In tropical lakes, thermal stratification is essential for oxygen dynamics and ecosystem function, and it responds sensitively to short-term weather variation. Using high-resolution temperature profiles and weather data in 2016–2017, this study examines the effects of meteorological variability on water column stratification and oxygen levels in Lake Maninjau, a eutrophic tropical lake in West Sumatra, Indonesia. The results show that seasonal drops in air temperature were the primary factor influencing stratification in 2016, while, wind speed and sunshine duration had a greater impact on its occurrence in 2017. Furthermore, in 2016, stratification breakdown triggered full-depth mixing and a sharp drop in dissolved oxygen (DO) from >3 mg/L to <2 mg/L at 5 m depth. Generally, stratification occurs at the minimum air temperature (Tmin) of above 20.25°C. At lower Tmin, the water column can either be stratified or mixed, notably when the average wind speed (Vave) exceeds ~2.75 m/s, in which stratification tends to break down. These findings highlight how thermal and mechanical forces contribute to weakening stratification and increasing the risk of hypoxia which are detrimental to aquaculture in floating net cages, and are linked to fish kills. Recognizing these thresholds can guide risk forecasting and adaptive management of tropical lakes.
Human-induced climate change is accelerating and is profoundly impacting remote aquatic ecosystems. In the Sierra Nevada, these climatic shifts exacerbated by increased Saharan dust inputs are likely driving major transformations in lake environments. This study presents paleolimnological research reconstructing ecological and environmental trends in Sierra Nevada lakes and their catchments over the past two centuries. We analyzed multiple independent paleoindicators from high-resolution, chronologically, dated sediment cores, including spectrally inferred chlorophyll-a, sedimentary ancient prokaryotic DNA, and subfossil remains of diatoms, cladocerans, and chironomids. A compilation of the paleolimnological research conducted in Sierra Nevada lakes was made, examining the effects of environmental variables on indicators of the lake structure and function, which were grouped accordingly. Results reveal that ecological changes began subtly over a century ago, intensifying in the 1960s-1970s, coinciding with re-gional warming, reduced precipitation, and intensified Saharan dust deposition. Generalized linear models (GLM) and Redun-dancy Detrended Analyses (RDA) were applied to analyze the effects of climate variables on community assemblages. Results indicate major shifts in aquatic community composition and recent algal biomass increases, with temperature emerging as the dominant driver, and Saharan dust and precipitation as secondary factors. Species shifts indicate rising water temperature and alkalinity and greater eutrophication. Microbial communities show significant restructuring, with increased archaeal and bac-terial diversity and abundance, suggesting heightened microbial activity and functional changes in biogeochemical processes. The synchrony among proxies and climate variables across sites suggests a region-wide phenomenon. These changes are linked to prolonged ice-free seasons, elevated lake water temperatures, and reduced hydrological input, factors that influenced lake volume and water residence time, and reflect the increasing severity of summer droughts in the Sierra Nevada highlands over the past five to six decades. Continued global warming, reduced precipitation, and increased Saharan dust transport are expected to intensify these ecolo-gical shifts in the future.
Global change stressors ar anticipated to trigger eutrophication and deteriorate water quality in high mountain lakes. To accurately predict the future of these villnerable aquatic "Systeins, research must adopt a holistic approach that integrates sediment-water interactions-processes often underestimated in oligotrophic high mountain lakes compared to external drivers. This paper provides a historical review of the primary chemical, physical, and biological mechanisms governing sedimentary phosphorus (P) mobilization and highlights how these dynamic interactions are influenced by global change. Subsequent sections focus on two Sierra Nevada lakes (Rio Seco and La Caldera, Granada, Spain) with contrasting watershed and hydrological characteristics to assess how desiccation and re-flooding influence sedimentary P dynamics, and water quality. Furthermore, the study explores sedimentation and resuspension processes, emphasizing their crucial role in coupling planktonic and benthic communities. Lake desiccation decreases sedimentary P adsorption capacity due to the reduction in fine mineral fractions (rich in iron and aluminium oxides) and organic matter. Long-term data from La Caldera over 20 years confirm significant P increases in lake water during droughts. Overall, understanding how water level fluctuations (WLFs) influence the biogeochemistry in these high-mountain lakes, and Mediterranean wetlands more broadly, is pivotal for accurately forecasting the responses of inland waters within the evolving global change scenario.
