EFFECTS OF NATURAL FACTORS (SALINITY AND BODY-WEIGHT) ON CADMIUM, COPPER, ZINC AND METALLOTHIONEIN-LIKE PROTEIN-LEVELS IN RESIDENT POPULATIONS OF OYSTERS CRASSOSTREA-GIGAS FROM A POLLUTED ESTUARY
C. Mouneyrac et al., EFFECTS OF NATURAL FACTORS (SALINITY AND BODY-WEIGHT) ON CADMIUM, COPPER, ZINC AND METALLOTHIONEIN-LIKE PROTEIN-LEVELS IN RESIDENT POPULATIONS OF OYSTERS CRASSOSTREA-GIGAS FROM A POLLUTED ESTUARY, Marine ecology. Progress series, 162, 1998, pp. 125-135
The Gironde estuary has been shown to be the most Cd-contaminated area
in France. Oysters Crassostrea gigas of different size classes were s
ampled from 3 sites between the mouth and 25 km upstream, to study the
relative importance of natural and contamination factors on metal acc
umulation and metallothionein-like protein (MTLP) induction. The highe
st metal and MTLP concentrations were observed in the digestive gland.
In all organs, the 3 metals were mainly cytosolic. An inverse relatio
nship was generally observed between weight of soft tissues and metals
or MTLP concentrations in the whole soft tissues, whereas the influen
ce of weight on metal distribution among cytosolic and insoluble fract
ions was small. When oysters with similar weight of soft tissues were
considered, no influence of salinity at different sites was found for
Cu and Zn whereas the lowest soluble and insoluble Cd concentrations w
ere observed at the mouth of the river. Salinity did not influence Cu
and Zn distribution among the cytosolic or insoluble fractions whereas
cytosolic Cd in gills and digestive gland (%) was higher at the mouth
of the estuary than upstream. MTLP and metal concentrations were gene
rally positively correlated except at those sites where metal concentr
ations were lowest. However when multiple regression analyses were per
formed, weight appeared also as a major or an important factor to expl
ain variations of MTLP levels, the prevalence of this natural factor v
ersus contamination factors being different at different sites.