Iberian Rivers Research Articles

Analysis of Precipitation and Drought in the Main Southeastern Iberian River Headwaters (1952–2021)

This study evaluated the long-term changes in precipitation patterns and drought conditions in one of the key recharge areas of the hydrological system of southern and southeastern Spain, namely, the Sierra de Cazorla y Segura, which contains the headwater sectors of the catchment basins of two important rivers, namely, the Guadalquivir and the Segura. The research covered a period of 70 years (1952–2021) and undertook an exhaustive analysis of data from 348 pluviometric stations. The most relevant results are as follows: (1) most areas experienced a decrease in the precipitation volume and number of rainy days during the study period; (2) summer and winter showed the most significant decreases; (3) weak and moderate precipitation (<40 mm/d) showed significant decreases in both volume and frequency, while heavy precipitation (≥40 mm/d) showed the opposite behavior; (4) the durations of dry periods increased, while the durations of wet periods decreased in most areas; and (5) the SPEI showed an increase under drought conditions. This research underscores the need for water resource management and resilience strategies with interdisciplinary relevance in the face of changing hydrological patterns.

Fish Use of a Borland-Type Fish Lock in an Iberian River

Fish locks were fitted at dams to improve fish migration in Europe, but also in America and Australia. In Iberia, several dams were equipped with locks in the 1970s and 1980s, and in this study the fish use of the Borland fish lock installed in the most downstream dam in the Douro River was investigated by visualizing fish during each cycle. Moreover, a creel survey was conducted encompassing the same period to characterize the fish caught downstream. During the study, 770 lock cycles were completed, with 58,982 fish being observed in 234 cycles, mostly moving upstream. Eels (Anguilla anguilla) were the most numerous, being followed by the mugilids (Chelon ramada and Mugil cephalus). The number of fish using the lock was low from November to April, increasing from May to July, and was related to tide height, discharge at the powerplant tailrace, moon phase and time of day. Sea lamprey (Petromyzon marinus) and shads (Alosa spp.) were caught downstream of the dam but were never found using the lock. While more research is needed to assess the fate of the eels moving upstream, management of the anadromous taxa in the Douro River must rely on the last 20 km of the river.

External parasites: how anchor worms affect Iberian endemic fish

Lernaea cyprinacea, commonly known as anchor worm, is a cosmopolitan invasive copepod that parasitizes a wide variety of freshwater fish, including several native and endemic species of the Iberian Peninsula (Sánchez-Hernández 2017), like the Squalius alburnoides from the Guadiana River basin depicted in the photograph, with 3 different individuals attached. Anchor worm was introduced to Iberia from Asia in the 1970s (Simon Vicente et al. 1973). While males are free-living, adult females attach their anchors – a modification of the head – to the fish host, usually in the fins, gills or mouth. Infestation by this external parasite is easily recognised by the wounds, ulcers and inflammatory processes that it induces in the fish skin and muscle (Hossain et al. 2018, see photograph). It may also induce anaemia, malformations, reduced growth and increased susceptibility to secondary infections (Sánchez-Hernández 2017). Small fish are specially affected in their swimming ability, respiration and health condition due to infections and mechanical compression of internal organs, both resulting from the ulcerous skin lesions developed at anchoring sites (Guagliardo & Tanzola 2016). Since infestation prevalence are hypothesised to be positively correlated with higher water temperatures (Marcogliese 2001), outbreaks are expected to increase in intermittent southern Iberian rivers under a global climate change scenario (Macedo-Veiga et al. 2019), which will likely contribute to the aggravation of the conservation status of the already imperilled native fish species. Although broader studies are needed, reported prevalences are higher in native Iberian fish than in sympatric alien species (Macedo-Veiga et al. 2019)

Adaptation and convergence in circadian\u2010related genes in Iberian freshwater fish

