Hyporheic zone and resilience in intermittent mountain streams

In Northern Italy, alpine and perialpine streams are facing an intensification in magnitude, frequency and timing of droughts due to the combined effects of global and local pressures. These aquatic ecosystems are changing from perennial to intermittent systems with possible but still largely unknown detrimental ecological effects. In this context, a great attention has been paid on the response of stream invertebrates because of their importance in terms of biomass, diversity, and functionality. We investigated the impacts of droughts in low order systems that have recently become intermittent in the Po River watershed (NW Italy), focusing on the biotic exchange between the benthic and hyporheic habitats occurring over different time scales. A first site was selected the headwaters of the Po River (Piedmont) with two stations (one perennial, one intermittent) with piezometers installed in the riverbed, instrumented with temperature and pressure dataloggers, where we monitored two supraseasonal droughts over a period of two years (2017-2019) over a large time scale (sampling conducted approximately monthly during. A second site was chosen in the Po Valley, where during a drought event in summer 2018we monitored at short-time intervals (3-4 days) three Apenninic tributaries of the Po River with a gradient of intermittence. The composition, abundance, functional groups of meio- and macro-invertebrates collected in the hyporheic habitat showed which faunistic components used of the hyporheic zone as a refuge from drought, and its role to increase the resilience/resistance of the aquatic system. In general, we observed a loss of taxa susceptible to drying rather than a replacement of perennial-flow specialists with intermittent-flow specialists along flow intermittence gradients. This work was realized within the framework of the Project of national interest (PRIN) NOACQUA Risposte di comuNità e processi ecOsistemici in corsi d'ACQUA soggetti o intermittenza idrologica"--codice 2O1572HW8F, funded by the Italian Ministry of Education, University and Research.

Anticonvulsant and antiarrhythmic effects of nifedipine in rats prone to audiogenic seizures

Calcium ion participates in the regulation of neural transmission and the presynaptic release of neurotransmitters. It is also involved in epileptic events, cardiac arrhythmias and abnormal conduction of stimuli. The purpose of the present study was to evaluate the effects of nifedipine, a calcium channel blocker, on epileptic seizures and on reperfusion arrhythmias in rats prone to audiogenic epileptic seizures (Wistar audiogenic rats, WAR) and in normal Wistar rats (N = 6/group). The seizure severity index was applied after an intraperitoneal injection of 20 or 40 mg/kg nifedipine (N20 and N40 groups, respectively). The Langendorff technique was used to analyze cardiac function, as well as the incidence and severity of the reperfusion arrhythmias after ligature and release of the left coronary artery in rats treated or not with nifedipine. We found that nifedipine treatment decreased seizure severity (0.94 ± 0.02 for WAR; 0.70 ± 0.10 for WAR + N20; 0.47 ± 0.08 for WAR + N40) and increased the latent period (13 ± 2 s for WAR; 35 ± 10 s for WAR + N20; 48 ± 7 s for WAR + N40) for the development of seizures in WAR. Furthermore, the incidence and severity of the reperfusion arrhythmias were lower in WAR and normal Wistar rats injected with nifedipine. In WAR, these effects were mediated, at least in part, by a decrease in heart rate. Thus, our results indicate that nifedipine may be considered to be a potential adjuvant drug for epilepsy treatment, especially in those cases associated with cardiac rhythm abnormalities

Effects of intermittence on Alpine streams ecosystems: hyporheic zone and resilience

Over the last few years, a significant portion of rivers in Northern Italy have been progressively shifting from naturally perennial to intermittent systems, with prolonged dry phases occurring in summer and also in winter . However, the aquatic communities of Alpine rivers lack strategies and adaptations to survive such hydrological and physico-chemical changes. Aim of this study is to explore the impact of intermittence in previously-perennial Alpine stream reaches, considering biodiversity, taxonomic and functional aspects. In detail, we aimed to assess the role of the hyporheic zone in increasing the resilience of these aquatic systems to drought. The hyporheic habitat was monitored in 2017 in two sites (one perennial and one intermittent) in the upper course of the Po River (Val Po, Cuneo province) with piezometers installed in the riverbed, reaching -1 m (both sites) and -3 m depth (intermittent site). Sampling was conducted from July to March 2018 at short time intervals to follow the strongest drought recorded in the area from the 1800s. Sampling was resumed at both stations in January 2018 following the onset of winter precipitations, and conducted at short time intervals during the rewetting phase, and monthly after both stations were permanently submersed. Relative and total abundances of hyporheic and benthic invertebrates changed differently in the two stations during the different phases of the hydrological cycle, suggesting that the hyporheic and benthic communities respond quickly to the onset of the drought. As expected, where water is permanent, the hyporheic communities are abundant; conversely, increasingly harshness (i.e, reduction of the water table) affects hyporheic communities and increases the use of the hyporheic habitat as a refuge by benthic taxa

