10-year time course of Hg and organic compounds in Augusta Bay: Bioavailability and biological effects in marine organisms

Abstract

In the last century, many Mediterranean coastal areas have been subjected to anthropogenic disturbances from industrial activities, uncontrolled landfills, shipyards, and high maritime traffic. The Augusta Bay (eastern Sicily, Italy) represents an example of a strongly impacted coastal environment with an elevated level of sediments contamination due to the presence of one of the largest European petrochemical plants, combined with an extensive commercial and military harbor. The most significant contaminants were represented by mercury (Hg) and hexachlorobenzene (HCB), derived from a former chlor-alkali plant, and other organic compounds like polycyclic aromatic hydrocarbons (PAHs) and polychlorobiphenyls (PCBs). Since the 1970s, Augusta Bay has become internationally recognized as a contaminated marine environment, although very little information is available regarding the temporal trend of contaminants bioavailability and biological impacts on aquatic organisms. In this study, the Hg and HCB concentrations were investigated over 10 years (from 2003 to 2013) in sediments and invertebrate and vertebrate organisms; these two contaminants' ecotoxicity was further evaluated at a biochemical and cellular level by analyzing the induction of organic biotransformation processes and DNA damages. The results showed high concentrations of Hg and HCB in sediments and their strong bioaccumulation in different species with significantly higher values than those measured in reference sites. This trend was paralleled by increased micronuclei frequency (DNA damage biomarker) and activity of the biotransformation system. While levels of chemicals in sediments remained elevated during the time course, their bioavailability and biological effects showed a gradual decrease after 2003, when the chlor-alkali plant was closed. Environmental persistence of Hg and HCB availability facilitates their bioaccumulation and affects the health status of marine organisms, with possible implications for environmental risk, pollutants transfer, and human health.

Keywords: bioavailability; biomarkers; hexachlorobenzene; marine organisms; mercury; trophic transfer.

Figure 1

Augusta Bay with the sea bottom depth. In gray color, the industrial area. In the small box is reported, in addition to Augusta Bay (green area), the whole extension of the Site of National Interest named “Priolo-Gargallo” on land (red area) and sea (blue area).

Figure 2

Sediment sampling stations (from A to P), native mussels stations (from 1M to 6M), transplanted mussels stations (from 1T to 6T), fish stations (from 1F to 3F) from 2003 to 2013 and hauls for different years (1H, 2003; 2H, 2004; 3H, 2008; 4H, 2013).

Figure 3

Micronuclei frequency in the haemolymph of native (A) and transplanted (B) mussels. Data are expressed as mean ± SEM and n = 5. Letters indicate differences among all the sampling sites for each year p < 0.01; n.d., not detectable.

Figure 4

Micronuclei frequency in M. barbatus gills. Data were expressed as mean ± SEM and n = 5. Letters indicate differences among all the sampling sites, p < 0.01.

Figure 5

EROD activity in M. barbatus. Data are expressed as mean ± standard deviation. Letters indicate differences among all the sampling sites, p < 0.01.