Abstract
Environmental conditions of two coastal lagoons situated on the Saudi Arabian coastal waters of the Red Sea were monitored after the implemented rehabilitation program and official cessation of sewage dumping. Based on salinity and nutrients at both Al Arbaeen and Al Shabab lagoons waters were still contaminated by sewage dumping. The average dissolved oxygen in Al-Shabab and Al-Arbaeen lagoon was 5.3 mg/L and 4.77 mg/L respectively. The subsurface water of these lagoons considered as hypoxic to anoxic environment containing hydrogen sulfide about 4 μM at 2 m depth in Al-Arbaeen lagoon. Even though the salinity of Red Seawater shows 39-42 psu, the salinity of both lagoons are in the range of 21.5–37.6 psu. The observed pH at discharging point of both lagoons exhibits low values and in the entire location it is ranging from 7.96–8.42 at Al-Shabab to 7.6–8.03 at Al-Arbaeen. The nutrient cycling was quite an interest and the results reflect the nitrogen loading at both lagoons. The results of the study give rise to concern on potential environmental risks on the Saudi Arabian marine environment, particularly the nutrient cycling and the behavior and availability of dissolved oxygen. It will also light on the future developing and recommendations on both environmental and biogeochemical aspects along both lagoons.