Alpha and beta diversity of encrusting foraminifera that recruit to long-term experiments along a carbonate platform-to-slope gradient: Paleoecological and paleoenvironmental implications Sally E. Walker a, ⁎, Karla Parsons-Hubbard b , Suzanne Richardson-White a , Carlton Brett c , Eric Powell d a Department of Geology, University of Georgia, Athens, GA 30602, USA b Department of Geology, Oberlin College, 52 W. Lorain Street, Oberlin, OH 44074, USA c Department of Geology, University of Cincinnati, Cincinnati, OH 45221, USA d Haskin Shellfish Research Laboratory, Rutgers University, 6959 Miller Avenue, Port Norris, NJ 08349, USA abstract article info Article history: Received 13 August 2010 Received in revised form 21 April 2011 Accepted 21 April 2011 Available online 4 May 2011 Keywords: Beta diversity Dispersal Invasibility Ecological incumbent Encrusting foraminifera Opportunistic Carbonates The spatial and temporal distribution and diversity of sediment-dwelling foraminifera are reasonably well known, but encrusting (hard-substrate dwelling) foraminifera are little studied. Encrusting foraminifera are common in the world's oceans, attached to floating debris or marine animals in the water column to living on rocks, sand grains and organisms in benthic environments from shallow to deep marine regions. With projected ocean acidification and warming conditions, these important calcifying protists that comprise beaches, buffer sediments, and contribute to complex food webs are potentially in peril. Results indicate that calcifying foraminifera were the first to colonize experimental molluscan substrates within the first year in shallow habitats, with colonization offshore in subsequent years. Agglutinated foraminifera become more common after one year. Species richness (α diversity) remained relatively similar throughout the study, but species turnover (β diversity) was greatest within the first year and between the shelf/slope break and deeper water, following the thermocline and photic zone regions. The equivalent of the Shannon Entropy Index provided important information on β diversity and community structure. Paleobathymetric distributions can be resolved after six years into four distinct foraminiferal distributional zones: shallow shelf (15 m), outer shelf (33 m), shelf/slope break (73–88 m), and slope depths (N 213 m to 267 m). Some encrusting foraminifera are invasive, settling in high numbers within the first year, and increasing their abundance through the duration of the experiment. A foraminiferan, Discorbis bertheloti, was discovered to bioerode carbonate, and is a potentially excellent paleobathymetric indicator for 15–33 m depths. Results differ from previously reported pioneer and climax foraminiferal communities documented for Caribbean coral reefs, because long-term experiments reveal the spatial and temporal development and distribution of carbonate-producing encrusting foraminifera in these climatically-sensitive regions. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Encrusting organisms that grow attached or cemented to hard substrates create communities that may reflect ambient environmen- tal conditions. If these organisms secrete hard skeletons, they can be preserved in the fossil record and thereby become valuable tools in paleoecological and paleoenvironmental analysis (Taylor and Wilson, 2003). Because of this potential, studies have focused on encrusting organisms that recruit to corals or coral rubble (Palmieri and Jell, 1985; Gischler and Ginsburg, 1996; Hart and Kench, 2007), cavity surfaces (Rasmussen and Brett, 1985; Holmes et al., 1997; Richter et al., 2001), molluscan shells (Driscoll and Swanson, 1973; Walker, 1988; Walker and Carlton, 1995; Parsons-Hubbard, 2005) and many other invertebrate substrates (e.g., Jackson and Buss, 1975; Osman, 1977; Sutherland and Karlson, 1977; Jackson, 1979; Mook, 1981; Greene et al., 1983; Nebelsick et al., 1997; Patil and Anil, 2000; Rodland et al., 2006). Despite these studies, there is limited knowledge about how encrusting organisms vary along environmen- tal gradients (Martindale, 1992; Walker et al., 1998; Parsons-Hubbard et al., 1999; Lescinsky et al., 2002; Parsons-Hubbard, 2005; Mallela, 2007). Additionally, little is known about encrusting species diversity (species richness, α diversity), abundance and species turnover (β) and how these diversities vary spatially and temporally. Such studies would refine the ecological dynamics that underpin paleoecological, paleoenviromental and paleoclimatic reconstructions (Debenay and Payri, 2010). Palaeogeography, Palaeoclimatology, Palaeoecology 312 (2011) 325–349 ⁎ Corresponding author. E-mail addresses: swalker@gly.uga.edu (S.E. Walker), karla.hubbard@oberlin.edu (K. Parsons-Hubbard), sukeyvet@gmail.com (S. Richardson-White), brettce@ucmail.uc.edu (C. Brett), eric@hsrl.rutgers.edu (E. Powell). 0031-0182/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2011.04.028 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo