An assessment of the changes in water chemistry and in the macroinvertebrate community produced during the creation of the new Llobregat river mouth (Barcelona, NE Spain)

In 1999, a set of coordinated projects and investments whose principal objective was to transform Barcelona into one of the main distribution points of southern Europe resulted in the relocation of the Llobregat River mouth. The mouth was relocated by draining the old river mouth and constructing a new one. The aim of this study was to characterise the physico-chemical properties and the aquatic macroinvertebrate communities of the new river mouth and to monitor the changes experienced by the estuarine environment during its creation. A sampling point was established in the river 1.8 km upstream from its connection with the new mouth, and two sampling points were established in the new mouth. Samples of water and macroinvertebrates were collected every two months from May 2004 to June 2005, covering the periods before (from May to September 2004) and after (from September 2004 to June 2005) the new mouth was connected to the river and the sea. During the period before its connection to the river and the sea, the new mouth was functionally similar to a lagoon, with clear waters, presence of Chara and a rich invertebrate community. After the connection was completed, seawater penetrated the river mouth and extended to the connection point with the river (approximately 3.9 km upstream). An increase in conductivity from 4-6 mS cm-1 to 24-30 mS cm-1 caused important changes in the macroinvertebrate community of the new mouth. An initial defaunation was followed by a colonisation of the new mouth by brackish-water and marine invertebrate species. Due to its design (which allows the penetration of the sea) and the decreased discharge from the lower part of the Llobregat River, the new mouth has become an arm of the sea.En 1999 la desembocadura del Río Llobregat fue desviada como consecuencia de una acción coordinada de proyectos cuyo principal objetivo era el de transformar Barcelona en uno de los principales puntos de distribución de mercancías del sur de Europa. En el presente estudio se caracterizan las propiedades físico-químicas y la comunidad de macroinvertebrados acuáticos de la nueva desembocadura, y se monitorizan los cambios experimentados por el ecosistema durante su creación. Un punto de muestreo se situó en el Río Llobregat, 1.8 km aguas arriba de su conexión con la nueva desembocadura, y dos puntos de muestreo se situaron en la nueva desembocadura. Se recogieron muestras de agua y de macroinvertebrados cada dos meses desde Mayo de 2004 hasta Junio de 2005, período que incluyó el antes (desde Mayo hasta Septiembre de 2004) y el después (desde Septiembre de 2004 hasta Junio de 2005) de que la nueva desembocadura fuera conectada al río y al mar. Durante el período anterior a su conexión con el río y el mar la nueva desembocadura funcionaba como una laguna, presentando aguas claras, presencia de Chara y una comunidad de macroinvertebrados rica en especies. Después de ser conectada al río y el mar, el agua de mar penetró en la desembocadura hasta el punto de conexión con el río (aproximadamente unos 3.9 km aguas arriba). La conductividad de la desembocadura aumentó de 4-6 mS cm-1 a 24-30 mS cm-1, causando importantes cambios en la comunidad de macroinvertebrados acuáticos. Se registró una pérdida de fauna inicial seguida de una colonización de fauna marina y de aguas salobres. Debido a su diseño (que permite la entrada de grandes cantidades de agua de mar) y al escaso caudal del tramo bajo del Llobregat, la nueva desembocadura se ha convertido en un brazo de mar

Freshwater ecosystems are becoming increasingly salty. Here’s why this is a concern

Although it has been considerably less studied than other environmental problems, salinization presents major challenges for biodiversity in freshwater and coastal areas

Impact of potash mining in streams: the Llobregat basin (northeast Spain) as a case study

Potash mining is significantly increasing the salt concentration of rivers and streams due to lixiviates coming from the mine tailings. In the present study, we have focused on the middle Llobregat basin (northeast Spain), where an important potash mining activity exists from the beginning of the XX century. Up to 50 million tonnes of saline waste have been disposed in the area, mainly composed of sodium chloride. We assessed the ecological status of streams adjacent to the mines by studying different physicochemical and hydromorphological variables, as well as aquatic macroinvertebrates. We found extraordinary high values of salinity in the studied streams, reaching conductivities up to 132.4 mS/cm. Salt-polluted streams were characterized by a deterioration of the riparian vegetation and the fluvial habitat. Both macroinvertebrate richness and abundance decreased with increasing salinity. In the most polluted stream only two families of macroinvertebrates were found: Ephydridae and Ceratopogonidae. According to the biotic indices IBMWP and IMMi-T, none of the sites met the requirements of the Water Framework Directive (WFD; i.e., good ecological status). Overall, we can conclude that potash-mining activities have the potential to cause severe ecological damage to their surrounding streams. This is mainly related to an inadequate management of the mine tailings, leading to highly saline runoff and percolates entering surface waters. Thus, we urge water managers and policy makers to take action to prevent, detect and remediate salt pollution of rivers and streams in potash mining areas

Un mundo cada vez más salado

La actividad humana está provocando la salinización de ríos, lagos y otros sistemas acuáticos. Este fenómeno afecta a la calidad de las aguas y tiene graves consecuencias para los seres vivos

Human activities disrupt the temporal dynamics of salinity in Spanish rivers

Human activities are not only increasing salinization of rivers, they might also be altering the temporal dynamics of salinity. Here, we assess the effect of human activities on the temporal dynamics of electrical conductivity (EC) in 91 Spanish rivers using daily measures of EC from 2007 to 2011. We expected rivers weakly affected by human activities to have low and constant ECs, whereas rivers strongly affected by human activities should have high and variable ECs throughout the year. We collected information on land use, climate, and geology that could explain the spatiotemporal variation in EC. We identified four groups of rivers with differences in EC trends that covered a gradient of anthropogenic pressure. According to Random Forest analysis, temporal EC patterns were mainly driven by agriculture, but de-icing roads, mining, and wastewater discharges were also important to some extent. Linear regressions showed a moderate relationship between EC variability and precipitation, and a weak relationship to geology. Overall, our results show strong evidence that human activities disrupt the temporal dynamics of EC. This could have strong effects on aquatic biodiversity (e.g., aquatic organisms might not adapt to frequent and unpredictable salinity peaks) and should be incorporated into monitoring and management plans

Editorial : Spatio-Temporal Dynamics of Metacommunities - Implications for Conservation and Management

According to metacommunity theory (Leibold et al., 2004), the structure of local communities results from the interplay between local factors (e.g., environmental filtering, species interactions) and regional factors (e.g., dispersal rates, landscape configuration). The relative importance of these factors is highly dependent on the organisms’ biological traits, landscape connectivity, and the spatial and temporal scales considered (Heino et al., 2015; Tonkin et al., 2018; Viana and Chase, 2019; Almeida-Gomes et al., 2020; Cañedo-Argüelles et al., 2020; Lansac-Tôha et al., 2021). However, the differences in metacommunity assembly mechanisms found among studies are far from being fully understood. The evaluation of temporal dynamics of metacommunities has only emerged recently (Cañedo-Argüelles et al., 2020; Jabot et al., 2020; Li et al., 2020; Lindholm et al., 2021) and the application of the metacommunity theory in other fields, such as biomonitoring, conservation biology or ecosystem restoration, is yet to be fully explored (Bengtsson, 2010; Heino, 2013; Leibold and Chase, 2018; Chase et al., 2020; Cid et al., 2020; Heino et al., 2021). In this Research Topic, our aim was to invite researchers working in different biogeographic regions and ecological systems (Figure 1) to publish a number of innovative papers on metacommunity spatio-temporal dynamics. We expect to obtain a better understanding of how the factors and processes that structure metacommunities vary in space and time, as well as the implications of such dynamics for biodiversity conservation and ecosystem management