MICROBIOLOGICAL, PHYSICOCHEMICAL AND GENOTOXICOLOGICAL CHARACTERISTICS OF WATER, SEDIMENTS, AND SOIL FROM COASTAL AREAS OF ONDO STATE, NIGERIA

Abstract

The study investigated microbial communities, physicochemical parameters, concentrations of various heavy metals, and genotoxic potential of water, sediment, and soil of Ilaje community of Ondo state, Nigeria, during wet and dry seasons. Heterotrophic bacterial and fungal counts were evaluated using standard microbiological techniques. Standard methods were used to analyse physical and chemical parameters, including pH, electrical conductivity, total dissolved solids (TDS), total hardness (TH), and total alkalinity, cations (Ca2+, Na+, K+, Mg2+, and Fe2+), and anions (S2-, N2-, NO3 −, PO4 3−, Cl−, and SO4 2−). Heavy metals (cadmium, arsenic, lead, nickel, chromium, vanadium, copper, zinc, and iron) were analysed using standard analytical methods. Genotoxic potential of samples was evaluated using the Ames test and SOS chromotest. Also, questionnaires were administered to 3,370 individuals living and working in the sample locations. The microbial counts in water samples ranged from 5.67 to 59.00 (x 103) cfu/ml for bacteria and 2.20 x 103 to 9.00 x 103 sfu/ml for fungi, that of sediments ranged from 5.33 x 103 to 48.33 x 103 cfu/ml for bacteria and 2.67 x 103 sfu/ml to 57.67 x 103 sfu/ml for fungi, while soil samples ranged from 2.67 x 103 cfu/ml to 74.33 x 103 cfu/ml for bacteria and 3.00 x 103 sfu/ml to 61.67 x 103 sfu/ml for fungi. Microbial counts were higher in the dry season compared to the wet season. Twenty eight (28) bacterial and 18 fungal isolates were identified in samples, including known hydrocarbon degrading microorganisms (Acinetobacter baumannii and Bjerkandera adjusta). pH in water, sediment and soil samples ranged from 5.94 to 7.32, 5.58-6.56, and 4.08-6.41 respectively. The temperature of water, sediment and soil ranged from 27.14 to 29.42°C, 27.58 - 29.29°C and 27.48-32.02°C, respectively. Electrical conductivity (EC) content in water, sediment and soil samples was higher during the dry (96.15, 298.46, 235.26 μS/cm) than the wet season (78.37, 241.56, 239.17 μS/cm), and organic matter content was also higher during dry (6.60%) than wet season (5.58%) in sediment samples only. Cation (calcium, potassium, ammonia, and magnesium) and anion (sulphate, nitrate, vii and phosphate) contents in water were higher in the dry season compared to the wet season. The concentration of heavy metals (cadmium, vanadium, copper and lead) in water were also higher during the dry season compared to the wet season. All samples from all locations produced frameshift mutations, suggestive of mutagenicity. Genotoxic potency was higher during the dry season than the wet season which was highest in sediment samples, followed by soil and water. Despite the detection of microorganisms associated with gastrointestinal (GI) problems, questionnaire data suggested that only a minority of individuals reported GI problems (cholera, 5%; diarrhoea, 12%; dysentery, 19%; typhoid, 15%). Therefore, the array of microorganisms, physicochemical and genotoxicological characteristics of the samples indicated negative environmental and health implication on the residents in the study area.