Abstract
Marine ecosystems are vital natural resources that contribute to the global biogeochemical cycle, food, and energy production. In order to monitor and evaluate variations of different factors for decision making processes, validated ecosystem models were used in this study to analyze the evolution of different variables: temperature and salinity concentrations (from 1987 to 2014) and nitrate, phosphate, dissolved oxygen, chlorophyll concentrations, and phytoplankton biomass (from 1999 to 2014) in four sites (from 0 to 66 m depth) along the Levantine Sea: Lebanon, Turkey, Egypt and in the Open Sea. Principal component analysis and TRIX were then applied. Spatio-temporal analysis and PCA results showed that phytoplankton biomass is temporally affected by temperature and nutrients (in all stations) as well as salinity in some cases, in addition to its decrease with depth. TRIX analysis showed that all stations had higher primary productivity, in the first half of the year (January-May). Intense anthropogenic activities in Turkey and Egypt have altered the ecosystem’s stability and affected the phytoplankton biomass.