Chlorophyll–Nutrient Relationships of an Artificial Inland Lagoon Equipped with Seawater Replenishment System in the Northern Red Sea (Gulf of Aqaba)

Data are reported for an inland artificial lagoon (Ayla) to evaluate the impact of the lagoon’s modeled design and water replenishment system on its water quality and the coastal ecosystem. This study focused on Ayla’s upper lagoon (UL) only, due to its isolation from the two other lagoons and the ambient seawater in the Gulf of Aqaba (GoA). Nutrient measurements (nitrite, nitrate, ammonium, phosphate, and silicate) in addition to Chlorophyll a (Chl a) data were collected between July 2012 and June 2013. Chl a values in the UL were not significantly different from ambient seawater in the GoA, and the UL did not show seasonal differences (p = 0.456). Significant variability for nitrite was observed in the UL between spring and summer (p < 0.0001) and between fall and winter (p < 0.0001). Nitrite showed a stronger seasonal effect in the GoA seawater than in the UL (p = 0.056). Phosphorus showed a seasonal effect and remained similar between the UL and GoA. Nutrient stoichiometry showed a Redfield-like nitrogen-to-phosphorus (N:P) ratio for the ambient GoA seawater around the inlet pumping source and an increased N:P ratio inside the UL. This study emphasizes the importance of modeled lagoon design and seawater replenishment system in preventing and inhibiting eutrophication of the lagoon and therefore minimizing contamination in the coastal ecosystem.