Understanding the dynamics of aquatic ecosystems is essential for biodiversity conservation, as ecological processes and species interactions respond sensitively to environmental variation. It is well established that various environmental factors influence species distribution in aquatic systems, both in surface (epigean) and subterranean (hypogean) environments. However, the absence of light in subterranean habitats can create distinct environmental conditions that may alter the composition and structure of biological communities compared to those in surface habitats. In this study, we analyzed the physicochemical parameters of the water and the structural organization of aquatic benthic invertebrate communities along a 300-meter stream that flows through both epigean and hypogean sections. Environmental variables differed markedly between the two sections, and these differences were reflected in the measured parameters along the sampling gradient. A tributary draining epikarst infiltration influenced the environmental conditions within the main cave passage. The species composition of the aquatic invertebrate community also varied between surface and subterranean sections. However, certain species were dominant in both and were key components of the lotic system. Most species were sensitive to the extreme conditions in the cave, including total darkness and limited food availability. The main cave passage was identified as an ecotonal transition zone, where the interface between hypogean and epigean environments acts as a selective filter along the stream continuum, directly shaping the structure of the aquatic community. The findings of this study offer valuable insights for conservation strategies aimed at preserving biodiversity in hypogean ecosystems with similar environmental characteristics.
The food web in the fishless lakes of Sierra Nevada is largely shaped by several environmental factors, primarily depth and morphometry. Over the past 50 years, numerous studies have explored the trophic compartments of these ecosystems, with a primary focus on the taxonomy and ecology of planktonic species and coleopterans. This paper synthesizes research in these areas. In terms of taxonomy, several species have been recorded for the first time worldwide, such as the chrysophyte Chromulina nevadensis. Other plankton species have been newly documented in Spain, including the diatom Achnanthidium macrocephalum and the rotifer Trichocerca relicta, while Daphnia cf. pulex have been reported for the first time in European high mountain lakes. Ecological research has also focused on biodiversity, life history strategies, stoichiometry and trophic interactions. Key findings include: (i) low species richness and the Shannon-Wiener diversity in planktonic communities; (ii) temperature and mineralization as likely primary drivers of zooplankton composition; (iii) evidence supporting the concept of rheostasis in zooplankton; (iv) pioneering insights into links between organismal stoichiometry and life-history strategies; (v) broad trophic niches in dytiscid beetles, which primarily feed on zooplankton; (vi) discovery of a mutualistic relationship between an epibiont green algae and Daphnia; and (vii) the significant role of multiple interacting environmental factors on the algae-bacteria relationship.
The last 50 years of research in streams and rivers from the Sierra Nevada have provided numerous contributions that, added to the previous studies carried out in the massif, have built a great body of knowledge on particular animal groups, among other organisms. From those, Ephemeroptera, Plecoptera, Trichoptera and aquatic Coleoptera have focused the attention of the researchers in the last decades, while more recently also the brown trout has been intensely studied. The data generated from these studies have laid the groundwork for the development and implementation of biomonitoring techniques and protocols, now coordinated through the Sierra Nevada Global Change Observatory. In this article we summarize the main milestones of this period, the major findings on the biology and ecology (including recent studies on ecological stoichiometry) of these organisms and the current framework of biomonitoring, which should be maintained in the future to keep on providing data for proper management programmes. We conclude by identifying the main challenges that must be addressed to ensure the long-term conservation of stream and river fauna in Sierra Nevada.
Los cambios en el uso del suelo y la pérdida de cobertura vegetal, fenómenos crecientes en el Neotrópico, generan alteraciones fisicoquímicas en los ecosistemas acuáticos que modifican su composición biológica y funcionamiento. Este estudio evaluó la relación entre la diversidad funcional de macroinvertebrados bentónicos y variables ambientales a múltiples escalas espaciales en sistemas lóticos andinos de la cuenca del río Garagoa, Orinoquia colombiana. Se recolectaron macroinvertebrados en 36 sitios y se caracterizó su diversidad funcional mediante 11 rasgos, 49 atributos, y tres componentes primarios: riqueza, uniformidad y divergencia. Para cada sitio se obtuvieron variables ambientales a escala local y de paisaje, organizadas en cuatro conjuntos: 1) condiciones fisicoquímicas en transectos de 100 m, 2) proporción de usos del suelo en la microcuenca, 3) usos del suelo en la red hidrográfica (buffer de 30 m) y 4) usos del suelo en un buffer de 500 m. Los rasgos funcionales de tamaño, respiración, locomoción y duración del ciclo de vida se relacionaron significativamente con variables locales (temperatura, oxígeno disuelto, precipitación, calidad de la vegetación ribereña y composición del sustrato) y de paisaje (áreas agrícolas, pastos para ganadería, industria y extracción minera en escala de microcuenca, red hidrográfica, zonas urbanizadas, vegetación herbácea y bosques). De manera similar, los tres componentes primarios de la diversidad funcional se asociaron significativamente con variables de ambas escalas espaciales. Estos resultados evidencian la importancia de incorporar enfoques multiescala en la evaluación ambiental para la gestión y conservación de los ecosistemas lóticos andinos.
