Shell width growth was significantly greater in oysters exposed to 30 and 90 g L−1 lead, yet significantly decreased in oysters exposed to 270 g L−1 lead compared with control treatments(F 4.6, P 0.02, Fig. 4d). Exposure to the longer chain hydrocarbon,octacosane, also resulted in increased shell width growth (Fig. 4d), but no significant differences to shell width were observed for oysters exposed to zinc and hexadecane (Fig. 4b, c).