Effect of the Hebei Spirit Oil Spill on the Condition, Reproduction, and Energy Storage Cycle of the Manila Clam Ruditapes philippinarum on the West Coast of Korea

Abstract

Seasonal variations in the condition, biochemical composition, and reproduction of Ruditapes philippinarum were investigated from August 2009 to October 2010, 18 months after the Hebei Spirit oil spill off Malipo Beach on the west coast of Korea. No significant differences in physical and nutritional conditions were found between the oil-damaged and the undamaged control beaches. At the undamaged Mongsanpo Beach, all the biometric components (dry tissue weights and biochemical components) remained at low levels during autumn–winter but increased rapidly through spring, followed by a dramatic drop in August. In contrast, at the oil-damaged beach, no clear seasonal fluctuations were detected in the biometric components during the study period. Absolute values of all the components were much higher at the control than at the damaged site. This lack of energy reserves in the clams in the damaged area likely resulted in a failure of gametogenic development. Gonadal maturity index peaked in summer at both beaches. However, the gross egg weight was much higher at the control than at the damaged site during June–July. In addition, its different peak timing between sites indicated a month’s lag in the major spawning pulse at the oil-damaged beach. The spatial variations in all the biometric components of the clams observed in this study clearly implied that the Hebei Spirit oil spill may interfere with the clam phenology at Malipo Beach within 2 to 3 years after the incident.