Lower Ebro Research Articles

An inter-comparison of approaches and frameworks to quantify irrigation from satellite data

Abstract. This study provides the first inter-comparison of different state-of-the-art approaches and frameworks that share a commonality in their utilization of satellite remote-sensing data to quantify irrigation at a regional scale. The compared approaches vary in their reliance on either soil moisture or evapotranspiration data or their joint utilization of both. The two compared frameworks either extract irrigation information from residuals between satellite observations and rainfed hydrological models in a baseline framework or use soil water balance modeling in a soil-moisture-based inversion framework. The inter-comparison is conducted over the lower Ebro catchment in Spain where observed irrigation amounts are available for benchmarking. Our results showed that within the baseline framework, the joint approach using both soil moisture and evapotranspiration (ET) remote-sensing data only differed by +37 mm from the irrigation benchmark (922 mm) during the main irrigation season over 2 years and by +47 and −208 mm for approaches relying solely on soil moisture and ET, respectively. A comparison of the different frameworks showed that the main advantage of the more complex baseline framework was the consistency between soil moisture and ET components within the hydrological model, which made it unlikely that either one ended up representing all irrigation water use. However, the simplicity of the soil-moisture-based inversion framework, coupled with its direct conversion of soil moisture changes into actual water volumes, effectively addresses the key challenges inherent in the baseline framework, which are associated with uncertainties related to an unknown remote-sensing observation depth and the static depth of the soil layers in a conceptual model. The performance of the baseline framework came closest to the irrigation benchmark and was able to account for the precipitation input, which resulted in more plausible temporal distributions of irrigation than what was expected from the benchmark observations.

Angler’s preferences, perceptions and practices regarding non-native freshwater fish

It is globally recognized that freshwater anglers can have a decisive role in promoting fish introductions. The aim of this study was to analyze freshwater anglers’ actions and perceptions regarding fish introductions, comparing two distinct situations, one with recently arrived non-natives fishes and another with older fish introductions, using the Iberian Peninsula as a case study. To achieve this goal, a bilingual survey was implemented on-line in Portugal and Spain and in person (direct inquiries) in two Iberian regions: Lower Ebro (older fish introductions) in Spain; and Lower Tagus (recent fish introductions) in Portugal. Results showed spatial differences in perceptions and actions, namely about the target species, awareness of the impact of non-native fishes, fish introductions reported and proportion of anglers that wanted new fish species. In the Ebro river there is a high percentage of foreign anglers, higher awareness of fish introduction impact and lower introduction rates reported than in the Tagus river. However, popularity of non-native species like European catfish, was higher in the Ebro. In general, although risk behaviors such as use of fish as life bait was of low prevalence for both countries (approx. 5%), it corresponds to large numbers of fish being introduced. Our conservative estimates revealed 273,600 events of bait discharge per year. Regarding the intentional introductions, we estimated a total of 140,000 intentional introduction (illegal) events per year. These findings may help to improve monitoring, awareness and fisheries management programs led by governmental agencies.Graphical abstract

Where have all the sediments gone? Reservoir silting and sedimentary justice in the lower Ebro River

At the intersection of natural and social sciences, interest in river sedimentary fluxes and their alteration by human activities is increasing in the context of general retreat of delta formations. Since the 1950s, the construction of large dams in the main course of rivers has produced, among other impacts, a radical decrease in sedimentary fluxes — a key factor in the worldwide sedimentary crisis. While sediment accumulates in reservoirs, the resulting sediment scarcity downstream contributes to land subsidence and coastal erosion, endangering livelihoods in low lying areas such as river deltas. Focusing on the case of the Ebro River and delta (Spain), this article builds on Katherine Dawson's notion of sedimentary justice to examine the articulation of a social demand to mobilise the sediments trapped in reservoirs to counter delta subsidence and coastal erosion. Using a historical perspective and paying attention to matters of both sediment quantity and quality, we show how this demand has developed hand in hand with the emergence of a scientific interpretation of the Ebro delta's origins that emphasises non-human forces and the importance of sedimentary fluxes before human interferences. Activists have taken up this argument to demand the restoration of sedimentary fluxes, exposing corporate hydropower interests and insisting on the mobilisation of sediment trapped in reservoirs. Overall, by scrutinizing the power relations embedded in the immobilization of river sediments, this article contributes to recent work that integrates the materiality of sediment to the hydrosocial framework of analysis and argues that sedimentary justice provides new avenues to incorporate the non-human world to the literature on environmental and water justice.

