CHARACTERIZATION OF RHIZOBIA AND ARBUSCULAR MYCORRHIZAL FUNGI IN AREAS IMPACTED BY GRAVEL MINING IN BRAZIL

Felipe Ferreira Da Silva,Ederson Da Conceição Jesus,Thainá Alves Dos Santos,Guilherme Montandon Chaer

doi:10.1590/1983-21252019v32n416rc

Abstract

ABSTRACT On-shore oil exploration is one of the main economic activities in the semiarid region (Caatinga biome) of the state of Rio Grande do Norte (RN), Brazil. Gravel mining is an activity associated with oil exploration that causes environmental impacts. Gravel is a base-material for constructions, such as roads and pumpjack bases. The areas of gravel mining and other decommissioned areas where the gravel has been deposited must be revegetated with species native to the biome at end of the activity in the site. An efficient strategy for revegetation of degraded areas has been the planting of leguminous species that can associate with rhizobia and arbuscular mycorrhizal fungi (AMF). Nevertheless, the impact of mining activities on the autochthonous populations of these microorganisms is unknown. The objective of the present work is to characterize the density of rhizobia and AMF spores in four areas impacted by the oil exploration in RN when compared to non-impacted adjacent areas. Gravel samples were collected in dry and rainy seasons in two mining areas: one in a pumpjack base, and one in a waste disposal area. Surface soil (topsoil) samples were collected in adjacent areas with native Caatinga vegetation. Assays were carried out to evaluate the most probable number (MPN) of rhizobia and to identify the type and density of arbuscular mycorrhizal fungi (AMF), using rhizobia trap plants Mimosa tenuiflora (Mart.) Benth. and Mimosa caesalpiniifolia Benth. The MPN of rhizobia was low in all areas, but higher in the rainy season. The highest amount and diversity of AMF spores were found in the dry season. Among the symbiotic microorganisms studied, the AMF presented lower densities in the evaluated areas when compared to those in the adjcent native vegetation areas, denoting the impact of this activity.

Highlights

On-shore oil exploration is one of the main economic activities in the semiarid region (Caatinga biome) of the state of Rio Grande do Norte (RN), Brazil
The overlaps of the confidence intervals of their most probable number (MPN) indicated no significant differences between J1-native Caatinga vegetation (NV), J2-P, and J2-NV (Figure 1B)
The rhizobia found in the rainy season had, in general, higher MPN than in the dry season (Figure 2), rhizobia were not found in the WDANV, PB-NV, and J1-P areas

Summary

Introduction

On-shore oil exploration is one of the main economic activities in the semiarid region (Caatinga biome) of the state of Rio Grande do Norte (RN), Brazil. After the end of the mining activity, the impacted areas should be revegetated with native species to the biome, which must be able to survive and develop in the substrate of the area Decommissioned areas such as pumpjack bases and waste disposal areas, which often received a level of gravel, should be revegetated as defined in a recovery plan for degraded areas previously agreed with the environmental state agency. The revegetation of these areas usually requires the improvement of soil chemical and physical characteristics through fertilizers and mechanical decompaction and trough the selection and introduction of adapted species that can grow and restore the natural succession processes (RESENDE; CHAER 2010)

Objectives

Methods

Results

Conclusion