ID04: Alpine aquatic biodiversity

Abstract ID 208 | Date: 2022-09-12 10:15 – 10:30 | Type: Oral Presentation | Place: THEOLOGIE – SRVI |

Niedrist, Georg H; Füreder, Leopold

Global warming intensifies environmental change in high-altitude ecosystems worldwide, with rising air temperature among the main stressors. While past research in Alpine river ecology has primarily focused on how retreating glaciers might affect the ecology of glacier-fed streams on the long-run and mostly used space-for-time substituted study designs, observations of real-time alterations in such pristine environments are scarce.

This study presents observations of stream temperature and invertebrate communities in 18 sites in 14 different streams with distinct water sources (glacial and non-glacial) and found that all studied alpine streams are warming consistently and at high rates, linked to size of the rivers. Using benthic datasets from these streams over several years (2011, 2014, and 2015), this study is the first to demonstrate real-time shifting community metrics, and group-specific changes in relative and absolute abundance within the invertebrates. Further, this work demonstrates partial discrepancies between results derived from space-for-time substitutions and real-time observations of these communities.

This study identifies that the rate of recently reported fast warming of alpine rivers during summer highly depends on the size of rivers with smaller rivers showing maximum rates beyond 7°C decade^-1. Besides this, we revealed that cold-adapted invertebrate species (i.e., Diamesinae) unexpectedly expand their dominance over the observed years, while other groups (e.g., Ephemeroptera, Plecoptera, Trichoptera) remained stable or increased only marginally. These observed changes, which remain hidden in space-for-time substituted study designs, therefore demonstrate that milder conditions during summer generally alter benthic habitat conditions and population densities, but that group-specific adaptations lead to differently strong responses to these changes.

The observation of this coherent warming of all investigated streams makes clear that this is a general pattern and will affect lowland and high-order streams as the atmospheric warming continues and accelerates in the near future. In particular, however, it is the aquatic communities in smaller rivers that will experience the greatest summer warming and consequential changes within the next years.

Abstract ID 237 | Date: 2022-09-12 10:30 – 10:45 | Type: Oral Presentation | Place: THEOLOGIE – SRVI |

Sudlow, Karson Ian; Vinebrooke, Rolf

Rapid deglaciation is altering the unique abiotic conditions and biodiversity of glacially fed alpine streams while the functional consequences for downstream communities remain knowledge gaps in mountain limnology. We quantified taxonomic and trait-based functional shifts in algal and macroinvertebrate communities as related to environmental variables along a deglacierization gradient consisting of 14 streams in Banff and Jasper National Parks. Deglacierization (i.e. reduced glacial discharge and less turbidity) appears to stimulate species diversity and trait-based shifts towards larger body-size and increased resource competition based on multivariate community analyses. Our preliminary findings suggest that shrinking glaciers will increase the productive capacities of certain mountain stream ecosystems at the cost of specialized glacial biodiversity.

Abstract ID 359 | Date: 2022-09-12 10:45 – 11:00 | Type: Oral Presentation | Place: THEOLOGIE – SRVI |

Consoli, Gabriele (1); Kastenhofer, Olivier (2); Doering, Michael (2); Chanut, Pierre (1); Robinson, Christopher T. (1)

Dams cause major hydropower-related environmental change in alpine streams, altering natural flow and sediment regimes, and releasing stable flows. This shift in the habitat template affects the assembly of aquatic organisms, thereby modifying ecosystem function by filtering for specific traits favoured by stable flow conditions. Adaptive dam management aims at mitigating flow-related alterations, implementing ecologically-based water releases (environmental flows). In alpine rivers, seasonal floods play a fundamental role for stream and riparian ecosystems, sustaining important ecological processes. In regulated rivers, these seasonal high flows are lost but can be partly restored by releasing experimental floods (i.e. controlled high-flows from dams). Understanding how stream ecosystems respond to flow restoration enables the design of ecologically-sound environmental flows based on empirical evidence. In this study, we analysed macroinvertebrate and environmental data collected during the monitoring of a 17-year experimental flood program on the Spöl, a regulated alpine river, and of two unregulated streams in the same catchment. We used fuzzy correspondence analysis, and calculated functional diversity indices and individual trait patterns, to detect functional adaptations of macroinvertebrates to the experimental floods. We observed a progressive adaptation of the macroinvertebrate community to the new flow regime, with multiple functional shifts following an increase in the frequency of traits linked to resistance/resilience. Despite notable improvement of the river’s ecological conditions, the experimental floods did not result in a complete ecological restoration, indicating that the environmental impacts of flow regulation may be deeply embedded in the system. This study supports the importance of long-term monitoring to evaluate the ecological effects of flow restoration on stream ecosystems.

