MEPS 215:37-47 (2001)  -  doi:10.3354/meps215037

ABSTRACT: Epibiotic assemblages have been shown previously to differ between pontoons and rocky reefs. This may occur for a variety of reasons, one of which is that pontoons move, whereas reefs do not. Effects of movement of the substratum are particularly pertinent to studies involving settlement panels because these experimental units are often suspended from pontoons such that they can move up and down, or attached to ropes such that they can rotate. The development of epibiotic assemblages on panels that were fixed, moved up and down, or rotated, was studied to test hypotheses about the effects of movement on sessile organisms. The covers of barnacles, sponges and ascidians increased greatly with increasing movement and/or rotation of the substratum, whereas species of red and brown foliose algae and tubiculous polychaetes generally decreased with increasing movement and/or rotation of the substratum. In general, assemblages on panels that moved up and down were most similar to those on rotating panels. One of the most obvious differences was the 2 to 3-fold greater biomass on rotating panels compared to fixed panels, which was attributed to the greater abundance of barnacles. It was concluded that, although movement of a surface can influence the composition of assemblages, this factor on its own may explain only some of the differences reported between pontoons and reefs. Furthermore, the method of deployment of settlement panels was shown to have great effects on the types of assemblages that develop. Differences in water flow were proposed to explain some of the observed patterns, but this idea needs to be investigated further.

KEY WORDS: Artificial habitats · Fouling · Epibiota · Movement · Flow · Urban structures · Sampling · Barnacles