Monitoring fish and space use over time helps us understand the processes occurring in populations and communities within the aquatic ecosystem. To carry out this monitoring, it is advisable to use methods that are not harmful to the species or the environment, avoiding disruption of the natural habitat. The upper Limay River serves as a crucial corridor for various native and exotic species. Along its course, it features diverse types of habitats in its main channel and secondary and temporary channels throughout its course. The main of this study was to evaluate the effectiveness of underwater cameras in the detection and estimation offish abundance in riparian areas of a large northern Patagonian River and compare the results obtained with the electrofishing method, a traditional technique used until now. in this river. Forty-nine river sites were sampled in the main channel and active and temporary secondary arms. Filming was conducted with fixed underwater video station (UVS), and after 50 minutes of recording, electrofishing was carried out in the area offish influence that was recorded on video. The results indicated that the video technique was effective for species detection and the analysis of relative abundance. Moreover, the use of cameras improved the observation offish assemblages and reduced fish mortality. Underwater videos are an effective tool that, along with other sampling techniques, are excellent for monitoring fish species in river ecosystems.
Dry rivers constitute the extreme end of the group of non-perennial rivers characterised by the total absence of water during the annual hydrological cycle. Despite the lack of water, these ecosystems can provide a wide range of benefits to humans, which only become evident when analysed from a socio-limnological perspective. However, they are the most despised and mistreated river ecosystems by water and land managers and by society. Dry rivers without their main asset, water, are perceived as a poor system, devoid of life and of little value to humans. The pejorative social perception of these ecosystems has to do with the way in which we humans value and relate to nature. In this paper, we delve into the world of relationships between humans and aquatic ecosystems to try to understand the reasons why dry rivers are considered useless and unproductive. Using, although not exclusively, the results of the work carried out by the Inland Water Ecology group of the University of Murcia, I will try to show that it is only through co-production processes, where both human and social capital cooperate, that ecosystem services are obtained. However, human-dry-river relationships are complex and arouse polarised feelings (e.g. affection/fear) probably because of the way they are perceived and connected to. Furthermore, the disregard for the experience and traditional knowledge of different social actors (e.g. women) generates social inequalities that have yet to be unravelled, but which exclude an important set of information that would help to manage these ecosystems more sustainably.
Healthy freshwater ecosystems provide essential ecosystem services to society such as clean water. However, freshwater ecosystems are degraded, and freshwater biodiversity is severely threatened due to anthropogenic impacts and stressors. Climate change interacts with existing stressors and may compromise the resilience of freshwater ecosystems and their services in the future. Here the aim is to review advances in assessing freshwater ecosystem services and their resilience to environmental change. This work reviews the ecosystem services provided by freshwaters, the conceptual background on ecological resilience, and examples on the resilience of freshwater ecosystems and their services. Examples from African lakes, the Pantanal wetland in Brazil and the Murray-Darling Basin riparian forests in Australia are used to understand the resilience of freshwater ecosystem services to recent and ongoing climate changes and disturbances. This work illustrates the diverse responses of freshwater socio-ecological systems to environmental change and highlights examples of declining resilience of freshwater ecosystems and their services due to climate change and extreme events. However, a high degree of uncertainty still surrounds the identification of regime shifts and future ecosystem trajectories. Research is needed to understand the dynamics of freshwater socio-ecological systems and ensure resilient ecosystems and societies.
Although lakes represent only 0.26% of the total freshwater on Earth, they provide essential environmental services, such as public water supply and irrigation. Water temperature, which drives the lake’s physical, chemical, and biological processes, is a parameter typically used for lake management plans. To explore the effects of climate change on Lake Mangueira, a subtropical coastal shallow lake, we assessed the cumulative intensity index, which links heatwave duration to mean intensity. The Air2Water model was calibrated using time series of observed daily air temperature data and water surface temperature data obtained via remote sensing. Based on climate projections obtained from 26 global climate models, the Air2Water model was used to generate water temperature time series for a historical period and future scenarios, including SSP1-2.6, SSP2-4.5, and SSP5-8.5. We found that at least 75% of the projections indicated lake heatwaves with a cumulative intensity exceeding 50 °C days under the SSP5-8.5 scenario, compared to 18 °C days in the historical period. Even in the least severe future scenario (SSP1-2.6), 75% of the projected average cumulative intensities were equal to or exceeded every value from the historical period. These findings highlight a concerning shift in the thermal dynamics of Lake Mangueira. The lake is expected to experience more intense and/or longer-lasting heatwaves that have the potential to significantly affect its aquatic communities. The cumulative intensity index can therefore be used to monitor extreme events in these ecosystems, which will help to properly manage them.
Despite advances in understanding methane dynamics in dry inland waters, the potential of dry riverbeds to act as sinks of methane, as soils do, and the controlling factors remain unclear. Here, we tested three main factors controlling methane oxidation in soils and freshwater ecosystems in sediments from a dry riverbed (decreasing in modulation degree): gravimetric water content (GWC), temperature, and light quality and intensity. We measured the rates of potential methane oxidation (PMO) along a gradient of GWC (1%, 5%, 8%, 10%, and 100%), temperature (10 ºC, 20 ºC, and 30 ºC) and light (in darkness, at photosynthesis-limiting (i.e., green) and photosynthesis-promoting (i.e., grow) light). Our results revealed that dry streambed sediments have the potential to oxidize methane. GWC, as the major controlling factor, followed a nonmonotonic function, with the highest PMO of around 5% GWC. As the secondary control, temperature affected PMO from dry sediment only but not from 100% GWC sediment. PMO was the lowest at 10 ºC and highest above 20 ºC. Interestingly, light reduced PMO by 3–6× compared to dark conditions, and grow light reduced PMO by ~2× compared to green light. Our results indicate that there will be day–night and seasonal variations in methane oxidation from dry riverbeds as a function of temperature, GWC and light, and between reaches, depending on the canopy cover and associated riverbed shading. Overall, our results highlight the potential of dry riverbeds to act as sinks of methane from the atmosphere.
Salar de Pedernales basin is located at 3370 meters above sea level in the Atacama Desert, Chile, covering an area of 3620 km2. This ecosystem is characterized by high exposure to ultraviolet radiation, low humidity, huge variations in ions content and extreme thermal gradients. Despite these extreme conditions, it has a rich fauna and flora. However, the aquatic biodiversity in the basin remains poorly documented. Our study assessed compositional changes of planktonic and benthic communities across several salt flats (Pedernales S-O, Piedra Parada, La Laguna), natural water courses (wetland and creeks), an artificial stream and lagoon (Pedernales N-E), and their relationship with local physicochemical parameters. Our results show that the Salar de Pedernales basin is a highly heterogeneous ecosystem principally influenced by conductivity, pH, and major ions. Community diversity was high at all locations except for the artificial stream. Microalgae were spatially similar with major changes observed in the disturbed habitats. The composition of the invertebrate communities strongly varied among habitats but displayed distinct composition in the perturbed ones (Salar Pedernales N-E). Distance-based redundancy analysis revealed that phytoplankton and benthos composition were driven by changes in trace metals and nitrate, whereas zooplankton community composition were mainly related to osmotic stress. Our data highlight the remarkable biodiversity of the natural water bodies of the Salar de Pedernales basin and the potential effects of anthropogenic perturbations on the biota in these extreme habitats.