Fate of pharmaceuticals in the Ebro River Delta region: The combined evaluation of water, sediment, plastic litter, and biomonitoring

The increasing consumption of pharmaceuticals, alongside their limited removal in wastewater treatment plants (WWTPs), have led to their ubiquitous occurrence in receiving aquatic environments. This study addresses the occurrence of 68 pharmaceuticals (PhACs) in the Ebro River Delta region (NE Spain), as well as their distribution in different environmental compartments, including surface water, sediments, biota (river biofilm and fish tissues), and field-collected plastic litter. In addition, their concentrations in serving WWTPs, as possible sources of environmental contamination, were also determined.Our study confirmed the widespread occurrence of PhACs in riverine and, to a more limited extent, coastal environments. Most frequently detected PhACs belonged to analgesics/anti-inflammatories (e.g., ibuprofen) and psychiatric drugs (e.g., venlafaxine) therapeutic groups, followed by antihypertensives (e.g., valsartan) and antibiotics (e.g., azithromycin). Seasonal differences in cumulative levels of PhACs were reported for water and sediments (winter>summer). Despite spatial gradients were not clear along the river, a non-negligible contribution of upstream Ebro sites (reference area) was highlighted, which was unexpected based on the low anthropogenic pressure. Sediments represented a minor attenuation pathway for the selected PhACs, whereas they were more heavily accumulated in biota: fish liver (up to 166 ng/g dw), river biofilms (up to 108 ng/g dw), fish plasma (up to 63 ng/mL), and fish muscle (up to 31 ng/g dw).These findings highlight the importance of biomonitoring in the characterization of polluted areas and prioritization of hazardous substances (e.g., psychiatric drugs) in aquatic systems, and a particular interest of fish plasma as non-destructive biomonitoring matrix. PhACs were also detected on plastic litter, demonstrating their role as environmental sinks for certain PhACs (e.g., analgesics/anti-inflammatories, psychiatric drugs). Overall, the widespread detection of PhACs in a variety of biotic and abiotic matrices from the lower Ebro River and Delta warns about their possible environmental implications.

Source areas of the Eastern Ebro Valley loess (NE Iberian Peninsula): Heavy mineral composition as a provenance indicator

AbstractLoess deposits of the Eastern Ebro Valley (NE Iberian Peninsula) occupy an area of ~2000 km2 mostly on the east of the Ebro depression and locally in the Móra Basin. We studied 38 samples of loess and 47 samples of their possible source areas, in order to determine the location of the origin of the loess materials, based on their particle size distribution and composition of heavy minerals. Our results clearly differentiate two depositional loess basins disconnected by the reliefs of the Pre‐Coastal Range with different mineralogical signatures: the Ebro Basin and the Móra Basin. The most relevant variables to discern source areas were the percentage of heavy minerals, the concentrations of zircon, staurolite, rutile and inosilicates, and the presence of gypsum. In the Ebro Basin, the largest set of loess deposits is located around a depocenter in the Batea region and along several lateral areas, with materials that come from the central alluvial plain of the Middle Ebro River (25 to >100 km travel distance), in addition to deflated materials from Miocene interfluvial substrates. On the other hand, loess deposits of the Móra Basin come from more proximal source areas (<15 km), originating from the alluvial materials of the Lower Ebro River that contain the contributions of its tributaries, the Cinca and Segre rivers. Taking into account the homogeneity in the mineralogical composition of complex loess sequences, we deduced a general WNW–ESE wind direction, which would have remained constant over the last two cold periods (MIS‐2 and MIS‐6). Along this axis, the Pàndols–Cavalls Range, with a height difference of 200–350 m, acted as a wind barrier separating the loess of Ebro Basin from the loess of Móra Basin.

New perspectives on the Sertorian War in northeastern Hispania: archaeological surveys of the Roman camps of the lower River Ebro

AbstractIn recent decades, conflict archaeology has renewed study of the Roman Republican military, with Hispania as one of the most prolific areas of research. Following this trend, since 2006 the University of Barcelona has conducted archaeological investigations at several sites in the lower Ebro basin. When no structures or archaeological layers remained in situ, surface survey became a key methodology. Based on the artifacts retrieved during surface survey, this article identifies four new military establishments dated to the first half of the 1st c. BCE and reinterprets the campaigns of the Sertorian War in northeastern Spain.

