Interspecific competition among fouling organisms in Tomioka Bay, Japan

Time series observations of interspecific competition anlong fouling organisms on experimental panels were carried out in Tomioka Bay, Japan, using a photosampling technique for 122 d . Altogether 17 species of fouling organisms belonging to various taxonomic groups such as Ascidia, Bryozoa, sponges, Crustacea, Polychaeta and algae were observed. The results of 990 interspeclfic interactions among the 13 dominant species are presented in the form of a matrix, with significance of the interactions tested using the Chi-square contingency test. The hierarchical order followed the sequence ascidians > sponges > bryozoans > brown algae > barnacles > polychaetes > green algae. The main type of interaction observed during the study was overgrowth of one species by another (71.58 %), while standoffs accounted for the rest. The competitive dominance followed a hierarchical order wlth numerous back-loops. According to the Chi-square results, the colonial ascidian Diplosoma m~ t sukur i i was ranked as the most dominant species. The correlation between the area coverage of a species and the number of its interactions was found to be highly sign~ficant. The merits of time series observations in a competition study of sessile invertebrates compared with static n~ethodology are emphasized.