www.cerf-jcr.org Character of Shell Beds Flanking Herod Point Shoal, Southeastern Long Island Sound, New York Lawrence J. Poppe { , S. Jeffress Williams { , and Ivar G. Babb { { Coastal and Marine Geology Program U.S. Geological Survey Woods Hole, MA 02543, U.S.A. lpoppe@usgs.gov { National Undersea Research Center University of Connecticut Avery Point Groton, CT 06340, U.S.A. ABSTRACT POPPE, L.J.; WILLIAMS, S.J., and BABB, I.G., 2011. Character of shell beds flanking Herod Point Shoal, southeastern Long Island Sound, New York. Journal of Coastal Research, 27(3), 493–501. West Palm Beach (Florida), ISSN 0749-0208. High biogenic productivity, strong tidal currents, shoal topography, and short transport distances combine to favor shell- bed formation along the lower flanks of a cape-associated shoal off Herod Point on Long Island, New York. This shell bed has a densely packed, clast-supported fabric composed largely of undegraded surf clam (Spisula solidissima) valves. It is widest along the central part of the western flank of the shoal where topographic gradients are steep and a stronger flood tide results in residual flow. The bed is narrower and thinner toward the landward margins where currents are too weak to transport larger valves and topographic gradients are gentle, limiting bed-load transport mechanisms by which the shells are concentrated. Reconnaissance mapping off Roanoke Point suggests that shell beds are also present at the other cape-associated shoals off northeastern Long Island, where relatively similar geomorphic and oceanographic conditions exist. These shell beds are important to the Long Island Sound ecosystem because they provide complex benthic habitats of rough and hard substrates at the boundary between the muddy basin floor and mobile sand of the shoals. ADDITIONAL INDEX WORDS: Cape-associated shoal, shell accumulations, Roanoke Point Shoal, surf clams, winnowing, benthic habitats, benthic complexity. INTRODUCTION Shell beds are ecologically, economically, and sedimentolog- ically important. Ecologically, shell beds form critical habitats that shelter juvenile finfish and benthic infauna from mobile predators (Dumbauld et al., 2000; Gutierrez, Palomo, and Iribarne, 2000; Stewart et al., 1999), provide hard substrates for sessile fauna and flora, and supply shelter for boring species (Bower, McGladdery, and Price, 1999). These characteristics create a benthic complexity that benefits species from many trophic levels (Harding and Mann, 2001; Posey et al., 2000). Commercially, shell deposits are used for construction aggre- gate, poultry feed, cattle roughage, and culch for oyster aquaculture; as a component of cement; in the preparation of lime; and in the chemical industry (Arndt, 1974; Grace, 1995). Sedimentologically, shell beds constitute conspicuous parts of the stratigraphic record, and as such, they are important sources of paleoenvironmental and evolutionary information. For example, shell-size distributions, species content, disartic- ulation, fragmentation, internal bed discontinuities, right–left valve sorting, postmortem encrustation or damage by borers, shell orientation, matrix sediment, and bed grading and thickness all provide diagnostic sedimentological information (Furisch and Oschmann, 1993; Kidwell, Fursich, and Aigner, 1986; Maiklem, 1968; Tomasovych, Fursich, and Olszewski, 2006). During most years, the dockside value of hard clams landed in New York, including surf clams and quahogs, exceeds that of all other marine species caught in the state (Gall, 1999), and the total harvest of hard clams in 2007 from Long Island Sound exceeded 61,000 bushels (Long Island Sound Study, 2008). Surf clams are most abundant in sandy sediments and more turbulent, colder waters, such as shoals; quahogs prefer shallower, lower energy coastal-bay waters. Both of these species are commercially harvested along the north shore of Long Island. Although limited in scope, previous work suggests that there are at least three distinct types of shell beds in Long Island Sound: accumulations of mussel shell debris off rocky head- lands in the eastern Sound (Poppe et al., 1998a); oyster mounds associated with aquaculture in the north-central Sound (Poppe et al., 2001); and bivalve accumulations flanking cape-associ- ated shoals (Poppe et al., 1999). Each type is unique in that they have different species compositions, form in different sedimen- tary environments, and support different benthic communities. Despite the ecologic and commercial importance of shell beds to the Sound and their potential to provide useful information on benthic habitat dynamics, the details of their distribution and character remain largely unstudied. The purpose of this paper is to describe the geometry, composition, and fabric of a shell bed flanking one of the cape-associated shoals in southeastern Long Island Sound and to discuss the physiographic and oceanographic factors controlling its formation. DOI: 10.2112/JCOASTRES-D-09-00079.1 received 6 July 2009; accepted in revision 21 January 2010. ’ Coastal Education & Research Foundation 2011 Journal of Coastal Research 27 3 493–501 West Palm Beach, Florida May 2011