Small mountain reservoirs in the Alps: New habitats for alpine freshwater biodiversity?

Abstract

1. Today, aquatic biodiversity suffers from many pressures linked to human activities, including climate change, which particularly affects alpine areas. Many alpine freshwater species have shifted their geographical distribution to colder areas, but a reduced availability of suitable habitats is also forecasted. New artificial water bodies could provide habitat enhancement opportunities, including small mountain reservoirs built to overcome a lack of snow during winter.2. To investigate the role of reservoirs as a habitat for freshwater invertebrates, a case study was conducted on eight reservoirs in the Swiss Alps. The study aimed to compare the water quality and freshwater biodiversity of the reservoirs with those of 39 natural and newly excavated ponds. Data were collected on physicochemistry, freshwater habitat structure, and aquatic insects (dragonflies and aquatic beetles).3. The study showed that the mountain reservoirs investigated did not differ from natural ponds in terms of surface area, conductivity, and trophic level. Similarly to natural ponds, reservoirs showed signs of impairment owing to surface run-off carrying pollutants linked to ski tourism. They presented a low diversity of mesohabitats, and in particular lacked vegetation. Compared with natural ponds, the species richness in reservoirs was lower for dragonflies but not for beetles. At the regional scale, the community from the reservoirs was a subset of the natural ponds community, supporting 38% of the regional species richness for these two insect groups. 4. The results suggest that mountain reservoirs are likely to be important for biodiversity in alpine areas, both as habitats and as stepping stones for species shifting their geographical range. These water bodies can be enhanced further by some nature-friendly measures to maximize benefits for biodiversity, including margin revegetation or the creation of adjacent ponds. Ecological engineering needs to be innovative and promote freshwater biodiversity in artificial reservoirs. K E Y W O R D S benthic macroinvertebrates, climate change, freshwater biodiversity, mountain reservoirs, Swiss Alps water bodies, water quality

Scientists' warning of threats to mountains

“…Among their very many consequences, these interventions may lead to the gradual drying up of natural aquatic ecosystems due to excessive water extraction and diversion, as well as changes in the water level of (dammed) lakes, in the flow regime of streams, and in hydrological connectivity. These consequences in turn impact on the structure and function of the unique biodiversity that is characteristic of these habitats, and which includes many endemic and threatened species absent from the lowlands (Fait et al, 2020;Mayerhofer et al, 2021;13 Schabetsberger et al, 2013). Importantly, ongoing modifications in high-mountain freshwater ecosystems may also directly and profoundly impact on the wellbeing and livelihoods of peoples (Schmeller et al, 2018).…”

Contribution of artificial waterbodies to biodiversity: A glass half empty or half full?

“…Artificial ponds are created for economic and socio-cultural reasons, which include a variety of functions such as flow regulation, stormwater drainage, fish production, gravel extraction, providing livestock with drinking water, for their aesthetic value or for leisure activities, among others (European Pond Conservation Network 2008;Oertli 2018). Moreover, multifunctional artificial waterbodies have recently been reported as providing suitable habitats for several threatened species, even improving their survival rates (Dafforn et al 2015;Fait et al 2020).…”

“…In the case of macrophyte assemblages, artificial ponds were seen to support 65% of regional diversity in Central Europe, although the contribution was significantly lower than for natural ponds (Bubíková & Hrivnák 2018). If well designed, artificial ponds can provide suitable habitats even for threatened J o u r n a l P r e -p r o o f species, as is the case for beetles and dragonflies in small Alpine reservoirs (Fait et al 2020) and for amphibians in small manmade waterbodies in semiarid regions of Spain (Egea-Serrano et al 2006). However, all these studies had a limited range, as they focused on a single type of artificial ponds of a single region, and mostly investigated only one taxonomic group.…”

Taxonomic and functional macroinvertebrate diversity of high‐altitude ponds in the Macun Cirque, Switzerland

“…Mountainous freshwater habitats provide important biodiversity reservoirs for species adapted to colder climates (Fait et al, 2020). There is clearly a need to identify the key environmental variables influencing taxonomic and functional diversity within pond habitats to provide the required information to protect, manage and restore high‐altitude pond networks.…”

“…Mountainous freshwater habitats provide important biodiversity reservoirs for species adapted to colder climates (Fait et al, 2020).…”