Applying Electrical Resistivity Tomography and Biological Methods to Assess the Hyporheic Zone Water Exchanges in Two Mediterranean Stream Reaches

The hyporheic zone (HZ) is a critical area of all river ecosystems. It is the area beneath the stream and adjacent to the stream, where the surface water and groundwater are mixed. The HZ extends both vertically and laterally depending on the sediment configuration, namely their porosity and permeability. This influences the hyporheic communities’ structural pattern and their active dispersal among distinct rivers compartments and alluvial aquifers. It is still difficult to assess the spatial extent of the HZ and the distribution of the mixing zones. This study applies time-lapse images obtained using electrical resistivity tomography (ERT) of 20 m wide and 5 m deep alluvial streams, with regards to the structural pattern of hyporheic communities represented by cyclopoids and ostracods, in order to assess the extent of the HZ in the riverbed and the parafluvial sediment configurations. The ERT images obtained at the hyporheic Site 1 are characterized by alluvial deposits dominated by coarse and very coarse sands with resistivity values ranging from ~20 to 80 Ohm.m, indicating a permeable zone up to ~0.5 m thick and extending laterally for ca. 5 m from the channel and associated with the hyporheic zone. The sediment configurations, texture, and structure indicate an active surface–hyporheic water exchange and low water retention into the sediments. This is also indicated by the hyporheic copepods and ostracods communities’ structure formed by a mixture of non-stygobites (five species) and stygobites (two species). A low-resistivity (<70 Ohm.m) permeable zone located 2.3 m below the streambed and unconnected with the river channel was also detected and associated with the associated alluvial aquifer. In contrast, the resistivity image at Site 2 dominated by coarse, medium, and very fine sands, shows a low-permeability zone in the upper ~0.5 m of the profile, with a resistivity value ranging from ~45 to 80 Ohm.m, indicating a reduced HZ extension in both vertical and lateral dimensions. Here the sediment configurations indicate that the water retention and interaction with the sediment is higher, reflected by more diverse hyporheic communities and with highly abundant stygobite species. The two examples show that non-invasive ERT images and biological assessments provide complementary and valuable information about the characterization of the sub-channel architecture and its potential hydraulic connection to the floodplain aquifer.info:eu-repo/semantics/publishedVersio

Living on the edge – An overview of invertebrates from groundwater habitats prone to extreme environmental conditions

Groundwater ecosystems from cold polar and circumpolar regions, hot springs, as well as those developed in salt, gypsum or in volcanic rocks are one of the environments considered to exhibit extreme environmental conditions such as low (below 0°C) or high (over 45°C) temperatures, hypersaline waters, or with elevated content of toxic gases like hydrogen sulfide or methane. They represent the “unseen ecosystem beneath our feet” and are inhabited by a large diversity of organisms, persisting and flourishing under severe environmental conditions that are usually hostile to the majority of organisms. These types of groundwater ecosystems are remarkable “evolutionary hotspots” that witnessed the adaptive radiation of morphologically and ecologically diverse species, whereas the organisms living here are good models to understand the evolutionary processes and historical factors involved in speciation and adaptation to severe environmental conditions. Here, we provide an overview of the groundwater invertebrates living in continental groundwater habitats prone to extreme environmental conditions in one or more physico-chemical parameters. Invertebrates are represented by a wide variety of taxonomic groups, however dominated by crustaceans that show specific adaptations mostly metabolic, physiologic, and behavioral. Symbiotic associations among bacteria and invertebrates are also discussed enlightening this biological interaction as a potential adaptation of different groundwater invertebrates to cope with severe environmental conditions. Given the high pressures that anthropogenic activities pose on groundwater habitats worldwide, we predict that several of these highly specialized organisms will be prone to extinction in the near future. Finally, we highlight the knowledge gaps and future research approaches in these particular groundwater ecosystems by using integrative-omic studies besides the molecular approach to shed light on genetic variation and phenotypic plasticity at species and populational levels.GRAPHICAL ABSTRAC

From Naples 1963 to Rome 2013 - A brief review of how the international research group on Ostracoda (IRGO) developed as a social communication system