Abstract ID 140 | Date: 2022-09-12 11:00 – 11:15 | Type: Oral Presentation | Place: THEOLOGIE – SRVI |

Quenta-Herrera, Estefania (1); Crespo-Pérez, Verónica (2); Mark, Bryan (3); Gonzales, Ana Lía (4); Kulonen, Aino (5)

Although protected areas (PAs) play an important role in ecosystem conservation and climate change adaptation, no systematic information is available on PA protection of high-elevation freshwater ecosystems (e.g., lakes, and watersheds with glaciers), their biodiversity and ecosystem services in the tropical Andes. We therefore combined a literature review and map analysis of PAs of International Union for Conservation of Nature (IUCN) and national systems of PAs, and freshwater ecosystems. We found that seven national parks were created for water resources protection, but were not designed for freshwater conservation (i.e., larger watersheds). High-value biodiversity sites have not been protected, and new local PAs were created due to water resource needs. We quantified 31 Ramsar sites, and observed that PAs cover 12% of lakes, 31% of glacial lakes, and 12% of the total stream length in the tropical Andes. Additionally, 120 watersheds (average area 631 km²) with glaciers and 40% of the total glacier surface area were covered by PAs. Future research about the role of PAs in ecosystem services provision, and more detailed freshwater inventories within and around PAs, especially for those dependent on glacier-runoff, will fill key knowledge gaps for freshwater conservation and climate change adaptation in the tropical Andes.

Abstract ID 444 | Date: 2022-09-12 11:15 – 11:30 | Type: Oral Presentation | Place: THEOLOGIE – SRVI |

Niedrist, Georg H (1); Hilpold, Andreas (2); Grund, Hannes (3); Agreiter, Andreas (3); Kranebitter, Petra (1)

Introduction and/or immigration of non-native fish species is a major threat to the freshwater biodiversity and an accelerated spread of multiple invasive species has been observed worldwide. However, only few studies investigated distributions of such fish species in rivers of mountain regions, and region-wide estimates of population dynamics are rarely available, which has prevented effective management of invasive species so far.

Here, we analyzed a dataset of >1300 electrofishing surveys in 650 different sites across a mountain region (South Tyrol, a province in northern Italy, ranging over 7400 km² of the European Alps) to firstly give an overview of key-species, prone river types or population trends. We analyzed the occurrences of non-native fish species in different types of rivers and estimated trends of population in abundance and biomass at sites that have been fished multiple times from 2000 to 2020.

Among the 38 fish species, we found 19 species considered invasive for European waters, eleven of which are non-native in the study region. While most species are restricted to low-elevation warm rivers and to few sites only, we found significantly increasing population sizes for Lepomis gibbosus and Pseudorasbora parva (two invasive species of Union concern) in lowland ditches in the South, supposedly supported by increasing water temperatures in these slow waters. Populations of non-native species relevant for recreational fishing and therefore stocked throughout the region, developed differently during the last decades: across the region and within the last 20 years, Oncorhynchus mykiss significantly increased (+7 ±3% year^-1), Salmo trutta remained stable, and Salvelinus fontinalis significantly decreased (-7.4 ±3% year^-1). We suggest this being linked to the different stocking intensities of these species (compared to the others, the stocking level of S. fontinalis has been minimal).

Our results show that non-native and invasive fish species are a relevant part of fish communities in mountain rivers. Given that increasing river temperatures are expected to further enhance dispersion and population growth of such species, our work can be helpful to guide the fish management of rivers in mountain regions.

The study has been financed by the Research fund of the Museums of South Tyrol

Abstract ID 668 | Date: 2022-09-12 11:45 – 12:00 | Type: Oral Presentation | Place: THEOLOGIE – SRVI |

Cantonati, Marco (1,2); Filippini, Maria (1); Gargini, Alessandro (1); Segadelli, Stefano (3)

Mountain freshwater ecosystems are of undisputed relevance, not only as strategic water resources but also for the important biodiversity they shelter and for the ecosystem goods and services they provide. Therefore, research on mountain aquatic habitats should be fostered not only in mountain regions but also in administrative geographic areas where economic reasons determine an emphasis of policy and management on the more productive lowlands. Our aim is to provide a synthetic overview on research themes that we pursued in the Alps and Apennines in the last decades, with an emphasis on those planned for the years to come. The main topics of investigations that we carried out in the Alps are as follows: springs (in particular springs in National Parks and other types of nature preserves) as sites of paramount importance for aquatic biodiversity conservation); characterization of the biodiversity of high-mountain lakes under the pressure of water-spilling for hydropower (artificial snow) generation, eutrophication, and acidification risk; neo- and paleolimnology of a high-mountain lake on holocrystalline substratum (early-warning system & archive of global-change effects for the whole Late Glacial and Holocene); paleoecological study of mountain mires (diatoms and chemical characteristics of peat cores) with a focus on grazing effects; ecological effects of water-level fluctuations in mountain lakes. Research topics tackled in the Apennines are as follows: explorative research on the biodiversity of springs representative of the lithotypes and ecomorphological spring types found in the Emilia-Romagna Region; springs as hotspots of landscape-level (ɣ) diversity; limestone-precipitating springs (LPS) and conceptual models of LPS’ distribution to support the implementation of regional LPS information systems. Both in the Alps and in the Apennines we dealt with springs as ideal sites where to develop our understanding of geo- biodiversity relationships and ecohydrogeological approaches. An important research program to be continued in the Alps is long-term ecological research (first data collected in the early 1990s) on selected mountain springs and on a hyper-dilute high-mountain lake. New research themes that are being developed in the Apennines: spring discharge as an indicator of climate change throughout the last century as related to evapotranspiration increase and snow-fall decrease, innovative methods to evaluate the resistance and resilience capability of small mountain springs to climate-change effects; environmental archives (paleoecological study of a small mountain lake and associated mire), recorded data, and modeling to understand and predict changes in the frequency of extreme-precipitation events during the Holocene.

