chemistry and the abundance of organisms responsible for nutrient turnover.

The chemical composition of groundwater and related surface water ecosystems can be modified by intensive agricultural activities. This is the case of the Natural Reserve of P&eacute, trola saline lake (Albacete, SE Spain), which constitutes the discharge area of an unconfined aquifer. The extended use of fertilizers and pesticides poses a threat to ecosystem sustainability. One of the most applied herbicides worldwide has been atrazine. Despite being prohibited in Spain since 2007 by European regulations, atrazine can still be detected due to its high persistence in the environment. Atrazine degradation pathways are mediated by biological processes performed by microorganisms with adapted metabolic mechanisms that make in situ bioremediation possible. To evaluate the presence of such microorganisms in the unconfined aquifer, groundwater was collected from a flowing 37.9 m deep piezometer. DNA was extracted, and the bacterial 16S rRNA gene was amplified and cloned. Later, 93 clones were sequenced, providing the first molecular assessment of bacterial community structure in the deep zones of the aquifer. Some of these bacteria have been previously described to be involved in atrazine degradation. In addition, 14 bacteria were isolated from the groundwater samples and identified by 16S rRNA gene sequencing. DNA from these bacteria was subjected to PCR assays with primers designed for the genes involved in the atrazine degradation pathway. Positive results in the amplification were found in at least three of these bacteria (Arthrobacter sp., Nocardioides sp. and Pseudomonas sp.). The atrazine-degrading genetic potential was shown to be dependent on the trzN and atzA,B,C gene combination. These results suggest for the first time the adaptation of the bacterial population present in deep aquifer zones to atrazine exposure, even after more than 15 years of its ban in Spain. In addition, this study provides the baseline data about the bacterial communities found in deep aquifer zones from the hypersaline lake-aquifer system.

Endorheic or closed drainage basins in arid and semi-arid regions are vulnerable to pollution. Nonetheless, in the freshwater-saltwater interface of endorheic saline lakes, oxidation-reduction (redox) reactions can attenuate pollutants such as nitrate (NO3−). This study traces the ways of nitrogen (N) removal in the Pétrola lake-aquifer system (central Spain), an endorheic basin contaminated with NO3− (up to 99.2 mg/L in groundwater). This basin was declared vulnerable to NO3− pollution in 1998 due to the high anthropogenic pressures (mainly agriculture and wastewaters). Hydrochemical, multi-isotopic (δ18ONO3, δ15NNO3, δ13CDIC, δ18OH2O, and δ2HH2O) and geophysical techniques (electrical resistivity tomography) were applied to identify the main redox processes at the freshwater-saltwater interface. The results showed that the geometry of this interface is influenced by land use, causing spatial variability of nitrogen biogeochemical processes over the basin. In the underlying aquifer, NO3− showed an average concentration of 38.5 mg/L (n = 73) and was mainly derived from agricultural inputs. Natural attenuation of NO3− was observed in dryland farming areas (up to 72%) and in irrigation areas (up to 66%). In the Pétrola Lake, mineralization and organic matter degradation in lake sediment play an important role in NO3− reduction. Our findings are a major step forward in understanding freshwater-saltwater interfaces as reactive zones for NO3− attenuation. We further emphasize the importance of including a land use perspective when studying water quality-environmental relationships in hydrogeological systems dominated by density-driven circulation., his work was financed by a PhD grant (BES-2012-052256) from the Spanish government, the PEIC-2014-004-P project from the Castilla–La Mancha regional government, the projects CICYT CGL2014-57215-C4-1-R, CGL2017-87216-C4-1-R and CGL2017-87216-C4-2-R from the Spanish Ministry of Economy and AEU/FEDER UE, and the project 2017SGR1733 from the Generalitat de Catalunya.