Along the Valencian coastline, numerous coastal wetlands persist as remains of extensive alluvial plains that once dominated the region. Historically, many of these wetlands were drained due to human activity, accelerated by urban development along the Mediterranean coast. Despite this, several larger or strategically located wetlands have endured and are now under protection. These ecosystems encompass diverse aquatic habitats including marshes, springs, canals, and shallow lagoons that support a rich variety of organisms, notably zooplankton, that are essential to aquatic food webs. This research aims to study the diversity (α, β and γ) of zooplankton and to assess how environmental variables influence their composition and diversity. Seasonal samples of zooplankton and water were collected from multiple sites within six selected wetlands: Prat de Cabanes-Torreblanca, Marjal dels Moros, Albufera de Valencia, Marjal Pego-Oliva, Salinas de Santa Pola, and Hondo de Elche. Zooplankton species were identified and quantified, and richness and different diversity metrics were estimated: Shannon and inverse Simpson indices (to estimate α-diversity), local contribution to beta diversity -LCBD- (for β-diversity), and Chao index (for γ-diversity). Physicochemical parameters, nutrient levels, and pigment concentrations were also measured, and their influence on diversity metrics was evaluated through multiple linear regression. The findings indicated that key factors influencing structure and diversity of the zooplankton community included water conductivity, phosphate concentration, chlorophyll-a concentration, seasonal changes, and type of waterbody. Freshwater wetlands showed greater α and γ-diversity. The Albufera de Valencia sites showed a significantly higher contribution to beta diversity than other sampling sites during all seasons, reflecting consistently unique communities
Leaf litter breakdown plays a crucial role in detrital-based ecosystems, and understanding the factors that influence this process is essential, particularly in data-poor semi-arid riparian zones. This study investigated the influence of land use (upstream and downstream of an urban area) on the decomposition of leaf material from common species in the area (Erythrina velutina, Anacardium occidentale, Tabebuia aurea, Croton sonderianus, and Hymenaea courbaril). Litter bags (single-species, fine and coarse mesh) containing senescent leaves were used to evaluate invertebrate density and richness, shredder and scraper abundance, and litter mass loss after oven drying. Leaf litter with high nutrient content and a low C:N ratio decomposed significantly faster than more recalcitrant litter, likely due to enhanced microbial and invertebrate colonization. Also, litter breakdown was higher when invertebrates had access to leaf material. The effect of invertebrate exclusion was pronounced for high-quality litter, where invertebrate scrapers (Thiaridae, Lymnaeidae, and Planorbiidae) seemed to play a central role in litter fragmentation. Urbanization significantly influenced breakdown rates, but its effects were contingent on litter quality and invertebrate access. Litter breakdown was higher at location under the influence of urbanization, likely due to increased nutrient availability and microbial activity. Ultimately, strong interactions were observed between litter quality, invertebrate access, and urbanization, with the urban effect being most pronounced for high-quality litter, while invertebrate-mediated effects were also stronger for high-quality litter, creating a complex and dynamic ecological condition in the studied semi-arid river.
Rivers provide vital ecosystem services for populations. However, these ecosystems face several anthropogenic threats, including macrolitter pollution, and their impacts remain inadequately understood. This study aimed to evaluate the ecological status of the Leça river (northern Portugal) according to the elements defined by the Water Framework Directive (WFD) and to quantify marginal macrolitter as a new ecological tool for river water quality assessment. Physical, chemical, and biological (photosynthetic pigments; benthic macroinvertebrates) elements were quantified to evaluate the ecological status, of seven sites (P1 to P7) along the Leça river throughout four seasons (autumn/23, winter/24, spring/24, summer/24). Macrolitter was collected on the riverbank of each site and was quantified and categorized according to standard protocols. Based on the physical and chemical elements, Leça river achieved Good ecological status in P1, and Moderate in P4 to P7 (mainly due to nutrient enrichment) with P2 and P3 varying between Good and Moderate. The ecological status according to the macroinvertebrate community varied between: Good and Moderate in P1; Moderate and Poor in P2 and P3; Poor in P4 and P5; and Poor and Bad in P6 and P7. From the 1717 macrolitter items (belonging to 86 categories), artificial polymer/plastic items were the most frequent (56.67 %). More abundance and diversity of items were collected in sites P3 to P7, coinciding with the increasing anthropic presence. A multivariate analysis revealed that items originating from recreational activities were associated with fewer alterations in the macroinvertebrate community, while items originating from the deposition of domestic, industrial, and commercial residues were associated with more degraded conditions. The results suggest that the evaluation of macrolitter can be used to indicate anthropogenic activities that threaten aquatic ecosystems.
The Guiana Shield contains multiple freshwater ecosystems that support high species diversity. This ecoregion represents a stable landscape resulting from infrequent large-scale natural disturbances (i.e., Andean orogeny, marine incursions), favoring biological adaptations and endemisms (e.g., loricariids). However, disturbing human activities in nearby areas is a warning for the future of the Colombian Guiana Shield, and this requires assembling evidence that might contribute to the conservation of the region's biodiversity. We summarize information already available for the region and use field observations and laboratory studies to characterize the region's environmental variables and freshwater biodiversity. The Colombian part of the Guiana Shield is one of the best preserved because of low human density and reduced impacts. Although still relatively pristine, this region is already experiencing high growth in farming, contributing to forest loss. Other threats include infrastructure development, small-scale mining, livestock and water contamination. We developed a typology of river systems in the Colombian Guaina Shield that might be useful for conservation. There is ample evidence of the uniqueness of freshwater biodiversity and the threats affecting its conservation in the region. We present a conceptual relationship between the drivers, pressures and impacts currently existing in the Colombian Guiana Shield. Growing environmental impacts and future transformations require preserving these systems as a necessary step to expand our knowledge of their diversity and functions. To minimize current or future impacts requires involving local communities as well as the implementation of more strict policies, leading to a respectful development. Our recommendations could be useful for other areas in the Guiana Shield.