Low-Frequency Atmospheric Variability Patterns and Synoptic Types Linked to Large Floods in the Lower Ebro River Basin

Abstract This study analyzes the atmospheric variability that caused the largest floods affecting the town of Tortosa, Spain, in the mouth of the Ebro River (northeast Iberian Peninsula). The Tortosa flood database and flood marks in the nearby town of Xerta are used to define the more relevant flooding episodes (discharges >2900 m3 s−1) of the 1600–2005 period. We explore the atmospheric variability based on low-frequency patterns and synoptic types applying a multivariable analysis to grids at sea level pressure and geopotential at 500 hPa provided by the twentieth-century V3 Reanalysis Project for the instrumental period (since 1836). Output from the Last Millennium Ensemble Project was used to analyze the sea level pressure over the pre-instrumental period (before 1836). Our analysis includes 33 flood episodes. Four synoptic types are related to floods in Tortosa since 1836, characterized by low pressure systems that interact with the Mediterranean warm air mass and promote atmospheric destabilization. Flooding in Tortosa is related to relative high values of solar activity, positive Northern Hemisphere temperature anomalies, and NAO in positive phase. This result indicates that the major floods are related to zonal atmospheric circulations (west-to-east cyclone transfer). During winter, the main impact of the floods is located at the western part of the basin, and the Pyrenean subbasins are affected during autumn. The major finding is that similar flood behavior is detected since 1600, improving our understanding of past climates, enhancing the knowledge base for some aspects and impacts of climate change, and reducing uncertainty about future outcomes. Significance Statement A total of 33 large floods (>2900 m3 s−1) were registered since 1600 in Tortosa, Spain, located at the mouth of the Ebro River (northeast Iberian Peninsula). They occur associated with low pressure systems that interact with the Mediterranean warm air mass promoting atmospheric destabilization. The floods in Tortosa are also associated with other important processes occurring at significantly longer time scales: high values of solar activity, positive Northern Hemisphere temperature anomalies, and NAO in positive phase, indicating that the major floods are related to zonal atmospheric circulations. The major finding is that we detect similar flood behaviors since 1600, improving our understanding of past climates, enhancing the knowledge base for some aspects and impacts of climate change, and reducing uncertainty about future outcomes.

Hydraulic technology as means of Christian colonisation. Watermills and channels in the Lower Ebro (Catalonia)

ABSTRACT In this study, evidence provided by written records generated after the conquest of Tortosa in 1148 and the results of archaeological survey have led to the identification of several farmland areas and their associated Andalusi settlements on both banks of the River Ebro, in the hinterland of Madīna Ṭurṭūsha. These field systems were formed by compact and discontinuous cultivation areas on the riverbanks. Drainage channels and wells with water-lifting wheels comprised the main hydraulic techniques used. One of the most relevant changes as a consequence of feudal conquest was the introduction of new hydraulic systems consisting of water catchment in the hills above the river and long channels, whose main purpose was to drive watermills. These channels were rather complex in terms of technology and distinct from those of the Muslim peasant tradition and we can recognise the political power behind them.

Environmental Flows in the Lower Ebro River and Delta: Current Status and Guidelines for a Holistic Approach

Deltas are a particular type of estuarine system in which the dependence on river flow (water, sediments and nutrients) is very strong, especially in river-dominated deltas such as the Mediterranean ones, but environmental flow (e-flow) proposals for deltaic systems are scarce. The Ebro Delta is one of the largest wetland areas in the western Mediterranean and one of the most important estuarine systems in Europe. The aim of this paper is to review the state of the art regarding e-flows and to carry out a critical analysis of the proposals for the lower Ebro River and Delta, in order to highlight the possible environmental and socioeconomic impacts arising from the e-flow regime currently approved. Additionally, based on existing scientific information, methods to establish an e-flow regime that allows the maintenance of the main socio-ecological functions and values are discussed; including those functions and values for which not enough information is available. The study concludes that the currently approved e-flows are not suitable for maintaining most functions and values, as they would not prevent the proliferation of alien fish species and macrophytes in the river, the intrusion of the salt wedge in the estuary, the deficit of sediment/nutrient transport and the degradation of riparian habitats or the decline of coastal fisheries. Socioeconomic consequences on coastal fisheries, river navigation, salt water intrusion, sediment deficit, biodiversity, water quality, aquaculture and hydropower are also considered. Other e-flow proposals such as the proposed by the Catalan government would be more suitable to maintain the main socioecological functions and values of the lower Ebro River and Delta. Nevertheless, additional studies are needed to validate e-flows in some relevant aspects such as the capacity of the river to transport sediments to the delta to avoid coastal regression and mitigate the effects of sea level rise and subsidence, as well as the capacity of floods to control the spread of macrophytes. The lower Ebro River and delta is among the case studies where more quantitative and qualitative criteria to set e-flows with a holistic approach have been established.