BackgroundThe circadian clock is a biological timing system that improves the ability of organisms to deal with environmental fluctuations. At the molecular level it consists of a network of transcription-translation feedback loops, involving genes that activate (bmal and clock – positive loop) and repress expression (cryptochrome (cry) and period (per) – negative loop). This is regulated by daily alternations of light but can also be affected by temperature. Fish, as ectothermic, depend on the environmental temperature and thus are good models to study its integration within the circadian system. Here, we studied the molecular evolution of circadian genes in four Squalius freshwater fish species, distributed across Western Iberian rivers affected by two climatic types with different environmental conditions (e.g., light and temperature). S. carolitertii and S. pyrenaicus inhabit the colder northern region under Atlantic climate type, while S. torgalensis, S. aradensis and some populations of S. pyrenaicus inhabit the warmer southern region affected by summer droughts, under Mediterranean climate type.ResultsWe identified 16 circadian-core genes in the Squalius species using a comparative transcriptomics approach. We detected evidence of positive selection in 12 of these genes using methods based on dN/dS. Positive selection was mainly found in cry and per genes of the negative loop, with 55 putatively adaptive substitutions, 16 located on protein domains. Evidence for positive selection is predominant in southern populations affected by the Mediterranean climate type. By predicting protein features we found that changes at sites under positive selection can impact protein thermostability by changing their aliphatic index and isoelectric point. Additionally, in nine genes, the phylogenetic clustering of species that belong to different clades but inhabit southern basins with similar environmental conditions indicated evolutionary convergence. We found evidence for increased nonsynonymous substitution rate in convergent lineages, likely due to positive selection at 27 sites, mostly in cry genes.ConclusionsOur results support that temperature may be a selective pressure driving the evolution of genes involved in the circadian system. By integrating sequence-based functional protein prediction with dN/dS-based methods to detect selection we uncovered adaptive convergence in the southern populations, probably related to their similar thermal conditions.

Applicability of DNA-based identifications for the WFD-guided monitoring using macroinvertebrates: a large-scale DNA metabarcoding study for implementing routine ecological status assessments in Iberian rivers

Over the last decade, remarkable improvements have been made in the field of metabarcoding-based tools for routine ecological status assessments. However, important issues are yet to be solved to fulfil the European Water Framework Directive (WFD) requirements and standards. These limitations, which include problems related to e.g. the lack of a complete COI macroinvertebrate barcode database available for the Iberian Peninsula Murria 2020, or the scarce recovery of specific taxa due to DNA extraction and/or PCR amplification bias, are especially difficult to overcome for routine freshwater macroinvertebrate monitoring. For that purpose, a large-scale study is on going to test how metabarcoding data can infer existing macroinvertebrate morphotaxonomy-based biotic indexes and ecological status of Iberian rivers. Freshwater macroinvertebrates were selected as a Biological Quality Element and identified by using both morphological and metabarcoding approaches. The mitochondrial gene for cytochrome c oxidase subunit I (COI) was used as a DNA Barcode. Taxonomic coverage, taxonomic composition metrics and ecological status obtained from both approaches were analysed. Physical and chemical variables obtained during the routine biomonitoring, as well as other ecological parameters including biodiversity indexes, were also assessed. Multivariate data analysis of these environmental and biotic data obtained from both approaches were compared. Results seem to support the hypothesis Kuntke 2019 that the DNA-metabarcoding approach might deliver similar quality assessments results to the morphological approach, though some refinement must be done at the different steps of the process prior to establish a reliable procedure allowing the alternative use of both methods giving similar results for the ecological status classes marked by the WFD.