[EN] Groundwater flow models have been increasingly used to support policy making. A substantial amount of research has been dedicated to improving, validating and calibrating models and including stakeholders in the modelling process. However, little research has been done to analyze how the choices of model makers and steering by policy makers result in models with specific characteristics, which only allow specific modelling outcomes, and how the use of these modelling outcomes leads to specific social, economic and environmental consequences. In this study, we use the social construction of technology framework to explore the development, characteristics and uses of the groundwater model of the Mancha Oriental aquifer in Spain. The specific characteristics and functioning of this model influenced the policy implementation, implying that involving stakeholders in the development and use of models is crucial for improved democratic policy making., This work was carried out as part of the collaboration agreement between the University of Castilla–La Mancha and Wageningen University. The research is also part of Femke Rambags’ MSc Thesis. David Sanz was supported by the Grants for Stays at Other Universities and Research Centres (UCLM). Special thanks go to the Júcar Water Authority (CHJ) and stakeholders (JCRMO) in the Mancha Oriental System for the necessary information. We would also like to thank Dr A. Sahuquillo of the Universitat Politècnica de València de Valencia and Dr S. Castaño of the University of Castilla–La Mancha for comments and participation in the first stage of modelling. The contents of this paper do not represent the views of CHJ or JCRMO. Finally, we thank the two anonymous reviewers of this article for their valuable comments and suggestions.

Water in sufficient amounts and quality is essential for meeting both human and ecological needs. Most water used by mankind is destined for agriculture, and demand is steadily growing. Under this pressure, water management faces significant environmental problems. In the case of groundwater, these difficulties are exacerbated by intensive, unregulated exploitation, and the spatial distribution of wells. Challenges to current water management therefore encompass multiple levels (environmental, technological, social, economic, and political), and their solution requires focus and a range of spatial and temporal scales to ensure integrated water resource management. Knowledge, participation and transparency are all crucial to help in conflict prevention and resolution. New challenges require new technologies that can help to resolve them. This paper analyses how the coordinated use of new technologies provides important results to support decision-making in planning and water management in irrigated agriculture. This case study is especially applicable to groundwater management in large areas where conventional planning, monitoring and control methods are extremely expensive and imprecise. The specific case of the Mancha Oriental Aquifer (SE Spain) is examined as it is an area where such conventional methods have proven to be inadequate.

Sulfur (S) plays a significant role in saline environments, and sulfate (SO42 −) is an important component of the biogeochemical S-cycle since it acts as the main electron acceptor in anoxic sediments. The purpose of this paper is to evaluate the fate of S, its origin, and processes affecting sulfate outcome in the hypersaline Petrola Lake in the Castilla-La Mancha region (High Segura Basin, SE Spain). The lake is the terminal discharge zone of an endorheic basin with considerable anthropogenic pressures. Anthropogenic activities (mainly agricultural inputs and wastewater discharge), together with bedrock leaching of sulfate and sulfide-rich sediments, increase dissolved SO42 − in surface and groundwater up to 123,000 mg/L. The source and fate of sulfate in this environment was investigated coupling hydrochemistry, including hydrogen sulfide (H2S) microprofiles, isotopic analyses (δ34S, δ18OSO4, δ2HH2O, δ18OH2O, and tritium), mineralogical determinations, and molecular biology tools (16S rDNA amplification and sequencing). The origin of dissolved SO42 − in water is related to pyrite oxidation from Lower Cretaceous sediments, and secondary gypsum dissolution. Under the lake, dissolved SO42 − decreases with depth, controlled by three main processes: (1) seasonal evaporation cycles, (2) hydrodynamic instability caused by the different density-driven groundwater flow, and (3) sulfate-reduction processes, i.e. dissimilatory bacterial sulfate reduction (BSR). These processes control the continuous recycling of sulfur in the system. Lake water and groundwater are in hydraulic connection, and a density-driven flow (DDF) is able to transport reactive organic matter and dissolved SO42 − towards the underlying aquifer. Hydrochemical evolution in depth, H2S production (up to 0.024 nmol/cm3·s) and the presence of sulfate-reducing bacteria suggest the existence of BSR processes. However, isotope techniques are insufficient to elucidate BSR processes since their isotopic effect is masked by low isotope fractionation and high SO42 − concentrations. The pattern here described may be found in other saline basins worldwide.