Abstract ID 641 | Date: 2022-09-12 13:30 – 13:45 | Type: Oral Presentation | Place: THEOLOGIE – SRVI |

Chanut, Pierre (1); Datry, Thibault (2); Schaer, Bettina (1); Robinson, Christopher (1)

Flow intermittence is prevalent in glaciated alpine catchments, where kryal streams may typically dry in winter and rhithral streams dry at the end of summer. But with thermal changes and reductions in snow and ice cover, flow intermittence is expected to intensify and become more spatially synchronized within alpine stream networks. While the effects of single drying events on macroinvertebrates are well documented, much less is known about the ecological effects of drying regimes differing in frequency, duration, timing and spatial extent. Here, we used modified light sensors to characterize intermittence regimes in 75 alpine streams from 4 glaciated alpine catchments in the Swiss Alps. We also sampled macroinvertebrates at three dates and quantified organic matter decomposition rates using standardized leaf bags and cotton strip bioassays. We investigated how frequency, duration and timing of drying events as well as habitat features affect structural and functional aspects of stream ecosystems. We also examined the linkages between intermittence, community attributes and decomposition rates. Finally, we simulated theoretical metacommunity patterns and compared these with observed data to better understand how connectivity and dispersal influence community resilience to drying. The analysis is ongoing, but preliminary results suggest taxonomic and functional diversity as well as the abundances of specific functional groups responded negatively to increasing drying frequency. Leaf litter and cotton strip decomposition were also negatively affected by increasing intermittence. Interestingly, the upper quantiles of these response variables showed the strongest responses along the intermittency gradient. This shows that high flow intermittence exerted a strong constraining effect on biota and functional properties, whereas other factors may influence these variables at low intermittence levels. Overall, our research suggests that increasing intermittence in glaciated alpine catchments may drive significant changes in the biodiversity of alpine streams. Importantly, these changes may in turn affect the functional properties of aquatic ecosystems (e.g., organic matter decomposition), which could affect downstream ecosystems through changes in resource flows.

Abstract ID 494 | Date: 2022-09-12 13:45 – 14:00 | Type: Oral Presentation | Place: THEOLOGIE – SRVI |

Fenoglio, Stefano (1); Bona, Francesca (1); Falasco, Elisa (1); Ercole, Giorgia (1); Doretto, Alberto (2); Cauvy-Fraunie, Sophie (3); Arthaud, Florent (4)

Alpine lakes and rivers shelter biodiversity treasures, host essential ecological processes and protect quality and quantity of water resources. Unfortunately, several mountain aquatic habitats are experiencing dramatic water scarcity, due to global climate change and increasing water abstraction, with expected detrimental effects on their biodiversity and functionality. In particular, mountain streams in western European Alps are increasingly shifting from perennial to intermittent flow due to the combined effects of climate change and local anthropogenic pressures. Because such flow reduction or intermittency is a recently documented phenomenon in the Alps, only scattered studies have investigated their effects, and only few data are available on benthic communities. In this study we summarized some of our results related to the consequence of water shortage on aquatic ecosystems. First, we analyze the impact of flow reduction/droughts comparing biodiversity, taxonomic richness and functionality of benthic macroinvertebrates and algae in control (i.e., permanent) versus intermittent Alpine stream reaches. Then, we report some case-studies related to the combining effect of water shortage and human use (i.e., hydroelectric plans and dam management). In addition, we present the first results of a new line of research aiming at investigating how the reduction of flow can affect the effectiveness of wastewater treatment plants in mountain areas, thus impacting biodiversity and altering the environmental conditions of the rivers of the Alps. Finally, we also want to present here the great opportunity for collaboration offered by the UNITA consortium (Universitas Montium), as a network for teaching and research in the mountain environment, to which belong among others the Université Savoie Mont Blanc (with the CARRTEL – Alpine Center for research on trophic networks and lake ecosystems, Le Bourget-du-Lac) and the Università degli Studi di Torino (with ALPSTREAM – Alpine Stream Research Center, Ostana).

