This study aims to evaluate the health status of Bizerta lagoon using a
sentinel species, the Neogastropod Murex trunculus. Trace metal concentrations (Cd, Cu and
Zn) in the foot and digestive gland, and biomarkers such as
acetylcholinesterase (AChE), catalase (CAT) and glutathione transferase
(GST) activities in the digestive gland, were determined in samples
collected at four sites at different periods of the year. One site, in the
North of the lagoon, is influenced by urban and industrial waste waters.
Another, to the south, is located at the outfall of Ichkeul Lake. A third
site is one that may be impacted by eutrophication processes, and the last,
in the center of lagoon, is considered as less polluted. Temperature and
salinity were simultaneously measured during the mollusc samplings. They
varied greatly, from 13.5 °C and 30 psu in February to much higher
values in summer-autumn: 30.7 °C and 37 psu. Metal concentrations were
always higher in the digestive gland than in the foot. In the digestive
gland, the lowest Cd and Cu concentrations were found in the center of the
lagoon (mean ± standard deviation: 9.35 ± 0.78 µg Cd g−1 and 84.5 ± 15.3 µg Cu g−1) and no significant Zn variations were noted (682
± 38 µg g−1) between sites. Metal concentrations in
both types of tissue were higher in winter than in summer. AChE varied
significantly among sites with high activities for individuals in the center
of lagoon (15.4 ± 0.3 nmol min−1 mg-1 protein),
whereas GST were low (12.2 ± 0.8 nmol min−1 mg−1 protein); CAT
activities were low in this site 8.7 ± 0.5 µmol
min-1 mg-1 protein. Season also had an influence on biomarkers,
with low AChE in winter and rather low CAT and GST in summer. Principal
component analysis showed that the center of lagoon can be considered as a
reference site, whereas high chemical and biochemical responses were found
in M. trunculus from other sites; particularly at the site which may be subject to
eutrophication.