Spatial & Temporal Variability of Electrical Conductivity of The Atlantic Ocean, Gulf of Guinea, Nigeria
Medina Omo Kadiri *
Department of Plant Biology and Biotechnology, University of Benin, Benin City, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
This study examined the spatial and seasonal variability of electrical conductivity in the Atlantic Ocean across two major Nigerian coastal systems—the Bight of Benin and the Bight of Bonny—over four seasonal periods (dry, dry–wet, wet, and wet–dry). Integrated ocean-water samples were collected from a depth of 10 metres to the surface during four seasons: the dry season (January), dry–wet season (March), wet season (June), and wet–dry season (October), between 2014 and 2015. The real-time data showed ranges of 42.83–45.41 mS/cm in the Bight of Benin and 16.73–40.00 mS/cm in the Bight of Bonny. Conductivity, a proxy for salinity and ionic strength, exhibited pronounced regional contrasts associated with freshwater–seawater mixing, tidal dynamics, and river-discharge intensity. The values showed a dichotomy between south-southern and south-western Nigeria. The Bight of Benin consistently recorded high conductivity, particularly at Badagry, Lekki, and Bar Beach, where values remained above 42 mS/cm during most seasons, reflecting strong marine influence and minimal freshwater dilution. In contrast, the Bight of Bonny recorded substantially lower conductivity, especially in Cross River, Akwa Ibom, and Rivers States, where values frequently ranged from 16 to 30 mS/cm, depending on the season, owing to high freshwater input from major river systems. Bayelsa was the only location in the Bight of Bonny where values approached those of the Bight of Benin, indicating localised marine dominance. The data revealed temporal and spatial variability. Seasonal analysis revealed the highest conductivity during the dry season and the strongest dilution during the wet and transitional periods, particularly in the eastern sector. Values in Delta State showed spatial anomalies, with persistently low readings. Overall, the conductivity patterns highlighted a discernible gradient between the two bights: a stable, marine-dominated western zone and a freshwater-influenced eastern zone.
Keywords: Atlantic Ocean, Bight of Benin, Bight of Bonny, electrical conductivity, freshwater–seawater mixing, salinity proxy, seasonal variability, spatial variability