Fungal Bioaugmentation and Plant-Based Biostimulation for Petroleum Hydrocarbon Degradation in Mangrove Sediments

Mangrove ecosystems are highly vulnerable to petroleum contamination, with long-lasting environmental consequences due to the persistence of complex hydrocarbon fractions. While bioremediation strategies such as bioaugmentation and biostimulation are widely studied, their comparative effectiveness in mangrove sediments remains poorly understood. This study evaluates the degradation of total petroleum hydrocarbons (TPH) in mangrove sediments contaminated with Recôncavo Basin crude oil (1% w/w) using fungal bioaugmentation (Aspergillus sp.), plant-based biostimulation, and their combination. A controlled mesocosm experiment simulated tidal dynamics over 45 days using 80 bioreactors. Significant reductions in unresolved complex mixture (UCM) and TPH concentrations were observed across all treatments, with UCM reductions reaching up to 78.4% in the biostimulation treatment. However, no statistically significant differences were found among treatments at the end of the experiment (p > 0.05). This suggests a dominant role of intrinsic biodegradation processes, indicating that natural attenuation can be as effective as engineered strategies in specific mangrove environments over the long term. Changes in diagnostic ratios (pristane/phytane and n-alkanes) confirmed the preferential degradation of linear hydrocarbons. These findings highlight the potential of low-cost, nature-based remediation and suggest that intrinsic processes may suffice for long-term recovery, emphasizing the need for extended studies to fully evaluate engineered treatment advantages.