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Jumping into the grids: mapping biodiversity hotspots in groundwater habitat types across Europe
Full text linkBiodiversity hotspots are routinely identified by grid-based analyses, despite grids encompassing different habitats, thus hindering the potential to assess which habitat type accounts for the conservation priority assigned to a grid. In this study, we aimed at identifying the main hotspots for the conservation of the European stygobitic Crustacea Copepoda Harpacticoida at the groundwater habitat scale. A multi-metric approach was used, based on six biodiversity indicators: species richness, endemicity, evolutionary origin, phylogenetic rarity, taxonomic distinctness, habitat specificity. The Hot Spot Analysis, based on the statistics Getis-Ord Gi*, was used to compare the local to the global average values of each indicator to identify hotspots of conservation. The operational units used to perform the analyses were the groundwater habitat types, in order to gather all the possible patterns of spatial occupancy in terms of habitat variability. Eight biodiversity hotspots of stygobitic Crustacea Harpacticoida were highlighted: 1) the Pyrenees (Spain and France), 2) the Jura Massif (France), 3) the Alpine arc (France, Switzerland and Italy) embracing southward the River Po alluvial plain and the Slovenian External Dinarides, 4) the Central Apennines (Italy), 5) the Carpathian and Balkan mountains in Romania and at the boundary between western Bulgaria and north-west Macedonia, 6) the Dinaric Alps (from Croatia to Albania), 7) the Sardinia Island, 8) an area in central-northern Europe embracing Denmark, the Netherlands and Germany. The hotspots showed a clear spatial distribution in southern Europe where they were distributed predominantly south to the 45th parallel, in line to what reiteratively observed in previous studies. Many hotspots embraced more than one habitat type. The adoption of discrete groundwater habitat types as working spatial units rather than grids provided a higher resolution of where the stygobitic harpacticoid species effectively live, with the possibility of intervening more precisely to preserve them and their habitats
Spatial distribution of stygobitic crustacean harpacticoids at the boundaries of groundwater habitat types in Europe
No full textThe distribution patterns of stygobitic crustacean harpacticoids at the boundaries of three different groundwater habitat types in Europe were analysed through a GIS proximity analysis and fitted to exponential models. The results showed that the highest frequency of occurrences was recorded in aquifers in consolidated rocks, followed by the aquifers in unconsolidated sediments and, finally, by the practically non-aquiferous rocks. The majority of the stygobitic harpacticoid species were not able to disperse across the boundaries between two adjacent habitats, with 66% of the species occurring in a single habitat type. The species were not evenly distributed, and 35–69% of them occurred from 2 to 6 km to the boundaries, depending on the adjacent habitat types. The distribution patterns were shaped by features extrinsic to the species, such as the hydrogeological properties of the aquifers, and by species’ intrinsic characteristics such as the preference for a given habitat type and dispersal abilities. Most boundaries between adjacent habitat types resulted to be “breaches”, that is transmissive borders for stygobitic harpacticoids, while others were “impermeable walls”, that is absorptive borders. Our results suggest that conservation measures of groundwater harpacticoids should consider how species are distributed within the different groundwater habitat types and at their boundaries to ensure the preservation of species metapopulations within habitat patches and beyond them
The impact of nitrate on the groundwater assemblages of European unconsolidated aquifers is likely less severe than expected
No full textIn this study, we analyzed the structure of the stygobiotic copepod assemblages of an unconsolidated European aquifer (VO), in southern Italy, that has been subject to persistent nitrate contamination for over 15 years. To this end, we monitored 25 bores where groundwater was contaminated only by nitrate, and no other chemical pollutants were reported as being above detection limits from 2009 to 2014. We monitored these bores three times, namely in autumn 2014 and in spring and autumn 2015. We expected that the chronic exposure to high nitrate concentrations had a significant and evident impact on the stygobiotic copepod assemblages. Unexpectedly, the assemblages were highly diversified. The stygobiotic species richness (SSR) accounted 17 species, a value that exceeded the European mean value (SSR = 12 species). However, the species density was only 0.6 species/km2, lower than the European mean value (= 1.6 species/km2). Moreover, the juvenile copepods were numerically less abundant than the adults and the biomass-abundance model showed signs of alteration of the structure of the copepod assemblages. This study highlighted that (i) nitrates, even at high concentrations, probably have a less severe impact on groundwater assemblages of unconsolidated aquifers than expected and (ii) the analysis of population traits and biomasses can detect signs of alteration of these assemblages that would, otherwise, not be visible from the analysis of the sole species richness and abundances
Hydroelectric Dams Affect Hyporheic Copepod Diversity