Endorheic basins are frequently exposed environments to nitrate (NO 3 − ) pollution where groundwater may be the primary fresh water resource. The Petrola basin (Central Spain) is an outstanding example of this type of basin that is affected by NO 3 − pollution where natural attenuation capacity observed in the field is limited. A three-stage flow-through experiment was developed to evaluate the viability of induced heterotrophic denitrification to remove NO 3 − using chemical, microbial and isotopic tools. The proposed biostimulation involves periodically injecting glucose to act as an electron donor to promote complete NO 3 − removal. The C/N ratio tested is nearly stoichiometric to avoid the generation of undesirable compounds such as NO 2 − or H 2 S. Nitrate reduction was achieved after 13 days, along with transient NO 2 − accumulation that was observed until day 27. In addition to attenuating NO 3 − , the glucose injection also represses the dissimilatory nitrate reduction to ammonium (DNRA), reducing the NH 4 + concentration in the outflow. Changes in the C/N ratio during the experiment reduced the amount of glucose discharged from the system. However, despite these changes, NO 3 − attenuation continued because secondary carbon sources (dissolved organic carbon in the input water or biomass) were present during the experiment and accounted for approximately 30% of the total attenuated NO 3 − . Isotopic characterisation of the sulphate (SO 4 2 − ) proved that the SO 4 2 − reduction did not occur, even though carbon excess and low redox conditions were present. This is attributed to the lack of time for SO 4 2 − reduction to occur inside the column. The N and O isotopic fractionation obtained during the induced attenuation were − 8.8‰ and − 8.0‰, respectively; these values were lower (in absolute values) than the fractionation from natural denitrification processes observed in the Petrola basin. This variation was caused by differences in the experimental conditions that affected the denitrification rate. Overall, periodically injecting glucose might be a feasible method to remove NO 3 − from groundwater; a pilot-scale test should be performed to verify its applicability during long-term treatments in the field.

Biogeochemical cycling involves the exchange of electrons between chemical species through redox reactions. Microorganisms can utilize energy released by redox reactions for their metabolism following a thermodynamic sequence. Among these reactions, the dissimilatory reduction of sulfate (SO42−) to produce hydrogen sulfide (H2S) is one of the most important microbially-mediated pathways. The use of microelectrodes at the water-sediment interface provided a better understanding of sulfate reduction processes in the suboxic and anoxic zones. The goal of this study was to assess the microzonation of H2S and O2 under different conditions of light and oxygen in the water column. For this purpose, organic-rich lacustrine sediments from Pétrola Lake (SE Spain) were used. Sediment incubations were performed in mesocosm devices. The highest production of H2S (up to 0.36 nmol/cm-3s-1) was observed under anoxic and dark conditions. Production under those conditions was several orders of magnitude higher than those measured when oxygen was present in the water column. Furthermore, the absence of O2 in the water column significantly altered the microzonation of H2S in depth. The absence of light seems not to affect the dynamics of O2 and H2S in depth. The study contributes to our understanding of microzonation in organic-rich sediments.

Endorheic basins located in semiarid or arid regions constitute one of the most vulnerable and exposed environments to NO 3 - pollution. The Petrola basin (Central Spain) is an outstanding example of one of these endorheic system. Several constraints have been observed that impede correct identification of the denitrification pathway and its degree at the field scale. To better understand the key factors controlling NO 3 - attenuation, a five-stage column experiment was performed using organic and pyrite rich sediments from the Utrillas Facies (Lower Cretaceous) as a possible electron donor source to promote denitrification. A chemical and multi-isotopic characterization (δ15NNO3, δ18ONO3, δ13CDIC, δ34SSO4, δ18OSO4) of the outflow of the column experiment showed that NO 3 - attenuation was driven by organic matter. The amount of organic C consumed during denitrification was 2% of the total organic C present in the sediment. Both the degree and rate of denitrification were related to flow rate variations. Lower flow rates favored bacterial growth at the beginning of the experiment producing an increase of complete denitrification rate (CDR). When NO 3 - reduction was greater than 15%, CDR remained constant (around 30 μmol L−1 d−1) under different flow rates. In the last stage, flow rate had no effect on output NO 3 - concentration because the organic C supply was limited and had become the main kinetic factor in denitrification. Isotopic fractionations (e of 15N– NO 3 - and 18O– NO 3 - between reaction products and remaining reactants were calculated using representative column samples. The results for the two attenuation stages observed were −11.6‰ and −15.7‰ for eN, and −12.1‰ and −13.8‰ for eO. Most of the field samples showed a percentage of attenuation ranging from 0% to 60% of NO 3 - removal.

