Benthic foraminifera from the transitional zone naturally exhibit high tolerance to highly varying conditions. In the harbor of Boulogne-sur-Mer (Northern France), historical data have demonstrated a correlation between the decline of benthic foraminiferal communities and pollution levels. A total of 241 samples were collected during three campaigns, all organized early spring: in 2008, immediately after the dismantling of industrial facilities, followed by sampling in 2014 and 2019. The aim was to observe the evolution of benthic foraminifera communities alongside environmental changes, as reflected by the sediment nature and texture, as well as organic and inorganic geochemistry. The density of foraminifera showed a noteworthy increase in parallel with a decrease in trace metal elements concentrations in the sediment. Species richness also increased over time: 31 alive species were identified in 2008, whereas 41 were observed in 2019. These included commonly described species in such environments: Cribroelphidium magellanicum, C. excavatum, Haynesina germanica, and Ammonia group. Calculated diversity, however, exhibited minimal variation over time. Consequently, assessing foraminiferal density provides a dependable indicator of sediment quality, without the need for detailed species and diversity analysis. Nonetheless, interpretations of potential pollution effects must be nuanced, considering sediment texture, e.g. coarse sediments may not support foraminiferal development.