Influence of river regulation and instream habitat on invertebrate assemblage’ structure and function

• Published in: The Science of the total environment Vol. 794; p. 148696
• Main Authors: Calapez, Ana Raquel, Serra, Sónia R.Q., Rivaes, Rui, Aguiar, Francisca C., Feio, Maria João
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 10.11.2021
• Subjects: Bioassessment; Biological traits; Hydromorphology; Mesohabitats; River damming; River damming; Mesohabitats; Hydromorphology; Bioassessment; Biological traits
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2021.148696

Dams modify geomorphology, water quantity, quality and timing of stream flows affecting ecosystem functioning and aquatic biota. In this study, we addressed the structural and functional macroinvertebrate community alterations in different instream mesohabitats of two Portuguese rivers impaired by dams. We sampled macroinvertebrates in riffles, runs and pools of river sites downstream of the dams (i.e. regulated; n = 24) and in sites without the influence of the dams (i.e. unregulated; n = 7), assessing a total of 64 mesohabitats, following late spring-early summer regular flows. We found a distinct taxonomic structure and trait composition of macroinvertebrate assemblages between regulated and unregulated flow sites, and also between mesohabitats in which the differences were more evident. When analysing each mesohabitat individually, the effect of flow regulation was detected only in run-type mesohabitats for both taxonomic and trait composition, leading us to infer that a selective macroinvertebrate assessment on run mesohabitats would be a valuable contribution to detect regulated flow effects on ecosystems impaired by dams. Additionally, there is evidence that respiration and locomotion traits could be effective tools to identify damming flow alterations. This study supports that the quality assessments of rivers impacted by dams could benefit from a sampling approach focused on run mesohabitats and the detection of some key traits, which would improve assessment accuracy. [Display omitted] •Macroinvertebrate community structure and function were studied in two dammed rivers.•Bioassesment was done in pools, runs and riffles in regulated and nonregulated sites.•Flow regulation and mesohabitats revealed distinct community structure and traits.•Dams have a detectable impact on invertebrate assemblages in run-type mesohabitats.•Sampling run mesohabitats would improve bioassessment accuracy in regulated rivers.