Alpha and beta diversity of planktonic microcrustaceans are associated with environmental heterogeneity in the Frades River Basin, Brazil

Abstract

ABSTRACT Plankton in rivers are good indicators of water quality and their study along the longitudinal axis allows for understanding the interactions between natural and anthropogenic variations and diversity at different spatial scales. We compared the taxonomic biodiversity of planktonic microcrustaceans in two sections of the Frades River Basin, Brazil. Water and microcrustaceans were sampled in August 2018, April 2019, July 2019, and October 2019 in the basin. We recorded 43 taxa as the regional diversity of microcrustaceans. Alpha diversity was statistically higher in the upper section of the basin. The analysis of indicator species showed that nine species were characteristic of the studied sections. The upper section was represented by Nicsmirnovius paggii, Acroperus tupinamba, Alonella dadayi, Alona guttata, and Microcyclops finitimus and characterized by higher dissolved oxygen, higher values of pH of water and lower nitrate and total coliforms concentrations. Diaphanosoma birgei, Alona sp., Grimaldina brazzai, and Ilyocryptus spinifer were characteristic of the lower sections of the basin, with the highest concentrations of nitrate and total coliforms. The microcrustaceans in the lower sections were limited by the gradient of environmental conditions, making local communities simpler (low species richness) and with few species probably adjusted to narrow ranges of environmental conditions.