Effect of Campsurus notatus on NH+4, DOC Fluxes,O2 Uptake and Bacterioplankton Production in Experimental Microcosms with Sediment‐Water Interface of an Amazonian Lake Impacted by Bauxite Tailings

The aim of this study was to evaluate the influence of Campusurus notatus Eaton 1868 (Ephemeroptera: Polimitarciydae) and the impact of bauxite tailings on ammonium (NH₄⁺) and dissolved organic carbon (DOC) fluxes, oxygen uptake and bacterioplankton production in the sediment‐water interface of Lake Batata, a shallow Amazonian floodplain lake. Mesocosms were constructed from natural and impacted areas of Lake Batata, to reproduce the sediment‐water interface. The cores were incubated with 0 to 2,388 ind m^–2 of Campsurus notatus nymphs, and the changes in NH₄⁺, DOC, O₂ concentration and bacterioplankton production in the overlying water column were measured. Ammonium efflux (F = 9.8, p < 0.05, multiple regression) and oxygen uptake (F = 11.8, p < 0.05) showed a significant correlation with the density of C. notatus in the cores with natural sediment. No differences on DOC release were observed in cores with natural or impacted sediment. In the cores incubated with natural sediment and nymphs of C. notatus, a significant increase (Two‐way ANOVA, p < 0.05) in bacterial production (0.44 μg C l^–1 h^–1) was observed after 3 hours of incubation. In cores incubated with sediment impacted by bauxite tailings, there was no difference in bacterial production with and without C. notatus. We conclude that C. notatus is an important bioturbator in Lake Batata, increasing the turnover rate of nitrogen (NH₄⁺) at the sediment‐water interface and bacterial production in cores incubated with natural sediment. It is also clear that bauxite tailings reduce the nutrients turnover rates in impacted regions of Lake Batata and influence bacterial production.