Since 1980, southern Spain has registered a cycle of drought with magnitudes consistent with forecasts by the European Environment Agency on climate change for a 20 % decrease in precipitation in southern Europe due to the acceleration of global warming. The impact of this climatic event has been taken into account in drawing up water management plans for the basins affected. However, it has barely been considered in terms of the evolution of groundwater reserves or in their modelling, possibly because the effects are often masked by intensive anthropic withdrawals from regional water resources. This research uses a mathematical groundwater flow model to evaluate the reserve evolution in the Mancha Oriental aquifer system (SE Spain) due to impacts from this drought cycle. Its influence has been quantified (from 1980 to 2008) in the aquifer's storage deficit 23 Mm3/year and in the discharge volume of the Jucar River of 21 Mm3/year. Finally, three plausible scenarios are modelled with respect to 2027, the end date of the planning horizons proposed by Directive 2000/60/EC. These scenarios examine the economic repercussions on current groundwater resource management measurements. If the drought was to persist, the costs involved in the storage deficit were calculated in the range from 21.7 to 34.9 M€.

The change from a traditional agricultural model to a modern, more productive one, coupled with population growth, has entailed an increased consumption of water, fertilizers and pesticides. This transformation has led to a greater risk of groundwater contamination. This study has analysed for this purpose a total of 314 samples (period 2010–2013). In addition, 332 samples from the Mancha Oriental groundwater body (period 2001–2003) were also examined in order to gain a better perspective on the temporal evolution of pesticides in groundwater bodies. Using this database, this study aims to characterize pesticide pollution and to examine possible processes. Triazine herbicides are the most common pesticides found and also appear in the highest concentrations, with terbuthylazine having a noteworthy concentration of 900 ng/L. The irrigated agriculture and the physicochemical properties of pesticides are the most important factors influencing the concentration and type of pesticides that can reach groundwater. The spatial distribution of nitrate and pesticides do not correspond as they would if the two behaved similarly. Pesticides can completely biodegrade before reaching the saturated zone, but it is also possible that their degradation products have not been analysed and, therefore, their concentrations are underestimated.

Among the main difficulties and uncertainties in determining the water balance of an area there is the calculation of groundwater withdrawals. This factor is particularly important in the case of aquifers, whose extension and intensive agricultural use make direct quantification methods unfeasible (i.e. flow meter measurements and electricity consumption). This paper presents a method for quantifying groundwater withdrawals used for agriculture supported by remote sensing and Geographic Information System (GIS). Through the process of obtaining a classification of irrigated crops with a high degree of accuracy by analyzing multi-temporal and multi-spectral satellite imagery, these data are integrated into a GIS, intersected with a correct estimation of needs values crop irrigation and corrected to adapt agricultural practices in the area. The result provides information about the spatial and temporal distribution of the volume of groundwater pumped and used in agriculture with greater accuracy than traditional methods and with much lower cost than any system of direct measurement (about 1 $/ha from the irrigation of the 50,000ha). This methodology has been applied and validated in Mancha Oriental Aquifer System (Spain, 7,260 km), in which withdrawals used for agriculture (approx. 400 Mm) is over 90% of water consumed. Keywords-Water Resources; Agriculture; Groundwater; Pumping; Remote Sensing

This study examines student workload after a change in teaching style from lecture to Problem Based Learning and Cooperative Learning, and its relationship with student outcomes. Results show that the change clearly overloads students if it is not adequately planned and monitored. Marks, drop-outs and attendance were markedly better with the new instruction method, but also with a higher workload. The main conclusion is that calculating student workload in terms of hours is very important, but especially when implementing a change in teaching style.

Among the difficulties and uncertainties that arise when determining water balance is the calculation of groundwater abstraction. This factor is particularly important in aquifers whose extension and heavy agricultural use make direct quantification methods unfeasible (i.e. flow meters and power consumption data). This study presents a method of quantifying groundwater abstractions for irrigation based on the analysis of multitemporal and multispectral satellite images. The process begins with a highly detailed classification of irrigated crops; these data are entered in a Geographic Information System, overlain with a correct estimate of the irrigation requirements of the crop, and corrected in accordance with the agricultural practices of the area. The results reveal the spatial and temporal distribution of the groundwater volume abstracted and used for agriculture. This methodology has been applied in the Mancha Oriental Hydrogeological System (Spain, 7,260 km2), where abstractions for agriculture comprise more than 90% of the hydrological resources consumed. In this context, accuracies of over 95% have been obtained with a cost sixty times lower than that of traditional methods.

