1. Department of Animal Sciences, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel, Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, The Volcani Center, Bet-Dagan, Israel, Israel Oceanographic and Limnological Research, National Center for Mariculture, Eilat, Israel, and Max Plank Institute for Marine Microbiology, D-28359 Bremen, Germany