Plasticity in Reproductive Traits, Condition and Energy Allocation of the Non-Native Pyrenean Gudgeon Gobio lozanoi in a Highly Regulated Mediterranean River Basin

The invasion success of non-native fish, such as Pyrenean gudgeon Gobio lozanoi in several Iberian rivers, is often explained by the expression of its life history traits. This study provides the first insights into the reproductive traits, fish condition, and energy allocation (protein and lipid contents of tissues) of this species, along a longitudinal gradient in one of the most regulated river basins in the Iberian Peninsula, the Segura river. Larger sizes of first maturity, higher fecundity and larger oocytes were found in fluvial sectors with the most natural flow regimes, characterised by a low base flow with high flow peaks in spring and autumn. A delay in the reproductive period, lower fish condition and no differences in sex-ratio were observed in fluvial sectors with a high increase in base flow and notable inversion in the seasonal pattern of flow regime. Lipid contents in the liver and gonads were stable during the reproductive cycle and decreases in muscle were noted, whereas ovarian and liver proteins increased. In relation to energy allocation for G. lozanoi, an intermediate energy strategy was observed between income and capital breeding. Our results support the hypothesis that the high plasticity of G. lozanoi population traits plays a significant role in its success in a highly regulated Mediterranean river basin. Understanding the mechanisms by which flow regulation shapes fish populations in Mediterranean type-rivers could inform management actions.

Interpopulation Variability in Dietary Traits of Invasive Bleak Alburnus alburnus (Actinopterygii, Cyprinidae) Across the Iberian Peninsula

The bleak Alburnus alburnus is native to most of Europe. This cyprinid fish is a successful invader in the Iberian Peninsula. No studies exist on its foraging strategies on a large scale for this ecoregion. The aim of the present study was to compare dietary traits of invasive bleak among the main Iberian rivers and a ‘reference’ native bleak population from France. Bleak were sampled during May–June 2019 from the Iberian Rivers Ebro, Tagus, Guadiana, Segura and Guadalquivir and the River Saône (France). Diptera larvae and zooplankton were common food categories in the River Saône. Insect nymphs were more important in the River Ebro. The intake of plant material was higher in the River Tagus. Flying insects were more consumed in the River Guadiana. Nektonic insects were important in the River Guadalquivir. Detritus was a frequent food category for all populations, in terms of occurrence and mass. Dietary parameters followed a unimodal response in relation to the latitudinal gradient, with the maximum values for the Tagus and Guadiana populations. Overall, results suggest that this wide interpopulation variability will contribute to the species’ successful establishment throughout Mediterranean Europe, which poses a serious risk to its highly valuable native fish fauna.

A new method to include fish biodiversity in river connectivity indices with applications in dam impact assessments

Abstract Different indices have been developed to quantify the extent and severity of river fragmentation. These indices vary depending on the specific goals of the study. Here, we present a new Conservation Connectivity Index (CCIP) for potamodromous fish species that considers the conservation value (richness, rarity and vulnerability) of river segments. The Iberian Peninsula holds > 20 endemic and endangered potamodromous fish species as well as > 1000 large dams (> 1 hm3 of capacity). The CCIP was calculated for the eight most important river basins of the Iberian Peninsula and compared to the Dendritic Connectivity Index (DCIP) developed by Cote et al. in 2009, which uses only river length as a habitat variable. With the use of both DCIP and CCIP, the dams were analysed and ranked according to their impacts on the river basin. The main results show that Iberian river basins are heavily fragmented, with river basin connectivity percentages of less than 20% in most cases using both DCIP and CCIP. CCIP values are slightly higher than DCIP values in almost all cases. When the impact of individual dams is analysed, differences also appear between the DCIP and CCIP. CCIP highlights the impact of dams located in areas of high fish conservation value while DCIP emphasize the impact of dams fragmenting large river segments. The CCIP appears to be adequate to highlight important sites for conservation in river connectivity studies. It could be applied in different studies and river basins around the world to prioritize dam removals or plan new dam locations.