The Mancha Oriental System (MOS) has a surface area of 7,260 km2, making it one of the largest carbonate aquifer systems in Spain. The system sustains about 1,000 km2 of irrigated crops and supplies groundwater to 275,000 inhabitants. The economic transformation brought about by the development of extensive irrigated cropland has led to a water-balance disequilibrium of about 75 million m3/year. This input–output deficit has negative consequences in the quantity and quality of the available resources, in the river–aquifer relationship, and in the associated ecosystems as well. To understand the hydrogeological behaviour of the system, it is necessary to design a conceptual model. Further, the conceptualisation of a groundwater flow system is a requirement of the European Water Framework Directive for the characterisation of groundwater bodies. The robustness of the conceptual model depends heavily on the user capability of representing the real system. In this work, a multidisciplinary approach has been used to represent the three-dimensional geological framework and the groundwater flow conceptualisation of the MOS. Data management and three-dimensional visualisation have been carried out by means of geographical information system (GIS) tools and software for contouring and three-dimensional surface mapping.

This study determines the spatial and temporal distribution of nitrate content within the water-supply wells in the Mancha Oriental System (MOS) for the period 1998–2003 and presents an example of the multiple nitrate pollution sources in the El Salobral–Los Llanos Domain (SLD, southwestern Albacete). The groundwater resources of the MOS are used to maintain approximately 800 km2 of irrigated crops and are the sole water supply for a total population of 275,000 inhabitants. The average nitrate content varies from

To determine, for chronostratigraphic purposes, whether the Maastrichtian seawater 87 Sr/ 86 Sr ratio has been preserved in calcite shells, oxygen, carbon, and strontium isotope analyses have been carried out on carbonate matrix and inoceramid shell samples from deep-sea carbonate sediments at the Sopelana and Bidart sections in the Basque-Cantabrian Basin. These analyses were compared with clay-mineral distributions from the same locations. In contrast to Sopelana I samples, Bidart shells are characterised by the lowest 87 Sr/ 86 Sr ratios, the highest d 18 O values, and the highest strontium contents. These geochemical trends correlate with clay distributions in these sections as mineralogical analyses, for instance, indicate that clay minerals show a higher degree of maturation at Sopelana I. Furthermore, in comparison to carbonate matrix results, and regardless of the section, inoceramid shell remains usually yield the lowest 87 Sr/ 86 Sr isotope values, the highest d 18 O values, and highest strontium contents. These results suggest a palaeogeographic control on isotope exchange during burial diagenesis and that the carbonate matrix and inoceramid shells have reacted differently to the same diagenetic environment. Although inoceramid shells from Bidart show evidences of fairly good preservation and fall close to the Maastrichtian seawater 87 Sr/ 86 Sr curve, the original strontium isotope compositions have not been retained.

The sections of Sopelana I and II are mainly characterised by couplets of alternating marly limestones and marls that were deposited in a deep-sea basin environment of Maastrichtian age in the Basque Arc Domain. Both are characterised by a great abundance of inoceramids, which disappear below the Lower/Upper Maastrichtian boundary. Petrographic and isotopic evidence suggests that the carbonate sediment and inoceramid shells have undergone the diagenetic effects of burial processes. Nevertheless, the trends in palaeoenvironmental signals are still recognised on the isotopic curves plotted, albeit somewhat attenuated. Three stages have been defined and named E1 to E3, from oldest to youngest. Stage E1 is characterised by an abundance and diversity of inoceramids in a Transgressive Systems Tract (TST), as well as by a close parallelism between δ18O and δ13C curves in both the inoceramid shells and the matrix. Stage E2 comprises the final part of the TST and the Highstand Systems Tract (HST), showing a positive excursion of δ18O values. However, there are some fluctuations, and this excursion is more clearly seen in the inoceramid shells (>3‰) than in the matrix (>1.5‰) of the Sopelana I section. Following a decline in abundance and diversity, inoceramid extinction is observed in the Basque Arc Domain. Finally, stage E3 is at the base of the Upper Maastrichtian, and characterised by a drastic lithologic change to red marls and a depletion in δ13C values, an isotopic pattern typical of lowstand stages (LST). The record of the boreal inoceramid Spyridoceramus tegulatus, which is coincident with the positive δ18O excursion in stage E2, suggests the entry of deep, cold, oxygenated waters arriving from the North Atlantic. These observations confirm the modification of the thermocline and the onset of climatic cooling close to the Early/Late Maastrichtian boundary, which might have been one of the main causes of the inoceramid disappearance in the Basque Arc Domain.

