Physical habitat modeling for river macroinvertebrate communities

Habitat models rarely consider macroinvertebrate communities as ecological targets in rivers. Available approaches mainly focus on single macroinvertebrate species, not addressing the ecological needs and functionality of the whole community. This research aimed at providing an approach to model the habitat of the macroinvertebrate communities. The study was carried out in three rivers, located in Italy and characterized by a braiding morphology, gravel riverbeds, and low flows during the summer period. The approach is based on the recently developed Flow-T index, together with a Random Forest (RF) regression, which is employed to apply the Flow-T index at the mesohabitat scale. Using different datasets gathered from field data collection and 2D hydrodynamic simulations, the model was calibrated in the Trebbia River (2019 field campaign) and validated in the Trebbia, Taro, and Enza rivers (2020 field campaign). The RF model selected 12 mesohabitat descriptors as important for the macroinvertebrate community. These descriptors belong to different frequency classes of water depth, flow velocity, substrate grain size, and connectivity to the main river channel. The cross-validation R2 coefficient (R2cv) of the training dataset was 0.71, whereas the R2 coefficient (R2test) for the validation dataset was 0.63. The agreement between the simulated results and the experimental data shows sufficient accuracy and reliability. The outcomes of the study reveal that the model can identify the ecological response of the macroinvertebrate community to possible flow regime alterations and river morphological modifications. Lastly, the proposed approach allowed to extend the MesoHABSIM methodology, widely used for the fish habitat assessment, to a different ecological target community. Further applications of the approach can be related to ecological flows design in both perennial and non-perennial rivers, including river reaches in which fish fauna is absent

Habitat Preferences of Italian Freshwater Fish: A Systematic Review of Data Availability for Applications of the MesoHABSIM Model

The MesoHABitat SImulation Model (MesoHABSIM) is the preferred method to calculate spatio-temporal variation in the fish habitat availability in Italian rivers. With the aim of improving the applicability of the MesoHABSIM approach in the Italian territory, we carried out a systematic review of physical habitat preferences for 31 freshwater fish species and three freshwater lampreys, representing 75% of the total indigenous freshwater fish community of Italy. Information related to suitable ranges of depth, flow velocity, biotic/abiotic substrates, covers/shelters was collected and summarized for two critical life stages (adult and juvenile) and two bioperiods (rearing/growth and spawning). Overall, 250 publications were reviewed, classified as 206 peer-reviewed papers, 20 books, 7 PhD thesis, and 17 grey literature sources. Our analysis revealed substantial deficits of information about habitat requirements for more than 30% of Italian freshwater fish species. This information is particularly scarce for the most threatened endemic species, especially for their most critical bioperiod (i.e., spawning). With the aim of preserving freshwater fish biodiversity as required in the EU Biodiversity Strategy for 2030 (European Commission, 2020), accurate information on physical habitat requirements for spawning is crucial. As an example application of MesoHABSIM, the collected habitat preference information was used to define and apply mesohabitat suitability criteria for one fish species (Telestes muticellus) in a regulated river reach of Argentina Creek (Province of Imperia, Italy). This analysis demonstrates the potential for applying information from the current review to other fish species

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

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

Asymmetric effects of a modelled tidal turbine on the flow and seabed

The extraction of power from the flow of water has become an important potential source of clean energy. In spite of significant interest in the interaction between energy extraction devices and water currents, comparatively little work has focused on flow asymmetry. Indeed, unusual wake behaviour and limits of turbine array efficiency have typically been attributed to boundary effects rather than the particular turbine geometry. The aim of the present study was to reveal the asymmetries in the hydrodynamic wake and the interactions with the sediment bed due to the presence of a hydrokinetic turbine. We combined: (i) computational fluid dynamics simulations; (ii) optical flow measurements from a series of flume experiments above a fixed rough bed; and (iii) acoustic measurements from a further series of flume experiments above a mobile sand bed. Results showed flow asymmetry due to the presence of the rotor which appeared to be related to the development of the wake and potentially to the gyre of the blades. Suspended sediments in the flume also exhibited asymmetrical characteristics due to the flow asymmetry. This imbalance in the flow field and sediment transport may decrease energy extraction efficiency in turbine arrays and also could have important environmental consequences

An ecosystem service approach to license new run of the river hydropower plants

Freshwater ecosystems provide several services (ES) to society. Hydropower production is one of the most relevant ES supported by Alpine rivers, and it is often in conflict with other river uses and services. Recently, the demand by local authorities, public or private agencies for new small hydropower plants have been increasing, and new conflicts have been arousing. We propose an approach to model the alterations of selected ES which integrates hydrological and habitat models and evaluates possible variations of the selected ES under different withdrawal scenarios. The case-study is the Noce River, a gravel-bed river in the Italian Alps (Trentino, North East Italy) which is subject to hydropeaking. We selected four ES: habitat for juvenile and adult marble trout as biodiversity proxy, rafting as recreational services, and small hydropower production as provisioning service. We evaluated the variations of these services for maximum and no hydropower production, chosen as different boundary conditions. Moreover, we simulated the presence of four new different small hydropower plants with increasing withdrawals. Large hydropower is the key driver, affecting all the selected ES. Small hydropower decreases the potential for rafting up to 64%, while it is often negligible for other services

Random forests to evaluate interspecific interactions in fish distribution models

[EN] Previous research indicated that high predictive performance in species distribution modelling can be obtained by combining both biotic and abiotic habitat variables. However, models developed for fish often only address physical habitat characteristics, thus omitting potentially important biotic factors. Therefore, we assessed the impact of biotic variables on fish habitat preferences in four selected stretches of the upper Cabriel River (E Spain). The occurrence of Squalius pyrenaicus and Luciobarbus guiraonis was related to environmental variables describing biotic interactions (inferred by relationships among fish abundances) and channel hydro-morphological characteristics. Random Forests (RF) models were trained and then validated using independent datasets. To build RF models, the conditional variable importance was used together with the model improvement ratio technique. The procedure showed effectiveness in identifying a parsimonious set of not correlated variables, which minimize noise and improve model performance in both training and validation phases. Water depth, channel width, fine substrate and water-surface gradient were selected as most important habitat variables for both fish. Results showed clear habitat overlapping between fish species and suggest that competition is not a strong factor in the study area.This research has been developed in the framework of the HolRiverMed project (FP7-PEOPLE-2010-275577, Marie Curie Actions, Intra-European Fellowships) and the SCARCE project (Assessing and predicting effects on water quantity and quality in Iberian rivers caused by global change, Consolider-Ingenio 2010 CSD2009-00065). Data collection was partially funded by the Spanish Ministry of Environment, Rural and Marine Affairs, the Jucar River Basin District Authority and the Spanish Ministry of Education and Science (POTECOL, CGL2007-66412). We thank Juan Diego Alacaraz-Hernandez, Matias Peredo-Parada and Aina Hernandez-Mascarell for their help with field work and suggestions on data analysis.Vezza, P.; Muñoz Mas, R.; Martinez-Capel, F.; Mouton, A. (2015). Random forests to evaluate interspecific interactions in fish distribution models. Environmental Modelling and Software. 67:173-183. https://doi.org/10.1016/j.envsoft.2015.01.005S1731836