How is the health status of Mya arenaria in the Saguenay fjord? A statement from a 14-year survey.
The Saguenay fjord has been submitted for many years to anthropogenic influences. We surveyed this ecosystem between 1994 and 2007 to assess if Mya arenaria health status was altered by the contamination present in this ecosystem. The physiological condition of clams was determined using grouped annual data from sites at the mouth and in the Saguenay fjord. The results were analyzed according to sex and sites for all the samplings done during the active gametogenesis. The aims of this paper are to compare results of condition signs, gametogenesis stages and hormonal levels between sites and according to sex, to finally identify which sites were less favorable for the growth and reproduction of clams. We have shown that clams from Baie-Sainte-Catherine had delayed gametogenesis while those from Tadoussac showed very low steroid hormonal levels. Portuary and naval circulation influences could explain these particular results that also correspond to those from phagocytosis. Upstream in Baie‐Éternité, portuary influences (oils, anti-fouling paints) and metallic inputs from urban and terrigenous sources were reported. In Anse-aux-Érables, metallic contamination comes from industrial sources, while Anse-Saint‐Jean is influenced by sewage discharges from domestic and urban origin. From upstream to downstream, clams from Anse‐à‐la‐Croix, Anse‐aux‐Érables, Petit‐Saguenay, Anse‐à‐la‐Barque, Tadoussac and Pointe‐aux‐Alouettes showed decreased growth. Baie‐Éternité, Anse‐aux‐Érables, Anse‐Saint‐Jean and Baie-Sainte-Catherine sites, with their lower sexual maturity index and decreased phagocytosis, were shown to be the more influenced by contamination. All these data show that physiological condition of Mya arenaria reflects the combined effects of abiotic factors such as contamination, trophic conditions and site characteristics.