Do wider riparian zones alter benthic macroinvertebrate assemblages’ diversity and taxonomic composition in neotropical headwater streams?

Abstract

Aim The maintenance and condition of riparian vegetation are important factors for conserving headwater streams and their species diversity. Thus, variations in the width of a riparian zone can have dramatic effects in the structure and functioning of the adjacent freshwater ecosystem. In this study, we aimed to determine if increased riparian zone width changed the benthic assemblages’ structure (diversity, taxonomic and functional composition) in headwater streams. Methods We tested two predictions: (1) increased riparian zone width will change the diversity and taxonomic composition of benthic macroinvertebrate assemblages because narrow riparian zones do not buffer the anthropogenic impacts from the surrounding landscape; (2) wider riparian zones will change benthic macroinvertebrate assemblages’ functional structure, due to changes to energetic input and quality. To test the first prediction, we assessed the benthic macroinvertebrate assemblages’ taxonomic composition, richness and Shannon-Wiener diversity index. To test the second prediction, we assessed functional feeding groups (FFG) and metrics based on their proportion. Results Our results showed that our first prediction was not corroborated, because taxonomic structure and diversity did not show significant variation with increased riparian zone width. Our second prediction was partially corroborated, because there were significant alterations in the functional structure of benthic macroinvertebrate assemblages between the narrowest riparian zone width (30 m) and the others two (50 and 100 m). Conclusions Our results suggest that, contrary to the Brazilian Federal Law 12651/2012, 30-m wide riparian zones are insufficient to protect headwater stream ecosystem functioning.

Land-use effects on aquatic macroinvertebrate diversity in subtropical highland grasslands streams

“…Based on this inventory of benthic macroinvertebrate communities, average family richness and density were calculated for each sampling site. This methodology has yielded good results in studies of Neotropical streams (Firmiano et al, 2021;Hamada et al, 2014;Linares et al, 2021;Martins et al, 2021;Rezende et al, 2014b).…”

“…scale have on aquatic macroinvertebrate communities in stream systems (Clarke et al, 2008;Firmiano et al, 2021;Linares et al, 2021), special attention should be given to α and β diversities (Doretto et al, 2021;Mendes et al, 2021;Rezende et al, 2019a).…”