Meeting Abstract

2.2  Thursday, Jan. 3  The Pleistocene Encruster Scene: Comparison of Epibionts on Molluscan Shells from Different Habitats VON DASSOW, YJ*; DROSER, ML; Carnegie Museum of Natural History; Univ. of California, Riverside yasmin.vondassow@gmail.com

Encrusters are sessile, suspension feeding, marine organisms such as bryozoans, barnacles, and tube-building worms, that live permanently attached to a substratum. They are often abundant in fossil molluscan assemblages, but their paleoecology is not as well studied as that of their hosts. Because gastropods and bivalves have very different life habits and undergo different post-mortem processes, the following questions were examined: do encrusting rates differ between bivalves and gastropods depending on which is more abundant? Can the influence of environmental setting be seen in fossil encrustation patterns? The Late Pleistocene localities studied represent three southern California environments: a protected muddy bottom habitat (Isla Vista), a high-energy sandy bottom habitat (Newport Bay), and a high-energy rocky bottom habitat (Point Loma). Each locality contains both bivalves and gastropods, but the rate of encrustation is not necessarily correlated to dominance of one or the other. The epibiont pattern on shells from Isla Vista and Newport Bay appears to be the result of environmental controls. Specifically, the amounts of shell transport and reworking after death impact the pattern at both localities. However, at Point Loma, the encrusting pattern for the locality is driven by the specific ecology of one type of host. Shells of the rocky shore gastropod Tegula, when occupied by hermit crabs, attract especially large numbers of encrusters. The results of this study show the importance of placing encrusters and borers in their ecological context. Environmental setting determines what hosts are present in an assemblage and what taphonomic processes operate on epibionts, thus strongly influencing the fossil epibiont pattern.