No 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.

No abstract

Physical-biogeochemical models help us to understand the dynamics and the controlling factors of primary production. In this study, the outputs of a validated hydrodynamic and biogeochemical model were used to elucidate the primary production dynamics between 1992 and 2012 for three studied sites on the Lebanese coast: Naqoura, Beirut, and Tripoli. The results showed that primary production presents a homogeneous spatial distribution along the Lebanese coastline. The phytoplankton community has a low optimal temperature. The thermocline develops in March, with maximum stratification in August and fades in October. Chlorophyll, dissolved oxygen and salinity were positively correlated throughout the water column. A significant increasing trend of sea surface temperature was found on the Lebanese coast over 27 years, between 1986 and 2013. Annual averages increased from 22°C in 1986 to 23.1°C in 2013 with the highest recorded average temperature of 23.7 °C in 2010.