Assessment of Inorganic Nutrients and Redfield Ratios in Waters Along Abobo-Doume Fish Market, Cote Divoire

Abstract

Dissolved inorganic nitrogen and phosphorus are among the pollutants that are used worldwide for coastal waters quality assessment due to their ecological and toxicological effects on the aquatic ecosystems. Waters quality along the Abobo-Doume Fish Market in Ebrie Lagoon was assessed using five (5) stations by measuring pH, temperature, salinity, Electric conductivity, transparency and Total dissolved solids (TDS) on one hand, and on the other hand, inorganic nutrients concentrations as ammonium (NH4+), nitrite (NO2-), nitrate (NO3-) and phosphates (PO43-) by colorimetric methods. To quantify the primary production limitation, the N:P ratios were calculated and then compared to the Redfield one (16:1). Temperature, pH, salinity, Electric conductivity, transparency and Total Dissolved Solids (TDS) were found in respective ranges of 27.99-28.71°C 8.23-8.39 28.50-30.43‰ 44.30-46.7mS/Cm, 0.5-1.0m and 27.48-29.11 mg/L. NH4+, NO2-, NO3- and PO43- were found in the respective ranges of 0.318-0.753, 0.060-0.067, 1.90-5.20 and 0.38-0.55 mg/L. The highest concentrations of nitrogen and phosphorus species were respectively observed in surface and bottom waters. The analyzed waters were of Bad Quality due to high nitrate, nitrite and phosphates concentrations that were more than three times above the Bad Quality Class defined by the European Environmental Agencys criteria. The N:P ratios ranged from 7.94 to 25.36, and the ratios observed in surface waters were higher than the bottom ones. Waters were generally phosphorus (P)-Limited in surface and nitrogen (N)-Limited in bottom layers. Due to the high nutrients concentrations observed, a long-term assessment is therefore recommended to evaluate the temporal trends of the waters quality along Abobo-Doume Fish Market.