EPIBIOSIS IN A GUILD OF SESSILE SUBTIDAL INVERTEBRATES IN SOUTH-EASTERN AUSTRALIA - A QUANTITATIVE SURVEY

We report the first quantitative survey of the degree to which a guild of subtidal invertebrates was fouled by macro-organisms. Twenty commo n invertebrate species from five sites on the exposed rocky coast of s outh-eastern Australia were included in the survey. The survey focusse d on representatives from four phyla, namely; ascidians (9), a bryozoa n (1), coelenterates (2) and sponges (8). An indication of temporal va riation in fouling was obtained by quantifying the number and cover of fouling organisms in autumn and spring. Considerable variation in fou ling was apparent between species. Only 3 species (2 colonial ascidian s and a coelenterate) competely lacked epibionts, while the highest co ver of foulers was observed on solitary ascidians; in one instance the mean cover of epibionts exceeded 98% on Pyura spinifera. Significant temporal variation in the cover or number of fouling organisms was obs erved for 7 of the species examined. Significant increases in cover du ring the spring sampling period were attributable to a greater cover o f non-calcareous algae, tube-dwelling spionid polychaetes or hydroids. The quantitative data presented here are in close agreement with publ ished, qualitative data collected in Bermuda, but reveal some discrepa ncies with other qualitative data on fouling from the western Meditter anean.