Responses of a native and a recent invader snail to warming and dry conditions: the case of the lower Ebro River

Aquatic habitats have been highly modified by human actions that reduce their native diversity and create conditions suitable for tolerant alien species. Pomacea maculata was detected in 2009 in both the alluvial plain and the final stretch of the Ebro River. Since then, a permanent population has stabilized in the littoral area of the river where the water level fluctuates according to the river discharge. Melanopsis tricarinata is an endemic snail species highly affected by the reduction in its natural habitat. Currently, the two species do not share the same reaches in the river, but the possibility exists, as the distribution of the P. maculata is constantly increasing. This study aims to analyse the diets and to assess the responses of both snails to global change. The diet of both species was analysed in the field and their responses to water warming and dryness compared under laboratory conditions. This study includes the calculation of future river water temperatures based on air temperature projections. In addition, based on water discharge management scenarios, the study estimated the increase in dry river bed area. The diet of both snail species was similar and based on Cladophora. P. maculata better resisted high temperatures and dry conditions than M. tricarinata. The projections of water temperatures showed an increase in daily temperatures, especially in summer. The hydraulic model suggested that a relevant increase in dry river bed areas will occur. Overall, these results provide insight into the global change factors that could favour P. maculata spread in the river and the reduction in suitable habitat for M. tricarinata and will be useful for future decisions of water discharge management.

The Influence of Flow Regime on Ecological Quality, Bird Diversity, and Shellfish Fisheries in a Lowland Mediterranean River and Its Coastal Area

Designing environmental flows in lowland river sections and estuaries is a challenge for researchers and managers, given their complexity and their importance, both for nature conservation and economy. The Ebro River and its delta belong to a Mediterranean area with marked anthropogenic pressures. This study presents an assessment of the relationships between mean flows (discharges) computed at different time scales and (i) ecological quality based on fish populations in the lower Ebro, (ii) bird populations, and (iii) two shellfish fishery species of socioeconomic importance (prawn, or Penaeus kerathurus, and mantis shrimp, or Squilla mantis). Daily discharge data from 2000 to 2015 were used for analyses. Mean annual discharge was able to explain the variation in fish-based ecological quality, and model performance increased when aquatic vegetation was incorporated. Our results indicate that a good ecological status cannot be reached only through changes on discharge, and that habitat characteristics, such as the coverage of macrophytes, must be taken into account. In addition, among the different bird groups identified in our study area, predators were related to river discharge. This was likely due to its influence on available resources. Finally, prawn and mantis shrimp productivity were influenced up to a certain degree by discharge and physicochemical variables, as inputs from rivers constitute major sources of nutrients in oligotrophic environments such as the Mediterranean Sea. Such outcomes allowed revisiting the environmental flow regimes designed for the study area, which provides information for water management in this or in other similar Mediterranean zones.

Taming a land. Power politics and the growth of complexity in the north‐east of the iberian peninsula during the first millennium BC: The lower ebro region

SummaryIn this paper we examine the structure of politically complex societies in the north‐east of the Iberian Peninsula during the first millennium BC, using the Lower Ebro region as an example. Drawing on data provided in recent years by archaeological research, we discuss the combination of territorially hierarchical and heterarchical phenomena. At the same time we reassess the chronological framework in which this sociopolitical process took place. To do so, we rely more on information about the evolution of the protohistoric societies in the region under study than on information about material culture. We present a model that may serve as a starting point for future research.