Effetti dell'intermittenza sugli ecosistemi dei flussi alpini: zona iporeica e resilienza

Nel corso degli ultimi anni, parte dei fiumi dell'Italia settentrionale si stanno progressivamente trasformando da sistemi naturalmente perenni a intermittenti, principalmente a causa del cambiamento climatico globale (ad esempio, diminuzione delle precipitazioni e ritiro glaciale, con conseguente alterazione dei cicli idrologici) e impatti umani (produzione idroelettrica, prelievo ad uso irrigui, ecc.). Si verificano quindi fasi di magra e di secca prolungate, soprattutto in estate, ma le comunità acquatiche dei fiumi alpini mancano di strategie e adattamenti per sopravvivere a tali cambiamenti idrologici e fisico-chimici, mentre al contrario, le comunità di corsi d’acqua naturalmente intermittenti mostrano alta resistenza e forte resilienza alle siccità stagionali. Esistono pochissime conoscenze sulle risposte biotiche alla siccità in corsi alpini precedentemente perenni. La zona iporeica (ZI) è un'area di biodiversità intermedia tra l'acqua superficiale del torrente e le acque sotterranee, e il suo ruolo di rifugio per gli invertebrati di superficie è stato ben documentato (Brunke and Gonser 1997). Dopo che il disturbo è passato, gli organismi possono ricolonizzare gli habitat bentonici e la ZI può servire a migliorare la resilianza della comunità bentonica al disturbo e influenzare il recupero del fiume in seguito a perturbazioni (Krause et al., 2011). Lo scambio faunistico tra gli habitat iporreico e bentonico è determinato dalla biologia dei diversi taxa (ad esempio, cicli vitali che richiedono una fase iporreica, interazioni biotiche quali competizione e predazione), dagli scambi idrologici e dalla disponibilità di habitat iporreico (es. , lo spazio interstiziale tra le particelle di sedimento) (Dole Olivier and Marmonier 1992). La connettività verticale contribuisce quindi in modo significativo alla biodiversità complessiva dei fiumi assolvendo pe rla fauna bentonica al ruolo di : (i) corridoio migratorio verso monte e fonte di colonizzazione di habitat bentonici, (ii) zona di alimenazione, (iii) area di rifugio ( da aumenti e diminuzione di portata, condizioni ambeintali avverse, predazioen da parte della fauna ittica), (iv) nursery in alcune fasi del ciclo vitale di organismi bentonici(uova, giovani larve ma anche pupe mature di insetti con una fase epigea obbligatoria). Le azioni di riqualificazione fluviale dovrebbero quindi includere il ripristino dei collegamenti verticali tra il fiume e le sue falde acquifere poco profonde, e studi che forniscono approfondimenti sui meccanismi che controllano le biocenosi di invertebrati iporeici sono rilevanti per valutare le opzioni di gestione (Boulton, 2006). Pertanto, lo scopo di questo studio è quello di esplorare l'impatto dell'intermittenza in portate del flusso alpino precedentemente perenne, considerando la biodiversità, gli aspetti tassonomici e funzionali. In dettaglio, abbiamo mirato a valutare il ruolo della zona iporeica nell'aumentare la relienza di questi sistemi acquatici a eventi di secca soprastagionali

Global climate change and local factors cause hydrological intermittence in Alpine rivers: what are the impacts on biological communities?

Alpine rivers are considered especially sensitive to climate change effects, because of their sensitivity to hydrological/thermal alterations and their specialised biological communities. In particular, a dramatic but almost neglected aspect of this problem is that Alpine rivers, naturally perennial, have been affected over the last decades by a conspicuous increase in frequency and intensity of droughts. We present here the results of the first sampling year of the PRIN NOACQUA project. In 15 alpine rivers, we have identified a ‘perennial’ reach (called M) that permanently maintains the surface running water and an ‘intermittent’ section (called V), where surface water disappears. In these stations, we investigated the benthic communities (diatoms and macroinvertebrates), allochthonous and autochthonous energy inputs and other environmental parameters. We report here only preliminary results for the benthic macroinvertebrate community analyses. Results of statistical models showed that intermittent reaches are functionally different and characterized by significant lower values of taxonomic richness compared to perennial sites and this is mainly due to the depletion of the most sensitive taxa (EPT taxa), indicating a homogenizing effect on benthic communities. Improving our knowledge on the possible evolution of Alpine lotic ecosystems is crucial, because these environments will be subject to an increasing human pressure under the current climatic scenario