The current and increasing problem of imported cases of Culicidae-transmitted diseases in Europe, together with the increasingly recurrent appearance of autochthonous cases of arboviruses in temperate latitudes and the history of areas previously endemic for them, have led to a great recovery in the research on these dipterans. The present study focuses on anopheline mosquitoes from Eastern Spain, – particularly from the Valencian Autonomous Region, which is a formerly endemic area of malaria. The geographical distribution as well as tolerance ranges to abiotic factors such as water temperature, salinity, pH and the altitude of the aquatic habitats occupied by their preimaginal stages are presented for the seven identified mosquito species of the genus Anopheles and subgenus Anopheles: Anopheles algeriensis Theobald, 1903; Anopheles atroparvus Van Thiel, 1927; Anopheles claviger (Meigen, 1804); Anopheles maculipennis s.s. Meigen, 1818; Anopheles marteri Senevet & Prunnelle, 1927; Anopheles petragnani Del Vecchio 1939 and Anopheles plumbeus Stephens, 1828. In this way, we have updated the knowledge on these species, which are considered potential vectors of malaria and other pathogens that cause disease at a local level in the studied area. Therefore, new insights of great consequence for the public health, epidemiology, entomology, ecology and pest control sectors are provided, which should be taken into consideration in surveillance and control programmes.
The study of simuliids in Spain is of the utmost importance, not only because of the key role they play in food chains both as agents recirculating matter and as a source of food for countless organisms, but also due to the negative impact that females of blood-sucking species have on animal and human health and welfare, and the economic damage that they can cause to health, veterinary, agriculture and tourism sectors. Therefore, a deeper knowledge of blackflies is crucial. To this purpose, the specimens collected in 1997 along the Cidacos River from two Spanish provinces were studied. The objective of this study has been to improve the knowledge of this family in Spain. As a result, 12 species of the genus Simulium have been identified, belonging to four subgenera and classified into four species groups. Three species are first records for La Rioja and one species for Soria. The elevational and water temperature ranges have been described for each one of the species. The sampled stations with the highest species richness have been indicated and the species composition of several sampling stations has been analysed. The species with the highest and lowest relative abundances are described in detail and provincial distribution maps of the four species recorded for the first time in the area studied area are provided. The species whose females require obligatory intake of blood to develop their eggs are highlighted, as well as the harm due to each species with this type of feeding behaviour.
Temporary rivers (TRs) are dynamic ecosystems that alternate between hydrological phases (i.e., flowing, disconnected pools, and dry). They are conservation refugia for aquatic species during dry seasons but are often neglected in bioassessment programs. To assess the biological quality of these ecosystems, morphological methods can be invasive, disrupting communities and diminishing their function as refugia. Environmental DNA (eDNA) metabarcoding provides a minimally invasive method, gathering community information from eDNA in water or sediment. We tested the effectiveness of eDNA methods alongside bulk DNA metabarcoding to characterize the macroinvertebrate communities and assess the biological quality of disconnected pools in TRs, comparing them with morphological methods. Additionally, we tested how the community patterns evolve over time using eDNA and how community composition shifts during disconnection. Biological quality was determined through macroinvertebrate indices widely used in Spain (i.e., IBMWP, family richness, and IASPT). eDNA samples were collected biweekly from three TRs in Catalonia, NE Spain. Macroinvertebrates were sampled during the three hydrological phases (connected, disconnecting, and disconnected pools). Macroinvertebrate samples were used to identify organisms using morphology and to sequence bulk DNA. eDNA and bulk DNA samples were analysed via DNA metabarcoding targeting the mitochondrial COI gene. Although communities determined by sediment eDNA did not detect variations in biotic indices (i.e., IBMWP and family richness), the method was useful to detect the replacement of EPT (Ephemeroptera, Plecoptera, Trichoptera) by OCH (Odonata, Coleoptera, Heteroptera). Additionally, sediment eDNA revealed significant impacts of hydrological changes on meiofauna (Ostracoda, Cladocera, Copepoda), a group often overlooked in stream assessments. These results indicate that sediment eDNA metabarcoding can serve as a valuable tool for the bioassessment of TRs, capturing the transitions between hydrological phases while preserving ecosystem integrity.