Abstract ID 665 | Date: 2022-09-12 14:00 – 14:15 | Type: Oral Presentation | Place: THEOLOGIE – SRVI |

Bonacina, Luca (1,2); Fornaroli, Riccardo (1); Cauvy-Fraunie, Sophie (2)

Water temperature is recognized as one of the most important drivers shaping both aquatic ecosystem structure and functioning. Indeed, temperature controls metabolic processes, primary production, growth rates, life cycle duration, and constitute a physiologic threshold for the different species. Despite the pivotal role of temperature on aquatic communities, a detailed investigation of the effects of different water thermal regimes on macroinvertebrates has been rarely carried out, especially in alpine streams. In the present study, we studied the response of macroinvertebrate communities to environmental conditions in alpine streams of the Serio River catchment (BG, Italy). Selected streams are characterized by different thermal regimes linked to the different water sources (snowmelt/stormwater and groundwater-fed streams) and human alterations (presence of reservoirs). At five stream sites, each month for one year, we sampled macroinvertebrates and organic matter (allochthonous and autochthonous) and measured water physical-chemical conditions and nutrient concentrations. Moreover, flood disturbance was quantified monthly using painted tracers while water temperature was measured continuously (every 10 min). We examined the ecological effect of environmental variables on the macroinvertebrate abundance, life cycle, and growth rate. Results showed a strong co-inertia between monitored environmental variables and macroinvertebrate assemblage with first floods and then temperature as the main driver structuring the communities. High annual thermal variability (range ~0-15 °C) promotes a high temporal turnover of macroinvertebrates compared to a stable thermal regime (range ~8.0-8.6 °C). In addition, we found a temporal mismatch in the life cycle of certain taxa (Amphinemurae sp., Ephemerella sp., Protonemura sp.,) between individuals captured in different thermal conditions. Finally, we observed significant temperature-abundance correlations for various genera such as Epeorus sp., and Leuctra sp. The study highlights that the thermal regime could be very different among alpine streams with strong ecological implications on macroinvertebrate communities. Although other variables as lithology and organic resources had a significant effect on the spatial macroinvertebrate assemblage, temperature mainly drove the temporal pattern. Under global warming, we thereby expect a significant change in taxa assemblage, with more temporal heterogeneity in community composition due to higher annual thermal variability and loss of cold stenothermal species where upper thermal limits will be exceeded.

Abstract ID 677 | Date: 2022-09-12 14:15 – 14:30 | Type: Oral Presentation | Place: THEOLOGIE – SRVI |

Arthaud, Florent (1); Meymy, Chloé (1); Toury, Julie (1); Moine, Rémy (1); Cunillera, Guillaume (2); Avrillier, Jean-Noël (1); Millery, Annie (1)

High-altitude lakes are sensitive ecosystems and appear to be good indicators for studying the effects of global change on biodiversity. However, their ecological functioning is still poorly understood, especially in terms of the aquatic vegetation in the lakes and the various roles of plants that are important to the functioning of aquatic ecosystems. Understanding the impact of global change in mountain lakes requires understanding how environmental factors govern the organization of aquatic plant communities.

We present a study that focused on monitoring aquatic plant communities in 30 high-altitude lakes and conducting transplantation experiments with measurements of morphological and physiological traits for a common alpine species.

Plant diversity was low with high dissimilarity between lakes, but plant cover was relatively high and correlated with fine sediment area. Two plant strategies were observed with high dispersal species characterized by thin leaves, low abundance levels but present in many lakes and with relatively tall species with high abundance levels but present in very few and neighbouring lakes. Plant colonization appears more limited by the probability of dispersing to the lake than by local environmental factors, as suggested by the decrease in species richness according to elevation between the lake and car park. Transplantation experiments were performed with Ranunculus trichophyllus eradicatus, the most frequent species in northern French lakes. The growth of the plants and their organs over 2 weeks was similar at 7 or 17 °C, regardless of the population of origin. The variability in photosynthetic capacity was mainly explained by the experimental temperature conditions during the measurements, weakly explained by the temperature of the two-week cultures, and not explained by the temperature of the lakes of origin. These results confirm the high plasticity of aquatic plants and that numerous species are able to develop under highly contrasting environmental conditions.

Spatial factors favouring connectivity and dispersion were more dominant than local abiotic factors in explaining community diversity. Thus, the amount of aquatic plants contributing to the primary production of lakes could therefore be greatly underestimated, especially since climate change, eutrophication and human activities should encourage their colonization in these high-altitude ecosystems.

Abstract ID 325 | Date: 2022-09-12 14:30 – 14:45 | Type: Oral Presentation | Place: THEOLOGIE – SRVI |

Scotti, Alberto; Marsoner, Thomas; Klotz, Johannes

Several anthropic activities such as agricultural practices, wastewater disposal, or de-icing operations of roads are continuously increasing the salinity of freshwater habitats. The rate at which freshwater salinization is currently rising caused some scholars to identify it as one of the primary drivers in shaping benthic macroinvertebrates communities.
In this study, we evaluated the composition of benthic macroinvertebrate communities in four catchments, located in the Italian Central-Eastern Alps, which have been sampled with monthly frequency during the winter season (from December to March). The catchments were selected to be geographically close – bordering each other – and very similar in terms of surface area and overall water discharge, but they greatly differ in the potential detrimental effects that application of salt for de-icing could have on the riverine ecosystems. Indeed, the catchments vary with regard to the number of kilometers of roads present within their boundaries, and in terms of the proximity of the roads to the river network present in the catchment.
We developed an index able to quantify the salinization risk of each point in the river network of each catchment based on distance from the road and topography of the terrain. Concurrently, we assessed the salinity effects on the freshwater habitats using a recently developed index that makes use of the bioindication power of benthic macroinvertebrates.
The two indices exhibit concordant results, and showed that, despite the different risk of salinization of our catchments, a significant impact of salt application could not be detected on the freshwater habitats under study.

