Urban Pollution Promotes Biotic Simplification of the Zooplankton Community in Ponds in Northeastern Brazil

Abstract

Pollution significantly impacts aquatic biodiversity by limiting the species pool. However, considerable uncertainty remains regarding which community attributes should be used to demonstrate the effects of this anthropogenic disturbance. We propose that zooplankton taxonomic biodiversity could serve as a reliable pollution indicator in lentic water bodies. Our study encompassed seven urban and nine rural ponds in the extreme south of Bahia, Brazil. We collected zooplankton samples and measured the physical and chemical properties of the water, including chlorophyll-a concentration, and examined land use surrounding the ponds. The landscape was primarily used for pasture, forest formation, urbanised areas and coffee monoculture. Rural ponds exhibited higher values for water temperature, Secchi disk readings, chlorophyll-a concentration and dissolved oxygen levels. Conversely, urban ponds demonstrated elevated nutrient concentrations and electrical conductivity. We identified a total of 109 species of zooplankton. Gamma and alpha diversity were more pronounced in rural ponds, primarily due to the diversity of Rotifera and Cladocera. Beta diversity was higher in urban ponds. The composition and frequency of species occurrence also varied between the pond types. The ponds, grouped by indicator species, were associated with electrical conductivity and Secchi disk depth in the water. Based on these findings, we propose a model that describes the impact of pollution on communities. And we suggest that water pollution in urban ponds gradually alters community attributes and biodiversity components.