ABSTRACT

 Studies were carried out to assess the impact of Nipa populations on mangrove ecosystems and livelihoods of communities in Oron and Eastern Obolo estuaries, Akwa Ibom State. The following aspects were considered in the research: socio-economic analysis of the two areas under review, remote sensing, physic-chemical analysis as well as determination of the polycyclic aromatic carbons (PAHs) contents of the two estuaries. A total of 200 questionnaires were administered in Oron and Eastern Obolo, 100 in each location out of which 85 were recovered in Eastern Obolo and 77 in Oron. Demographic characteristics such as gender, age, years of working experience, educational level, occupation and duration of stay in the community etc, were considered in the questionnaire. Results for socio-economic analysis revealed that the respondents in both locations were familiar with the mangrove as well as the nipa palm. A significant proportion of the respondents agreed to the advantage of the mangroves over the nipa palms. Remote sensing of estauries revealed a progressive succession of the Nipa palms over the mangroves within a period of three decades (1986- 2018). The result showed a significant reduction (P > 0.05) in the population of mangroves and an increase in Nipa palms, from 7610 in 2000 to 5540 in 2018, while Nipa palm increased from 3411 to 6229. Satellite imageries obtained for both Oron and Eastern Obolo showed a decrease in the land area covered by mangroves while there was an increase in the area of land covered by Nipa palms. Physical parameters such as temperature, pH, salinity, electrical conductivity and total dissolved solids (TDS) all varied within the transects and between the two estuaries. Chemical parameters such as Alkalinity, acidity, Phosphate (PO₄^3-), Chloride (Cl^-), Ammonium (NH_4-N), Sulphate (SO₄^2-), Nitrate (NO₃^-) were analysed using titrimetric methods and they all varied within the transects and between the two estuaries. Anova result for the concentration of particles in the sediment showed that the proportion of sand was highest in the two estuaries (91.40^a±0.01 and 76.33^a±0.01%) in Eastern Obolo and Oron respectively, followed by silt, with clay being the least (8.10^e±0.03 and 4.22^e±0.02%) respectively.  pH of the sediment varied between 5.88^e±0.03 to 6.94^a±0.01 in Oron estuary and 5.42^e±0.09 to 6.91^a±0.04 in Eastern Obolo estuary. Other parameters analysed in the sediment included electrical conductivity, organic matter content, total Nitrogen, Available Phosphorus, calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), exchangeable bases, exchangeable acidity, effective cation exchange capacity (ECEC), base saturation were also analysed and they varied significantly within the transacts and between the two estuaries. Analysis of polycyclic aromatic hydrocarbons (PAH) showed a significant variation the various transects and between the two estuaries with the highest values of 45.3^a±0.06ng/g and 23.3^a±0.05ng/g obtained from Oron and Eastern Obolo control respectively. In summary, the outcome of the research shows a progressive succession of nipa palm over the mangroves. This calls for urgent action such as awareness campaigns, reforestation programs, government policies to protect the mangroves; if the ecosystem services performed by these mangroves will have to be sustained.