The status and dynamics of water quality attributes of the three river estuaries in the Gulf of Guinea (Nigeria)

Background/Question/Methods

The Niger Delta region of Nigeria in which the three estuaries are located is very rich in petroleum hydrocarbon with increasing oil activity and anthropogenic perturbations including gas flaring. The status and dynamics of the water quality of Cross River estuary (CRE), Qua Iboe River Estuary (QIRE) and Imo River Estuary (IRE) which empty into the Gulf of Guinea was investigated for six years (Jan. 2007 – Dec. 2012 inclusive) to evaluate spatial and temporal patterns, in relation to the increasing oil activity and major trade wind patterns. The three estuaries drain different catchments part of which are forested, covering >120km with considerable anthropogenic perturbations. Standard analytical procedures including in situ determinations were employed to evaluate water quality attributes, organic carbon load, transport and sediment characteristics.

Results/Conclusions

The water quality attributes of the three estuaries varied remarkably with significant (p<0.002) spatial differences. Each of the estuaries exhibited distinct spatial variations in the water quality attributes particularly conductivity, total alkalinity, total dissolved solids and total hydrocarbon concentrations (THC) and was influenced by watershed characteristics. Segments that drain forested catchments received large amounts of total organic carbon (TOC) load in the form of dissolved (DOC) and particulate (POC) carbon. Majority of the water quality attributes cumulated significantly with precipitation. Temporal trends in the water quality attributes were influenced by the major trade wind regimes, particularly ionic conductivity (480.95 – 4500.00 µScm^-1), FDS (620.80 – 3800 mg/L) and THC (9.45 – 112.69 mg/L) with lowest values recorded during the wet tropical maritime trade mind regime. The water quality of the three river estuaries varied from slightly to highly perturbed and were influenced by precipitation, anthropogenic perturbation and episodic events. The results show that the water quality of all the three estuaries of the Gulf of Guinea were affected by the diverse anthropogenic activities and this in turn may affect the prevalent biota.