From the lab to the river: Determination of ecological hosts of Anodonta anatina

Abstract Coextinction is the simplest form of secondary extinction and freshwater mussels (Bivalvia, Unionida) may be particularly prone to this phenomenon as their life cycle includes an obligatory parasitic larval stage on fish hosts. The main aims of this study were to determine the possible ecological fish hosts of Anodonta anatina (Linnaeus, 1758) in several rivers of the Douro basin in northern Portugal and to assess possible spatial and temporal differences in glochidial (larval) loads. In order to achieve this, electrofishing was conducted from December to April, the fish fauna was characterized, and levels of infestation with A. anatina glochidia were determined. Native cyprinid species, mainly Luciobarbus bocagei (Iberian barbel) and Squalius carolitertii (northern Iberian chub), together with the non‐native Lepomis gibbosus (pumpkinseed sunfish) and Alburnus alburnus (common bleak), were found to have the highest glochidial loads. Clear differences in infestation between rivers and throughout time were detected, with an infestation period from January to March, and with the Tâmega River having the highest prevalence. Anodonta anatina is able to infest a variety of fish species, and this together with earlier studies showed that the metamorphosis into juveniles occurs mainly in native cyprinid species, although non‐native species like common bleak can also be considered suitable hosts. However, the larvae infesting other non‐native species, such as the pumpkinseed sunfish, do not metamorphose and can be considered ‘dead ends’. Overall, the results reported here are important for the conservation of A. anatina (and other unionoid species) because several Iberian rivers (and worldwide) have been subjected to the extirpation of native fish species and the introduction of non‐native fish species. Therefore, careful assessments of fish communities should be conducted to assess possible negative interactions with freshwater mussels.

Unexpected recent records of twaite shad (Alosa fallax) in two North-eastern Iberian rivers: recolonization or recovery of remnant populations?

espanolLa presencia de saboga Alosa fallax (Lacepede, 1803), un pez anadromo que migra a los tramos bajos y medios de los rios para desovar, se cita en los rios Fluvia y Ter (NE de Espana) despues de varias decadas de ausencia de registros confirmados. De 2015 a 2017, un total de 32 especimenes fueron capturados en el rio Fluvia, incluyendo un juvenil, y un individuo en el rio Ter. El origen estos peces podria ser la recuperacion de una escasa poblacion local que habria permanecido sin ser detectada, pero tambien existe la posibilidad de una recolonizacion de individuos errantes procedentes de poblaciones vecinas. La presencia de un solo individuo en el Ter, junto con la ausencia de citas por mas de un siglo en este rio, sugiere que el especimen puede proceder de una poblacion vecina. Si se confirma en los proximos anos la presencia de una poblacion estable de saboga en el Fluvia, la construccion de pasos de peces aumentaria la disponibilidad de habitats de freza y podria mejorar sus perspectivas de conservacion EnglishThe presence of twaite shad Alosa fallax (Lacepede, 1803), an anadromous fish that migrates to lower and middle river reaches to spawn, has been reported in the Fluvia and Ter rivers (NE Spain) after several decades of absence of confirmed records. From 2015 to 2017 a total of 32 specimens, including one juvenile fish, were captured by angling in the River Fluvia, and a single individual was captured in the River Ter. The origin of these fish in the Fluvia may be the recovery of a scarce local population that remained undetected or a recolonization by individuals straying from neighbouring populations. The presence of a single individual in the Ter and the absence of records for over a century in this river suggest that this specimen may have come from a nearby population. If the establishment of a twaite shad population in the Fluvia is confirmed in the next few years, the construction of fish passages would increase the availability of spawning habitats and improve the species’ conservation prospects.

Vegetation encroachment ratios in regulated and non-regulated Mediterranean rivers (Spain): An exploratory overview

