ABSTRACT: Sixty- three bottom sediment samples were collected from the Burullus Lagoon with the purpose of determining the distribution pattern of the palynomorphs and microfauna, the relationship between dominant species and different environmental variables, and environmentally assessing pollution impacts following construction of a major motorway (the International Highway Project). Salinity played an important role in the distribution pattern of the living biocoenose, while temperature, dissolved oxygen and organic carbon have had a negligible effect. The biodiversity of the Burullus Lagoon is threatened by dilution of the marine water with freshwater entering the basin from irrigation canals. The high content of iron, as well as drainage water from agricultural activities, could have polluted the southern fringe of the lagoon. Heavy metal concentrations in the basin’s eastern sector could also have a fatal effect on biodiversity. The opportunity is taken tomake mitigation recommendations concerning on-going environmental impacts in the lagoon.