Annual variations of catalase activity in mussels and clams from Lake Bizerte

The variations of catalase activity, which is a biochemical biomarker of ex posure to an oxidative stress, were followed month by month (from May 1998 to May 1999) in Mediterranean clams (Ruditapes decussatus) collected at thr ee stations (J, A and F), and mussels (Mytilus galloprovincialis) collected at two stations (J and C) in Lake Bizerte (Tunisia). Several oceanographic parameters were measured together with catalase activity in the animals to evaluate the quality of waters in the lake. Whatever the station taken int o consideration, catalase activity in clams significantly varied as a funct ion of the season, with marked increases in September, when the quality of waters was poor. Clams originating from station A presented the highest mea n activity (147.27 +/- 10.69 mu mol min(-1) mg(-1) proteins), those from J had the most fluctuating monthly activity with a minimum of 68.98 mu mol mi n(-1) mg(-1) proteins (April 1999) and a maximum of 189.32 mu mol min(-1) m g-' proteins (September 1998). In mussels, the response of the anti-oxidant activity was comparable to that observed with clams. Monthly catalase acti vity was generally high in summer. This seasonal increase was especially si gnificant in mussels from station J, which is submitted to a hyper-eutrophi cation phenomenon in summer. Catalase activity in mussels originating from station C, fairly constant throughout the year, varied in the range 64.23 m u mol min(-1) mg(-1) proteins (June) to 83.54 mu mol min(-1) mg(-1) protein s (September). The level of dissolved oxygen, negatively and significantly correlated with temperature, reached a minimum in summer. These environment al factors may, thus, exert an influence upon catalase activity measured in bivalves from the Lake Bizerte. (C) 2001 Editions scientifiques et medical es Elsevier SAS.