Although the polychaete Hydroides elegans and bryozoan Bugula neritina are dominant members of the fouling community in Hawaiian waters, these organisms were rarely found on macroalgae and seagrasses. Three explanations for this lack of fouling on macrophytes were considered:
(1) larvae did not settle on these surfaces, (2) physical characteristics of the macrophytes prevented firm attachment, and (3) macrophyte flexibility exceeded animal flexibility. To determine if either invertebrate would settle on 40 species of macrophytes, settlement bioassays were run.
When exposure was toxic to larvae, chemical anti-fouling mechanisms were suggested. Macrophytes that were not toxic, but avoided by settling larvae, may have been chemically protected by non-toxic, deterrent compounds, or avoided because of unacceptable morphologies or surface energies. When
larval settlement occurred, adhesion strength was tested. To determine if macrophytes were more flexible than attached invertebrates, the macrophyte with attached animals was bent around rods of decreasing diameter until animals were dislodged, or the lamina broke. One or more of the tested
types of anti-fouling protection could explain the lack of H. elegans on all 40 macrophytes. Pre-settlement defenses explained the lack of H. elegans on 23 species; post-settlement processes could explain its absence on the remaining 17 species. The lack of B. neritina
could only be explained on 18 species of macrophytes.
The Bulletin of Marine Science is dedicated to the dissemination of high quality research from the world's oceans. All aspects of marine science are treated by the Bulletin of Marine Science, including papers in marine biology, biological oceanography, fisheries, marine affairs, applied marine physics, marine geology and geophysics, marine and atmospheric chemistry, and meteorology and physical oceanography.