McLean, Elizabeth L.

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    Ecology of the encrusting sponge Desmapsamma anchorata
    (2006-09) McLean, Elizabeth L.; Yoshioka, Paul M.; College of Arts and Sciences - Sciences; Appeldoorn, Richard S.; Vicente, Vance P.; Aponte, Nilda E.; Department of Marine Sciences; Ojeda, Edgardo
    Sponges are a prominent component of the invertebrate fauna of Caribbean reefs. This study describes various aspects of the ecology of the demosponge Desmapsamma anchorata, Carter 1882, off southwest Puerto Rico. The distribution of Desmapsamma was examined at various sites (San Cristobal reef, Pelotas reef and Guayanilla Bay) and more detailed studies (field experiments, spatial dispersion pattern, population dynamics and interactions with other organisms) were largely conducted at Media Luna reef. This sponge occurs in depths ranging from 2 to more than 20m in inner, middle and outer reefs systems as well as in other habitats (mangrove roots, Thalassia beds, etc.). The spatial dispersion pattern of Desmapsamma is aggregated, probably because of the patchy distribution of suitable substrates. In addition to its presence on inanimate substrates, Desmapsamma is often associated with other organisms (gorgonians, other sponges, corals, zoanthids). The biological associations involve positive (mutualistic), negative (competitive), and no effect (standoff) interactions depending upon the specific organism. In addition, competitive interactions included both overgrowth and allelopathic effects depending upon the associated species. For instance Desmapsamma overgrew scleractinians and killed tissues of the gorgonian Gorgonia ventalina through allelopathy. Mortality of Desmapsamma was size-dependent, with the highest survival for medium size colonies. The greater drag forces associated with wave action are probably responsible for the high mortality of large colonies. Recruitment was largely the result of sexual reproduction rather than asexual fragmentation. A size-specific matrix model indicated that the Desmapsamma population was decreasing during the study period. The results of this study indicate that Desmapsamma populations are affected by a complex interplay of physical effects and biological interactions.