BAD-BOY BRYOZOAN BIOMARKERS: CHEILOSTOME DISTRIBUTION PATTERNS ALONG A BAHAMIAN DEPTH GRADIENT

Paleoecology seeks to identify and reconstruct the physical and biological communities of the past in an effort to infer their ecological and evolutionary significance. Examining organ is mal patterns of distribution and abundance provides insight into the intricate workings and preservation of habitats through time.

In 1993, several samples of sea urchins were deployed at 24 sites along the continental shelf/slope of the Bahamas. The deployment sites were at depths of 15, 30, 70, 73, 88, 183, 210, 226, 264, and 267 meters. Samples were then retrieved at one, two, and six-year intervals for examination and comparison of epibiont accumulation.

This project investigates the encrustation of Cheilostome Bryozoa on the tests and spines of the sea urchin Eucidaris. Of all the encrusted epibionts, Cheilostomes were singled out because of 1) their pervasive nature, they are found on a variety of substrates and are common in both shallow and deeper waters; and 2) their calcitic skeleton, which is almost a necessity for incorporation in the fossil record. Thus, the Cheilostomes appear to be abundant and distinctive representatives of community dynamics, with high potential for retaining the taxonomic richness of a community assemblage.

Taxonomic identification of bryozoans on urchin spines was used to assess genus distribution and abundance with depth. Genera were plotted as rare, common, or abundant. The following general observations have thus far been made: 1) the distribution of genera is a less distinct parameter than overall abundance patterns. 2) Genera that were common or abundant were more, although not exclusively, restricted in their depth range. 3) The majority of the specimens identified were collected from depths within the photic zone. Further analyses including urchin tests in addition to spines will be incorporated in the study to produce a more complete data set. Analysis of video taken at deployment sites indicates that burial of substrates may also influence bryozoan distribution. Preliminary results show that Cheilostomes may be useful biomarkers, at least in modern environments.