Quantitative sampling of sessile animals and monitoring of water quality in Dokai Bay, northern Kyushu, Japan, were carried out from 1991 to '92 for four times to evaluate the water condition in the bay, Kitakyushu heavy and chemical industry area.
In this study, seventy four species of sessile animals ware collected, which include Mytilus galloprovincialis, Limnoperna fortunei, Crassostrea gigas, Mytilopsis sallei, Balanus amphitrite, Balanus trigonus, Balanus eburneus, Ciona intestinalis, and Styela plicata. These nine reprentative species in the bay showed characteristic distribution and seasonal occurrence patterns. We noted eight immigrated species of sessile animals including an ascidian Polyandrocarpa zorritensis recorded first in Japanese coastal water.
Eutrophic level of water in Dokai Bay was classified according to the occurrence of the sessile animals in the bay. Water conditions of the inner most and central parts of the bay were classified as hyper eutrophic level, and those of the bay mouth were at intemediate one between hyper eutrophic and eutrophic levels. We suggest that six dominant species, including a mussel M. galloprovincialis, are useful as biological indicator organisms of hyper eutrophic level of coastal water.