In the Atlantic French coast, significant mortalities were observed in oyster communities during gametogenesis. These deaths possibly result from the cumulative effects of various stressors such as seasonal temperature variations, pesticide application and the release of contaminants from the resuspension of sediments. A field survey, based on aquaculture conditions at 15 and 70 cm from the sediment bed with genetically-resistant (R) and -sensitive (S) lines, showed a stress condition. Significant weight loss was observed during May 14th through June 10th for both R and S lines. On one hand, the levels of the egg yolk vitellin in females were decreased at May 14th for both R and S lines. On the other hand, a significant increase in vitellin production was observed for the S line while its production was constant for the R line at 15 cm from the sediment bed during June 2nd. Sediment proximity of oysters was important because some biomarkers such as catalase activity was enhanced suggesting oxidative stress. Moreover, these sediments were shown 1) to release substances from anaerobic activity (ammonia and sulfides) during the spring when the mean temperature reaches 18oC, 2) to have embryotoxic properties to oyster larvae and 3) to be more contaminated by an herbicide. Indeed, trifluraline was detected during April to July reaching concentrations of 2 - 6 µg.kg-1 dry weight. During the gametogenesis, the response pattern of various metabolic biomarkers indicates rather an influence from genetic factors (R and S lines) than proximity to the sediment bed and water column.