Microbiological Properties and Population Dynamics of Atmosphere in Mesotidal Estuarine of Iko River, Akwa Ibom State, Nigeria

Abstract

The microbiological properties and population dynamics of atmosphere in mesotidal estuarine of Iko River were investigated using standard microbiological and analytical procedures. The results revealed that the densities of culturable microbes in the estuary were influenced by tidal regimes. Their abundance varied between both tides as well as locations. Proportionately more fungal isolates were found in the estuarine air. There was a significant positive correlation (r = 0.717, p < 0.05) between the total heterotrophic bacteria in the atmosphere and wind speed, and between the fungi in the atmosphere and wind speed (r = 0.799) during high tide, indicating that increase in wind speed resulted in a corresponding effect in heterotrophic bacterial and fungal counts during high tide. A comparison of the relation between atmospheric temperature and microbial load showed little or no correlation (r =0.30). The results of the air quality attributes of Iko Estuary during low tide and high tide showed that the quality of air in the estuarine environment was affected. The air quality in the estuarine environment was relatively "clean" and wholesome as most criteria gaseous pollutants (HCN, NO2, SO2) except CO and SPM were below detectable limits and within the FMENV and WHO acceptable limits. However, the recorded levels of CO in some parts of the fishing settlement were above Federal Ministry of Environment (FMEnv) limits of 10.0 - 20.0 ppm for daily average of 8 hourly values in Nigeria. The levels of atmospheric contaminants varied between low and high tides. The 2.0 ppm level of SPM recorded during high tide is higher than the FMEnv limits of 0.25ppm and is dangerous. The study has revealed significant emission of CO from the fish smoking activity which is common in the settlements. Geographic Information System (GIS) models of microbial communities revealed marked variation which ranged between tidal influences and microhabitats. The model revealed high concentrations of microorganisms in the north-west zone during both tides, while fungi were highly concentrated in the north-east zone during high tide. High species richness was observed, but with little or no tidal influences and isolates included known pathogenic species. The findings revealed that tidal bars and flats in shallow mesotidal estuary are subject to the action of tidal currents and waves. These complex events give rise to large variations in microbial communities in estuarine microhabitats which may be harnessed for effective environmental monitoring.