Vegetation encroachment is an expected response of rivers to a decrease in their flow variability and flood magnitude and frequency. It frequently occurs together with channel narrowing and a decrease in braiding, both of which are likely associated with different human alterations but most frequently with river damming. Vegetation encroachment ratios display a wide range of values according to local hydrologic and geomorphic contexts and dam operation management, and thus, they are very site specific. As vegetation interacts with fluvial processes, understanding the mechanisms that promote encroachment is important for predicting river trends and designing proper management and restoration measures. Our research aimed to explore the causal relationship between flow regulation and vegetation encroachment in Mediterranean rivers in Spain. We quantified vegetation encroachment and channel changes over the last 50 years in 13 river reaches, 5 of which corresponded to non-regulated rivers and 8 of which were located in rivers regulated by large dams. We analysed aerial orthophotographs from 1956, 1977 and 2011 or later up to 2014, according to image availability. We considered 1956 conditions as a reference and quantified ratios of changes in riparian vegetation cover, active channel width and braiding index over two periods, 1956–1977 and 1978–2011. We quantified the changes in the flow regime and clustered rivers according to their hydrological pattern, looking for potential hydrological drivers of the observed changes over time.Vegetation encroachment, channel narrowing and braiding decreases occurred in all the studied rivers. Significant differences in annual ratios between the studied periods were found for both vegetation encroachment and channel narrowing, but no statistically significant differences were found between the regulated and non-regulated rivers or between the hydrological river groups previously clustered by flow variables. After discussing existing literature, we suggest a multi-scale approach to understanding river changes over time, encompassing larger historical perspectives. We hypothesize a generalized hydrologic decline since the beginning of the 20th century affecting rivers at the broad-regional scale would be overlapping the effects of land cover changes (i.e., renaturalization) at the catchment scale in reducing flood intensity and sediment supply. River damming would reinforce these patterns at river segment scale, in turn overlapping the influence of local geomorphic and ecological features. This hypothesis, which should be tested by further research, may explain the constancy of encroachment and channel narrowing regionally reported but with a wide variety of change ratios, determining converging trajectories of Iberian rivers that have also been found in other regions.

Behavioral Interactions and Trophic Overlap between Invasive Signal Crayfish Pacifastacus leniusculus (Decapoda, Astacidae) and Native Fishes in Iberian Rivers

The signal crayfish Pacifastacus leniusculus Dana, 1852 is a successful invasive species in the Iberian Peninsula. This is of particular conservation concern, as fish fauna is highly endemic and also threatened within this ecoregion. The aim of this study was to analyze behavioral interactions and trophic overlap between signal crayfish and native fishes in Iberian rivers (northern Spain). Video cameras were used to record fish “dominance/evasion” after spatial encounters with crayfish. Diet composition and isotopic signatures (δ13C and δ15N) were compared to evaluate the niche overlap. Fish were dominant in 25% of the encounters with juvenile crayfish, whereas this percentage was only 4% with adult crayfish. Observations showed a high fish “evasion” response for Pyrenean stone loach Barbatula quignardi (Bǎcescu-Meşter, 1967) (>30%). Dietary results showed a high trophic overlap between signal crayfish with the pelagic Pyrenean minnow Phoxinus bigerri Kottelat, 2007 and the benthic loach. However, the isotopic niche overlap was low, with brown trout Salmo trutta L., 1758 showing the highest area (only 0.1 ‰2). Overall, our findings suggest that interferences may occur with native species for food (i.e., benthic invertebrates). Consequently, measures should be applied to control invasive crayfish in Iberian rivers.

Fish diversification at the pace of geomorphological changes: evolutionary history of western Iberian Leuciscinae (Teleostei: Leuciscidae) inferred from multilocus sequence data

