LAUSR

Abstract Organic pollution is a major global environmental issue for coastal ecosystems. In order to assess the effects of this pollution, environmental parameters and phytoplankton community were monitored during a two-year period (from April 2010 till March 2012) in the central coast of Lebanon in the Levantine Sub-basin. Data were collected for temperature, salinity, nutrients, chlorophyll- a and phytoplankton community. Temperature followed its normal seasonal and annual cycles, usually noted in the Lebanese coastal waters, whereas salinity varied spatially and temporally presenting sometimes low values due to continental inputs (19.07–39.6). Significant fluctuations of nutrients ( N – NO 2 = 0.004 – 4.28 μ M L − 1 ; N – NO 3 = 0.25 – 39.15 μ M L − 1 ; P – PO 4 = 0.014 – 5.77 μ M L − 1 ), Chl- a concentrations ( 0.03 – 8.9 mg / m 3 ) and density of total phytoplanktonic cells ( 40383 – 22.1 0 6 cells/L ) were observed between the sites and through the years ( P 0.05 ). Environmental conditions were largely influenced by continental inputs. A perturbation of the natural phytoplanktonic succession and an occurrence of toxic or potentially harmful algae were noticed in the polluted sites, reflecting the influence of wastewater effluents on the coastal seawater equilibrium and thus on the Lebanese marine biodiversity. The overall study provides a good outline on the prevailing condition of few coastal areas which could facilitate the management of their pollution sources.