Meander reconnection method determines restoration success for macroinvertebrate communities in a German lowland river

Abstract

Re-meandering of degraded rivers is a frequently implemented measure in river restoration. A simple solution is reconnection of old meanders; however, its success likely depends on the reconnection method. We conducted a field study to analyze the benefits of a fully reconnected (fully opened meander, blocked main channel) and a partially reconnected meander (opened downstream, pipe bypass from main channel upstream, still open main channel) for macroinvertebrate communities in a German lowland river. Immediately upon reconnection of the two meanders, habitat diversity, and macroinvertebrates were recorded for three years with sampling in spring and in summer each year. The results of a principal response curve analysis show that the macroinvertebrate community in the fully reconnected meander reflected main channel reference conditions after 1.5 years. The macroinvertebrate community composition was not improved relative to in-stream reference conditions within the partially reconnected meander, which could be attributed to the almost complete lack of flow changes that resulted in missing improvements of substrate diversity. Our results show that the meander reconnection method must sufficiently affect the basic hydromorphological requirements to achieve reference macroinvertebrate community composition. Measures including hydromorphological conditions are therefore recommended for employment in environmental management.

Greater macroinvertebrate diversity and freshwater mussel density in meander margins of an Amazon river

“…Similarly, Graf et al (2016) found that Chironomidae dominated the assemblage and showed a preference for sandy substrates in an Austrian lowland river. Other taxa are adapted to more stable substrates, such as in the meander margins in the Caet e river, which support a greater diversity of the insect orders Ephemeroptera and Trichoptera (Lorenz et al, 2016), especially Other taxa are adapted to more stable substrates, such as in the meander margins in the Caet e river, which support a greater diversity of the insect orders Ephemeroptera and Trichoptera (Lorenz et al, 2016), especially…”

“…Some taxa are adapted to unstable substrates with strong flow, for example, members of the beetle family Elmidae, which have rigid elytra that resist the impact of sand grains moving in the current, and Chironomidae, which have structures for attachment to the substrate (Hamada et al, 2014). Other taxa are adapted to more stable substrates, such as in the meander margins in the Caet e river, which support a greater diversity of the insect orders Ephemeroptera and Trichoptera (Lorenz et al, 2016), especially…”

“…In general, meandering rivers have longitudinal and lateral variation, creating structural heterogeneity along the river channel and exhibiting asymmetry mainly by meandering flows (Palmer, Menninger, & Bernhardt, 2010). In meander margins, predominantly fine substrates occur, along with woody debris and roots (Lorenz, Leszinski, & Graeber, 2016) creating microhabitats, which include flow refuges (Lancaster & Hildrew, 1993) with stable substrates and organic matter deposits. Such microhabitats are minimally affected during high flow events and facilitate the establishment of a diversified benthic assemblage (Rempel, Richardson, & Healey, 2000).…”

Temporal and spatial changes of macrobenthos community in the regions frequently occurring black water aggregation in Lake Taihu

“…It is widely studied that the changes in community structure of macrobenthos correlated well with the variations in environmental factors 7–10 . Thus, macrobenthos commonly serve as useful bio-indicators for aquatic environment monitoring and assessment in river, marine and lake ecosystem 11–15 .…”

Disentangling multiple pressures on fish assemblages in large rivers

“…Hence, increased velocities provide favorable habitat conditions for rheophilic fish species which contribute to higher diversity. Similarly, in reconnected meanders of a large river, Lorenz et al (2016) observed increased diversity of rheophilic macroinvertebrates due to higher flow velocities therein. In our study, increased velocities were found having considerably higher influences on biodiversity metrics than on guild densities.…”