Floodplain restoration by reinforcing hydrological connectivity: expected effects on aquatic mollusc communities

Abstract

Summary 1.One of the main targets of river-floodplain restoration is the reconnection of former side channels. While there is information about the overall impact of such measures, far less is known about specific species' response patterns to hydrological connectivity. 2. The present study examined the composition of aquatic mollusc communities based on the performance of individual species with respect to hydrological connectivity in the Donau-Auen National Park, Austria. Species' traits were used to make generalizations about community responses to hydrological changes. 3. We introduced a connectivity parameter (Cd, expressed in days year −1 ) that could easily be derived from the river hydrograph and altitude of the inflow areas. This parameter integrated several key features of floodplain waterbodies and reflected the causeeffect chain of restoration schemes, thus allowing the outcome of restoration measures to be quantitatively predicted. Endangered rheophilic mollusc species reached higher frequencies as connectivity increased; for most eurytopic molluscs, however, increased connectivity reduced abundance. 4. With respect to species' traits, the proportion of large gastropods declined continuously with increasing Cd, whereas the percentage of gastropods with globolose shells and the relative number of strongly calcified (thick-shelled) individuals both increased. Species dominating in isolated sites were characterized by a higher resistance to desiccation, a food preference for higher plants and a preference for less shaded habitats. They matured later and typically had more offspring than rheophilic species. 5. Species number peaked at connectivity (Cd) values of about 1 month year −1 . Isolated and lotic habitats hosted significantly fewer mollusc species. Species turnover was highest when Cd was between 0 days and 2 months. 6. Synthesis and applications. Empirical models based on a connectivity parameter can be used to predict the consequences of restoration measures on the aquatic mollusc community in the Donau-Auen National Park. The analysis of species' traits also allows general prognoses for other river-floodplain systems. Furthermore, initial results based on other taxa indicate a broad applicability of the parameter. The methodology thus provides both an urgently needed and a practical tool for predicting the impact and success of restoration schemes.

Can biological invertebrate traits resolve effects of multiple stressors on running water ecosystems?

“…functional feeding group), which is obtained by weighting the categories with the raw or logtransformed abundance (e.g. Johnson et al, 2004;Vieira et al, 2004;Reckendorfer et al, 2006;Bonada, Dolédec & Statzner, 2007a). Alternatively, the presence-absence of taxa has been used to weight trait categories (e.g.…”

Ecological Drivers of Cladoceran Diversity in the Central European City (Łódź, Poland): Effects of Urbanisation and Size of the Waterbody

“…However, due to extensive anthropogenic activities such as river regulation, channelization and the building of embankments to reduce flood risk and to protect anthropogenic infrastructure and agricultural activities on the floodplain, many rivers are hydrologically disconnected from the floodplain (Nilsson et al, 2005;Paillex et al, 2013). This has resulted in a long term trend of terrestrialization of floodplain habitats and the reduction in freshwater biodiversity (Tockner and Stanford, 2002;Reckendorfer et al, 2006). There has been a recent drive to reconnect rivers with their floodplains to rehabilitate and restore aquatic habitats (wetlands and ponds) on the floodplain and support faunal and floral biodiversity (Reckendorfer et al, 2006;Paillex et al, 2013).…”

“…This has resulted in a long term trend of terrestrialization of floodplain habitats and the reduction in freshwater biodiversity (Tockner and Stanford, 2002;Reckendorfer et al, 2006). There has been a recent drive to reconnect rivers with their floodplains to rehabilitate and restore aquatic habitats (wetlands and ponds) on the floodplain and support faunal and floral biodiversity (Reckendorfer et al, 2006;Paillex et al, 2013). However, most natural river-floodplain ecosystems remain highly fragmented and endangered in European lowland landscapes (Ward et al, 1999;Schindler et al, 2013).…”

Development of fauna of water beetles (Coleoptera) in waters bodies of a river valley – habitat factors, landscape and geomorphology

“…That is why scientists have been showing a growing interest in relations between river-dwelling fauna and the fauna of other water bodies within the floodplains of rivers (Castella et al, 1984;Stanford et al, 1996;Van den Brink et al, 1996;Stanley et al, 1997;Ward et al, 1999;Robinson et al, 2002;Biesiadka and Pakulnicka, 2004a). Papers describing the faunistic and ecological features of hydrobiont groups are now available, and point to these being shaped by the system's lasting hydrological interconnection (Kajak, 1959;Castella et al, 1984Castella et al, , 1991Castella and Amoros, 1988;Ward et al, 2002;Biesiadka and Kurząt-kowska, 2003;Biesiadka et al, 2004;Biesiadka et al, 2004;Czachorowski, 2004;Jurkiewicz-Karnkowska, 2006;Reckendorfer et al, 2006;Obolewski et al, 2009;Stryjecki and Kowalczyk-Pecka, 2013;Zawal and Kowalik, 2013;Kowalik et al, 2014;Zawal et al, 2016d).…”

“…The question that comes to mind -what are the factors affecting the formation of groups of fauna in river valleys -has been raised not only by hydroentomologists, but also researchers of other groups of organisms (Kajak, 1959;Castella et al, 1984Castella et al, , 1991Castella and Amoros, 1988;Ward, 1998;Ward et al, 2002;Jurkiewicz-Karnkowska, 2006;Reckendorfer et al, 2006;Obolewski et al, 2009). Biesiadka and Pakulnicka (2004a) point out that for water beetles, which are usually perfect fliers and are characterized with high biological dispersal (Bilton, 1994;Lundkvist et al, 2002), faunistic integration between the river and the water bodies located on the floodplain is influenced by two mechanisms: active overflights and migration of beetles in the floodplain area in time of spate.…”