Benthic foraminifera and environmental changes in northern Sardinia: the case of the La Maddalena Harbour

Benthic foraminifera are reliable tools to paleo-environmental reconstructions because they are wide spatial-temporal spread, and they are sensitive to short-time environmental changes induced by both natural and anthropogenic events. Their community structure provides useful information on the general characteristics of the environment quality and some species are sensitive to specific environmental parameters. Changes in benthic foraminifera abundance, species composition and variation in test morphology provide evidence of fluctuation in several environmental factors and can therefore be used as an efficient method for determining the ecosystems conditions. This study presents the first micropaleontological data obtained through the analysis of a sediment core drilled from the shallow seabed (maximum depth ∼15 m) in the Ex-military arsenal of the La Maddalena harbour located on the southern-eastern coast of La Maddalena island (Sardinia, Italy). This area underwent different scenarios and environmental stresses over its history, in particular the investigated harbour worked as naval arsenal for nearly one century with heavy impact on the coastal zone. This study has been carried out to have information on the main environmental changes and to propose the most likely factors that caused these changes. The results showed that in the examined core, benthic foraminiferal assemblages were composed by over 90 species. The most frequent species were Elphidium crispum, Ammonia tepida, Planorbulina mediterranensis, Spiroloculina ornata, and Quinqueloculina spp.. Several biotic indices (species diversity, foraminiferal density, Shannon, Dominance, etc.) were also calculated. In general, the diversity indices show a decreasing from the first 50 cm of the core to the bottom. This slight decline is accompanied by changes in the foraminiferal assemblages. The results concerning changes in foraminiferal species composition, their abundance and biodiversity, supported by statistical analyses (cluster analysis), allowed identification of three major foraminiferal associations corresponding to different coastal-marine environmental settings.