Effects of different levels of metal exposure and precipitation regimes on chlorophyll a fluorescence parameters in a coastal Brazilian restinga species

Abstract

This work aimed to investigate whether there was a relationship between precipitation regimes and concentrations of trace elements (Cu, Mn, Fe and Zn) deposited on the coast from ore tailings released in the Mariana disaster (Minas Gerais, Brazil) in 2015. We also sought to answer if there would be a synergistic effect of increased precipitation and trace element levels affecting photosynthesis. The combination of these factors was evaluated using the dynamics of chlorophyll a fluorescence in plants of Byrsonima sericea, a shrub species, used as a model in restinga studies. In situ studies showed that, throughout the year, the photosynthetic performance of B. sericea exhibited seasonal variability. The combination of both trace elements in soil and leaves and precipitation regimes drives the variability of the chlorophyll fluorescence parameters on restinga vegetation. Significant negative correlations were observed between the high concentrations of metals (mainly Cu and Fe) and photosynthetic performance indices and the oxygen evolving complex (OEC) activity in PSII. Combined effects of high concentrations of Cu, Fe, Mn and Zn and different rainfall regimes were manifested in the alteration of Chlorophyll a Fluorescence parameters related to quantum efficiency, specific energy fluxes and performance indices. Data presented in this study conclusively proved that Byrsonima sericea respond to different environmental conditions and that the dry season was more damaging to plants than the rainy season in terms of the impacts of both the rain regime and metal availability; metal availability also varied according to rainfall patterns and transport via marine aerosols.