Effects of caging on the development of a sessile epifaunal community

In previous published studies on the effects of predation pressure in epibenthic communities, predator exclusion experiments (caging) have generally been employed.In the present study, the effects of caging on a fouling community were examined using experimental panels and several different types of control.The data show that caging per se, and not predation, accounts for the observed differences in species composition and abundance between treatments, mainly by affecting the settlement of larvae.Caging dramatically increased abundance of the solitary ascidians Ciona intestinalis and Ascidiella aspersa, while significantly reducing cover of the barnacle Elrninius modestus.Differing effects on other abundantly occurring speciescolonial ascidians, hydroids and tubicolous amphipodswere also determined.We suggest that caging exerts its effects on the contained communities by reducing water movement and light intensity.This was tested by using controls designed to separate these variables.The results indicate that the most important effect on barnacles and hydroids is reduced current speed, whereas solitary ascidians are influenced by current speed, light and the presence of earlier colonists.