Ecotoxicological Assessment of Nigeria Locally Refined Diesel and Kerosene on Aspergillus niger a Key Fungal Pollution Biomarker

Aim: To evaluate the effect of locally refined diesel and kerosene on Aspergillus niger a key fungal pollution biomarker in three aquatic bodies (marine, brackish and freshwater).

Study Design: The study employs experimental examination and statistical analysis of the data and interpretation.

Place of Study: Fresh water, brackish water, and marine water samples were collected in sterile bottles from Ugama Ekede Stream, Ugama Ekede River and at the foot of the Atlantic ocean in Udun Ama all in Andoni Local Government Area Rivers State, using sterile sampling bottles. These samples were transported to the microbiological laboratory with ice pack within 24 hours for both isolation of test organisms and toxicity.

Methodology: Standard microbiological techniques were used; toxicity testing procedures were carried out by preparing locally refined diesel and kerosene at concentrations of 0%, 5%, 10%, 25%, and 50%, tested for durations of 0 h, 24 h, 48 h, 72 h, 96 h. The cultures were incubated at 35°C for 48 hours. LC50 was determined.

Results: The results specify that percentage (%) logarithm of mortality of Aspergillus niger increases with increased toxicants concentration and exposure time. The median lethal concentration (LC50) of the locally refined diesel and kerosene increases in the following order: (Note: The higher the LC50, the lower the toxic effect. Aspergillus niger in locally refined diesel in fresh water (47.77%) < Aspergillus niger in locally refined kerosene in fresh water (48.02%) <Aspergillus niger in locally refined diesel in brackish water (48.09%) < Aspergillus niger in locally refined kerosene in brackish water (48.14%) < Aspergillus niger in locally refined diesel in marine water (48.09%) < Aspergillus niger in locally refined kerosene in marine water (47.98%).

Conclusion: Locally refined diesel in fresh water (LC50 = 47.77%) is the most toxic, having the lowest LC50while locally refined kerosene in brackish water (LC50 = 48.14%) have the lowest toxicity effect. These results show that locally refined diesel and kerosene can inhibit the growth of Aspergillus niger in an aquatic ecosystem; noting that Aspergillus niger is one of the most effective biodegrading fungi in ecological biogeochemical cycles, pollutant removal/remediation and a key fungal pollution biomarker.