The evolutionary history of western Iberian Leuciscinae, obligatory freshwater fish, is directly linked to the evolution of the hydrographic network of the Iberian Peninsula after its isolation from the rest of Europe, which involved dramatic rearrangements such as the transition from endorheic lakes to open basins draining to the Atlantic. Previous phylogenetic research on western Iberian leuciscines, using mainly mitochondrial DNA and more recently one or two nuclear genes, has found contradictory results and there remain many unresolved issues regarding species relationships, taxonomy, and evolutionary history. Moreover, there is a lack of integration between phylogenetic and divergence time estimates and information on the timing of geomorphological changes and paleobasin rearrangements in the Iberian Peninsula. This study presents the first comprehensive fossil-calibrated multilocus coalescent species tree of western Iberian Leuciscinae (including 14 species of Achondrostoma, Iberochondrostoma, Pseudochondrostoma and Squalius endemic to the Iberian Peninsula, seven of which endemic to Portugal) based on seven nuclear genes, and from which we infer their biogeographic history by comparing divergence time estimates to known dated geological events. The phylogenetic pattern suggests slow-paced evolution of leuciscines during the Early-Middle Miocene endorheic phase of the main Iberian river basins, with the shift to exorheism in the late Neogene-Quaternary allowing westward dispersals that resulted in many cladogenetic events and a high rate of endemism in western Iberia. The results of this study also: (i) confirm the paraphyly of S. pyrenaicus with respect to S. carolitertii, and thus the possible presence of a new taxon in the Portuguese Tagus currently assigned to S. pyrenaicus; (ii) support the taxonomic separation of the Guadiana and Sado populations of S. pyrenaicus; (iii) show the need for further population sampling and taxonomic research to clarify the phylogenetic status of A. arcasii from the Minho basin and of the I. lusitanicum populations in the Sado and Tagus basins; and (iv) indicate that A. occidentale, I. olisiponensis and P. duriensis are the most ancient lineages within their respective genera.

Trace metal characterization and fluxes from the Guadiana, Tinto-Odiel and Guadalquivir estuaries to the Gulf of Cadiz

Metals transported into the coastal zone by the South Iberian rivers are key to understand the biogeochemical cycles and distribution of trace elements in the Gulf of Cadiz (GoC hereinafter) and the exchange with the Mediterranean Sea. Previous studies carried out in the 80s have suggested that metal enrichment in the Alboran Sea (Western Mediterranean) is related with fluvial inputs from acid mine drainage from the Tinto and Odiel rivers. The present study evaluates the contribution of dissolved trace metal concentrations (i.e. Cd, Co, Cu, Fe, Mo, Ni, Pb, V, Zn) from the three main rivers discharging into the GoC (i.e. Guadiana, Tinto-Odiel and Guadalquivir rivers). Our results show that the metal composition of water discharged from each river is impacted by the activities developed in the course of the rivers, which clearly influence the GoC coastal surface waters composition. Metal fluxes from the Guadalquivir river are quantitatively higher than those from the Tinto-Odiel (e.g. up to 73% and 19% higher for Ni and Cu, respectively). Although the metal concentrations spatial distributions in the GoC are dominated by the circulation pattern between the Atlantic and the Mediterranean Sea, the concentrations within the GoC continental shelf could be explained by a greater contribution from the Guadalquivir estuary (e.g. 80.5%, 54.6%, 56.5% and 56.6% for Ni, Cu, Mo, and V respectively).

Evaluating freshwater macroinvertebrates from eDNA metabarcoding: A river Nalón case study.

Rivers are a vital resource for human wellbeing. To reduce human impact on water bodies, the European Union has established an essential regulatory framework for protection and sustainable management (WFD; 2000/60/EC). In this strategy, reliable and economic bioindicators are a fundamental component. Benthic macroinvertebrates are the group most commonly used as bioindicators through all European countries. However, their conventional assessment currently entails serious cost-efficiency limitations. In this study, we have tested the reliability of metabarcoding as a tool to record river macroinvertebrates using samples from a mock community (in vitro validation) and eDNA extracted for field validation from water from six sites within a north Iberian river (River Nalón, Asturias, Spain). Two markers (V4 region within the nuclear 18S rDNA and a fragment of the mitochondrial COI gene) were amplified and sequenced using an Illumina platform. The molecular technique has proven to be more sensitive than the visual one. A cost-benefit analysis shows that the metabarcoding approach is more expensive than conventional techniques for determining macroinvertebrate communities but requires fewer sampling and identification efforts. Our results suggest metabarcoding is a useful tool for alternative assessment of freshwater quality.

