Recent environmental changes of Al-Salam Lagoon as inferred from core sediment geochemistry and benthic foraminifera, Jeddah City, Saudi Arabia

The Al-Salam Lagoon is located at the center of Jeddah’s coast, showing unhealthy conditions such as evolving bad odor and spread of a thick sludge layer on its beach. The succession of its recent bottom sediments at the upper intertidal area was investigated through a sediment core SALAM1 (220 cm long) in order to evaluate the impact of pollution on the Al-Salam Lagoon’s environment, comparing with the conditions that existed prior to the industrial revolution. The principal component analysis and variations of benthic foraminifera in the core divided the recent bottom sediments of the lagoon into three intervals. The basal interval (below 110 cm) composed of low organic carbon, high carbonate, white-grey, bioclastic sandy mud enriched in oligotrophic, clear water, hypersaline symbiont-bearing species indicating deposition under unpolluted, natural lagoonal conditions with clear, high salinity waters. The middle interval (45 cm thick) showed a very rapid environmental change with deposition under unpolluted, natural lagoonal conditions as well but in a normal Red Sea salinity water due to a rapid overturn as evidenced by the decrease of hypersaline symbiont-bearing species. The upper interval (65 cm thick) composed of organic-rich, low-carbonate, reduced, black, sludgy mud indicating high anthropogenic activities. This black mud is devoid of benthic life except only two stress (pollution)-tolerant species, suggesting that the upper Al-Salam Lagoon is in its final stage of pollution.