An assessment of maintenance works and their impact on macroinvertebrate communities and long-term recolonization to small lowland watercourses

• Published in: Journal of environmental management Vol. 367; p. 121849
• Main Authors: Brysiewicz, Adam, Czerniejewski, Przemysław, Sieczko, Leszek
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.09.2024
• Subjects: Animals; anthropogenic activities; Biodiversity; Conservation; Dredging; ecoregions; Ecosystem; environmental management; fish feeds; hydrochemistry; Invertebrates - physiology; Macroinvertebrates; Macrophyte cutting; macrophytes; Management; Rivers; sediments; species richness; Stream; taxonomy; vegetation; water flow; Dredging; Stream; Management; Macrophyte cutting; Macroinvertebrates; Conservation
• DOI: 10.1016/j.jenvman.2024.121849
• ISSN: 0301-4797; 1095-8630

Due to their small size and high anthropogenic pressure, small watercourses are particularly prone to severe siltation and are densely overgrown with macrophytes. Many of these watercourses are subject to regular maintenance works (RMW), consisting of seasonal desilting and vegetation clearance, in order to ensure unobstructed water flow. The aim of the study was to assess the impact of three types of maintenance works: dredging and mud removal (DMR), river channel vegetation removal (RCVR) and river bank vegetation removal (RBVR) on taxa species richness, macroinvertebrate density and the Shannon-Wiener diversity index, as well as their changes and long-term benthic recolonization one and two years after completion of the works. The study was carried out in 21 habitats on eight rivers in the European Central Plains Ecoregion. A total of 107 zoobenthic taxa were found at all sites, and their species composition was characteristic of highly hydrophytic waters with low hydrological and hydrochemical quality parameters. A significant decrease in macroinvertebrate taxa richness was observed one year after the works, as the average number of taxa had dropped from thirteen to eight, with a further fall to seven taxa two years after the RMW. The same was true for density, which had decreased from an average of 2496 to 786 individuals per square meter one year after the RMW, while, a gradual recolonization was recorded two years after the RMW, with an average density of 1295 individuals per square meter. The Shannon-Wiener index, which had averaged 2.528 before the RMW, also decreased, falling to 1.982 and 1.832 one and two years after. BACI statistical analyses showed that of the three types of maintenance work, desilting and bottom sediment removal had the largest negative impact, significantly reducing taxonomic composition (by an average of 53%), density (by an average of 43%), and ecological index values (by an average of 40%). Over-frequent maintenance can prevent macroinvertebrate populations from recovering, thus depleting the environment of valuable taxa, including those that provide food for fish and other vertebrates. [Display omitted] •BACI (before-after-control-impact) designs are helpful to assess ecological impacts.•Dredging of the riverbed is most damaging to macroinvertebrates.•We observed a community changes in the 1st and 2 nd year after a river maintenance works (RMW), indicating that the macroinvertebrates population is sensitive to changes resulting from the works.•Maintenance works on watercourses, especially their de-silting and removal of bottom sediments, are responsible for creating habitats and niches for mainly eurytopic macroinvertebrate taxa.•The BACI statistical analysis showed that despite partial habitat restoration, even a two-year period after RMW does not allow for recolonization of the macroinvertebrates and re-establishing their previous population.