Inoceramid bivalve shells from outcrops of mid-Maastrichtian deep-water carbonate, hemipelagic beds in the Bay of Biscay exhibit post-depositional diagenetic alteration. New data from isotopic analysis (carbon and oxygen), together with observations of the inoceramid shells and carbonate host-rock using cathodoluminescence (CL) and scanning electron microscopy (SEM), confirm a lateral, westerly increase in the degree of diagenesis, without any substantial textural changes in the alternating dark and clear growth lines of the shell microstructure. Under CL, a bright yellowish to red colour is observed in the most diagenetically altered inoceramid samples. Non-luminescent areas are restricted to the central parts of the less altered shells. A detailed geochemical analysis by electron microprobe, along intrashell profiles of the non-luminescent and luminescent zones has revealed that Mg/Ca, Sr/Ca, Na/Ca, Fe/Ca and Mn/Ca ratios show oscillatory curves but behave differently. Fe/Ca, Mn/Ca and Na/Ca ratios are well correlated but usually show an opposite relationship when compared with the Mg/Ca and Sr/Ca ratios of both luminescent and non-luminescent shell areas. Our findings have palaeoenvironmental implications in that the geochemistry of the regular, alternating dark and clear growth lines seems to be related to the input of seasonally controlled phytodetritus to the basin floor.

Quartz geodes and nodular chert have been found within middle–upper Campanian carbonate sediments from the Lano and Tubilla del Agua sections of the Basque-Cantabrian Basin, northern Spain. The morphology of geodes together with the presence of anhydrite laths included in megaquartz crystals and spherulitic fibrous quartz (quartzine-lutecite), suggest an origin from previous anhydrite nodules. The anhydrite nodules at Lano were produced by the percolation of marine brines, during a period corresponding to a sedimentary gap, with δ34S and δ18O mean values of 18.8‰ and 13.6‰ respectively, consistent with Upper Cretaceous seawater sulphate values. Higher δ34S and δ18O mean values of 21.2‰ and 21.8‰ recorded in the Tubilla del Agua section are interpreted as being due to a partial bacterial sulphate reduction process in a more restricted marine environment. The idea that sulphates may have originated from the leaching of previously deposited Keuper sulphate evaporites with subsequent precipitation as anhydrite, is rejected because the δ34S, δ18O and 87Sr/86Sr values of anhydrite laths observed at both the Tubilla del Agua and Lano sections suggest an origin from younger marine brines. Later calcite replacement and precipitation of geode-filling calcite is recorded in both sections, with δ13C and δ18O values indicating the participation of meteoric waters. Synsedimentary activity of the Penacerrada diapir, which lies close to the Lano section, played a significant role in the local shallowing of the basin and the formation of quartz geodes. In contrast, eustatic shallowing of the inner marine series of the Tubilla del Agua section led to the generation of morphologically similar quartz geodes. Copyright © 2002 John Wiley & Sons, Ltd.

Complex lacustrine systems, such as hypersaline lakes located in endorheic basins, are exposed to nitrate (NO 3 − ) pollution. An excellent example of these lakes is the hypersaline lake located in the Petrola basin (central Spain), where the lake acts as a sink for NO 3 − from agricultural activities and from sewage from the surrounding area. To better understand the role of the organic carbon (C org ) deposited in the bottom sediment in promoting denitrification, a four-stage flow-through experiment (FTR) and batch experiments using lake bottom sediment were performed. The chemical, multi-isotopic and kinetic characterization of the outflow showed that the intrinsic NO 3 − attenuation potential of the lake bottom sediment was able to remove 95% of the NO 3 − input over 296 days under different flow conditions. The NO 3 − attenuation was mainly linked with denitrification but some dissimilatory nitrate reduction to ammonium was observed at early days favored by the high C/N ratio and salinity. Sulfate reduction could be neither confirmed nor discarded during the experiments because the sediment leaching masked the chemical and isotopic signatures of this reaction. The average nitrogen reduction rate (NRR) obtained was 1.25 mmol d − 1 kg − 1 and was independent of the flow rate employed. The amount of reactive C org from the bottom sediment consumed during denitrification was 28.8 mmol, representing approximately 10% of the total C org of the sediment (1.2%). Denitrification was produced coupled with an increase in the isotopic composition of both δ 15 N and δ 18 O. The isotopic fractionations (e of 15 N-NO 3 − and 18 O-NO 3 − ) produced during denitrification were calculated using batch and vertical profile samples. The results were − 14.7‰ for eN and − 14.5‰ for eO.

