BENTHIC FORAMINIFERA OF THE WESTERN GULF OF MAINE 60 YEARS LATER: A PILOT STUDY COMPARING CHANGES IN SPECIES DISTRIBUTIONS STEPHEN A. NATHAN 1,4 , R. MARK LECKIE 2 AND STEPHEN B. MABEE 3 ABSTRACT The Merrimack River paleo-delta formed during the late Pleistocene as post-glacial rebound produced a local low stand in sea level. Subsequent sea-level rise drowned and eroded the paleo-delta, which is now reworked by a variety of processes. This study used benthic foraminifera as a biotic and environmental proxy to evaluate the sand and gravel resources of the paleo-delta. Nineteen box-core sediment samples were collected from the paleo-delta along two east–west depth transects east of the Merrimack River mouth and off Plum Island, Massa- chusetts. From these samples, 62 species of benthic forami- nifera were identified. When compared with distribution studies published over 60 years ago, some species have shifted landward in their distributions (e.g., Adercotryma glomer- atum, Cibicides lobatulus, Reophax curtus, Trochammina squamata), while a few exhibited wider and more distal occurrences (e.g., Elphidium excavatum and Elphidium subarcticum). These differences point to variations in the Merrimack River outflow and its effects upon water column nutrient delivery, productivity, and organic matter flux over the past six decades. Other mitigating factors affecting benthic foraminiferal distributions may include increased seafloor disturbance from strong winter storms or fishing activity. Species richness and evenness peak at the delta break, coincident with low species dominance at about 50-m depth. Q-mode cluster analyses show three distinct assemblages: ‘‘shallow’’ (#30-m water depth), ‘‘deep’’ ($40 m), and ‘‘delta edge’’ (,50 m). There are no apparent correlations between foraminiferal distributions and deltaic bedforms or sediment type. This implies that foraminiferal distributions are controlled by other environmental variables other than grain size, such as food availability. INTRODUCTION OBJECTIVE In early September 2005, sediment samples and the microfossils within were collected along two depth transects across the Merrimack River paleo-delta in the Merrimack Embayment of the western Gulf of Maine to characterize offshore sand and gravel resources for potential use as construction aggregate and beach replenishment (Fig. 1). The project was a pilot study funded by the former Minerals Management Service, U.S. Department of the Interior. Researchers at Boston University characterized these marine resources using geophysical and sedimento- logical techniques, while researchers at the University of Massachusetts Amherst used micropaleontology tech- niques. This project presents and interprets the collected biotic data in light of the geophysical and sedimentological data published elsewhere (e.g., Hein et al., 2007, 2012; Barnhardt et al., 2009). It demonstrates how micropaleon- tological analyses can complement geophysical analyses to provide information unavailable through geophysical tech- niques. Most importantly, this project illustrates the utility of studying benthic foraminifera as a proxy for substrate conditions pre- and post-sediment disruption (e.g., from offshore mining of sand and gravel resources). Thus, benthic foraminifera can be used to gauge biotic recovery by analyzing recolonization trends. PROXIES This study uses benthic foraminifera as a biotic and environmental proxy to study the benthic ecology of the Merrimack Embayment. Benthic foraminiferal distribu- tions on the continental shelf are influenced by factors such as water temperature, depth, salinity, dissolved oxygen, grain size of seafloor sediments, and food availability (e.g., Murray, 1991; Jorissen et al., 1995; Goldstein, 1999; Jorissen, 1999; Sen Gupta, 1999; Leckie & Olsen, 2003). In general, their distributions trend parallel to the coast with both increasing water depth and distance from the shore (e.g., Phleger & Parker, 1951; Phleger, 1960; Upshaw & Stehli, 1962; Walton, 1964; Gibson & Buzas, 1973; Murray, 1973, 1991; Culver & Buzas, 1981; Poag, 1981; Culver, 1988). Foraminiferal abundances also vary season- ally (e.g., Korsun & Hald, 2000; Murray & Alve, 2000; Scott et al., 2003). Thus, although the data presented in this study represent a one-day snapshot of the seasonal progression of changing foraminiferal assemblages in the Merrimack Embayment, useful trends can be observed. In this study, benthic foraminiferal distributions and abundances are coupled with geophysical and sedimentary analyses to: 1) develop a model of foraminiferal distribution patterns to assess depositional environments and establish a modern base line of the data; 2) confirm geophysical techniques such as side-scan sonar to delineate sedimentary facies and grain-size distribution; and 3) test the applica- bility of foraminifera as a biotic monitor of post- disturbance ecosystem recovery (e.g., following offshore sand mining operations; Scott & Lipps, 1995; Yanko et al., 1999; Dabbous & Scott, 2012). A similar study was conducted by Phleger (1952) and Parker (1952) over 60 years ago, which spanned the western Gulf of Maine from Cape Ann to Portsmouth, New Hampshire, and seaward from the coastline to Jeffreys Ledge. They examined foraminiferal abundances and distributions using 738 seafloor sediment samples collected Journal of Foraminiferal Research fora-44-03-02.3d 21/5/14 02:02:20 230 Cust # 2277 1 Department of Environmental Earth Science, Eastern Connecticut State University, Willimantic, CT, 06226, USA 2 Department of Geosciences, 611 N. Pleasant St., University of Massachusetts, Amherst, MA 01003, USA 3 Massachusetts Geological Survey, 611 N. Pleasant St., University of Massachusetts, Amherst, MA 01003, USA 4 Correspondence author. E-mail: nathans@easternct.edu Journal of Foraminiferal Research, v. 44, no. 3, p. 230–254, July 2014 230