Normalized abundance spectra of fish community reflect hydro-peaking on a Mediterranean large river

The European Water Framework Directive requires the integration of body size characters as an important part of fish-based bioassessment tools for freshwaters ecological status determination. The study of the entire fish community size-structure provides valuable information about food web capacity, food web stability and ecological efficiency of aquatic ecosystems. One of the most used representations of community size structure is the Normalized Abundance Spectra (NAS) that provides an approximation of the total fish abundance and food web capacity (through the parameter y-intercept) and an estimation of food web efficiency (through the slope of the linear regression). In this study we explored NAS of the lower Ebro River fish community by integrating data from monthly electrofishing samplings during a whole year (November 2014- October 2015). We found that the percentage of total alien and alien-prey individuals were directly related with y-intercept and inversely related with slope of NAS. This is because the bulk of the community consists of introduced species of small body length. Furthermore, we detected significant relationships between NAS-related parameters and the hydrological variables describing diel flow oscillations and daily flow variability. Based on this, we suggest that high flow variability conditions and, above all, high hydro-peaking conditions, caused a diminution of the total abundance of fish and a decrease of the proportion of small sized fish (i.e. lower y-intercept and flatter slopes of NAS, respectively). Finally, a significant interaction between hydro-peaking and the percentage of alien-predators suggests that high hydro-peaking conditions benefit predation by facilitating predator-prey encounters. This is reflected by strong linear relationship between NAS parameters and percentage of piscivorous at high hydropeaking conditions that disappears at low hydro-peaking fluctuations. We concluded that the high proportion of alien fishes and the presence of a hydropower generation plant that operates by hydro-peaking are important factors determining fish size structure in the lower Ebro River.

Neogene-Quaternary onshore record in the lower Ebro river incised palaeovalley (Ebro margin, Catalan Coastal Range, NE Iberia)

The lower Ebro is a bedrock-alluvial mixed incised valley with a persistent degradational stacking architecture developed from latest Serravallian(?) to Holocene. This degradational pattern was probably controlled by isostatic rebound in NE Iberia and punctuated by major relative sea level changes that temporally accentuated or attenuated the palaeovalley entrenchment and sediment retention. Six allostratigraphic units in the palaeovalley constitute the onshore record of its evolution and the opening and connection of the Ebro Basin with the Mediterranean. This paper deals with the analysis and reinterpretation of these units in order to precise the sequence of events that took place on the onshore part of the Catalan continental margin during the Ebro River drainage entrenchment. Plausible chronology and palaeogeographic evolution of the Neogene-Quaternary drainage incision in the lower Ebro are also proposed. The early evolutionary stages of the incised palaeovalley (Latest Serravallian?-Tortonian-Early Messinian, from 11.63–9? to near 5.6Ma) were dominated by entrenchment and intense sediment transfer from the onshore to the offshore zones (erosion surface S2). These processes were only punctuated by the sedimentation of the alluvial palaeovalley unit M2 (late Messinian). The polygenetic onshore erosion surfaces S2 and S3 are linked here with the onshore erosive processes that fed the sedimentation of the terrigenous shelf-slope system of the offshore Castellon group and considered coeval with the offshore Messinian erosion surfaces (reflectors M and m). During a further evolutionary stage (Pliocene to Early Pleistocene from 5.3 to approximately 2Ma) the Early Pliocene major Mediterranean reflooding caused some sediment retention in the incised palaeovalley (sedimentation of unit P) but sediment transfer into the offshore remained very effective. In the last evolutionary stage (Early Pleistocene-Holocene, from 2Ma to present) the palaeovalley became again mainly degradational (generation of erosion surfaces S4 to S6 and sedimentation of stepped alluvial terraces Q1-2 to Q4). The onshore stratigraphic record, including the allostratigraphic units P and Q1-2 to Q4 and the related bounding surfaces S3 to S6, is correlated with the sedimentation of the terrigenous shelf-slope system of the offshore Ebro group.

Impact of a reservoir system on benthic macroinvertebrate and diatom communities of a large Mediterranean river (lower Ebro river, Catalonia, Spain)

