Influence of river regulation on macroinvertebrate assemblages in a semiarid region: A trait-based approach

Abstract

Water availability is critical for economic and social development, especially in arid and semi-arid regions. Dams, while beneficial for humans, alter the natural regime of rivers, impacting natural ecosystems. This study used a trait-based approach to determine which attributes allow macroinvertebrates to thrive under the new environmental configuration imposed by flow regulation. To link traits to the impacts of dams, we selected 13 high gradient streams and compared unregulated and regulated reaches, where we (i) evaluated macroinvertebratetrait responses to hydromorphological characteristics, water chemistry, and habitat shifts and ii) identified the traits associated with stress caused by flow regulation. We classified macroinvertebrates according to 13 traits and 46 modalities. We performed an RLQ analysis, which links environmental features (R) with biological traits (Q) through taxonomic composition (L) followed by a fourth-corner analysis to further confirm trait-environment associations. Body shape, locomotion, feeding habits, respiration, adult ability to fly, flow preference, swimming ability, and adaptations to flow were the traits that most strongly influenced taxa composition. Cylindrical bodies (Oligochaetes), burrowers or clingers, poor swimming abilities, filtering collectors (Simuliidae), non-flying adults, and respiration by pigments (Chironomidae), spiracles (other dipterans), or lung respiration (Mollusca) are some of the traits that enabled organisms to persist at regulated sites. Some environmental features that filtered traits were total width of the channel, discharge, and water chemistry. This investigation provides evidence that trait-based analyses are valuable tools for assessing the ecological health of dam-impacted rivers. Identifying key biological traits will enhance biomonitoring programs and the management of regulated rivers.