Coastal pollution monitoring: Foraminifera as tracers of environmental perturbation in the port of Boulogne-sur-Mer (Northern France)

Abstract

Abstract: Benthic foraminifera are increasingly used as environmental indicators of natural and/ or anthropogenic stress in coastal and marginal marine settings. A study of both living (Rose Bengal stained) and dead foraminifera was carried on 317 sediment samples collected in the port of Boulogne-sur-Mer (France). Here we present an initial status report on the port ecosystem as recorded from a selected set of sediment samples that cover the full range of habitats within the port. A surprisingly high diversity assemblage of benthic foraminifera was recovered, reflecting the varied habitats within the port. Among the total of 82 species recorded, 34 were found alive (rose Bengal stained). Four key species were identified as potential bioindicators and analyzed with regard to their distribution and correspondence with environmental parameters (sediment grain size, organic carbon content and heavy metal concentration, Cr, Cu and Zn). The benthic foraminifera Haynesina germanica and Bolivina pseudoplicata were found to live particularly well within the innermost parts of the port basins where the highest concentrations of organic carbon and heavy metals occur. Elphidium excavatum and E. magellanicum are well represented in the external parts of the port and can be considered as indicators that tolerate certain threshold values of pollution and environmental stress. As the port is located in an estuarine setting, the relationship between the key indicator taxa for pollution and natural environment is discussed. This study emphasizes the need to address the anthropogenic impact on coastal environments by screening the ubiquitous record of foraminiferal protists as precision tools for bio-monitoring.