Shell Assemblages Research Articles

Estimating crown conch (Melongena corona) tissue weight from archaeological shell measurements: An allometric methodology for coastal historical ecological research

Coastal archaeologists and historical ecologists are taking an increasingly robust interest in marine shell assemblages recovered from coastal villages and civic-ceremonial sites. These assemblages must be quantified before archaeologists can make assessments of biomass flows and subsistence contributions. We present the results of an experimental allometric study on Melongena corona snails collected from the mangrove dominated shoreline of Weedon Island Preserve, Florida, USA. Our analysis produced regression constants for predicting tissue weight estimates from four independent linear shell metrics, including: length, aperture-length, height, and width. This study is unique in its integration of field and laboratory experimentation, and in the large sample size used to develop allometric constants. To exemplify the utility of our regression models, we apply our allometric constants to a late-Precolumbian (ca. 895–1268 CE) marine shell assemblage excavated from the Weeden Island site (8PI1), Pinellas County, Florida, USA.

Testate amoeba records indicate regional 20th-century lowering of water tables in ombrotrophic peatlands in central-northern Alberta, Canada.

Testate amoebae are abundant in the surface layers of northern peatlands. Analysis of their fossilized shell (test) assemblages allows for reconstructions of local water-table depths (WTD). We have reconstructed WTD dynamics for five peat cores from peatlands ranging in distance from the Athabasca bituminous sands (ABS) region in western Canada. Amoeba assemblages were combined with plant macrofossil records, acid-insoluble ash (AIA) fluxes and instrumental climate data to identify drivers for environmental change. Two functional traits of testate amoebae, mixotrophy and the tendency to integrate xenogenic mineral matter in test construction, were quantified to infer possible effects of AIA flux on testate amoeba presence. Age-depth models showed the cores each covered at least the last ~315years, with some spanning the last millennium. Testate amoeba assemblages were likely affected by permafrost development in two of the peatlands, yet the most important shift in assemblages was detected after 1960 CE. This shift represents a significant apparent lowering of water tables in four out of five cores, with a mean drop of ~15cm. Over the last 50years, assemblages shifted towards more xerophilous taxa, a trend which was best explained by increasing Sphagnum s. Acutifolia and, to a lesser extent, mean summer temperature. This trend was most evident in the two cores from the sites located farthest away from the ABS region. AIA flux variations did not show a clear effect on mineral-agglutinating taxa, nor on S.s.Acutifolia presence. We therefore suggest the drying trend was forced by the establishment of S.s.Acutifolia, driven by enhanced productivity following regional warming. Such recent apparent drying of peatlands, which may only be reconstructed by appropriate indicators combined with high chronological control, may affect vulnerability to future burning and promote emissions of CO2 .

Shell carbon isotope indicators of metabolic activity in the deep-sea mussel Bathymodiolus childressi

The incorporation of metabolic carbon (Cm) into shells of mollusks has been used as an indicator of animal condition and availability of food resources in estuarine and freshwater settings. This study examines Cm in Bathymodiolus childressi, a marine cold seep mussel dependent on methanotrophic symbionts. As seeps develop, mature, and go quiescent, methane supply will vary and affect the amount of metabolic carbon deposited into the growing shell. B. childressi (n = 136) were live-collected from two seep sites over a 17 year period in the Northern Gulf of Mexico to investigate whether changes in Cm were detectable between sites and across years. Significant differences in Cm were observed between mussel populations at Brine Pool (15.4 ± 0.4%) and Bush Hill (10.3 ± 0.3%). Cm also changed significantly within each site across year (Bush Hill 1991: 12.2 ± 0.5%, 1992: 17.3 ± 0.8%) and decadal time scales (Brine Pool 1989: 15.5 ± 0.7%, 2006: 19.5 ± 0.7%). These findings agree with previous studies that found mussel condition was higher at Brine Pool and correlate well with a trophic mixing model that indicated significantly higher methane source utilization at the Brine Pool (65 ± 1.1%) than at Bush Hill (49 ± 1.6%). Further development of this method should allow for assessment of Cm in shell assemblages as an indicator of historical resource availability at both active and former cold seep sites.

