Comunidades de fungos micorrízicos arbusculares (Glomeromycota) em ecossistemas impactados por rejeito de mineração de ferro em Mariana-MG

Abstract

The deposition of the iron ore tailings from the rupture of the Fundão dam in Mariana-MG has impacted the entire length of the Doce river basin, altering soil physico-chemical characteristics, increasing the mortality of aquatic organisms and suppressing extensive areas, however it effect on soil microbial communities is practically unknown. The objective of this study was to evaluate the composition of arbuscular mycorrhizal fungi (AMF) communities in ecosystems impacted by different thicknesses of iron ore tailings deposition and adjacent non impacted ecosystems. Soil samples were collected in areas of untouched Atlantic Forest (MA Ref), Atlantic Forest with deposition of approximately 0,4 m of tailings depth (MA-0,4) and deposition of more than 1 m of tailings ( MA-> 1); and non-impacted eucalyptus plantation (PE-Ref), eucalyptus plantation with deposition of approximately 0,4 m of tailings (PE-0,4) and deposition of more than 1 m of tailings (PE-> 1). AMF spores were extracted from soil and collected epigeous sporocarps on the mining tail, being mounted on permanent slides for morphological identification. A total of 38 AMF morphospecies were recovered from the evaluated ecosystems. Glomeraceae was the family with the highest abundance, followed by Acaulosporaceae. Only four AMF species were shared among all sampled areas, and approximately 18% were exclusively sampled in one ecosystem. The taxonomic composition of AMFs allowed differentiating between impacted and non-impacted ecosystems. The spore density of AMF families showed differences among the ecosystems impacted by the tailings. Classes of frequency of occurrence of species show dominance of Glomeraceae, while two or three species showed relative spore abundance greater than 15% in each ecosystem. Rhizophagus irregularis was exclusively recovered in areas impacted by tailings deposition, always presenting a relative abundance of more than 10%. Large masses of sporocarps of Sclerocystis coremioides were collected on the tailings, increasing the knowledge about the occurrence of this species in impacted ecosystems. The presence of approximately 88% of the AMF species in the impacted areas, and sharing approximately 55% of the species between areas with and without tailings deposition, indicates that dispersion processes were efficient, and that the majority of the taxa sampled in non impacted environments are competent to establish themselves in areas with deposition of mining tailings, which can assist in the process of establishing vegetation, succession and assisting in the rehabilitation process of impacted areas.