Effects of small hydropower dams on macroinvertebrate and fish assemblages in southern Brazil

Couto, Thiago B. A., Rezende, Renan S., de Aquino, Pedro P. U., Costa-Pereira, Raul, de Campos, Gelso L., Occhi, Thiago V. T., Vitule, Jean R. S., Espírito-Santo, Helder M. V., Soares, Yan F. F. and Olden, Julian D. (2023) Effects of small hydropower dams on macroinvertebrate and fish assemblages in southern Brazil. Freshwater Biology, 68 (6). pp. 956-971. ISSN 0046-5070

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Abstract

Hydropower dams affect freshwater biodiversity by virtue of modifying flow regimes and degrading habitat conditions both above and below the water impoundment and diversion structure. In recent decades, there has been a global proliferation of Small Hydropower Plants (SHPs) propelled by incentive policies and a general perception that small dams are less harmful to the environment. However, limited science is available on the effects of SHPs on freshwater biodiversity, which is concerning considering their sheer numbers and the high variability in the size and operation of dams classified as SHPs. We investigated the ecological effects of 12 SHPs on macroinvertebrate and fish assemblages of the Chapecó River Basin, Brazil. Our study included sites located upstream of the SHPs and sites directly affected by their operations (i.e., reservoir, dewatering section and downstream of the powerhouse). This design allowed us to quantify shifts in taxonomic composition and examine the relative role of different SHP attributes (e.g., dam height, reservoir area, age) in explaining these changes. Our results reveal that SHPs modify the composition of both macroinvertebrate and fish assemblages, but the magnitude of such changes vary widely among dams. Both assemblages exhibited directionality in taxonomic shifts, resulting in a gradual replacement of taxa associated with fast-flowing habitats by other groups more commonly associated with standing waters. We also found that changes in assemblage structureare related to structural (dam height, reservoir area) and spatial attributes (distance from headwaters) of SHPs, although the predictive power of these attributes varied taxonomically and among reservoir, dewatering and downstream sites. Overall, our results demonstrate that SHPs have important and heterogeneous effects on freshwater assemblages, which may manifest individually or cumulatively across the riverscape. This suggests that it is unlikely that a priori classifications of dams based on their structural attributes can replace site-specific and cumulative impact assessments. The results also shed light on the need for better understanding of how SHP attributes shape their ecological effects, so that a full assessment of the potential environmental impacts of the wide range of "small" dams is possible.

Item Type:	Article
Additional Information:	DATA AVAILABILITY STATEMENT: Data are available from the authors upon reasonable request. FUNDING: DO was supported by H Mason Keeler Endowed Professorship from the School of Aquatic and Fishery Sciences, University of Washington, also supporting TBAC. Grants from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) support RSR (421288/2017-5; 405290/2018-7) and JRSV (310850/2012-6; 303776/2015-3). RCP is supported by the Serrapilheira Institute (grant no. Serra—R-2011-37572) and grant no. 2020/11953-2, São Paulo Research Foundation (FAPESP). TBAC was supported by CNPq/Science Without Borders Fellowship (203991/2014-1) and fieldwork activities were funded by Rufford Foundation, Society for Conservation Biology (LACA section), and National Geographic Society.
Uncontrolled Keywords:	dam cascades,flow regulation,lentification,run-of-river,water diversion,aquatic science,sdg 15 - life on land ,/dk/atira/pure/subjectarea/asjc/1100/1104
Faculty \ School:	Faculty of Science > School of Environmental Sciences
Related URLs:	http://www.scopus.com/inward/record.url?...
Depositing User:	LivePure Connector
Date Deposited:	30 Sep 2025 11:30
Last Modified:	04 Nov 2025 23:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/100566
DOI:	10.1111/fwb.14078

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