Full text linkThis study investigates the ecological impact of a small hydroelectric power plant (SHPP) on the hyporheic zone of the venacquaro stream (VEN), a low-order groundwater-fed stream in Central Italy. The hyporheic zone, a critical ecological interface where groundwater and surface water interact, plays a pivotal role in nutrient cycling, pollutant retention, and supporting aquatic biodiversity. However, hydrological alterations from activities such as damming pose significant threats to this zone. The research employs a three-pronged approach to assess the effect of a SHPP on hyporheic copepod communities. Copepods were selected as the focal group due to their dominance in this habitat. Initially, a generalized estimating equation (GEE) model was used to evaluate changes in copepod diversity, specifically alpha and beta diversity. The study then examines environmental shifts caused by the SHPP using permutational analysis of variance (PERMANOVA) and principal component analysis (PCA). Lastly, a multivariate species distribution model (mSDM) explores correlations between environmental variables and copepod abundances. Results reveal significant alterations in copepod assemblage structure and environmental variables downstream of the SHPP. The GEE model indicates a notable shift in beta diversity, primarily driven by disruptions in hyporheic connectivity rather than environmental changes alone. This disruption favours stygobitic species downstream, suggesting the influence of groundwater upwelling. Environmental analysis shows several differences between upstream and downstream sites, with changes in parameters such as pH, temperature, and dissolved organic carbon. The study highlights the need for effective management strategies to mitigate sediment accumulation and maintain habitat quality in SHPP-affected streams. Techniques like sediment bypass tunnels (SBTs) are recommended to preserve both economic and ecological values. This research contributes to the still limited understanding of SHPP impacts on hyporheic ecosystems, emphasizing the importance of considering these effects in hydropower development and riverine ecosystem conservation
How far may life venture? Observations on the harpacticoid copepod Phyllognathopus viguieri under extreme stress conditions
No full textThe authors report the first finding of living specimens of the harpacticoid copepod Phyllognathopus viguieri (Maupas, 1892) in the gut content of the teleost fish Merluccius merluccius (Linnaeus, 1758), and their extraordinary viability after the M. merluccius specimens had been stored at − 20 °C for more than 1 month and their stomachs been preserved in 70% ethanol for a further month. After their survival for such a long time in such harsh conditions, P. viguieri, after a few minutes of total immobilization, began to swim actively and fast, and after being reared in freshwater or seawater in Petri dishes under starvation, these animals reproduced, and the presence of nauplii, copepodids and adults which completed the whole life cycle in 3/5 days was observed in freshwater and seawater, respectively. The occurrence of P. viguieri in the stomach of a true marine demersal fish species enlarges the known habitat types the species may stably colonize. The potential for dormancy in fertilized adult females to escape adverse environmental conditions is hypothesized
Linking hydrogeology and ecology in karst landscapes: The response of epigean and obligate groundwater copepods (crustacea: Copepoda)
No full textGroundwater invertebrate communities in karst landscapes are known to vary in response to multiple environmental factors. This study aims to explore the invertebrate assemblages’ composition of an Apennine karst system in Italy mainly described by the Rio Gamberale surface stream and the Stiffe Cave. The stream sinks into the carbonate rock and predominantly feeds the saturated karst into the cave. For a minor portion, groundwater flows from the epikarst and the perched aquifer within it. The spatial distribution of the species belonging to the selected target group of the Crustacea Copepoda between the surface stream and the groundwater habitats inside the cave highlighted a different response of surface-water species and obligate groundwater dwellers to the hydrogeological traits of the karst unit. Our results suggest that fast endorheic infiltration routes promoted the drift of epigean species from the surface to groundwater via the sinking stream while most of the obligate groundwater dwellers come from the perched aquifer in the epikarst from diffuse infiltration pathways
A new protocol for assessing the conservation priority of groundwater-dependent ecosystems
No full textSpecies of conservation concern are usually considered important elements in site prioritization for biodiversity conservation. To overcome the lack of information on species conservation status, multidimensional measures of species rarity can be used as proxies of species vulnerability. Under this assumption, a two-step protocol for site prioritization of aquatic groundwater-dependent ecosystems is proposed using invertebrate vulnerability estimated from species' traits. In the first step, each species occurring in the sites of interest are scored according to their vulnerability. In the second step, sites are prioritized using species' scores. Species vulnerability scores are based on five dimensions, for which various traits are scored: (i) geography, (ii) ecology, (iii) biology, (iv) population, and (v) evolutionary history. For each species, the scores of the various traits belonging to the same dimension are multiplied to obtain a synthetic score. These scores are then ranked into four classes and, for each dimension, each species receives a new score that reflects its rank. The sum of these scores represents the species' overall score. Site conservation priorities are assessed by combining species scores into three indices: Sum of Species Scores, Biodiversity Conservation Concern (which relates the sum of species scores with the local species richness) and Groundwater Biodiversity Concern (which is the average of the former two). The protocol is illustrated using case studies in Italy and it is fully implemented in the software AQUALIFE which is freely available at: http://app.aqualifeproject.eu by registered users. Sensitivity analyses showed that the protocol is robust against the lack of information on species biology or sampling limitations. However, trait scoring rests with the user, who must be familiar with the study group. This approach can be applied at any spatial scale and to different types of aquatic groundwater-dependent ecosystems
Potential factors driving the distribution of subterranean invertebrates in karst groundwaters of the Rotolo Cave (southern Italy).
