Physicochemical Properties and Bacterial Population in the Rhizosphere of Mangrove Plant Species at the Upper Reaches of Santa Barbara River, Central Niger Delta, Nigeria

Abstract

The objective of this paper is to evaluate the physicochemical properties and bacterial population of the rhizosphere of five mangrove plant species (Rhizophora mangle, Rh. racemosa, Laguncularia racemosa, Avicennia africana, and Nypa fruticans) at the upper reaches of Santa Barbara River, central Niger Delta, Nigeria using standard methods. The population of bacteria was highest in the rhizosphere of Rh. racemosa, being 8.38 x 10⁶ cfu/g, which was followed by N. fruticans with a density of 5.04 x 10⁶ cfu/g, while others were significantly lower, with the least density occurring under A. africana with a population density of 1.41 x 10⁶ cfu/g. Nineteen species of bacteria were presumably identified in the study area. Bacillus sp dominated the rhizosphere of all the mangrove plants with a frequency of 15.52%, 20%, 19.67%, 20.51 and 13.43% for Rh. racemosa, Rh. mangle, A. africana, L. racemosa and N. fruticans respectively. The 16S rRNA sequencing of isolates confirmed the presence of diverse species of Bacillus including B. mycoides, B. paramycoides, B. pumilus, B. siamensis, B. velezensis, the closely related Priestia megaterium, among other species such as Klebsiella quasipneumoniae, and Photobacteriuum ganghwense in the rhizosphere of the mangrove trees. The study therefore revealed the culturable bacteria guides in the mangrove rhizospheres which could potentially be developed for restoration and rejuvenation of impacted mangrove ecosystem.