Paper No. 1-9
Presentation Time: 10:55 AM
NEOICHNOLOGY AS AN INDICATOR OF COMMUNITY HEALTH IN LONG ISLAND SOUND, CT, USA
Long Island Sound (LIS) is an economically important, urban estuary which has experienced environmental change from over 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 observed in Holocene fossils. The aim of this study is to use the neoichnology of epibionts (encrusters) and endobionts (borers) associated with the bivalve molluscan fauna as indicators of benthic community health within LIS. To assess the influence of host species on epibionts and endobionts, 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 real estate for potential borers and encrusters. In contrast to our predictions, the two species of nutrient-loving Crepidula were not more abundant in the western portion of the sound. Other encrusting organisms, such as 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, has been protected from commercial shellfish harvesting for the last 40+ years. In spite of differences in shell thickness and size, the average diversity of endo- and epibionts between sites is comparable regardless of which host species is examined. However, the maximum number of encrusters plus borers that an individual shell can host is higher for M. mercenaria than for the smaller P. morrhuanus. In addition to providing insights into animal behavior, the study of death assemblage neoichnology can also provide a non-invasive look at human impacts on an environment, including both water quality and commercial fishing, without disturbing the very organisms that we are trying to protect.