Bellwether of the Canaries: anthropogenic effects on the land snail fauna of the Canary Islands

Natural areas near human-modified landscapes experience factors that may affect local biodiversity at levels commensurate with natural environmental factors. The land snails of the Canary Islands provide excellent opportunities to evaluate the importance of anthropogenic agents in mediating the diversity and distribution of species. Land snails are particularly sensitive to disturbance and are an integral part of terrestrial ecosystems. This study analyzed the distributions and abundances of terrestrial macrosnail shell assemblages at 60 localities throughout the coastal scrub biome of the Canary Islands. This was accomplished using data on natural and anthropogenic variables to assess their relative importance in governing land snail diversity. A total of 34,801 dead shells represented a diverse malacofauna with highly localized endemism. Due to uncertain species identifications, samples from the 18 sites from the two easternmost islands are described, but excluded from statistical analyses. Regression tree analysis indicated that proximity to agricultural sites was the most important predictor of species diversity. Sites with no or very little agricultural area (≤ 0.167 km2) within a 1 km radius had significantly higher richness and diversity. These results have implications for Canary Islands conservation. Protected areas that are patchworks of natural and agricultural landscapes are still subject to native biodiversity loss because of anthropogenic impacts even when the footprint of agriculture is small.

Benthic communities under anthropogenic pressure show resilience across the Quaternary.

The Southeast Pacific is characterized by rich upwelling systems that have sustained and been impacted by human groups for at least 12 ka. Recent fishing and aquaculture practices have put a strain on productive coastal ecosystems from Tongoy Bay, in north-central Chile. We use a temporal baseline to determine whether potential changes to community structure and composition over time are due to anthropogenic factors, natural climatic variations or both. We compiled a database (n = 33 194) with mollusc species abundances from the Mid-Pleistocene, Late Pleistocene, Holocene, dead shell assemblages and live-sampled communities. Species richness was not significantly different, neither were diversity and evenness indices nor rank abundance distributions. There is, however, an increase in relative abundance for the cultured scallop Argopecten, while the previously dominant clam Mulinia is locally very rare. Results suggest that impacts from both natural and anthropogenic stressors need to be better understood if benthic resources are to be preserved. These findings provide the first Pleistocene temporal baseline for the south Pacific that shows that this highly productive system has had the ability to recover from past alterations, suggesting that if monitoring and management practices continue to be implemented, moderately exploited communities from today have hopes for recovery.

Epipaleolithic shell beads from Damascus Province, Syria

This paper presents an overview of three Paleolithic sites excavated in southwestern Syria between 1999 and 2007. The sites were discovered as part of a large-scale, regional survey conducted in Damascus Province by a multidisciplinary research team from the University of Tübingen. We focus on the Epipaleolithic shell assemblages from Baaz Rockshelter, Kaus Kozah Cave and Ain Dabbour Cave, examining the distribution of species and their potential relationship to group and personal identity. The four most frequent taxa include the gastropods, Columbella rustica, Theodoxus cf. jordani, and Tritia gibbosula (formerly known as Nassarius gibbosulus), as well as scaphopods. Most of the shells are perforated or, in the case of scaphopods, segmented. These taxa count among the most common shell beads observed at Upper Paleolithic and Epipaleolithic sites of the Levant, although their proportions change over time. Other taxa are also present, but to a much lesser degree, and often occur as unique specimens. We compare the shell assemblages from these localities to similar contexts in Syria, Israel and Jordan. The shell taxa observed are consistent with other Epipaleolithic sites. We hypothesize that the most common shells at Baaz, Kaus Kozah and Ain Dabbour signify group identity, although the proportion of scaphopods is considerably less than that observed from the wider region. We also posit that the unique specimens are an indication of personal identity, standing in contrast to the shared group identity shown by the most common shell taxa.

