GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 145-10
Presentation Time: 4:00 PM


CASEY, Michelle M., Physics, Astronomy, and Geosciences, Towson University, 8000 York Road, Smith Hall, Room 445, Towson, MD 21252 and WHITE, Marie N., Department of Earth and Environmental Sciences, Murray State University, Murray, KY 42071

Long Island Sound (LIS) is an economically important, urban estuary which has experienced environmental change from 150+ years of eutrophication and commercial fishing. Recent conservation paleobiology work on LIS has shown that the time averaged death assemblages have equilibrated and reflect the altered community rather than the pre-impact community. The aim of this study is to assess the utility of epibionts (encrusters) and endobionts (borers) associated with bivalve shells as indicators of recent benthic community health. Two abundant venerid bivalve species were compared from multiple sites along an east-west gradient in LIS. The hard shelled clam, Mercenaria mercenaria, has a large, thick shell that serves as an excellent hard substrate for benthic organisms. The false quahog, Pitar morrhuanus, is smaller with a thinner shell providing less potential habitat. In contrast to our predictions, the two species of nutrient-loving Crepidula were not more abundant in the west. The boring sponge Cliona celata and the jingle shell Anomia simplex, show promise for use as indicators of high water quality. The westernmost site, Rye, NY, had a greater number of shells containing barnacles and photosynthetic algae than the neighboring Greenwich, CT, site in spite of their similar water quality. This likely reflects increased turbidity in Greenwich, CT, which continues to experience commercial shellfish dredging, while Rye, NY, does not. In spite of differences in shell thickness and size, the average diversity of endo- and epibionts between sites is comparable regardless of host species examined. However, the maximum number of species that an individual shell can host is higher for M. mercenaria than for P. morrhuanus. The study of death assemblage ichnology can provide a non-invasive look at human impacts on an environment, including both water quality and commercial fishing, without disturbing the very organisms that conservation efforts are striving to protect.