The 1st International Symposiumon Ostracoda (ISO) was held in Naples (1963). The philosophy behind this symposiumand the logical outcome of what is nowknown as the International Research Group on Ostracoda (IRGO) are here reviewed, namely ostracodology over the last 50 years is sociologically analysed. Three different and important historic moments for the scientific achievements of this domain are recognised. The first one, between about 1963 and 1983, is related to applied research for the oil industry aswell as to the great interest in the better description of the marine environment by both zoologists and palaeontologists. Another important aspect during this period was thework by researchers dealing with Palaeozoic ostracods,who had their own discussion group, IRGPO. Gradually, the merger of this latter group with those dealing with post-Palaeozoic ostracods at various meetings improved the communication between the two groups of specialists. A second period was approximately delineated between 1983 and 2003. During this time-slice, more emphasis was addressed to environmental research with topics such as the study of global events and long-term climate change. Ostracodologists profited also from the research "politics" within national and international programmes. Large international research teams emerged using new research methods. During the third period (2003-2013), communication and collaborative research reached a global dimension. Amongst the topics of research we cite the reconstruction of palaeoclimate using transfer functions, the building of large datasets of ostracod distributions for regional and intercontinental studies, and the implementation of actions that should lead to taxonomic harmonisation. Projects within which molecular biological techniques are routinely used, combined with sophisticated morphological information, expanded now in their importance. The documentation of the ostracod description improved through new techniques to visualise morphological details, which stimulated also communication between ostracodologists. Efforts of making available ostracod information through newsletters and electronic media are evoked

Environment and Space Rule, but Time also Matters for the Organization of Tropical Pond Metacommunities

Metacommunities are dynamic systems, but the influence of time independently of environmental change in their configuration has been rarely considered. In temporary ponds, strong temporal effects are expected to influence their metacommunity structure, even in relatively constant environments such as tropical habitats. We therefore expect that time as an independent factor could modulate tropical pond metacommunities, which would be also less affected by niche-related processes than by dispersal-related processes. In addition, good dispersers should be more environmentally structured than bad dispersers, which should be more spatially structured. Finally, the relevance of temporal effects should vary among organisms with different generation times. To test these hypotheses, we surveyed 30 temporary ponds along the dry tropical region of western Costa Rica and Nicaragua at three different moments of their hydroperiod: shortly after the infilling of the water bodies, at the middle of the hydroperiod and just before desiccation. We obtained data on 56 environmental variables and used geographic coordinates to build spatial variables (Moran Eigenvector Maps). We collected biological samples and estimated the specific abundance of phytoplankton, zooplankton and benthic invertebrates. To evaluate the relative role of environmental, spatial and temporal (sequential sampling season) effects for metacommunity organization, we used variation partitioning with distance-based redundancy analyses for each group of organisms. The inclusion of time in the analysis highlighted that pure temporal effects explained part of metacommunity variance in almost every group, being as important as spatial or even environmental effects for some groups of organisms. In contrast to the assumed low environmental constraints in tropical areas (i.e., high and stable temperatures), we found strong environmental effects. Passive dispersers were more influenced by environmental factors than active ones. We also found a positive relationship between the body size of the different groups of organisms and the magnitude of the temporal effects, interpreted as related to generation time. Finally, when analyzing each sampling period separately, we found differences in the relative role of environment and space at different sampling periods, showing that snapshot surveys may not be representative of highly dynamic metacommunities

Listado de especies y subespecies cavernícolas (hipogeas) consideradas como troglobias y estigobias de la península ibérica e islas Baleares

La fauna hipogea o cavernícola ibero-balear ha sido a lo largo de muchos años puesta en evidencia por numerosos zoólogos en las distintas disciplinas. Especialistas de los distintos grupos faunísticos capaces de colonizar las cuevas y las aguas subterráneas que las recorren. Hoy sabemos que esta diversidad de troglobios y estigobios alcanza un total de 1364 taxones: 1285 especies y 79 subespecies hipogeas (cavernícolas) pertenecientes a cuatro filos: Plathyhelminthes (2), Annelida (23), Mollusca (122) y Arthropoda (1217) en todo el territorio ibero-balear. Una fauna que cuenta con numerosos ejemplos de elementos relictos de especial interés paleogeográfico. De la totalidad de taxones hipogeos o cavernícolas del territorio ibero balear, 438 taxones (430 especies y 8 subespecies) son estigobios y 926 taxones (852 especies y 74 subespecies) son troglobios. En lo referente a la distribución de los taxones troglobios es el distrito Cantábrico el que posee una mayor riqueza en especies y subespecies, un total de 208, seguido del Vasco con 163 taxones, el Pirenaico con 153 y el Bético con 142. Algo menos diversos son los distritos Levantino (124 taxones) y Catalán (104 taxones), seguidos de lejos por el Lusitánico con 46 taxones, el Balear con 41 y el Central con tan sólo 19. Entre los estigobios 156 especies y subespecies pueblan las aguas subterráneas de las regiones delimitadas por las cuecas lusitánicas. Le siguen en diversidad las cuencas pirenaicas con 154 taxones estigobios, las béticas con 114 y por último las aguas del subsuelo de las cuencas baleáricas con 47 taxones estigobios, algunos de los cuales son talaso-estigobios, propios de las aguas marinas costeras

