Tidal Dynamics And Physicochemical Parameters In A Tropical Estuary: Qua-Iboe River Estuary, Southeast Coast Of Nigeria

Abstract

Estuaries are important ecosystems that support biodiversity and influence the economy of the regions they occupy. Major physicochemical variables of Qua-Iboe River estuary in the Niger Delta region of Nigeria were assessed for ecosystem quality. The influence of tidal current on the spatial distribution of physicochemical parameters in the estuary was examined. Physicochemical parameters, including transparency, temperature, salinity, dissolved oxygen, density and pH were measured in-situ during the dry season. Tidal current velocities were monitored over spring and neap tidal cycles using the Langragian method and results indicated ebb dominance. The relationships between physicochemical parameters were statistically analyzed using Pearson’s correlation matrix. Based on Pearson’s correlation, density showed significant correlations (p < 0.05) with temperature, pH and salinity. Surface and bottom water temperatures significantly correlated (p < 0.05) with density, salinity, dissolved oxygen and pH. Spatial distribution maps of physicochemical parameters were plotted using ArcGIS Pro. Similarities and dissimilarities of surface and bottom water parameters were interpreted using cluster analysis. Results revealed two groups reflecting distinct physicochemical characteristics in the study area. Group one, representing upper and central portions of the estuary is defined by waters which are limnetic to oligohaline, slightly acidic to neutral with low dissolved oxygen (<4mg/l) conditions. The estuary showed limnetic conditions at the upper reaches due to the strong fluvial input by the Qua-Iboe River. Group two, representing the lower estuary, is characterized by mesohaline to normal marine waters; neutral to slightly alkaline pH, and low dissolved oxygen (< 4mg/l) conditions. This study is relevant for future monitoring and assessment of the estuary and similar tidal ecosystems.