Impacts of low-head hydropower plants on cyprinid-dominated fish assemblages in Lithuanian rivers

The meso-scale habitat simulation model MesoHABSIM was applied in three Lithuanian lowland rivers to study the effect of low-head hydropower plants (HPPs) on the fish habitats. Stream flow time series on a daily scale for the period 1970–2015 were used to describe flow regime downstream of HPPs for periods before and after their installation. Conditional habitat suitability criteria were developed for 4 species of cyprinid fish, schneider (Alburnoides bipunctatus), dace (Leuciscus leuciscus), roach (Rutilus rutilus) and vimba (Vimba vimba) to simulate their available habitat at different water discharges. Modelling results showed that HPPs have a significant impact on habitat availability in the low flow period in dry years below HPPs due to insufficient released flow. The environmental flow, as prescribed by the Lithuanian national law, is estimated between 80 and 95% exceedance probability of the mean minimum discharge of 30 days. This flow leads to a significant reduction in frequency and duration of available suitable habitats for vimba and schneider during low flow period. The roach habitat is the least affected. The results of habitat modelling are in line with the actual data on the occurrence and relative abundance of considered fish species in the studied river stretches. A general comparison of the relative abundance of modelled fish species in 42 natural river stretches and 20 stretches below the HPPs also showed that the relative abundance of roach is significantly higher, and that of schneider is significantly lower in river sections below the HPPs than the abundance in natural river sections. All results indicate that the current environmental flow does not secure survival of certain fish species. The applicability of the average low flow release during summer could be a plausible alternative to the current environmental flow in order to maintain ecosystem health and services

Ecological notes on an endemic freshwater lamprey, Lampetra zanandreai (Vladykov, 1955)

Lampetra zanandreai (Vladykov, 1955) is a non-parasitic, freshwater lamprey endemic to the ancient Po basin. A few, mostly very dated studies have investigated some aspect of the biology of this lamprey, but surprisingly, despite it being considered a threatened species, information on its ecology is practically absent. Specifically, information about habitat preferences is generic and qualitative. Since most of the life cycle is spent in the fossorial larval stage, which is also the only one in which organisms feed, information about ecological requirements of ammocoetes is essential for any conservation strategy. In this study we provide the first data about physical habitat preferences for lamprey ammocoetes by analyzing their presence within sampled hydromorphological units (HMUs), following the approach of habitat attribute description of the MesoHABSIM (MesoHABitat SImulation Model) methodology. To explore the relationship between lamprey presence and HMU characteristics, a random forest (RF) model was developed and tested using data collected in five stream reaches of the Po basin (NW Italy). The final parsimonious RF model performed well in terms of accuracy (95.2%) and true skill statistic (90.4%), allowing us to identify the most significant mesohabitat attributes for the considered species. Furthermore, in the Ghiandone River, where the highest density and number of individuals were found, a granulometric analysis of the riverbed material was carried out. Results showed that selected strains of sand and fine gravel, with low organic content, are preferred by ammocoetes. To our knowledge, this is the first study exploring the habitat preference of this endangered species, listed in Annex II of the European Habitats Directive

The combined impact of hydropower plants and climate change on river runoff and fish habitats in lowland watersheds

Aquatic ecosystems are particularly vulnerable to anthropogenic activity and climate change. The changes in flow regimes in Lithuanian lowland rivers due to the operation of hydropower plants (HPPs) and the impact of altered flow on some fish species have already been studied. The impact of climate change on future natural river runoff and the structure of fish assemblages was also investigated. However, it is still unknown how the combined effect of climate change and flow regulation related to hydropower generation may affect fish assemblages in the downstream river reaches below the Lithuanian HPPs. In this study, the physical habitat modelling system MesoHABSIM was used to simulate spatial and temporal changes in aquatic habitats availability for different fish species under the influence of HPP at different climate change scenarios. Changes in the available habitat were assessed for common fish species in four HPP-affected rivers representing different hydrological regions of Lithuania. The modelling results showed that the operation of HPP under climate change conditions in most rivers could be beneficial for small benthic fish species such as gudgeon Gobio gobio and stone loach Barbatula barbatula. Meanwhile, for larger fish species (e.g., chub Squalius cephalus and vimba Vimba vimba) the alteration in the temporal availability of suitable habitat was relatively higher

Vortical Patterns in the Wake of an Oscillating Airfoil

The vortical flow patterns in the wake of a NACA 0012 airfoil pitching at small amplitudes are studied in a low speed water channel. it is shown that a great deal of control can be exercised on the structure of the wake by the control of the frequency, amplitude and also the shape of the oscillation waveform. An important observation in this study has been the existence of an axial flow along the cores of the wake vortices. Estimates of the magnitude of the axial flow suggest a linear dependence on the oscillation frequency and amplitude

Managing floodplains using nature-based solutions to support multiple ecosystem functions and services

Floodplains include unique environments shaped over a long time horizon along rivers and smaller streams and formed by alluvial sediments. As floodplains are flat, often with highly fertile and well-accessible land, they have become the intrinsic focus of human society—while providing a variety of goods and ecosystem services. Intensive land use of floodplains is degrading their natural values and significantly reducing their ecosystem functions and services. A significant part of these key services is related with the ability of floodplains to retain water and nutrients, which can be understood as a flood control and a water-retention function. Although these ecosystems serve a number of other basic functions, the importance of floodplains as a place for water retention during extreme discharges caused by intense rainfall or snowmelt and the supply of water in times of drought are essential under conditions of global change. In order to increase the ability of floodplains to perform these functions, it is increasingly required to preserve the connectivity of rivers with surrounding floodplains and adapt human activities to maintain and restore river ecosystems. This article reviews the recent understanding of floodplain delineation, the most common causes of disturbance, the ecosystem functions being performed, discussing in turn the measures being considered to mitigate the frequency and magnitude of hydrologic extremes resulting from ongoing environmental changes. This article is categorized under: Water and Life > Conservation, Management, and Awareness Engineering Water > Planning Water