The Acanthocyclops kieferi Complex (Copepoda, Cyclopoida) from South-Eastern Europe, with Description of a New Species

International audienceThe Acanthocyclops kieferi (Chappuis, 1925) complex (Copepoda, Cyclopoida) includes exclusively stygobitic species, mainly widespread in the cave habitats of south-eastern Europe. A new species for the group, Acanthocyclops milotai n. sp., collected from pools supplied by percolation water in a cave in south-western Romania, is described. The new species is distinguished from its congeners by the following characters: the ornamentation pattern of the basis of the antenna with four spinules placed in an arch; the coxa of leg 4 with four spinules on its distal margin; furcal rami divergent, about 2.2 times as long as wide, with the lateralmost, terminal furcal seta 1.14 times as long as the medialmost one, and these both setiform. Inter-populational variability of some characters in the new species such as the shape of the anal operculum and the ornamentation of the coxa of leg P4 are discussed. Furthermore, the characters generally used to differentiate the taxa of the kieferi group are re-examined and discussed, and a brief description of the adaptive traits of these species to the groundwater is given. Biogeographical and ecological considerations about the kieferi species-complex in Romanian groundwater habitats are also mentione

An annotated checklist of groundwater Cyclopoida and Harpacticoida (Crustacea, Copepoda) from Romania with notes on their distribution and ecology

Romania, by its position in East-Central Europe has a complex geological history, high landscape heterogeneity and variable climatic conditions, ranging from temperate-continental in the northeast to sub-Mediterranean in the southwest. These conditions have created repeated waves of colonisation of groundwater by copepods, which raise particular interest in this group from a biogeographical perspective. The earliest investigations on groundwater copepods, dating back to the beginning of the 19th century, have resulted in a wealth of information on the richness of this group, making Romania one of the best studied regions from this perspective in Europe. Groundwater copepods in Romania are currently represented by 107 species and subspecies, of which 60 are harpacticoids (56%) and 47 are cyclopoids (43.9%). Of these, 50.5% are strict stygobites (32.7% harpacticoids and 17.7% cyclopoids). Among stygobite copepods 29 species (35 harpacticoids and 19 cyclopoids) are endemic to the country. Almost 86% of the species are single-site endemics (single cave, or single hyporheic or phreatic site) and the rest are restricted in distribution to a single aquifer or hydrographic basin. The aim of the present checklist represents a significant contribution to the knowledge of groundwater copepods in Romania and provides a sound baseline for future comparative faunal studies focused on the affinities and origins of copepods and the analysis of their biogeographical distribution patterns at regional and continental scales

A new species of Pseudomoraria from an alpine spring of Picos de Europa, North of Spain

Pseudomoraria triglavensis was described by Brancelj (1994) from specimens collected in a high-alpine reservoir at the Triglav National Park (NW Slovenia) at an altitude of 1690 m a.s.l. During an expedition in the Picos de Europa National Park (N Spain) in 2018, a new species of Pseudomoraria was collected in an epikarst spring (Fuente Escondido), below the ice cave of Altaiz at an altitude of 2112 m a.s.l. The new species can be easily distinguished from Pseudomoraria triglavensis by the presence of an inner seta on the edopodite 1 of female and male pereopod 1; absence of the outer spine on the exopodite 2 of the third and fourth female pereopods; four, instead of five setae on the second endopodite of the fourth female pereopod; and the female furca lacks the ventral distal patch of spinules characteristic of P. triglavensis. In the male, the new species differs from its congeners by the position and shape of the apophysis of the second edopodite of the pereopod 3, which is positioned in the outer, instead of the inner margin, and is bent around the distal inner spine; the second exopodite of the pereopod 4 has spines/setae, lacking the innermost seta which is present in P. triglavensis. The female armature of the pereopod 5 is highly variable, with 4-6 setae/spines on the exopod and 4-6 setae on the baso-endopod. According to Brancelj (1994), P. triglavensis could not be included in any genus known at the time and concluded, based on the armature of the pereopod 5 of both sexes, that it would be most closely related to Moraria. We disagree with this author and propose a close relationship of this genus with the genus Hypocamptus Chappuis, 1929 sharing similar male pereopod segmentation and armature. In addition, the species belonging to both genera are a characteristic for the fauna of the alpine water bodies. It is not yet clear the phylogenetic relationship between the two genera, but evidences suggest that Pseudomoraria may be a junior synonym of Hypocamptus

Correction: Brad et al. The Chemoautotrophically Based Movile Cave Groundwater Ecosystem, a Hotspot of Subterranean Biodiversity. Diversity 2021, 13, 128

The authors wish to make the following corrections to this paper [...