Seasonal variations in some physiochemical parameters of the Bonny estuary, Niger delta.

Abstract

This study is based on eight research cruises carried out on the bonny river system from December 1986-september 1988. Variations in some physico-chemical parameters of water [Transparency, temperature, pH, DO, salinity, conductivity, PO4, NH4 SiO2 and alkalinity] observed at 10 stations located in the main channel of the river are presented. Results showed that salinity, conductivity, pH, DO, and alkalinity exhibited spatial and temporal variations. In general, the upper estuary was slightly acidic while the middle and lower estuary were alkaline .A slight decrease in water temperature with depth was observed in most of the stations. The amplitude of variation in surface and bottom water temperature was generally between 0.5-2oC. Significant salinity variations were also observed. Minimum salinity values of 10-24 and maximum of 19-31 were recorded in the late wet season and late dry season respectively in both the upper and lower reaches of the estuary. Vertical salinity gradients also existed at most stations during both wet and dry seasons. On the basis of salinity, the Bonny estuary is classified into three zones. Upper reach [mesohaline at all seasons except in the late dry season, salinity less 18]. Middle reach [polyhaline at all season, salinity 18-27] and Lower reach [polyhaline at all season, salinity above 27].