The Efficiency of Flotation Compared with Other Methods for Recovering Assemblages of Terrestrial and Aquatic Gastropods from Archaeological Deposits, with Reference to the Site of Pico Ramos (Basque Country, Spain)

ABSTRACTWe analysed assemblages of shells of land snails and small aquatic and wetland gastropods from a late Mesolithic-early Neolithic deposit in the cave of Pico Ramos (Basque Country). Shells were recovered by hand during excavation and all excavated deposit was processed by flotation, with a 250 μm mesh to recover floating material and a 1.0 mm mesh to recover the heavy fraction. The total assemblage comprised 5780 individuals (MNI) among 33 taxa, the sieved sub-assemblage having the highest proportions of these (2841 MNI in 31 taxa) and the hand-picked sub-assemblage the lowest (698 MNI in 11 taxa). Eleven taxa were absent from the flotation sub-assemblage, although the recovered MNI (2241; 39% of the total MNI) was high. The palaeoecological implications of the results are considered. Adult and large-sized juvenile shells of the edible land snail Cepaea nemoralis are abundant in the hand-picked sub-assemblage, but it is the absence of small-sized juvenile shells in the flotation and wet-sieved sub-assemblages that permits the inference that the species was collected for consumption. Wet sieving is therefore essential, both for interpreting hand-picked samples and in particular for the recovery of representative assemblages of land molluscs.

Extreme waves in the British Virgin Islands during the last centuries before 1500 CE

Extraordinary marine inundation scattered clasts southward on the island of Anegada, 120 km south of the Puerto Rico Trench, sometime between 1200 and 1480 calibrated years (cal yr) CE. Many of these clasts were likely derived from a fringing reef and from the sandy flat that separates the reef from the island’s north shore. The scattered clasts include no fewer than 200 coral boulders, mapped herein for the first time and mainly found hundreds of meters inland. Many of these are complete colonies of the brain coral Diploria strigosa . Other coral species represented include Orbicella (formerly Montastraea ) annu­laris , Porites astreoides , and Acropora palmata . Associated bioclastic carbonate sand locally contains articulated cobble-size valves of the lucine Codakia orbicularis and entire conch shells of Strombus gigas , mollusks that still inhabit the sandy shallows between the island’s north shore and a fringing reef beyond. Imbricated limestone slabs are clustered near some of the coral boulders. In addition, fields of scattered limestone boulders and cobbles near sea level extend mainly southward from limestone sources as much as 1 km inland. Radiocarbon ages have been obtained from 27 coral clasts, 8 lucine valves, and 3 conch shells. All these additional ages predate 1500 cal yr CE, all but 2 are in the range 1000–1500 cal yr CE, and 16 of 22 brain coral ages cluster in the range 1200–1480 cal yr CE. The event marked by these coral and mollusk clasts likely occurred in the last centuries before Columbus (before 1492 CE). The pre-Columbian deposits surpass Anegada’s previously reported evidence for extreme waves in post-Columbian time. The coarsest of the modern storm deposits consist of coral rubble that lines the north shore and sandy fans on the south shore; neither of these storm deposits extends more than 50 m inland. More extensive overwash, perhaps by the 1755 Lisbon tsunami, is marked primarily by a sheet of sand and shells found mainly below sea level beneath the floors of modern salt ponds. This sheet extends more than 1 km southward from the north shore and dates to the interval 1650–1800 cal yr CE. Unlike the pre-Columbian deposits, it lacks coarse clasts from the reef or reef flat; its shell assemblage is instead dominated by cerithid gastropods that were merely stirred up from a marine pond in the island’s interior. In their inland extent and clustered pre-Columbian ages, the coral clasts and associated deposits suggest extreme waves unrivaled in recent millennia at Anegada. Bioclastic sand coats limestone 4 m above sea level in areas 0.7 and 1.3 km from the north shore. A coral boulder of nearly 1 m 3 is 3 km from the north shore by way of an unvegetated path near sea level. As currently understood, the extreme flooding evidenced by these and other clasts represents either an extraordinary storm or a tsunami of nearby origin. The storm would need to have produced tsunami-like bores similar to those of 2013 Typhoon Haiyan in the Philippines. Normal faults and a thrust fault provide nearby tsunami sources along the eastern Puerto Rico Trench.

