EFFECT OF FLOOD ON FRINGE MANGROVE IN SOUTH-EASTERN NIGERIA

Abstract

This study assessed the effect of flood on fringe mangrove in South-eastern Nigeria. The approach includes assessing historical climatic factors of about 50 years in comparison to field studied data with the standard method of sampling and analysis. The mean temperature of surface water in south-eastern Nigeria ranges from 26.7°C to 32.0oC, salinity record varied from 17.7 0/00 to 31.7 0/00 minimum and maximum respectively, dissolved oxygen (DO) which indicates the healthy nature of a water body ranges between 3.7 and 5.0 mg/l. Mangroves coverage in the study area between 1982, 2003 and 2021 is given as 55%, 31% and 14% respectively, with ANOVA test p-value of 0.02 and 0.03 for row and column data. The correlation of temperature to rainfall show negative r = -0.09194, annual sea level show a strong correlation (r = 0.831499) with temperature, pointing out that temperature is the main key factor contributing to the flooding and inundation of the south-eastern Nigerian coast. Temperature and salinity correlate positively (r = 0.981) with each other and both correlate negatively with dissolved oxygen (r = -0.70, -0.82), correlate positively with mangrove species abundance (r = 0.838, 0.927) and diversity in same range while correlating negatively with mangrove evenness distribution (r = -2E-16). The study showed that the mangrove ecosystem in south-eastern Nigeria had decreased in size due to changing environmental condition such as temperature, salinity, annual rainfall and sea level rise. The goods and services provided by this ecosystem also decreased posing a threat to poverty alleviation and climate change mitigation in south-eastern Nigeria. The study concluded that aside from human influence to mangrove ecosystem, flood poses a great threat through inundation and coastal erosion to the survival and sustenance of this ecosystem and its services rendered to the environment and mankind in general.