Geochemical, geological and hydrological influence on ostracod assemblages distribution in the hyporheic zone of two Mediterranean rivers in central Spain

Abstract

On the catchment spatial scale, rivers can be considered a patchy discontinuity from headwaters to mouth with significant implications on the structure and functioning of the hyporheic zone (HZ) biota. The present study aims to determine the spatial variation of ostracod assemblages from a fluvial HZ of two groundwater‐fed rivers of the Jarama basin (Central Spain). We hypothesised that ostracod abundance and composition are subject to changes in water condition, substratum type geology and surface water/groundwater exchanges along the hyporheic flow path. Individual measures of 29 physico‐chemical parameters, water discharge, sediment size and sediment organic matter (as loss of ignition) were measured at a depth of 20–40 cm at 20 hyporheic sites of the Henares and Tajuña Rivers. The results show that factors like elevation, carbonate water type, high permeable riverbed substratum and groundwater upwelling at headwaters contribute to shape a diverse, mixed assemblage formed by stygophyle and stygoxene ostracods (14 species). Conversely, low‐mineralised waters, siliceous riverbeds with poor permeability, and relatively low surface/ground water exchanges in the middle and lower sectors, limit species diversity and ostracod abundance to exclusively stygoxene elements (nine species). Ostracod abundance correlates positively with fine sands (0.125–0.25 mm) (Spearman, r = 0.70), and negatively with temperature (r = −0.40), SO42− (r = −0.45) and Mg2+ (r = −0.40). Trace metal (Cu, Mn, Ni) accumulation in the intermediate and lower sectors of both rivers appears harmful for Ilyocypris brady (r = −0.46) and Pryonocypris zenkeri (r = −0.40), whereas As relates negatively to the abundance of Candona candida (r = −0.51), Pryonocypris zenkeri (r = −0.60) and Herpetocypris brevicaudata (r = −0.72). The results highlight the significance of recent ostracods as a proxy to assess the water conditions in a HZ and to provide forthcoming approaches to depict surface‐subsurface hydrological exchanges.

Exploring the distribution of groundwater Crustacea (Copepoda and Ostracoda) to disentangle aquifer type features—A case study in the upper Tajo basin (Central Spain)

“…sp., was found only in this aquifer type, more specifically within the two northern aquifers that are geographically closer, Sigüenza‐Maranchón and Tajuña‐Montes Universales both located in the uppermost catchment of Tajo River (Alto Tajo region). This new species has previously been found in the Jarama catchment, within the hyporheic zone of the upper part of the Tajuña River—a stream channel where both aquifers Sigüenza‐Maranchón and Tajuña‐Montes Universales discharge their waters; and in the upper part of the Manzanares River, a tributary of the Jarama River (Iepure et al, , ; Rasines‐Ladero & Iepure, ; Rasines‐Ladero, ). Acanthocyclops n. sp.…”

“…oligarthrus and Paracyclops sp. Both species were previously documented from the hyporheic zone of the Henares River in its downstream part, indicating potential active exchange of the water between the Guadalajara aquifer and the stream reaches (Hernández‐García & Custodio, ; Iepure et al, , ; Rasines‐Ladero, ; Rasines‐Ladero & Iepure, ). The discharge part of the Guadalajara aquifer is further characterized by larger fluctuations in the piezometric level (>2.5 m) than the recharge zone, which might also disrupt the crustacean population's resilience and resistance.…”

“…The hydraulic conductivity of this alluvial aquifer is high, and this together with the recharge rate, determines its intrinsic vulnerability to anthropic contamination (Arauzo, Martínez‐Bastida, & Valladolid, ; Martínez‐Bastida, 2009). In this aquifer, the copepods and ostracods communities are dominated by nonstygobiont species with large ecological valences such as Acanthocyclops robustus also recorded from the hyporheic zone of rivers network of the Jarama catchment, the main tributary of Tajo (Iepure et al, , ; Rasines et al, 2016). The only stygobiont species found in this alluvial was Diacyclops clandestinus ssp.…”

“…Records on groundwater fauna are also reported from the northern Spain in alluvial aquifers of Bidasoa and Ebro Rivers from Navarra, Guipuzcoa (Espanol et al, ), and Cantabria (Camacho, , ; Camacho, Dorda, & Rey, ; Deharveng et al, ), and from alluvial aquifers of rivers from central and south‐east in Castilla‐La Mancha, and Valencia provinces (Baltanás, Beroiz, & Lopez, ; Camacho & Jaume, ; Camacho et al, ; Gibert & Culver, ; Notenboom, , ; Notenboom & Meijers, ; Poquet & Mesquita‐Joanes, ; Rodriguez‐Noriega, ; Sendra et al, ). More recent records are documented from Central Spain (Madrid region) from alluvial aquifers and hyporheic zone of rivers of the Tajo catchment (Iepure, Martinez‐Hernandez, Herrera, Rasines‐Ladero, & de Bustamante, ; Iepure, Meffe, Carreño, Rasines‐Ladero, & de Bustamante, ; Rasines & Iepure, ; Rasines‐Ladero, ). However, the paucity of data from large areas across the country with distinct present or historic climatic conditions (Mediterranean, oceanic, and semiarid), constrains our attempts to understand local scale variations in groundwater biodiversity and hampers conclusions that are made of the influence of environmental and climatic factors on groundwater fauna from local to regional scale.…”

The role of anthropogenic and natural factors in shaping the geochemical evolution of groundwater in the Subei Lake basin, Ordos energy base, Northwestern China

“…On one hand, a variety of human activities such as drinking, irrigation and industrial use are supported by groundwater; on the other hand, groundwater plays a vital role in the maintenance and restoration of ecosystems dependent on groundwater such as alluvial and rocky aquifers, hyporheic zones, springs and wetlands (Boulton, 2009;Hancock et al, 2005). It is well known that many important ecological processes can be disrupted by changes in groundwater chemistry (Amalfitano et al, 2014;Di Lorenzo et al, 2015;Iepure et al, 2014). Therefore, a sustainable groundwater management strategy requires a deeper understanding of geochemical evolution of groundwater in order to guarantee reliable supply for all purposes.…”