Biology subjects

Bonada, N.

Publications and source records attributed to Bonada, N..

6 recordsLinked to original sources

bioRxiv2026

Fine-scale movements and habitat use of fish in intermittent rivers: Behavioural insights from drying refuge pools

Intermittent rivers and ephemeral streams (IRES) are increasingly recognised as ecologically important freshwater systems, yet little is known about how fish behave during the critical disconnected-pool phase, when drying confines them to isolated refuge pools. We combined high-resolution orthomapping and depth reconstructions with repeated whole-pool observations and focal follows to quantify microhabitat use and fine-scale movements of fish in refuge pools of an intermittent Mediterranean river. Fish used only a small fraction of the available pool area and consistently preferred deeper, refuge-associated microhabitats. Body size strongly structured behaviour: fry and small juveniles concentrated in shallow margins and showed short, tortuous movements, whereas larger individuals occupied deeper, more structured areas, moved farther, and were more closely associated with refuges. These patterns were broadly similar in drying and non-drying pools and changed little as water levels declined. After rewetting, fish showed reduced activity and weaker depth-biased habitat use, revealing that drying history leaves carry-over imprints on behaviour even after water levels recover. Our results show that refuge pools are not homogeneous water bodies, but internally structured habitats whose fine-scale characteristics shape how fish cope with drying, underscoring their conservation importance in increasingly intermittent rivers.

ecology↗

bioRxiv2025

Simulating drying and human impacts on river networks to evaluate biological quality indices performance through the lens of metacommunity theory

O_LIIncorporating metacommunity perspectives into bioassessment represents a major challenge in the management of drying river networks, where drying-induced fragmentation compromises the performance of biological indices to assess their ecological status. Indeed, current indices focus on local community responses to stressors and neglect the effect of regional processes, such as spatiotemporal connectivity and dispersal, on metacommunity assembly. C_LIO_LIIn this work, we explored the effect of drying on the performance of a widely used biological index using metacommunity simulations on a synthetic drying river network. We assessed how different gradients of drying-driven fragmentation and human impact extent determine local richness and the biological index scores by combining simulations with biomonitoring information. C_LIO_LIWe used a coalescent metacommunity model to simulate the exchange of individuals between local communities along synthetic drying river networks. These networks were subjected to different drying extent, drying intensity and human impact extent scenarios. Additionally, we considered two major characteristics for each simulated taxon: (i) tolerance to human impacts and (ii) dispersal strategy (flying, swimming, or drifting). C_LIO_LIFor each simulation, we obtained local richness and the biological index value. Then, we calculated biological index performance, which we defined as the capacity to distinguish between impacted and non-impacted sites. Finally, we tested our approach in six non-impacted European drying river networks, from which drying information was available. C_LIO_LIOur results showed that low spatiotemporal connectivity consistently led to decreased local richness and low scores of the biological index (reflecting poor biological quality). As drying extent and intensity increased, drying-induced fragmentation significantly reduced the biological index performance. For example, with a 50% increase in drying extent, index performance fell over 70% and at high drying levels, this performance dropped more than 90%. This decay followed a convex pattern, with a marked drop in performance as soon as drying appeared in the catchment and leveling off at higher drying extents. C_LIO_LISynthesis and applications: We show how simulations can be used to incorporate network fragmentation and metacommunity dynamics into the design and validation of biomonitoring tools, thereby increasing their efficiency. C_LI

ecology↗

bioRxiv2025

Drying halves decomposition rates in river networks by disrupting structure-function linkages

River drying is intensifying worldwide due to climate change and water abstraction, with major consequences for biodiversity and ecosystem functioning. In river networks, drying not only alters local environmental conditions but also disrupts hydrological connectivity, reshaping the movement of organisms and resources at the network scale. Leaf litter decomposition--a key ecosystem function in freshwater systems--is particularly sensitive to changes in the structure of decomposer communities. We hypothesized that spatiotemporal patterns of drying regulate decomposition by altering the diversity and composition of detritivore macroinvertebrates, bacteria and fungi. We combined data from six European drying river networks (DRNs) spanning a wide latitudinal gradient to assess how local drying intensity and regional hydrological connectivity affect decomposition through changes in these decomposer groups. We found that short drying events ([≤] six dry days) reduced decomposition rates by up to 50% by shifting the control of decomposition from a balanced contribution of fungi, bacteria, and detritivores to one dominated by dry-tolerant but less efficient bacteria. These community shifts persisted after flow resumption, leading to sustained reductions in decomposition even under flowing conditions. Regional connectivity alleviated these negative effects of local drying by facilitating the recovery of more efficient aquatic decomposers through dispersal. However, this effect depended on DRN context. In particular, in southern, more arid DRNs, stronger fragmentation hindered the recovery of decomposer communities after flow resumption. Overall, our results provide mechanistic evidence that spatiotemporal patterns of drying can regulate the linkages between community structure and ecosystem functioning in river networks. As drying events become more frequent and prolonged, increasing disruption of these linkages will impact carbon cycling and energy fluxes in freshwater ecosystems under global change.

