Arbuscular Mycorrhizal Colonization in a Mangrove Forest Exposed to Weathering Oil for Half a Century

Abstract

Plants establish symbiosis with arbuscular mycorrhizal fungi (AMFs) for nutrient exchange and also for tolerance to contaminants. During February 2019, soil and rhizosphere samples of Laguncularia racemosa (Lr) and Avicennia germinans (Ag) were collected on 4.15 hectares of a mangrove forest established in Histosol affected since 1967 by chronic oil spill in southeastern Mexico. The site was divided into four zones based on the amounts of total hydrocarbons of weathered petroleum (THWPs) accumulated in the soil for half a century. The abundance of intraradical propagules and the colonization structure of the AMFs in the roots of the two mangrove species were compared. The density of phosphate-solubilizing bacteria (PSBs) in soil and rhizosphere samples was also evaluated. The degraded oil stimulated the amount of PSBs in Lr but not in Ag. AMF biodiversity was lower in the Ag root; however, spore abundance was higher. We found abundant spores of Glomus claroideum and Diversispora aurantium in tertiary and quaternary roots of the Ag in soils contaminated with 48462 mg of THWPs. This study provides evidence of the presence and abundance of intraradical propagules in different types of roots, which may be an alternative that contributes to the understanding of oil dissipation and in future applications for the restoration of degraded ecosystems.