Wildfire in the Surrounding Landscape Alters Limnological Conditions and Plankton Communities in a Tropical Reservoir

Abstract

Wildfires are becoming increasingly frequent and severe as a consequence of climate change. Their impacts on terrestrial ecosystems and on the atmosphere include the release of gases and ash, as well as enhanced soil susceptibility to erosion and the downstream transport of materials into aquatic systems. However, the effects of such disturbances on aquatic ecosystems remain poorly understood. In this study, we assessed short‐ and medium‐term limnological and biological responses of a tropical reservoir located in the Brazilian Cerrado (Lobo–Broa Reservoir) following a large‐scale wildfire. We conducted intensive weekly sampling during the first 5 weeks after the fire, embedded within a longer‐term monthly time series spanning 2 years prior to and 2 years after the disturbance. We hypothesized that the wildfire would have an impact on water transparency, suspended particulate matter, nutrient dynamics, and dissolved organic matter, with cascading effects on planktonic communities. We observed short‐term responses across multiple physical, chemical, and biological variables, although their timing and magnitude differed among ecosystem components. Most parameters returned to their pre‐disturbance trajectories within days to weeks. However, turbidity, euphotic depth, and the abundance of Synechococcus ‐like picocyanobacteria and cladocerans showed more persistent deviations extending beyond the immediate post‐fire period. Multivariate analyses revealed that post‐fire samples largely fell within the natural seasonal and interannual variability of the system. Spatial comparisons between nearshore and the pelagic zone indicated differences in variables such as phytoplankton biomass, dissolved oxygen concentration, total phosphorus, fulvic‐like organic matter, and the abundance of cyanobacteria and cladocerans. Overall, the wildfire was associated with detectable changes in limnological conditions and planktonic communities. Nevertheless, most variables exhibited a high degree of resilience over time.