This study aimed to provide relevant knowledge about the dynamics of the hydrological parameters in the river-estuary continuum of the Wouri-Nkam river estuary for a sustainable management program. The hydrological parameters were recorded in eleven stations spanned out on the basis of population density and human activities. Water quality parameters (Temperature, salinity, dissolved oxygen, pH, Total dissolved solutes, Redox potential and conductivity) were collected in subsurface water using a multiple parameter. Surface currents and morphometric (depth and width) parameters were recorded using a drifter, sonar depth and GPS. The field measurements took placed between 18/05/2019 to 08/09/2020 and were divided into six (06) cruises. The data were later subjected to an analysis of variance (ANOVA) and Principle Component Analysis using XLSTAT 2017 (2.7 version) software. Results obtained revealed that, the water quality parameters were spatially more stable not signficant at (df = 9, p < 0.05) with a relatively low temperature (25.5˚C -27˚C) during the wet period. The limit of the frontal zone extended to S5 (Bonalokan, 8.25 km from S1) during the snapshot of the dry period, spring phase and flood tide conditions. Inversely, during wet period, this extension reduced to S1 (Bridge) and relatively increases slightly to S3 (Bonangang) during the neap phase and ebb tides of this season. This result revealed a change in the axial gradient of about eight (08)

The aboveground biomass (AGB) of Gabonese mangroves is commonly estimated from equations calibrated in other countries, and is generally adapted poorly to the local context. This paper focuses on developing local allometric equations for the AGB estimation and to evaluate their accuracy compared to other general equations. The local equations for Rhizophora spp and Avicennia germinans were performed with tree volume, bark and wood densities, and are used with the diameter as an independent variable. The heights and diameters of 408 trees (314 Rhizophora spp and 94 Avicennia germinans) were measured at 13 sites in Estuaire Province. Sixty-four aliquots were taken from the trunks of both species at the Mondah site. This site has tree diameters ranging from 2 to 127 cm for Avicennia and from 1.4 to 75.8 cm for Rhizophora. The tree height ranges from 0.9 to 24 m for Avicennia, and from 1.1 to 53 m for Rhizophora. Avicennia has an overall trunk density of 0.88 g/cm3 and Rhizophora has 1.17 g/cm3. The coefficient of determination (R2) of the equations are 0.98 for Rhizophora spp, 0.97 for Avicennia germinans, and 0.99 for the general equation. The seven equation display biases that are less than 1% and the root mean square errors vary between 0.073 and 1.68. Compared to other equations generally used, these local equations improve the accuracy of aboveground biomass estimations of Gabonese mangroves.