Public knowledge of alien species: a case study on aquatic biodiversity in North Iberian rivers

Biological invasions have increased in recent decades due to globalization and human activities. These invasions are currently one of the main threats to biodiversity, and their early detection is essential for a rapid and effective response. Here, we explored the use of citizen science strategies to create an early alert to detect invasive species. Our main objective was to evaluate the general knowledge of volunteer participants of invasive freshwater species in Asturias (north of the Iberian Peninsula) and compare it with both real data from electrofishing surveys and official data from the regional government. A total of 140 volunteer surveys were conducted in four different rivers in Asturias. The largest group of participants consisted of males older than 50 years. Four species were identified as native to the four rivers: Anguilla anguilla; Mugil cephalus; Salmo salar; and, Salmo trutta. More than 50% of the native species surveyed by electrofishing were recognized by the locals in each river region. A total of 22.86% of the volunteers were able to correctly name an exotic species, and a total of 7 were correctly identified: Procambarus clarkii; Trachemys scripta; Cyprinus carpio; Esox lucius; Salvelinus fontinalis; Carassius auratus; and, Oncorhynchus mykiss. However, compared to the list of actual exotic species surveyed, less than 40% were recognized in the four rivers. Despite the poor correlation between local knowledge and real exotic aquatic fauna, citizens were able to detect one exotic species not yet found in the wild in this region (T. scripta). Finally, more than 70% of the volunteers were in favor of fighting against invasive species, although only 22.86% were able to identify any specific exotic species found in the region. The positive attitude to exotic species control was correlated with both the level of native species knowledge and the concern about the ability of exotic species to impact native fauna in the region. Better training will improve public awareness, reduce the non-intentional release of non-native species, and increase the detection of non-indigenous species. The attitudes of the citizens make the region a promising candidate for education efforts to reduce alien species introductions and help preserve fauna biodiversity.

Inter-population variability in growth and reproduction of invasive bleak Alburnus alburnus (Linnaeus, 1758) across the Iberian Peninsula

The native European freshwater cyprinid fish, common bleak Alburnus alburnus (Linnaeus, 1758), is an invasive non-native fish in the Iberian Peninsula, where it threatens the valuable endemic fish fauna. Despite the bleak’s invasive status, there is a dearth of studies on the biological traits of non-native populations in Europe’s Mediterranean region, and the present study aimed to compare bleak growth and reproductive traits across the principal rivers of Iberia with those from a native ‘reference’ bleak population in France. Non-native bleak from the River Tagus had the highest back-calculated total lengths (TLs), growth rate and body condition, but the lowest reproductive investment and smallest egg size of all studied populations. Whereas, these latter two traits were the highest in the River Ebro, where fecundity was the lowest for all Iberian rivers. The youngest age and the smallest TL at maturity were observed in the River Ebro. The River Segura had the lowest back-calculated TLs and growth rate, the highest fecundity and proportion of females, and the oldest age at maturity. Population traits of bleak in the River Saône (the native ‘reference’ population) were generally different from those in Iberian rivers, except for the River Ebro. This wide inter-population variability contributes to the species’ successful establishment in novel habitats.

Human pharmaceuticals in Portuguese rivers: The impact of water scarcity in the environmental risk

Pharmaceuticals occurrence and environmental risk assessment were assessed in Portuguese surface waters, evaluating the impact of wastewater treatment plants (WWTPs) and river flow rates. Twenty three pharmaceuticals from 6 therapeutic groups, including metabolites and 1 transformation product, were analysed in 72 samples collected from 20 different sites, upstream and downstream the selected WWTPs, in two different seasons. Analysis was performed by solid phase extraction followed by liquid chromatography coupled to tandem mass spectroscopy.Pharmaceuticals were detected in 27.8% of the samples. Selective serotonin reuptake inhibitors (SSRIs), anti-inflammatories and antibiotics presented the highest detection frequencies (27.8, 23.6 and 23.6%, respectively) and average concentrations (37.9, 36.1 and 33.5ngL−1, respectively). When assessing the impact of WWTPs, an increase of 21.4% in the average concentrations was observed in the samples located downstream these facilities, when compared with the upstream samples.Increased detection frequencies and concentrations were observed at lower flow rates, both when comparing summer and winter campaigns and by evaluating the different rivers.Risk quotients (RQs) higher than one were found for two pharmaceuticals, concerning two trophic levels. However, since Iberian rivers are highly influenced by water scarcity, in drought periods, the flow rates in these rivers can decrease at least ten times from the lowest value observed in the sampling campaigns. In these conditions, RQs higher than 1 would be observed for 5 pharmaceuticals, additionally, all the detected pharmaceuticals (11) would present RQs higher than 0.1.These results emphasize that the river flow rate represents an important parameter influencing pharmaceuticals concentrations, highlighting the ecotoxicological pressure, especially due to water scarcity in drought periods. This should be a priority issue in the environmental policies for minimizing its impact in the aquatic environment.