Agricultural regions in semi-arid to arid climates with associated saline wetlands are one of the most vulnerable environments to nitrate pollution. The Pétrola Basin was declared vulnerable to NO3(-) pollution by the Regional Government in 1998, and the hypersaline lake was classified as a heavily modified body of water. The study assessed groundwater NO3(-) through the use of multi-isotopic tracers (δ(15)N, δ(34)S, δ(13)C, δ(18)O) coupled to hydrochemistry in the aquifer connected to the eutrophic lake. Hydrogeologically, the basin shows two main flow components: regional groundwater flow from recharge areas (Zone 1) to the lake (Zone 2), and a density-driven flow from surface water to the underlying aquifer (Zone 3). In Zones 1 and 2, δ(15)NNO3 and δ(18)ONO3 suggest that NO3(-) from slightly volatilized ammonium synthetic fertilizers is only partially denitrified. The natural attenuation of NO3(-) can occur by heterotrophic reactions. However, autotrophic reactions cannot be ruled out. In Zone 3, the freshwater-saltwater interface (down to 12-16 m below the ground surface) is a reactive zone for NO3(-) attenuation. Tritium data suggest that the absence of NO3(-) in the deepest zones of the aquifer under the lake can be attributed to a regional groundwater flow with long residence time. In hypersaline lakes the geometry of the density-driven flow can play an important role in the transport of chemical species that can be related to denitrification processes.

The Lano quarry, located in the northern part of the Iberian Peninsula (Basque–Cantabrian Region), has yielded a diverse continental vertebrate assemblage from the Late Cretaceous (late Campanian to early Maastrichtian). The fossil assemblage consists of almost 40 species, including bony fish, amphibians, lizards, snakes, turtles, crocodilians, dinosaurs, pterosaurs and mammals. Lano is the most productive European vertebrate locality hitherto known from the Late Cretaceous. The sedimentology of the Lano section shows that the three associated fossiliferous beds (known as L1A, L1B and L2) were deposited in an alluvial system composed primarily of fluvial sands and silts. The sedimentary structures are consistent with channel areas within an extensive braided river. The L1A level was excavated in detail and mapped following a square-metre grid system. The main features of the multispecies vertebrate assemblage are as follows: wide range of body size (including microfossils); large proportion of adult individuals; rare articulated skeletal parts; size-sorting and dominance of small elements; high spatial density; long bones showing some preferential orientation; variable dip; variable degree of breakage and large proportion of splintering; wide range of weathering and abrasion; no evidence of predatory activity or chemical alteration. On the basis of these features, we suggest that the Lano association lies between the taphonomic modes for attritional vertebrate assemblages in fluvial channels, though it tends more toward the channel-fill than the channel lag mode. The L1A sample of Lano is a heterogeneous assemblage of elements ranging from isolated bones and teeth to articulated skeletons with allochthonous and para-autochthonous characteristics. It consists of a mixture of vertebrates from different palaeocommunities, and includes aquatic (or semi-aquatic) elements and remains transported from a variety of habitats on the alluvial plain. The dinosaur bones are commonly broken and show a greater degree of abrasion than those of freshwater vertebrates, indicating that they may be allochthonous. However, actinopterygians, amphibians, pleurodiran turtles and eusuchian crocodilians are interpreted as being para-autochthonous. Palaeobatrachid frogs, bothremydid turtles and alligatoroid crocodilians are the most relatively abundant vertebrates of the Lano fossil assemblage. The occurrence of pelomedusid turtles and crocodilians is indicative of an intertropical, warm climate.

© 2012 Sanz et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. GIS Applied to the Hydrogeologic Characterization – Examples for Mancha Oriental Aquifer (SE Spain)

To determine the effects of anthropogenic pressures on the ecology of rivers in the Segura Watershed, we examined stream physicochemistry and the macroinvertebrate community in relation to land use, flow regulation by reservoirs, and the Tajo-Segura Inter-basin Transfer. The inter-basin transfer is thought to be the most important stressor because it affects the flow regime as well as water quality and quantity in an arid, typically water-stressed environment. The concentrations of major ions were strongly impacted by agricultural and urban land uses and the inter-basin transfer. There was a significant increase in conductivity and the concentrations of SO42− and other major ions downstream of the Tajo-Segura Transfer. The macroinvertebrate community was less diverse and composed of more pollution-tolerant taxa in areas affected by flow regulation and the inter-basin transfer. The rivers of study are at risk for salinization because of inputs from land use and the Tajo-Segura Transfer. Therefore, major ion and nutrient concentrations should be monitored. Currently, there is no limit specified for SO42− concentration in relation to aquatic ecosystem health in Spain. Measures are needed to reduce the effects of contamination and flow regulation to protect the aquatic ecosystem within the Segura Watershed. Copyright © 2012 John Wiley & Sons, Ltd.