Abstract ID 335 | Date: 2022-09-12 11:30 – 11:45 | Type: Poster Presentation | Place: THEOLOGIE – SRVI |

Becquet, Juliette; Cauvy-Fraunié, Sophie; Lamouroux, Nicolas; Forcellini, Maxence

Alpine streams face rapid hydrological changes due to the combined effects of global warming and increased water abstractions. More and more small hydropower plants are built at high altitudes, changing local habitat conditions with profound effects on the aquatic biodiversity. Impacts of flow alteration can be mitigated by environmental flows (e-flows) assessment. Among existing tools, hydraulic habitat models allow predicting change in habitat suitability for aquatic species under different flow scenarios, coupling hydraulic models of stream reaches with hydraulic preference (biological) models. The hydraulic component predicts the frequency distributions of microhabitat hydraulic conditions at various discharges. The biological component describes the variation of species abundance with microhabitat hydraulic conditions. Initially developed for fish, hydraulic preference models have never been adapted to high-altitude, often fishless, streams. It is urgent to develop new hydraulic preference models on alpine species to assess the impact of flow alteration on alpine stream ecosystems. In this study, we aimed to (1) develop hydraulic preference models on dominant macroinvertebrate taxa in alpine streams, (2) test whether macroinvertebrate responses to hydraulics varied between streams with or without glacial influence, (3) identify the hydraulic drivers that best explain microhabitat selection by alpine taxa, and (4) compare hydraulic responses with those obtained at low altitudes. For this purpose, we analysed a database of 150 macroinvertebrate samples. Microhabitats were characterized by four hydraulic variables: bed shear stress, water column velocity, Froude number, and water depth. We performed generalized linear mixed models to examine the impact of each hydraulic variable on macroinvertebrate abundance and compared their performance for explaining microhabitat selection. We also compared our results with a similar study realized in low-altitude streams to assess the consistency of hydraulic response of macroinvertebrate between lowland and alpine environments for common taxa. Hydraulic preference models have been developed on 41 alpine taxa, of which 18, 20, 21, and 11 had a significant selection for shear stress, flow velocity, Froude number, and water depth, respectively. Macroinvertebrate response to hydraulics was similar among alpine stream types. Power of models with shear stress and flow velocity to predict macroinvertebrate abundances was higher than with Froude number and water depth. We also observed similar macroinvertebrate response to hydraulics between alpine and lowland streams for 11 common taxa. Our results showed a good transferability of macroinvertebrate hydraulic preference models among stream types that combined with hydraulic models, will be an effective tool to assess e-flows in alpine regions.

Abstract ID 223 | Date: 2022-09-12 17:45 – 17:47 | Type: Poster Presentation | Place: SOWI – Garden |

Quenta, Estefania (1); Daza, Antonio (2); Lazzaro, Xavier (3); Jacobsen, Dean (4); Dangles, Olivier (5); Cauvy, Sophie (6)

1. The impact of global warming on mountain ecosystems is predicted to be high, and particularly in the tropical region. Geothermal streams have provided comprehensive evidence about how aquatic biodiversity changes across natural thermal gradients, but current knowledge is restricted to arctic and temperate zones. Thermal tolerances are different in tropical biological communities, resulting in high thermal sensitivity and low capacity to endure change in their thermal environments. This feature can change the response of aquatic organisms to warming, yet there is little empirical evidence to support this assumption.
2. In this study, we address this issue by evaluating how water temperature affects biodiversity, and the structure of primary and secondary producers of a high-elevation geothermal stream system (4,500 m above sea level) in the Bolivian Andes. We analysed multi-taxa responses to increased water temperature using benthic macroinvertebrate families, benthic algae and cyanobacteria, fishes, and macrophytes as study organisms. Different models were run to assess the response of aquatic biota to temperature. In addition, threshold indicator taxa analysis (TITAN) was used to identify changes in macroinvertebrate taxa distributions along the thermal gradient.
3. We found that macroinvertebrate richness decreased at 24–25°C due to the different taxon-specific responses to temperature. Threshold indicator taxa analysis identified 17 temperature thresholds for each family of macroinvertebrates. Changes in macroinvertebrate community composition were significantly associated with changes in water temperature. Similarly, changes in macrophytes were associated with temperature differences, and high macrophyte richness was found at 19–20°C. Chlorophyll-a concentration of green algae and diatoms was higher at intermediate temperatures 20–22°C, macroinvertebrates density peaked at 27°C, and fish body size reduced linearly with temperature.
4. Temperature increase in the geothermal stream resulted in a reduction of aquatic diversity and primary and secondary producers by simplifying the community structure to a few warm-adapted taxa and reduced body size. These patterns differed from those obtained in temperate/arctic geothermal streams, but are similar to other studies at high-elevation. In a context of increasing warming, the ecological structure of high-elevation streams might lose cold-adapted taxa, and change to smaller populations. Additional studies based on ecosystem functioning of geothermal streams could lead to a better understanding on how warming affects high-elevation streams.