Reduced hippocampal GABAergic function in Wistar audiogenic rats

Epilepsy is a neurological disorder associated with excitatory and inhibitory imbalance within the underlying neural network. This study evaluated inhibitory γ-amino-butyric acid (GABA)ergic modulation in the CA1 region of the hippocampus of male Wistar rats and Wistar audiogenic rats (aged 90 ± 3 days), a strain of inbred animals susceptible to audiogenic seizures. Field excitatory postsynaptic potentials and population spike complexes in response to Schaffer collateral fiber stimulation were recorded in hippocampal slices before and during application of picrotoxin (50 µM, 60 min), a GABA A antagonist, and the size of the population spike was quantified by measuring its amplitude and slope. In control audiogenic-resistant Wistar rats (N = 9), picrotoxin significantly increased both the amplitude of the population spike by 51 ± 19% and its maximum slope by 73 ± 21%. In contrast, in slices from Wistar audiogenic rats (N = 6), picrotoxin caused no statistically significant change in population spike amplitude (33 ± 46%) or slope (11 ± 29%). Data are reported as means ± SEM. This result indicates a functional reduction of GABAergic neurotransmission in hippocampal slices from Wistar audiogenic rats

Artificial streams for studying the resilience of benthic assemblages to drought: a case study from Fersina river basin (Trento, NE Italy)

The hydrological alteration of flow regime due to the combined effects of global warming and increased water abstraction represents nowadays one of the major threats to streams and rivers. Many lotic ecosystems, especially in alpine areas, are shifting from perennial to intermittent, due to the increased frequency and intensity of drought events. As a consequence, negative effects are expected on the benthic communities, which degree of resilience depends on the species-specific adaptations and the availability of in-stream refugia (for example, persistent pools). Despite the scientific relevance of this topic, accurate field studies involve several logistic and theoretical difficulties for freshwater ecologists. As pointed out by many authors, in order to provide generalizable results, future research on these topics should include a more quantitative approach. However, this is very difficult to achieve, because droughts are usually unpredictable, and also several confounding factors can interfere with the assessment of the sampling design. In this context, the use of artificial streams may represent a remarkable tool to study this type of disturbance. In fact, they allow to simulate and replicate drought events, varying their duration and extent in a manipulative and experimental way. In this study, the post-drought recovery pattern of benthic communities (both macroinvertebrates and diatoms) was investigated for three weeks after a 5-day drought, in relation to the presence of instream refugia (i.e. remaining pools). The innovative aspect of the research was the experimental setting, represented by four artificial streams (20 m long, 30 cm wide and 30 cm deep) directly fed by a second-order, pristine alpine stream (Fersina, Trento, NE Italy). This poster illustrates the preliminary results of this stud

Role of the hyporheic zone in mountain streams progressively shifting from naturally perennial to intermittent systems

Aim of this study is to explore the impact of intermittence in previously-perennial Alpine stream reaches, where the aquatic communities lack strategies and adaptations to survive the hydrological and physico-chemical changes caused by droughts. We investigated specifically the role of the hyporheic zone in increasing the resilience of these aquatic systems to drought. A first site was selected the headwaters of the Po River (NW Italy) with two stations (one perennial, one intermittent) with piezometers installed in the riverbed, instrumented with temperature and pressure dataloggers, where we monitored two supraseasonal droughts over a period of two years. A second site was chosen in the Po Plain (N Italy), where we monitored three tributaries with a gradient of intermittence at short-time intervals (3 days) during a drought event in summer 2018. We collected hyporheic fauna with a Bou-Rouch pump, used hyporheic meio- and macro-invertebrate composition, abundance, functional groups to assess the use of the hyporheic zone as a refuge from drought. The hyporheic and benthic communities responded quickly to the onset of the drought; as expected, where water is permanent, the hyporheic communities are abundant; conversely, increasingly harshness (i.e, reduction of the water table) affects hyporheic communities and increases the use of the hyporheic habitat as a refuge by benthic taxa. This research was conducted within the framework of the project PRIN NOACQUA “Risposte di comuNità e processi ecOsistemici in corsi d'ACQUA soggetti o intermittenza idrologico” – code 2O1572HW8F_003, funded by the Italian Ministry of Education, University and Research