Surface waters are precious natural resources because of the various socioeconomic activities taking place in them (fishing, maritime transport, industrial activities, agriculture, etc.). Unfortunately, worldwide, the majority of wastewaters generated by these activities are rejected in the environment without any proper treatment. This investigation was carried out in February, July and October 2012 to assess the temporal and spatial gradients in organic matter (DOC, COD, BOD, PI, TOC, POC, UV254 and SUVA), and algal biomass (Chl-a) in Aghien Lagoon. The samples were analyzed according to standard methods. The results indicate that the organic pollution indicator parameters as well as chl-a are high in the rainy season (June) with significant differences (p<0.05) from those of the dry season. The highest values of turbidity (44.28 NTU), Electrical conductivity (71.63 µS.cm -1 ), DOC (177.3 mg.L -1 ) and TOC (15.65 mg.L -1 ) were recorded at Station 1 and also during this period. Moreover, the PCA tests conducted indicate that the measuring stations located upstream of the lagoon are more exposed to organic pollution because they receive river water and possibly wastewater from the surrounding localities. The data have revealed the necessity of the Aghien Lagoon Assessment… Kandana Marthe YEO et al.