In order to obtain basic information on potential adverse effects of trace chemicals onto benthic fauna, a nationwide survey of sediment quality and benthic macro fauna in Japanese major ports and harbors was conducted. Dioxins and heavy metals contents were compared with total wet weight or the number of species of benthic
macrofauna. The number of species of macrofauna was found to be more sensitive index to estimate the adverse effects of dioxins than the total wet weight. Heavy metal levels were compared with the benchmark ERL or ERM values. The number of species of macrofauna was associated with concentration of heavy metals. Thus, it is suggested that, in some port and harbors, present levels of pollution by heavy metals have adverse effects on macrofauna.