The Mancha Oriental System (MOS, 7,260 km2) is one of the largest aquifers within Spain, and is encompassed by the Jucar River Basin. Over the past 30 years, socioeconomic development within the region has been largely due to intensive use of groundwater resources for irrigating crops (1,000 km2). Groundwater pumping (406 million m3/year) has provoked a steady drop in the groundwater level and a reduction of MOS discharge to the Jucar River. The study aims to characterize the river-aquifer relationship, to determine the influence that groundwater abstraction has on the river discharge. This research has advanced a three-dimensional large-scale numerical groundwater-flow model (MODFLOW 2000) in order to spatially and temporally evaluate, quantify and predict the river-aquifer interactions that are influenced by groundwater abstraction in MOS. It is demonstrated that although groundwater abstraction increased considerably from the early 1980s to 2000, the depletion of water stored in the aquifer was lower than might be expected. This is mainly due to aquifer recharge from the Jucar River, induced by groundwater abstraction. The area of disconnection between the river and the water table (i. e. where groundwater head is lower than the riverbed) is found to have spread 20km downstream from its position before pumping started. © 2010 Springer-Verlag., This study was funded by the Spanish Government under research grant CGL2008-06394-C02-02/BTE. Special thanks go to the Jucar Water Authority (CHJ) and stakeholders (JCRMO) in the Mancha Oriental System for providing the information necessary. The content of this report does not represent the view of CHJ and JCRMO.

This project determines the nitrate content as well as spatial and temporal distribution in the water supply wells which extract groundwater from the Mancha Oriental System (MOS). The underground resources of the system are used in maintaining approximately 80,000 hectares of irrigation and are the water supply for a total population of 275,000 inhabitants. The average nitrate contents show a heterogeneous spatial distribution, varying between 0.1 mg l and 125 mg l. The highest levels are associated with areas with large areas of irrigated crops. However, there are also points that are not found to be spatially linked to this type of farming in which nitrate has been detected in significant quantities. The presence of nitrate in these areas can be explained considering other sources of pollution or transport of the pollutant from contaminated areas through groundwater flow. In general, average nitrate values show a growing tendency during the period 1998 and 2003.

New petrographic and isotopic data from inoceramid bivalve shells and belemnite rostra from the lower Campanian and belemnite rostra from the mid-upper Maastrichtian of the Marambio Group, James Ross Basin, Antarctica are presented. Most of the inoceramid data were processed from shell fragments of the large formAntarcticeramus rabotensis (Crame and Luther) at the stratigraphic level marking the extinction of the inoceramids in the James Ross Basin (uppermost early Campanian-basal late Campanian). Standard transmitted light microscopy and cathodoluminescence (CL) studies in thin sections ofA. rabotensis show clear evidence of environmental stress, which is reflected as marked growth breaks in the shell banding of this large inoceramid bivalve. At Redonda Point, CL and the mean oxygen isotopic value (δ18O=-3.11‰ 3 (PDB); n=11; t°=25.4°C) indicate a varied degree of diagenetic modification, but without any evidence of neomorphism along the prismatic microstructures. Early Campanian belemnite rostra are much less diagenetically modified (at the Brandy Bay section; and the Santa Marta section; δ18O=-0.50‰ (PDB); n=5; t°=14.0°C and 3 δ18O=-0.94‰ (PDB); n=21; t°=15.8°C) and are non luminescent 3 except for localized, organic-rich bands. The mean oxygen isotopic value for mid-late Maastrichtian belemnite rostra (at the Seymour Island section; δ18O=-0.11‰ 3 (PDB); n=5; t°=12.5°C) indicates a substantial drop in the sea-water paleotemperature, suggesting a causal relationship between the early extinction of the inoceramid bivalves in high latitudes of the Southern Hemisphere and the falling sea-water temperature. Fil: Elorza, Javier. Universidad del País Vasco; España Fil: Gómez Alday, Juan J.. Universidad del País Vasco; España Fil: Olivero, Eduardo Bernardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina