Association of the scallop Patinopecten yessoensis and epibiotic barnacle Balanus rostratus: inter-specific interactions and trophic relationships determined by fatty acid analysis

Marine mollusks provide shelter to epibiotic organisms which settle on the outer surface of their hard shells. Epibionts can exert beneficial or detrimental effects on the host mollusk. In this study, the ecology of the association of the commercially valuable marine mobile scallop Patinopecten (=Mizuhopecten) yessoensis with its epibiotic barnacle Balanus rostratus was investigated. Fatty acid analysis was performed to determine the trophic relationships between these species. The distribution of fatty acid markers in this scallop species suggests an important contribution of diatoms, flagellates and animal material in its diet. The fatty acid analysis indicated a predominance of diatoms in the diet of the adult barnacles and some detrital input into the diets of young individuals. It was found that adult barnacles may compete with the scallops for food sources such as diatoms and zooplankton. It was revealed that with a negligible biomass of epibionts, the interactions between the barnacle and scallop may be regarded as commensalisms. An increase in the weight of epibiotic barnacles resulted in decreases in the weights and shell heights of the scallops, testifying to the adverse influence of a high biomass of epibionts on their host.