Intestinal anti-inflammatory effects of RGD-functionalized silk fibroin nanoparticles in trinitrobenzenesulfonic acid-induced experimental colitis in rats

Background: Current treatment of inflammatory bowel disease is based on the use of immunosuppressants or anti-inflammatory drugs, which are characterized by important side effects that can limit their use. Previous research has been performed by administering these drugs as nanoparticles that target the ulcerated intestinal regions and increase their bioavailability. It has been reported that silk fibroin can act as a drug carrier and shows anti-inflammatory properties. Purpose: This study was designed to enhance the interaction of the silk fibroin nanoparticles (SFNs) with the injured intestinal tissue by functionalizing them with the peptide motif RGD (arginine–glycine–aspartic acid) and to evaluate the intestinal anti-inflammatory properties of these RGD-functionalized silk fibroin nanoparticles (RGD-SFNs) in the trinitrobenzenesulfonic acid (TNBS) model of rat colitis. Materials and methods: SFNs were prepared by nanoprecipitation in methanol, and the linear RGD peptide was linked to SFNs using glutaraldehyde as the crosslinker. The SFNs (1 mg/rat) and RGD-SFNs (1 mg/rat) were administered intrarectally to TNBS-induced colitic rats for 7 days. Results: The SFN treatments ameliorated the colonic damage, reduced neutrophil infiltration, and improved the compromised oxidative status of the colon. However, only the rats treated with RGD-SFNs showed a significant reduction in the expression of different pro-inflammatory cytokines (interleukin IL]-1ß, IL-6, and IL-12) and inducible nitric oxide synthase in comparison with the TNBS control group. Moreover, the expression of both cytokine-induced neutrophil chemoattractant-1 and monocyte chemotactic protein-1 was significantly diminished by the RGD-SFN treatment. However, both treatments improved the intestinal wall integrity by increasing the gene expression of some of its markers (trefoil factor-3 and mucins). Conclusion: SFNs displayed intestinal anti-inflammatory properties in the TNBS model of colitis in rats, which were improved by functionalization with the RGD peptide

River ecosystem conceptual models and non‐perennial rivers: A critical review

Conceptual models underpin river ecosystem research. However, current models focus on continuously flowing rivers and few explicitly address characteristics such as flow cessation and drying. The applicability of existing conceptual models to nonperennial rivers that cease to flow (intermittent rivers and ephemeral streams, IRES) has not been evaluated. We reviewed 18 models, finding that they collectively describe main drivers of biogeochemical and ecological patterns and processes longitudinally (upstream-downstream), laterally (channel-riparian-floodplain), vertically (surface water-groundwater), and temporally across local and landscape scales. However, perennial rivers are longitudinally continuous while IRES are longitudinally discontinuous. Whereas perennial rivers have bidirectional lateral connections between aquatic and terrestrial ecosystems, in IRES, this connection is unidirectional for much of the time, from terrestrial-to-aquatic only. Vertical connectivity between surface and subsurface water occurs bidirectionally and is temporally consistent in perennial rivers. However, in IRES, this exchange is temporally variable, and can become unidirectional during drying or rewetting phases. Finally, drying adds another dimension of flow variation to be considered across temporal and spatial scales in IRES, much as flooding is considered as a temporally and spatially dynamic process in perennial rivers. Here, we focus on ways in which existing models could be modified to accommodate drying as a fundamental process that can alter these patterns and processes across spatial and temporal dimensions in streams. This perspective is needed to support river science and management in our era of rapid global change, including increasing duration, frequency, and occurrence of drying.info:eu-repo/semantics/publishedVersio

Immunomodulatory tetracyclines ameliorate DNBS-colitis : impact on microRNA expression and microbiota composition

Objective: The use of immunomodulatory antibiotics to simultaneously target different factors involved in intestinal inflammatory conditions is an interesting but understudied pharmacological strategy. A great therapeutic potential has been obtained with minocycline and doxycycline in experimental colitis. Therefore, understanding the contribution of the different activities of immunomodulatory tetracyclines is crucial for the improvement and translation of their use into clinic. Design: A comparative pharmacological study including tetracyclines and other antibiotic or immunomodulatory drugs was performed in 2,4-dinitrobenzene sulfonic acid (DNBS)-induced colitis in mice. The correlation between the therapeutic efficacy of each drug and changes in the gut microbiota composition, markers of barrier integrity, inflammatory mediators, microRNAs and TLRs was analysed to identify the main mechanisms of action. Results: Tetracyclines counteracted most of the markers found altered in DNBS-colitis, which differed from effects of corticosteroid treatment. Of note, administration of tetracyclines led to increased mucosal protection, associated with up-regulated expression of CCL2, miR-142 and miR-375. All drugs with antibiotic activity ameliorated the progression of inflammation and reduced neutrophil-related genes, such as miR-223, despite their effects were not associated with restored intestinal dysbiosis. However, reduced bacterial richness was correlated with increased expression of TLR2 and TLR9 in antibiotic-treated groups and TLR6 was also up-regulated by the immunomodulatory tetracyclines with higher efficacy (doxycycline, minocycline and tigecycline). Conclusion: The anti-inflammatory effect of tetracyclines involves specific modifications in TLR and microRNA expression leading to an improved microbial-derived signalling and mucosal protection. These results support the potential of immunomodulatory tetracyclines to prevent inflammation-associated tissue damage in acute intestinal inflammation