Abstract ID 501 | Date: 2022-09-12 17:47 – 17:49 | Type: Poster Presentation | Place: SOWI – Garden |

Fenoglio, Stefano; Bertolotti, Silvia; Bona, Francesca; Bonetta, Silvia; Falasco, Elisa; Macrì, Manuela; Marino, Anna; Minella, Marco

Stream ecosystems are particularly sensitive to climate change, because variations in precipitation, temperature, and evaporation directly alter river flow regimes. Higher water temperatures and the disruption of hydrologic cycles, further exacerbated by anthropogenic activities (e.g. dams, water abstraction, streambed alterations) can lead, in turn, to dramatic ecological impacts One of the least considered but potentially most dangerous aspects of climate change is the impact this can have on the river quality in relationship to the discharge of wastewater treatment plants. In Alpine environments, the variation in the ‘quantity’ of water is always considered as a problem while the ‘quality’ of water and its repercussions on aquatic environments and biodiversity is rarely taken into consideration. Wastewater treatment plants are essentially calibrated on two factors: the number of equivalent inhabitants and the flow of the receiving river body. While the first tends to keep constant over time, the second has been gradually reducing in the last decades. With the current decrease in flow rates, Alpine rivers are experiencing an increasing water shortage. To monitor how this reduction in flow rates affects the sustainable efficiency of the wastewater treatment plants in mountain areas, we organized a sampling campaign in three Alpine rivers of Piemonte (NW Italy): Pellice, Stura di Lanzo and Malone. On a monthly basis, starting from January 2022, samplings were carried out in upstream and downstream sections considering: a) biodiversity (density, structural and functional organization of benthic macroinvertebrate and diatom communities); b) chemical quality (concentration of the main nutrients and determination of the most important chemical parameters); 3) microbiological quality (bacterial indicators and pathogenic bacteria ). The results were then analyzed in the light of the hydrometric data of the various stations. In conclusion, this work has a considerable applicative importance in the sustainable water use perspective, because it underlined the problems related to the indiscriminate withdrawals of water from rivers. We can combine the need to protect biodiversity with the urge to preserve ecosystemic services and protect human health. This work has been realized thanks to the multidisciplinary approach of the SUSTNET (Sustainable Development and Cooperation) Doctoral School, which includes groups from UNITO that study the sustainable use of water resources from different aspects such as stream biodiversity, water chemistry, environmental microbiology and hygiene.

Abstract ID 897 | Date: 2022-09-12 17:49 – 17:51 | Type: Poster Presentation | Place: SOWI – Garden |

Llodrà-Llabrés, Joana; Pérez-Martínez, Carmen

Mediterranean mountain freshwater ecosystems are among the most sensitive ecosystems to global change due to the increased summer drought in the region. Long-term paleolimnological studies of bioindicators in sediment records from these ecosystems are used for climate reconstruction and may be useful for studying lake diversity over time as they are a cumulative record of the communities across the lake. A better understanding of Mediterranean mountain lake ecosystem responses to global change can strengthen our ability to forecast and mitigate its deleterious effects allowing the conservation of such fragile ecosystems. Hence, the main aim of this study is to study the diatoms and cladocera biodiversity dynamics in sediment from Sierra Nevada lakes (Granada, Spain).

Sierra Nevada Mountains contain around 50 alpine lakes of glacial origin at an elevation of 2800-3100 m a.s.l. They are shallow (maximum depth <10 m), small (surface area <1 ha), low primary production and well-mixed lakes. During the summer, the water level in most of them is reduced and some of them become completely dry.

Several samples were taken: a) sediment cores were retrieved from six lakes of Sierra Nevada, covering the last 150 years; b) one long core from Río Seco Lake covering 6000 years and c) superficial sediment samples from 17 lakes. The lakes were selected to better characterise the regional variation in lake and valley types. Samples were processed and were analysed for diatoms and cladocera. For each sample, a minimum of 300 valves were counted for diatoms and a minimum of 200 remains were counted for cladocera. Biodiversity was measured using different biodiversity indexes such as the Hill numbers. Biodiversity dynamics for each bioindicator was analysed in terms of differences in structure, composition and turnover rate over time (from the deep cores) and space (from the surface samples).

Previous published studies show that changes in diatoms and cladocera assemblages in Sierra Nevada lakes reveal a regional-scale response to climate change especially during the 20th century consistent with a warmer and drier climate in the region. However, this new approach may allow us to analyse its effect on biodiversity metrics.

This work is part of Smart EcoMountains, the Thematic Center on Mountain Ecosystems of LifeWatch-ERIC.

