Connectivity restoration of floodplain lakes: an assessment based on macroinvertebrate communities

Abstract

Successful rehabilitation programmes of river-floodplain systems require understanding of environmental impacts of restoring hydrological connectivity. The present study is based on a field experiment carried out between 2008 and 2013 in a floodplain of a lowland river in northern Poland, in which two oxbow lakes isolated in the 1920s were reconnected to the main river channel. Water and macroinvertebrate samples were collected three to four times a year from six sites (n = 114). After reconnection, water quality in the oxbow lakes improved and diversity and abundance of macrozoobenthos increased, especially the density of Oligochaeta, Malacostraca, Trichoptera, Bivalvia and Gastropoda, while the density of Diptera decreased. Water flow and physico-chemical variables were the most important factors explaining their variance. A direct inflow of water into the reconnected oxbow lakes occurred only during the first 2 years of the study, followed by silting and overgrowing of the inlet to the upper arm. We propose that creating semi-lotic side channels connected to the river with one arm and only occasionally flushed with fresh river water is one of the most effective restoration strategies. However, at the whole river scale, the maintenance of diversified hydrological connections is the optimal solution.

From isolation to connectivity: the effect of floodplain lake restoration on sediments as habitats for macroinvertebrate communities

“…This sudden change in habitat conditions is a source of stress for hydrobionts, particularly highly sensitive benthic macroinvertebrates. We have demonstrated (Obolewski and Glińska-Lewczuk 2013;Obolewski et al 2016) that water flowing into floodplain lakes carries suspended matter that is deposited at the bottom, contributing to lake shallowing and inhibiting connectivity in the RFS.…”

“…Cut-offs quickly become filled with sediments as a result of autogenic processes and/or allogenic processes, i.e., accumulation of the material carried by the river during inundation events and by ground water (Sieczko and Peduzzi 2014). Soon after, the isolated water bodies undergo eutrophication and then terrestrialization (Obolewski et al 2016;Palmer et al 2005). The lakes accumulate organic matter and become shallower, with decreasing biodiversity due to progressive domination of species tolerant of the changes in environmental quality (e.g., Obolewski 2011;Paillex et al 2015).…”

“…Our previous studies (Obolewski and Glińska-Lewczuk 2013;Obolewski et al 2016) demonstrated that the restoration effects in RFSs can be analyzed at different temporal scales. Short-term effects are observed soon after reconnection when the system is not stable and the structures of the sediment, water quality, and biota (here: macrozoobenthos) vary significantly between seasons, whereas long-term effects, usually on a multi-year scale, may be assessed when the biota attains relative multiseasonal stability.…”

Preface: Wetlands biodiversity and processes—tools for conservation and management

“…Two papers address the relevance of river-wetland connectivity as a driver of zooplankton and macroinvertebrate communities (Gozdziejewska et al, 2016;Obolewski et al, 2016). Zooplankton communities which are often neglected in wetland studies, respond to increased eutrophication shifting from crustacean to rotifer dominance (Kuczynska-Kippen & Joniak, 2016).…”

Lateral and longitudinal patterns of water physico-chemistry and trace metal distribution and partitioning in a large river floodplain

“…Cut-off channels with no permanent connection are characterised by fine organic sediment, mostly organic SPM, higher conductivity due to groundwater inputs, higher DOC due to phytoplankton, and lower nutrients (Amoros and Bornette, 2002;Carrel and Juget, 1987;Hein et al, 2004;Tockner et al, 1999). While connected sites are strongly influenced by the mainstem and show comparable characteristics (Obolewski et al, 2015), disconnected sites are also influenced by local factors such as surrounding land-use or the hillslope aquifer.…”