Full Length Research Paper

Application of correlation analysis in assessment of relationships between mineral hydrocarbon levels and hydrocarbonoclastic bacteria count in tropical mangrove estuarine sediments

Joseph P. Essien¹, Nsikak U. Benson²* and Sylvester P. Antai¹

¹Environmental Microbiology and Biotechnology Unit, Department of Microbiology, University of Calabar, P. M B. 1115, Calabar, Nigeria.

²Department of Chemistry, College of Science and Technology, Covenant University, P. M. B. 1023, Ota, Nigeria.

*Corresponding author. E-mail: nsikak_benson@yahoo.com.

Accepted 20 February, 2008

Pearson’s Product-Moment correlation analysis of the relationships between total hydrocarbon content (THC) and hydrocarbon utilizing bacteria population (HUB) in mangrove sediments and overlying water of the Qua Iboe Estuary, Nigeria was carried out. The results show that there was in general a close relationship between the two variables, but also a large amount of variation not explained by the analysis.  The strongest positive relationships (p = 0.05) were found for THC in epipellic (intertidal) sediment and water (r = 0.65) while the relationship between THC in benthic (subtidal) sediment and water (r = 0.028) was weak, and positively insignificant (p = 0.05).  A correlation of HUB densities on THC in benthic sediment was strong and positive (r = 0.91) but characterized by high HUB/HET ratios. That is, the strength of the relationship with respect to the oil degrading potentials of the bacterial was fairly low. In contrast, the relationships between the two variables in epipellic sediment (r = 0.66) was positively significant (p = 0.05) but with a substantial presence of heterotrophic bacteria. This implies that a quick-analysis of hydrocarbon content in epipellic sediment in relation to hydrocarbon utilizing bacteria densities following an oil spill is reliable. However, such analysis on benthic sediment may not be reliable in estuarine environment with chronic exposure to crude oil pollution. This is despite the wide distribution of HUB (82.4% in benthic sediment, 43.1% in epipellic sediment, and 33.3% in surface water) in the ecosystem as revealed by the coefficient of determinations (R²) values.

Key words: Hydrocarbons, hydrocarbonoclastic bacteria, mangrove sediments, correlation analysis.