espanolEl presente estudio incluyo las principales categorias hidrogeomorfologicas de la parte baja del rio Ebro y tuvo como objetivo detectar los patrones de distribucion de macroinvertebrados y diatomeas bentonicas aguas abajo de un sistema de embalses. Se establecio la hipotesis que las comunidades biologicas reflejan un gradiente de alteracion relacionado con la distancia al impacto (por ejemplo, las presas). Se analizaron muestreos realizados a lo largo de cinco tramos del rio de 2 Km, integrando diferentes anos y estaciones. Diversos analisis estadisticos (MDS, SIMPER, ANOSIM) fueron utilizados para evaluar las diferencias espaciales y temporales en las comunidades biologicas. Tambien se analizo la relacion entre los datos biologicos y ambientales con el test BIOENV y los patrones de asociacion de las variables abioticas se analizaron a traves de un PCA. Se encontraron diferencias significativas en la composicion de las comunidades de macroinvertebrados entre la seccion mas cercana a los embalses y el resto de las secciones de estudio; la composicion actual de estas comunidades fue muy diferente de la encontrada en estudios de los anos 80-90. En el caso de las diatomeas, solamente se encontraron diferencias significativas a nivel estacional, pero no entre secciones de estudio. Ademas, los indices para la evaluacion del estado ecologico basados en macroinvertebrados (IBMWP) y diatomeas (IPS) mostraron puntuaciones mas bajas en la seccion E5, posiblemente como resultado del impacto de las presas. Los macroinvertebrados y las diatomeas respondieron de forma diferente a los factores antropogenicos en el tramo final del rio Ebro; los macroinvertebrados fueron mas sensibles a los impactos hidromorfologicos mientras que las diatomeas fueron mas sensibles a las alteraciones de calidad de agua. EnglishThis study included the main hydrogeomorphic categories of the lower Ebro River and aimed to detect spatial and temporal patterns of macroinvertebrates and diatoms communities inhabiting downstream a reservoir system. We hypothesized that biological communities will reflect a gradient of alteration related to the distance from the impact (i.e., dams). Surveys conducted along five river sections 2 km long integrating different years and seasons were analyzed. Non-metrical Multidimensional Scaling (MDS), Similarity Percentage Analysis (SIMPER) and 1-way Analysis of Similarities (ANOSIM) were performed to assess spatial and temporal differences in community structure. The relationship between biological and environmental data was investigated with BIOENV routine and a Principal Components Analysis (PCA) was also carried out. Significant differences in the composition of the macroinvertebrate community were found between the section closest to reservoirs (E5) and the rest of the study sections; the present community was also very different of that found in previous studies carried out in the 80’s and 90’s. For the case of diatoms, significant differences in community composition were only found between seasons but not between study sections. As well, indices for ecological status assessment based on both macroinvertebrates (IBMWP) and diatoms (IPS) showed lowest scores at section E5, likely caused by the impact of dams. Macroinvertebrates and diatoms responded rather differently to anthropogenic stressors in the lower Ebro River; macroinvertebrates were more sensitive to hydromorphological impacts, while diatoms were more sensitive to water quality alteration

Environmental flow management: An analysis applied to the Ebro River Basin

Abstract Environmental flows (EF) define the quantity, timing and quality of river flows needed to preserve freshwater ecosystems while assuring the continuity of human use. Insofar as they reduce water availability and condition agricultural and industrial uses, EF represent a constraint, but they also hold out new opportunities for development. This study focuses on the final stretch of the Ebro River (Spain) and on the competing environmental uses of water (the Ebro Delta is a biosphere reserve) and economic uses (irrigation and electricity generating). Environmental flows in the Ebro Delta are currently managed only from the Mequinenza dam and reservoir in eastern Aragon, and the resulting outflows have more than once driven the level of the reservoir down to critical environmental levels in recent years. In general, this management policy has also caused a range of negative environmental and economic impacts in the area. However, other alternatives exist, which could foster both more cooperative and equitable flow allocations, and the development and sustainability of the Ebro Basin. To this end, we develop a water management model to simulate scarcity scenarios and measure the associated environmental flow default rates assuming current productive uses. Our findings confirm that it is not possible to guarantee EFs in the delta without reservoir-based water management so as to ensure the compatibility of EFs with the irrigation and hydroelectric activities. Moreover, the existence of more equitable and cooperative water management options would reduce water pressures on Mequinenza dam and so help fulfill the subsidized irrigation commitments established in Aragonese Lower Ebro Plan.

Changes in Summer Pressure Patterns across the Late 1960s and Their Influence on Temperature Trends on the Eastern Coast of the Iberian Peninsula

During the second half of the 20th century, in the littoral and pre-littoral areas of the Valencia region, the diurnal temperature range (DTR) registered a significant drop in summer (July and August). Meanwhile, in the same period in the lower Ebro Valley (Ebro Observatory), to the north of the Valencia region, the maximum temperature and DTR increased steeply. In order to explain the DTR drop in the coastal areas of the Valencia region, some studies have proposed an increase in the summer sea-surface temperature (SST) and others have attributed it to the urban heat island effect. Nevertheless, this drop occurred well before the current climate change was evident and therefore, before the rise of the SST. Furthermore, regarding the second proposed explanation, the drop in the DTR does not disappear when working with selected stations away from heavily urbanized areas. In this work, we propose that both the DTR rise at the Ebro Observatory and the DTR drop in the Valencia region are linked to the same process: changes in atmospheric circulation on a synoptic-scale in the North Atlantic that occurred in the late 1960s.

