Distribution of Recent Benthic Foraminifera in the Southern Basin of the Venice Lagoon (Italy): Statistical Evaluation of Taxa Significance

Abstract

The total benthic foraminiferal assemblage (living and dead) is analyzed for 95 samples collected in the southern basin of the Venice Lagoon [Chioggia Basin, Italy]. Quantitative results of the identified 48 species are statistically treated by correspondence analysis and Fuzzy c-means cluster analysis to define both the zonal environmental similarities (biotopes) and the faunal similarities (biofacies). In this lagoon basin, the biotopes delineate the area of marine influence, areas of mixed sea/lagoon, and zones of greater human impact that seem less heavily polluted with respect to the other two lagoon basins. The faunal similarities identified distinguish present sea and lagoon influences from the salt marsh assemblage, which are linked to the paleoenvironment. We show through statistical analyses that abundance is not the only factor governing the importance of the different taxa in defining biotopes. The important factor we found out is significance assumed as the ratio between abundance and distribution for both abundant and rare species. Results complete the knowledge on the present environmental condition of the Venice Lagoon and suggest limits of feasible simplifications to better define biotopes. These limits are given by the significant value of each taxon, which is greater, the smaller the equidistribution of the taxon itself.