Abstract ID 822 | Date: 2022-09-12 17:51 – 17:53 | Type: Poster Presentation | Place: SOWI – Garden |

Esmaeili Ofogh, Ali Reza (1); Ebrahimi Dorche, Eisa (1); Consoli, Gabriele (2); Robinson, Christopher T. (2); Bruder, Andreas (3)

Worldwide, floods and droughts are occurring at an increasing rate due to climate change. The consequences of climate change are often exacerbated by flow regulation. These pressures further affect fluvial ecosystems, their biotic communities, and the ecosystem services they provide. Macroinvertebrate communities are an important element of a rivers’ biodiversity and govern many ecosystem functions and services. Changes in the natural flow regime due to climate change, in combination with anthropogenic pressures, have severe impacts on these communities. In spring 2019, mountain streams in the Karun River catchment, the largest river system of Iran, experienced three major waves of rain and floods within two weeks; i.e., a 1-in-100 years event. We will present how structural and functional characteristics of local macroinvertebrate communities responded to and recovered from these extreme floods. For this aim, we measured water quality parameters, physical habitat characteristics, and sampled macroinvertebrate communities in 53 sites before and after this flood event. We calculated functional community composition and functional diversity indices based on existing traits databases. Furthermore, we collected available high-resolution precipitation and discharge data covering the entire catchment, and calculated an index of flooding intensity, which revealed substantial differences for the different regions of the catchment. We combined functional and hydrologic data to identify patterns of macroinvertebrate communities response across a gradient of flood disturbance, to understand the mechanisms of resistance/resilience of macroinvertebrate community to such events. Our findings benefit our understanding of the impacts of extreme floods on benthic macroinvertebrate communities and their recovery in an understudied region.

Abstract ID 133 | Date: 2022-09-12 17:53 – 17:55 | Type: Poster Presentation | Place: SOWI – Garden |

Landmann, Armin

The pan-Alpine River network consists of more than 10.500 river units with a total length of about 57.000 km. However, only less than 5 % of the river network length of larger rivers have been assessed to still show a high ecological status. In particular, stretches of braided floodplains with high seasonal and year to year hydrological and morphological dynamics and their banks which are dominated by extensive gravel fields with sparse vegetation and are characterised by a high small-scale variability in soil structures, micro-topography and micro-climates are only scarcely preserved throughout the Alpine Arc.

For thousands of years such riverbanks have been keystone ecosystems in all parts of the Alps and served as refuge and hotspot for highly specialised, mainly semiaquatic or hygrophilous plants and animals. These habitats traditionally have also been refuges for xerophilic and geophilic grasshoppers. Overall, more than a dozen Caelifera species originally have been or still are typical for bare ground habitats along alpine rivers. However, most of these species also inhabit other habitats dominated by raw soils and even artificial environments like e. g. gravel pits. On the contrary, four highly specialised river dwelling Caelifera species, namely Tetrix tuerki, Epacromius tergestinus ponticus, Bryodemella tuberculata and Chorthippus pullus, in the Alps are more or less exclusively bound to dynamic habitats along wild rivers, and, accordingly, are listed in higher threat categories of the Red Lists of the countries which have a part in the Alpine Arc, and are even regarded as “Regionally Extinct” in some of them. In fact, all four species show decreasing population trends in the Alps, and most regional populations are severely fragmented and isolated and continue to decline due to habitat deteriorations caused by ongoing river regulation programs, hydropower use or gravel-mining. Conservation measures therefore are urgently needed to preserve the last remaining alpine populations of these species. The talk gives an overview about the current population and threat status of the species in the Alpine Arc and about conservation activities which have been implemented so far, and discusses their future conservations prospects.

Abstract ID 752 | Date: 2022-09-12 17:55 – 17:57 | Type: Poster Presentation | Place: SOWI – Garden |

Himmelsbach, Theresa; Baumgartner, Katharina; Jocham, Stefan; Aufleger, Markus

Alpine rivers are part of the life-supporting ecosystems in the world. Methods to quantify the ecological responses to hydro-morphological changes are the basis to evaluate the aquatic habitat situation. In order to capture the geometric situation in detail, strategies to extensively survey the riverbed, shorelines and parts of the inundated riverbanks are necessary. The continuous progress in remote sensing technologies enable river bathymetry surveys to a high degree of detail. Thereby, water-penetrating laser systems using the green region of the electromagnetic spectrum (wavelength = 532 nm) can provide valuable information. The laser scanners can be carried by aircrafts (Airborne Laser Bathymetry – ALB) to deliver large-scale high-resolution bathymetric survey data. Depending on the conditions, ALB-data achieve up to 20 – 40 survey points per square meter with accuracy in the range of 10 cm. Further developments in size and weight of the water-penetrating laser scanners, now even allow an unmanned aerial vehicle (UAV)-operated bathymetric survey. First results promise increased point densities and higher precision, however come with the drawback of lower spatial extension due to battery capacities.

The collected high-resolution bathymetric data builds the basis for multi-dimensional hydrodynamic-numerical and sediment transport models, which help to understand morphological processes and the related eco-hydraulic responses. Besides replicating status-quo of alpine waters to localize structural deficits, effects of restoration and renaturation measurements can also be pre-examined. The model output, such as flow variables, are used to identify and evaluate suitable habitat characteristics and aquatic living conditions.

The technology of Airborne Laser Bathymetry offers the opportunity to efficiently and repeatedly collect data of difficult to access alpine waters. As a result, the high-resolution survey data are able to form the basis for status-quo analysis and moreover, long-term monitoring of structural diversity and changes in aquatic environments. In order to create sustainable management solutions for stressed mountain aquatic ecosystems, high-resolution surveying data support identifying the drivers of eco-hydraulic changes in alpine waters.

