Functional and Structural Responses of Soil Fungi to Hydrocarbon Contamination in Gokana, Niger Delta region

Hydrocarbon contamination poses a major ecological challenge in the Niger Delta wetlands, disrupting soil health and microbial balance. This study investigated fungal community diversity and structure in hydrocarbon-polluted (PS-1) and unpolluted (UPS-3) wetland soils from Gokana, Niger Delta, using shotgun metagenomic sequencing. Total petroleum hydrocarbon (TPH) concentration was significantly higher in PS-1 (78.3 mg/kg) than in UPS-3 (10.8 mg/kg), exceeding the regulatory limit of 50 mg/kg. At the phylum level, Ascomycota dominated both soils (> 99% relative abundance) but exhibited reduced representation in PS-1, which showed a lower classification rate (18%) than UPS-3 (> 90%). The unpolluted soil was dominated by Sordariomycetes (~ 99%) and Dothideomycetes (~ 1%), whereas these classes were nearly absent in PS-1. At the family level, Ophiocordycipitaceae (~ 80%) predominated in UPS-3, indicating a stable decomposer community, while PS-1 lacked consistent family representation. Genus-level analysis revealed Purpureocillium (~ 85%) as dominant in UPS-3, while PS-1 contained poorly classified or hydrocarbon-tolerant genera such as Aspergillus and Fusarium . The unpolluted soil recorded higher diversity indices (Shannon = 8.4; Simpson = 0.97) compared to PS-1 (Shannon = 7.0; Simpson = 0.98), confirming reduced fungal richness and evenness under hydrocarbon stress. Overall, petroleum contamination suppressed sensitive saprotrophic fungi, favouring hydrocarbon-tolerant taxa, but the persistence of Ascomycota suggests adaptive resilience and potential for natural attenuation in contaminated wetland soils.