First data on the distribution and morphological anomalies of the recent foraminifers in the Marano and Grado Lagoon of (Adriatic Sea).

Abstract

The Marano and Grado Lagoon along the northern Adriatic coast, is an environment of naturalistic but also economic value, since it is exploited by man for industrial, farming and fishing activities. At the present, this area is constantly under quality control in accordance with the recent environmental directives. This environment historically experienced a significant input of mercury (Hg), carried from the Isonzo River draining the cinnabar deposits of the world\u2019s second largest Hg mine at Idrija (Slovenia), which has been in activity for 500 years. Recent studies indicate that Hg it is the most common contaminant in the sediments and previous studies have also revealed its presence in the aquatic food chain. Benthic foraminifers were investigated in the recent sediments collected during the \u201cMiracle Project\u201d (AA.VV., 2010). The diversity index is lowest in the stations in front of the Aussa-Corno River mouth, which is the area mostly affected by environmental stress (mercury pollution and/or natural salinity variations). Here, a greater dominance of brackish forms such as Ammonia tepida, Elphidium granosum, E. gunteri and Haynesina germanica has been recognized. Conversely, slightly higher values of diversity appear in less restricted areas of the lagoon or, at least, where physical parameters such as temperature and salinity are less variable (or more constant). Here, the association is characterized by more thalassic taxa, such as miliolids and arenaceous species. The greater frequency of E. granosum, E. gunteri and H. germanica is recorded in the western sector of the lagoon (Marano), which is more affected by industrial activities. On the contrary, the greater dominance of A. tepida is recognized in the eastern lagoon (Grado), where the sediments are enriched in Hg, mainly in mineral form. The deformation tests, carried out mainly on dead specimens, showed very high FAI (Foraminiferal Abnormality Index) values in the lagoon areas highly affected by riverine tributaries compared to the low values found in less restricted areas. However, the types of deformation are very often those involving only limited dimensional changes of the chambers. Concerning the study of some cores, higher FAI index coincides with the highest concentrations of Hgtot in the recent sediments, whereas the index decreases with depth in agreement with the decreasing Hg content. Plotting the concentration values of Hgtot and the deformation of the shell according to the calendar age scale, calculated on the basis of the 210Pb activity log distribution (AA.VV., 2010), a sharp increase of pollution and tests deformation following the period of great industrial expansion of 1950 is observed. AA.VV. , 2010 \u2013 Messa a punto di un metodo per l\u2019individuazione delle aree da destinarsi alla venericoltura (Tapes philippinarum) a minor rischio di contaminazione da mercurio in Laguna di Marano e Grado. Progetto Miracle. Rapporto tecnico 1- Commissario Delegato per la Laguna di Marano e Grado. Universit\ue0 degli Studi di Trieste, 279 pp