Shells and Humans: Molluscs and Other Coastal Resources from the Earliest Human Occupations at the Mesolithic Shell Midden of El Mazo (Asturias, Northern Spain)

Human populations exploited coastal areas with intensity during the Mesolithic in Atlantic Europe, resulting in the accumulation of large shell middens. Northern Spain is one of the most prolific regions, and especially the so-called Asturian area. Large accumulations of shellfish led some scholars to propose the existence of intensification in the exploitation of coastal resources in the region during the Mesolithic. In this paper, shell remains (molluscs, crustaceans and echinoderms) from stratigraphic units 114 and 115 (dated to the early Mesolithic c. 9 kys cal BP) at El Mazo cave (Asturias, northern Spain) were studied in order to establish resource exploitation patterns and environmental conditions. Species representation showed that limpets, top shells and sea urchins were preferentially exploited. One-millimetre mesh screens were crucial in establishing an accurate minimum number of individuals for sea urchins and to determine their importance in exploitation patterns. Environmental conditions deduced from shell assemblages indicated that temperate conditions prevailed at the time of the occupation and the morphology of the coastline was similar to today (rocky exposed shores). Information recovered relating to species representation, collection areas and shell biometry reflected some evidence of intensification (reduced shell size, collection in lower areas of exposed shores, no size selection in some units and species) in the exploitation of coastal resources through time. However, the results suggested the existence of changes in collection strategies and resource management, and periods of intense shell collection may have alternated with times of shell stock recovery throughout the Mesolithic.

Prehistoric Molluscan Faunas of the Yazoo River, Mississippi, USA: Archaeological Perspectives for Modern Conservation

ABSTRACTArchaeological faunal assemblages can provide data valuable to modern conservation ecology. For example, while freshwater mussels (Bivalvia: Unionidae, Margaritiferidae) are common constituents in the archaeological record of North America, today they are one of the world’s most imperiled faunal groups. Efforts to aid habitat restoration, population growth, and species reintroduction can be informed by studies of prehistoric mussel assemblages. These data can provide a historical perspective, cataloging communities as they existed prior to extensive modern impacts, thus representing an ecological baseline to be compared with modern populations. This study focuses on two late prehistoric (ca. 300–600 AD) sites on the Yazoo River, where nearly 24,000 freshwater mussel valves were recovered. Though modern data are extremely limited for the river, analysis revealed it once supported a diverse mussel community containing numerous species currently considered rare, endangered, or extinct in Mississippi. In total, the combined shell assemblages yielded 23 new river records for the Yazoo River. One species in particular, Quadrula fragosa, represents the second such occurrence in Mississippi, and bolsters its candidate status as a new state record, as argued in a recent report from a neighbouring river in the Yazoo Basin.

Compositional variability of Pleistocene land snail assemblages preserved in a cinder cone volcano from Tenerife, Canary Islands

A Pleistocene land snail rich scoria sequence was studied to determine if it was influenced by taphonomic bias, climate change, or both, using a multifaceted approach that combines taphonomic, ecological, body size, and stable isotope data. Shell assemblages were sampled from two layers (Units A and B) in a cinder cone volcano of southern Tenerife (Canary Islands), dated to the glacial interval MIS 8 (~299–302ka). The two units differed in taphonomy, species composition, and abundance, with the upper Unit B showing higher diversity, abundance, and lower alteration than the lower Unit A. Larger bodied species dominated Unit A and were better preserved than smaller species. These mismatches likely resulted from physical differences in the sediment matrix surrounding fossils, with larger scoria grains of Unit A enhancing destruction rates and thus favoring preservation of larger (more durable) taxa than smaller scoria grains of Unit B. Comparisons with modern assemblages from the coastal scrub, the plant biome in which the Pleistocene site currently resides, indicates that no modern analogue exists for these fossil assemblages within this biome. Shell oxygen isotope values reveal that the local climate was colder/wetter during MIS 8 than at present, which also may explain variations in species composition through time. These data suggest that both taphonomic and climatic factors appear to have induced temporal variations in taxonomic composition, but it is difficult to determine which of these has more significantly influenced the observed results.

