We thank the crew and the Shipboard Scientific Party of Leg 178 for taking samples for us and making this study possible. We wish to thank H. Grobe, H. Rhodes, and M. Seebeck for supporting our laboratory work. Our paper benefited from constructive criticism by our colleagues B. Diekmann, C. Pudsey, D. Fütterer, and T. Wolf-Welling. Furthermore, we thank A. Camerlenghi, C. Robert, and M. Setti for their helpful reviews of the manuscript. We gratefully acknowledge financial support from the Deutsche Forschungsgemeinschaft.