The effects of mining tailings and flood pulse on zooplankton in an Amazonian floodplain environment (Batata Lake, Pará, Brazil)

Elder De Oliveira Sodré,Francisco De Assis Esteves,Fábio Roland,Marcos Paulo Figueiredo-Barros,Paloma Marinho Lopes,Reinaldo Luiz Bozelli

doi:10.46357/bcnaturais.v10i2.483

Abstract

The flood pulse, as well as anthropogenic impacts, may shape the patterns of zooplankton communities. We evaluated the influence of bauxite tailings and water levels on zooplankton at sampling times precisely defined according to the water level. Our study area was Batata Lake, an Amazonian floodplain lake impacted by bauxite tailings. Zooplankton was sampled for seven years, four times a year, at two stations, one natural and the other impacted by bauxite tailings. Zooplankton was identified to the lowest possible taxonomic level. Differences in richness and densities between periods and stations were evaluated with a two-way ANOVA. An indicator species analysis was performed to assign species to sampling stations. Community richness was lower at low water and higher at high water, whereas densities showed the opposite result. Only one species was identified as an indicator, highlighting that the zooplankton composition in natural and impacted areas was similar. Densities were also similar at these stations, except for cladocerans, which showed higher densities at the impacted station. The use of samples taken at precisely defined flood pulse periods yielded expected but refined results, as the samples were based on a precise relationship with water levels that previous studies did not include.

Highlights

Amazonian floodplains undergo changes in the volume of water that they contain during the year because of the rainfall patterns at regional or even continental scale, according to dry and wet seasons
In addition to the role of water level variation, this study considered the presence of bauxite tailings from mining activity
How does the use of samples taken at precisely defined times during the flood pulse periods change or confirm our knowledge of zooplankton fluctuations in floodplains? We propose that the results obtained with this approach will be clearer and more accurate, making them more reliable for decision-makers and to the scientific community in general

Summary

Introduction

Amazonian floodplains undergo changes in the volume of water that they contain during the year because of the rainfall patterns at regional or even continental scale, according to dry and wet seasons. This variation has been characterized and described as the flood pulse (Junk et al, 1989). The sampling schedule to obtain, for example, zooplankton samples is based on aprioristic and artificial definitions of water level periods Another important characteristic is that, beyond this yearly variation in the volume of water, there is a variation among years; the strength of the flood pulse is usually not exactly the same in different years

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