Delayed gametogenesis of Mya arenaria in the Saguenay fjord (Canada): a consequence of endocrine disruptors?

The Saguenay fjord located in Canada on the north coast of the Saint-Lawrence Estuary, is well known for its multiple contaminations following a linear distribution upstream to downstream. Mya arenaria is well established in the fjord and potentially exposed to persistent sediment contamination as an endobenthic bivalve. From May to October 1997, clams energy storage and utilization in the gonad was shown to be closely linked with reproduction. Wherever the sampling site location in the fjord, a seasonal pattern is evident for lipid and glycogen levels in the gonad, this, reflecting the vitellogenic process. Nevertheless, in comparison with energy status and gametogenesis of clams collected on the north coast of the Saint-Lawrence Estuary, clams located in the fjord have to face limited nutritive conditions resulting in a single and shorter reproductive period. Although environmental factors could explain differences in physiological condition and reproductive status observed between clams from the fjord and the estuary, our results can discriminate clams from the upper part of the fjord, according to a delayed gametogenesis, concomitant with significant higher gonad glycogen concentrations observed in June 1996 and 1997. A persistent dysfunction of a vitellogenic process is suspected to be due to the exposure to anti-estrogenic contaminants.