Characterization of Iberian turbid plumes by means of synoptic patterns obtained through MODIS imagery

Turbid plumes formed by the main Iberian rivers were analyzed and compared in order to determine similarities and differences among them. Five Atlantic rivers (Minho, Douro, Tagus, Guadiana and Guadalquivir) and one Mediterranean river (Ebro) were considered. Plume extension and turbidity were evaluated through synoptic patterns obtained by means of MODIS imagery over the period 2003–2014.River discharge showed to be the main forcing. In fact, the dependence of plume extension on runoff is moderate or high for all rivers, except for Ebro. In addition, most of river plumes adjust immediately to runoff fluctuations. Only the extension of Tagus and Guadalquivir plumes is lagged with respect to river runoff, due to the high residence time generated by their large estuaries.Wind is a secondary forcing, being only noticeable under high discharges. Actually, the dependence of plume extension on wind is moderate or high for all rivers, except Guadalquivir and Ebro. All the Atlantic rivers show the maximum (minimum) near- field plume extension under landward (oceanward) cross-shore winds. The opposite situation was observed for Ebro River.Tide is also a secondary forcing although less important than wind. Actually, the dependence of plume extension on tide is only high for Guadiana River. Nevertheless, all Atlantic river plumes still have some dependence on semidiurnal tidal cycle, they increase under low tides and decrease under high tides. In addition, Tagus River plume also depends on the fortnightly tidal cycle being larger during spring tides than during neap tides. This is due to particular shape of the estuary, where the river debouches into a semi-enclosed embayment connected to the Atlantic Ocean through a strait.Ebro River constitutes a particular case since it has a low dependence on runoff and wind and a negligible dependence on tide. In fact, its plume is mainly driven by the Liguro-Provençal coastal current. Guadalquivir River also shows some unique features due to its high sediment load. It generates the largest Iberian plume in terms of turbid signal and extension even being the second smallest river in terms of discharge.

Environmental stressors as a driver of the trait composition of benthic macroinvertebrate assemblages in polluted Iberian rivers

We used the trait composition of macroinvertebrate communities to identify the effects of pesticides and multiple stressors associated with urban land use at different sites of four rivers in Spain. Several physical and chemical stressors (high metal pollution, nutrients, elevated temperature and flow alterations) affected the urban sites. The occurrence of multiple stressors influenced aquatic assemblages at 50% of the sites. We hypothesized that the trait composition of macroinvertebrate assemblages would reflect the strategies that the assemblages used to cope with the respective environmental stressors. We used RLQ and fourth corner analysis to address the relationship between stressors and the trait composition of benthic macroinvertebrates. We found a statistically significant relationship between the trait composition and the exposure of assemblages to environmental stressors. The first RLQ dimension, which explained most of the variability, clearly separated sites according to the stressors. Urban-related stressors selected taxa that were mainly plurivoltine and fed on deposits. In contrast, pesticide impacted sites selected taxa with high levels of egg protection (better egg survival), indicating a potentially higher risk for egg mortality. Moreover, the trait diversity of assemblages at urban sites was low compared to that observed in pesticide impacted sites, suggesting the homogenization of assemblages in urban areas.