Abstract ID 900 | Date: 2022-09-12 17:57 – 17:59 | Type: Poster Presentation | Place: SOWI – Garden |

Vila Duplá, María; Medina-Sánchez, Juan Manuel; Villar-Argáiz, Manuel; González-Olalla, Juan Manuel; Garrido Cañete, Guillermo; Fernández-Zambrano, Alejandra; Carrillo, Presentación

Frequency of dust deposition events has increased steadily in the Mediterranean region in the past few decades. While Saharan aerosols reduce transparency of freshwater systems, they are also important sources of macro- and micronutrients in oligotrophic high mountain lakes. Thus, the net effect of dust input on these systems is still unclear. To quantify the overall impact of dust as a global change driver, field mesocosm experiments were conducted in La Caldera, an oligotrophic high-mountain lake in the Spanish Sierra Nevada. Sampling design included setting up in-situ mesocosms with natural lake water and a gradient of five different dust concentrations in two-fold increases (0-320 mg/L). Mesocosms were replicated three times, and each contained 1000L of lake water extending down the water column. Samples were collected every week for two months (July 22-September 23, 2021). Physicochemical and biological factors such as light attenuation, nutrients, chlorophyll, and phytoplankton and bacterial abundances were measured. Overall, there was a direct correlation between Saharan dust concentration, inorganic nutrients and chlorophyll a. Chlorophyll a peaked after 1-2 weeks for all dust treatments, and reached five-fold higher concentration in the maximumdust-enriched treatment. There was a progressive delay in the response of chlorophyll a with increasing dust treatment. These results suggest there is a dust concentration threshold above which the beneficial effects of nutrient input overwhelm the damaging effects of shading by dust particles, resulting in an overall positive impact on the community.

This work is part of Smart EcoMountains, the Thematic Center on Mountain Ecosystems of LifeWatch-ERIC.

Abstract ID 555 | Date: 2022-09-12 17:59 – 18:01 | Type: Poster Presentation | Place: SOWI – Garden |

Vanek, Magdalena (1); Bottarin, Roberta (1); Hilpold, Andreas (1); Marsoner, Thomas (1); Tappeiner, Ulrike (1,2); Scotti, Alberto (1)

Freshwater ecosystems host a high biodiversity, which is crucial for the functioning of riverine systems and for the preservation of ecosystem services from a broader perspective. Especially running water habitats in mountainous regions face threats of ecological deterioration through changes in anthropogenic land use, habitat loss and degradation. In these environments, stream benthic macroinvertebrates are largely used as indicator organisms for assessments of riverine ecosystem health. However, as several studies have shown taxa richness and density of macroinvertebrates are highly dependent on physical environmental variables and substrates. Here, we summarize and discuss some results of the first sampling season of benthic macroinvertebrates within the project “Biodiversity Monitoring South Tyrol”. In 48 sites located across the Northern Italian province of South Tyrol, stream benthic macroinvertebrates and abiotic water parameters were collected and measured, and changes in macroinvertebrate assemblages and community structure across sites and among microhabitats were investigated. Higher abundances and taxa richness were found at lower elevations and in streams with high velocity and more natural streambed structure, whilst taxa richness and density of individuals were lower at higher elevations and on artificial surfaces. Overall, different substrates hosted distinct assemblages and therefore increased substrate diversity generally led to increased diversity of macroinvertebrate assemblages. We found that differing substrate availability at patch level is highly important for the distribution and composition of benthic macroinvertebrate assemblages in different types of mountainous streams. This could be an important aspect for assessing long-term biodiversity variations in monitoring programs, but also for potential actions dealing with ecological restoration.

Abstract ID 363 | Date: 2022-09-12 18:01 – 18:03 | Type: Poster Presentation | Place: SOWI – Garden |

Robinson, Christopher T. (1); Jolidon, Christa (2); Consoli, Gabriele (3); Peszek, Lukasz (4)

The Macun lakes form a high-alpine (>2,600 m asl) cirque landscape (3.6 km²) in the Swiss National Park, comprising 26 small lakes together with a number of temporary ponds. Streams interconnect the four largest lakes, forming the drainage network that flows into the Inn River at the town of Lavin. The drainage network of Macun consists of a north and a south basin that overlie an ortho-gneiss, meta-granitoid bedrock. The south basin is influenced by various rock glaciers. The physico-chemistry and diatoms of surface waters at 10 sites has been monitored annually in mid-summer since 2001. Around 350 species of diatoms were identified. Results showed clear diatom and physico-chemical differences between the two basins. Diatoms also demonstrated a lake order effect but no notable differences between lake inlets and outlets. Nitrogen values were two-fold higher and particulate phosphorus values two-fold lower in the south basin than in the north basin. Over time, the physico-chemistry in the two basins became more homogeneous, with a reduction in rock-glacial inputs in the south basin and an overall decrease in nitrogen in the catchment. Continuous temperature records showed north basin streams to be ca. 3°C warmer than south-basin streams, but with high inter-annual variation that reflected annual differences in weather and no evidence of a general change over time (increase or decrease). The results highlight the importance of long-term monitoring for understanding ecosystem state changes in alpine freshwaters, especially during periods of rapid environmental change.