No full textThe study of subterranean environments is hindered by the lack of information that does not allow to fully explain the subsurface abiotic and biotic dynamics, especially when considering the 3D interactions in the deep karst.
The fragmented knowledge of mechanisms and factors regulating the subsurface environment and its biological features makes it difficult to assess the connections between the various components, and the changes related to anthropogenic impacts. Challenges for data collection in karst are mainly referred to explorations and surveying in caves, because they are difficult to access.
Despite the limitation in accessing the subsurface, karst groundwaters offer privileged sites to study ecosystems of high intrinsic value due to their specialized fauna (stygofauna), often comprising rare and endemic species. The aquatic cave-dwelling organisms live in fissures of the rock mass and in larger conduits and channels, resulting in consequential relations with the aquifer hydrogeological dynamics.
The extreme vulnerability of karst and the occurrence of low resilient communities therein, requires urgent monitoring and conservation tools to protect the underground ecosystems in their entirety. This work offers the basis for setting practical conservation actions by means of a systematic and long-term scientific program in the Apulian karst. The carbonates of Apulia host significant groundwater resources and over 2000 caves in need of protection. Many efforts have to be made to assess the abiotic dynamics, together with the status of the stygodiversity. A first attempt was carried out at Grave Rotolo, the deepest cave in Apulia, where cavers have reached the groundwater bodies. A preliminary screening of both saturated and unsaturated karst (May-October 2021) allowed us to assess the minimum theoretical number of species living in the system through asymptotic species richness estimators (Chao1, Chao2, Abundance Coverage Estimator, Incidence Coverage Estimator). This karst system harbors a diverse and composite array of species across groundwater habitat types. Indeed, the faunal sampling underestimated the theoretical true baseline richness level of the cave (range 16.77-76.05%). In addition, the sites where the groundwater fauna live in the cave could be related to complex subsurface flow pathways or different recharge areas, as suggested by the differences observed in species compositions and species abundances among different cave water bodies.
Therefore, the combined biological and hydrogeological approach could shed light on their mutual information, where the biological component may work as hydrogeological tracer of the karst system. These tools are necessary to select proper monitoring sites, and define the most appropriate sampling and analytic techniques for achieving a better understanding of the groundwater dynamics and species partitioning in deep karst environments
Groundwater biodiversity and constraints to biological distribution
No full textGroundwater hosts a high diversity of living forms including viruses, prokaryotes (bacteria and archaea), microeukaryotes (fungi and protozoans), and metazoans, along with invertebrates, salamanders, and fish. Groundwater communities are not only diverse in terms of composition but also in terms of functions triggered by multiple trophic and nontrophic interactions among organisms. Due to the absence of photosynthetic primary production in aquifers, the composition, abundance, and activity of heterotrophic prokaryotes and eukaryotes (with the exception of chemoautotrophic microorganisms), are constrained to various degrees by the low amount of surface-derived organic matter (OM) reaching groundwater. Groundwater metazoans additionally experience further constraints in their spatial distribution. From local to regional scales, the composition of groundwater metazoan communities in consolidated and unconsolidated rocks is largely determined by the size of voids, their interconnectedness, and their connectivity to the surface environment. The latter exerts a major control on thermal variability, availability of OM, and dissolved oxygen (DO). Reduced thermal variability of deeper subsurface environments may select for low thermal tolerance of species, which may, in turn, constrain their dispersal along spatial temperature gradients. Increased OM supply to groundwater enhances the complexity of food webs and diversity of organisms present, with DO depletion due to microbial aerobic respiration affecting the survival of metazoans. The constraint on biological distribution imposed by the interplay between OM and DO depends on scales of heterogeneity of the two variables. Studies modeling the distribution of species and communities rarely integrate species interactions despite evidence that competition for scarce resources and/or predation may play a major role in species distributions. The next step is to build on the understanding of biological distribution for evaluating the fate of biodiversity in response to anticipated changes in temperature, recharge rate, and organic carbon concentration in groundwater
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