Benthic foraminifera as a bioindicator of the environmental quality: a case study from the lagoon of Santa Gilla (Cagliari, Italy)

Frontalini, F;BUOSI, CARLA;Coccioni, R;Cherchi, A;DA PELO, STEFANIA;Bucci, C.

2008-01-01

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Abstract

Benthic foraminifera are increasingly used as environmental bio-indicators of pollution in coastal and marginal marine settings. Their community structure provides useful information on the general characteristics of the environment quality and some species are sensitive to specific environmental parameters (e.g., ALVE, 1991, 1995; YANKO et alii, 1994, 2002; COCCIONI, 2000; SAMIR, 2000; DEBENAY et alii, 2001, 2005; GESLIN et alii, 2002; COCCIONI et alii, 2003, 2005; ARMYNOT DU CHÂTELET et alii, 2004; COCCIONI & MARSILI, 2005; FRONTALINI & COCCIONI, 2008). The lagoon of Santa Gilla, on an area of about 13 km2, is located on the southern coast of Sardinia (Italy) and communicates with the Mediterranean through a narrow channel. On the northern shore, the lagoon has two major freshwater inflows from the Rii Mannu and Cixerri rivers. On the west, the on-shore industrial area and the urban area of Cagliari discharged untreated wastewater from the mid-1960s to mid-1980s (DEGETTO et alii, 1997). Sediment samples were collected from 18 stations during October 2006. Physicochemical data of water, geochemical, sedimentological, and benthic foraminiferal data (biocenosis and trace element contents in foraminiferal tests) have been analyzed to investigate the relationship between these sensitive microrganisms and trace element pollution. The analysis of sediments indicated that the lagoon is deeply affected by trace element pollution (Cd, Ni, Pb, Zn and Hg). The biocenosis of the lagoon are largely dominated by Ammonia tepida, Haynesina germanica and Cribroelphidium oceanensis and, subordinately, by bolivinids. Foraminiferal species and trace element concentrations were investigated both with bivariate (correlation matrix) and multivariate techniques of principal component analysis (PCA) and cluster analysis. Statistical analysis shows a possible control of these pollutants both on the taxonomic composition of the benthic foraminiferal assemblages and the development of test malformations which is used as additional tool for the pollution monitoring. This study confirms and supports the suitability of studying benthic foraminifera as a technique for the in situ continuous bio-monitoring of trace element pollution of coastal marine sediments. This study was carried out within the framework of the ForamLag Project aimed at studying the response of benthic foraminifera to contaminants in the main Italian lagoons.