DISTRIBUTION OF VITAMIN-B-12 BINDER IN TH E WATER OF URANOUCHI INLET,JAPAN

The method for analizing vitamin B-12 binder in natural seawater was e valuated. Based on this evaluation, the distribution and seasonal vari ation of free and bound B-12 in the water of Uranouchi Inlet were inve stigated. Through these studies, the relationship between the content of B-12 compounds and other environmental factors in seawater is discu ssed. The protein-coated charcoal method was found to be an applicable and reliable why to determine the B-12 binder in seawater samples. Th e water of Uranouchi Inlet is rather eutrophied, and the content of to tal B-12 in the water ranged from 1.5 to 15.2 ng/l. The concentration of free B-12 was 0.02-12.9 ng/l. The content of B-12 bound to B-12 bin der (bound B-12) ranger from 0 to 5.1 ng/l in the water. The ratio of bound B-12 to total B-12 averaged 35%. The content of bound B-12 corre lated closely with the concentration of chlorophyll a, phosphorus, and GOD, therefore some of the sources of B-12 binder in seawater seem to be produced by phytoplankton and/or organic substances. The result re veals that the B-12 binder exists in eutrophic seawaters to some exten t all year round, and that the B-12 binder in the water could influenc e the growth of organisms requiring B-12 and the succession of phytopl ankton species.