Effects of high-altitude reservoirs on the structure and function of lotic ecosystems: a case study in Italy

Antonio Petruzziello,Luca Bonacina,Riccardo Fornaroli,Francesca Marazzi,Valeria Mezzanotte,Silvia Zaupa

doi:10.1007/s10750-020-04510-9

Antonio Petruzziello, Luca Bonacina + Show 4 more

Open Access

https://doi.org/10.1007/s10750-020-04510-9

Copy DOI

Abstract

Alpine and pre-alpine lotic ecosystems are often remote and not affected by humans, which makes them some of the world’s most pristine ecosystems. However, their status is often altered by the presence of reservoirs that are built to fulfill agricultural needs and hydroelectric demands. These reservoirs also disrupt stream continuity and alter the magnitude, timing, and frequency of natural flows. The present work assessed how high-altitude reservoirs affect the riverine ecosystems focusing on the following: (i) the macroinvertebrate communities, (ii) the breakdown of organic matter, and (iii) the thermal regime. Stretches altered by high-altitude reservoirs had the best conditions for most macroinvertebrate families due to a more stable flow conditions. The breakdown rate of coarse particulate organic matter was not affected by high-altitude reservoirs but its availability was higher in altered compared to pristine stretches. The presence of hydroelectric power plants modified the stream thermal regime. Reservoirs mitigate the atmospheric influence on stream water temperature while run of the river plants strengthen it in the diverted stretches. Where both these alterations were present, the thermal regime of the stream was more similar to the natural ones compared to stretches subjected to only one kind of alteration. This research showed how river impoundment alters the structure of macroinvertebrate communities and the function of the downstream lotic ecosystems and can provide the basis to correctly guide management strategies for lotic ecosystems affected by hydrological alterations.

Highlights

Alpine and pre-alpine lotic ecosystems are often remote and not affected by human presence and activities, which makes them some of the world’s most pristine ecosystems (Fureder et al, 2002; Hotaling et al, 2017)
It is well known that reservoirs disrupt the river continuity and produce hydrological alterations which can be defined as any anthropogenic disruption in the magnitude, timing, and frequency of natural flows (Zolezzi et al, 2009; Bocchiola, 2014)
In July, we placed in the riverbeds a total of 126 leaf bags following this scheme: in all the sites, we identified three habitats and in each of them, we placed 3 pairs of leaf bags (3 with coarse mesh ? 3 with fine mesh) for a total of 18 bags per site (Table 2)

Summary

Introduction

Alpine and pre-alpine lotic ecosystems are often remote and not affected by human presence and activities, which makes them some of the world’s most pristine ecosystems (Fureder et al, 2002; Hotaling et al, 2017). Global warming is pushing them upslope toward mountaintops and shrinking their habitat (McGregor et al, 1995; Brown et al, 2007) Considering their importance and vulnerability, studying and protecting alpine lotic ecosystems is a priority. Sediment accumulates in the slow moving water of the reservoir, while the water released downstream has low concentrations of suspended solids (Anselmetti et al, 2007) This modification of the sediment cycling in the river leads to major erosion downstream. As an example, Wiejaczka et al (2018) found that the presence of the CzorsztynSromowce Wyz_ne reservoir complex (Poland) decreased river water temperature in summer, winter, and spring (by 6.9, 0.7, and 7.9°C, respectively), whereas in autumn, it had an opposite effect, raising it by 7.9°C

Methods

Results

Discussion

Conclusion