Benthic Diatom Communities of a Large Mediterranean River under the Influence of a Thermal Effluent

The influence of a thermal discharge caused by the cooling system of a nuclear power station on benthic diatom communities was assessed at the lower Ebro River (in Spain), and the information generated could be useful to understand the effects of increasing temperature on large Mediterranean rivers. Surveys conducted at sites before and after the effluent and collected from natural and artificial substrate were analyzed and, Non-metrical Multidimensional Scaling (NMDS), Similarity Percentage Analysis (SIMPER) and 1-way Analysis of Similarities (ANOSIM) were performed to assess changes in community structure. The relationship between diatom assemblages and environmental variables was assessed with a multivariate distance-based linear regression model (DISTLM) and the model was visualized through a redundancy analysis (dbRDA). NMDS ordination was obtained with a stress of 0.18 and 0.17 for natural and artificial substrates, respectively. ANOSIM showed significant differences between Control and Impacted sites (p < 0.05). Simper analysis showed that the mean dissimilarity between Control and Impacted sites was of 42.22% for natural substrate and of 39.97% for artificial substrate. DISTLM selected a set of explanatory variables (dissolved oxygen, To difference, total phosphorus, pH and chlorophyll) with a 67.24% of fitted variation. Diatoms showed sensitivity to thermal changes, even though when these did not exceed 3℃. The factors that seemed to influence benthic assemblages the most were seasonal variation and the thermal increase caused by the nuclear power station.

Impact of urban chemical pollution on water quality in small, rural and effluent-dominated Mediterranean streams and rivers

The impact and occurrence of wastewater (treated and untreated) derived pharmaceutically active compounds (PhACs) have been investigated in small, rural and effluent-dominated tributaries of the lower Ebro River located in the North-Eastern Spain (Catalonia). We have observed the predominant effect of stream flow and consequently dilution factor on the concentration levels of detected PhACs that combined with the absence of wastewater treatment plants (WWTP) resulted in 12 times higher concentrations in streams with direct discharge of untreated wastewater. Non-steroidal anti-inflammatory drugs (NSAIDs) were the most ubiquitous compounds, in terms of both individual concentration and frequency of detection. In the sites impacted by raw wastewater, acetaminophen and ibuprofen showed the highest concentrations among all analyzed PhACs, reaching concentrations up to 7.78μgL−1 and 2.66μgL−1, respectively. However, PhACs detected in the sites impacted by treated wastewater showed generally lower concentration levels and frequencies of detection. Also, effluent-dominated streams showed higher concentration levels of PhACs due to a generally lower stream flows and small dilution factors. However, concentration levels of detected PhACs were dependent on the hydraulic travel time and distance from the discharge point and related with the in-stream attenuation. As a result, this study highlights the combined impact of hydrological and chemical stressors on the water quality of the rural Mediterranean aquatic ecosystems.

Geographical distribution of mortality by Parkinson's disease and its association with air lead levels in Spain

Background and objectiveParkinson's disease (PD) is the second most common neurodegenerative disease, and the aetiology of its sporadic form is unknown. The present study analyzes the temporal and spatial variations of mortality by PD in Spain over a period of 14 years and its relationship with lead concentration levels in the atmosphere. MethodAn ecological study was performed, in which deaths by PD and age group in 50 Spanish provinces between 2000 and 2013 were analyzed. The annual trend of PD mortality was assessed using the non-parametric Spearman's Rho test. Finally, the relationship between lead concentration levels in the air and mortality by PD was evaluated. ResultsBetween 2000 and 2013, 36,180 patients with PD died in Spain. There is an increasing trend in mortality through PD over the study period (p<.0001). La Rioja, Asturias, Basque Country and the Lower Ebro valley were the regions with the highest values of PD mortality. Those regions with the highest lead concentrations also showed higher mortality by this disease in people over 64 (p=0.02). ConclusionsOver our period of study, there has been an increase in mortality through PD in Spain, with the northernmost half of the country registering the highest values. Mortality in men was higher than mortality in women. Moreover, a direct correlation was found between lead levels in the air and mortality through PD.