ecology↗

bioRxiv2024

Natural disturbances and connectivity shape the seasonal variability of aquatic macroinvertebrate communities across Europe

Understanding the joint influence of natural disturbance, spatial connectivity and biogeography on biodiversity is essential to forecast its responses to climate change. Macroinvertebrate communities in drying river networks constitute an ideal study system to understand the interplay of these ecological processes. We analyze the taxonomic and functional structure of macroinvertebrate communities sampled across 126 reaches with perennial and intermittent streamflow, surveyed in six drying river networks (DRN) across Europe, six times over one year. Drying frequency decreased community richness and functional diversity of communities, whereas spatio-temporal connectivity increased community richness in intermittent reaches. Communities experiencing a high drying frequency increased the proportion of taxa with K-strategies and drying resistance traits. Communities experiencing a long drying duration compensated by high spatio-temporal connectivity had more taxa with a r-strategy and high dispersal ability. Perennial communities varied from taxa-poor communities of r-strategists in spring and autumn and taxa-rich communities of K-strategists in summer and had a constant functional diversity throughout the year. When drying frequency increased, communities showed a similar pattern except in autumn when they shifted towards species-poor communities of K-strategists. Functional diversity then peaked in summer. Community trait structure and in particular optimal drying resistance traits changed across biogeographical scales. It opposed communities from mountainous DRN (with more r-strategies and high dispersal ability) to non-mountainous DRN (with more K-strategies). Drying frequency, drying duration, and spatio-temporal connectivity drive divergent community structures, suggesting the presence of an ecological threshold that explains the variability of disturbed ecosystems across broad spatial scales. These factors also shaped seasonal community variations, particularly after summer, with intermittent communities influenced by stochastic recolonization events in spring and autumn. Spatial-temporal connectivity proved crucial for maintaining diversity in communities subjected to intense drying. Lastly, the effectiveness of drying resistance traits was dependent on the biogeographical and environmental conditions of drying river networks.

ecology↗

bioRxiv2022

Temporal variation of patch connectivity determines biodiversity recovery from recurrent disturbances

Understanding the capacity of ecological systems to withstand and recover from disturbances is a major challenge for ecological research in the context of environmental change. Disturbances have multi-scale effects: they can cause species extinctions locally and alter connectivity between habitat patches at the metacommunity level. Yet, our understanding of how disturbances influence landscape connectivity remains limited. To fill this gap, we develop a novel connectivity index that integrates the temporal variation of patch connectivity induced by disturbances, which can be applied to any spatially-structured habitat. We then combine this index with a metacommunity model to specifically investigate biodiversity recovery from drying events in river network metacommunities. We demonstrate that patch connectivity explains variations of species richness between groups of organisms with contrasting dispersal modes and captures the effect of drying intensity (i.e., fraction of patches that dry-up) and drying location on community recovery. As a general rule, loss of patch connectivity decreases community recovery, regardless of patch location in the river network, dispersal mode, or drying intensity. Local communities of flying organisms maintained higher patch connectivity in drying river networks compared to organisms with strictly aquatic dispersal, which explained the higher recovery capacity of this group from drying events. The general relationship between patch connectivity and community recovery we found can be applied to any spatial network subject to temporal variation of connectivity, thus providing a powerful tool for biodiversity management in dynamic landscapes.

ecology↗

bioRxiv2020

DISPERSE: A trait database to assess the dispersal potential of aquatic macroinvertebrates

Dispersal is an essential process in population and community dynamics, but is difficult to measure in the field. In freshwater ecosystems, information on biological traits related to organisms morphology, life history and behaviour provides useful dispersal proxies, but information remains scattered or unpublished for many taxa. We compiled information on multiple dispersal-related biological traits of European aquatic macroinvertebrates in a unique resource, the DISPERSE database. DISPERSE includes 39 trait categories grouped into nine dispersal-related traits for 480 taxa, including Annelida, Mollusca, Platyhelminthes, and Arthropoda such as Crustacea and Insecta, generally at the genus level. Information within DISPERSE can be used to address fundamental questions in metapopulation ecology, metacommunity ecology, macroecology and evolutionary ecology research. Information on dispersal proxies can be applied to improve predictions of ecological responses to global change, and to inform improvements to biomonitoring and conservation management strategies. The diverse sources used in DISPERSE complement existing trait databases by providing new information on dispersal traits, most of which would not otherwise be accessible to the scientific community.

ecology↗