Epistylid ciliates as epibionts on calanoid copepods in an Amazonian floodplain lake (Batata Lake)

Abstract Aim The main objective was to investigate changes in the prevalence and infestation intensity of the epibiotic relationship (ciliates/calanoids) in relation to the impact of bauxite tailings (natural and impacted areas) during two distinct periods of the hydrological pulse (rising and high-water). Methods The hydrological pulse of this system can be characterized with four distinct phases: rising, high-water, falling, and low-water. After degradation by bauxite tailings for ten years (1979-1989), and despite an ongoing long-term ecological restoration process, it is still possible to recognize two distinct regions in the lake: the area impacted by the tailings and the natural area. We sampled zooplankton (calanoids and epibiont ciliates) and limnological variables during the high-water period (March 2015) and rising-water period (June 2019) at twelve sampling points in Lake Batata, six in the impacted area and six in the non-impacted area. Results This is the first record of peritrichous epibiont ciliates Epistylis sp. colonizing calanoid copepods in Amazonian ecosystems (Lake Batata, Pará, Brazil). We recorded epibiont ciliates in the calanoid copepodite and adult stages, as well as the main location sites on the thorax and abdomen. Our study recorded a significant difference in the prevalence and mean infestation intensity between the natural and bauxite tailings-impacted areas, and in the prevalence of infestation between the rising -water (2015) and high-water (2019) collections. The prevalence of infestation was higher in the impacted area and during the rising-water period. Conclusions Although the host/epibiont/environment interaction is complex and requires analysis with a larger number of temporal samples, this study records a clear effect of flooding in this Amazonian system on the spatial and temporal dynamics of epibiont ciliates associated with calanoid copepods. Resumo Objetivo O objetivo principal foi investigar mudanças na prevalência e intensidade de infestação da relação epibiótica entre ciliados e calanóides em relação ao impacto por rejeito de bauxita (área natural e impactada) e em dois distintos períodos do pulso hidrológico (rising and high-water). Métodos O pulso hidrológico desse sistema pode ser caracterizado por quatro fases distintas: enchente, águas-altas, vazante e águas-baixas. Após longa deposição de rejeitos de bauxita (1979-1989), e apesar de um processo de restauração ecológica de longo prazo em andamento, ainda