Applied Zooarchaeology of Freshwater Mussel (Bivalvia: Unionidae) Shell from Golson (22HU508), A Deasonville-Period Site on the Yazoo River, Mississippi

ABSTRACTExcavations at Golson (22HU508), an archaeological site on the Yazoo River in western Mississippi, USA, produced an assemblage of over 4000 freshwater mussel shells, 77 percent of which were identifiable to species. Although limited spatial sampling of the deposits limits what can be said about past mussel community characteristics, twelve new river records for mussel species are derived from the assemblage. This typical result emphasises the value of archaeological shell assemblages for conservation biology and provides a rationale for why sites containing shell may be considered significant based upon their potential contributions to environmental history.

Late Quaternary Faunal Changes in Northeastern Patagonia (Argentina) according to a Dynamic Mosaic of Benthic Habitats: Taphonomic and Paleoecological Analyses of Mollusk Assemblages

The aim of this study was to describe and interpret the paleoenvironmental history of the San Matias Gulf (SMG) in northern Patagonia, Argentina, associated to possible biotic and abiotic changes occurred during the late Quaternary. In this regard a taphonomic (disarticulation, right/left valve ratio; fragmentation, abrasion, teeth preservation) and paleoecologic (alpha diversity, species abundance, life habit, substrate preference, feeding mode) analysis of A. purputata (the target species) and its accompanying faunal remains (the non-target species) in modern, Holocene and Pleistocene shell assemblages was performed. The general trend of the SMG throughout the late Quaternary is as a low energy environment, with varying intensity depending on the study area. Additionally, each study site contains different substrates showing patches of sand and rock, and this would also have determined the presence of certain species; in turn, the proportion of sandy and rocky patches may have changed over time which led to the development of different local paleocommunities. This gulf therefore presents a dynamic mosaic of environments over time, as evidenced by taphonomic and paleoecological analyses. Its waters would have been sufficiently rich in nutrients to allow the development of the filter fauna which have dominated the late Quaternary, especially A. purpurata. Dual feeder gastropods from hard substrates (Crepidula species) have increased in proportion through the Holocene. The variation in the composition of the fauna accompanying A. purpurata is due to certain physical, biological and even anthropic environmental conditions, which have changed through time. These changes coincided with the Last Glacial Maximum, the final configuration of the SMG and the Climatic Optimum of the Holocene.

Rolling Cockles: Shell Abrasion and Repair in a Living Bivalve Cerastoderma edule L.

ABSTRACTLive cockles were eroded from a tidal flat by a storm event and naturally transported to a nearby dike and beach. Their fate was observed regularly for two months. Some died from desiccation high on the shore, and some were consumed by oystercatchers. Others were caught by the byssus threads of mussels inhabiting the intertidal area, while a few tried to reburrow high on the shore. These cockles were supposedly rolled while being transported to the beach and were later observed being rolled by the waves just below the high water line. Hence, it was concluded that the shells were subjected to abrasion and that this was the cause of the holes that some individuals developed near the umbo of one or both of their (still articulated) valves. A few had repaired such holes, supporting the hypothesis that these holes were made during rolling transportation. Similar shell assemblages of articulated cockleshells partly with subumbonal; holes were later found elsewhere on the Wadden Sea coast of Texel. This “natural” experiment and the repair indicated that this abrasion occurred while the cockles were still alive, and not after their death. It may also help to better discriminate between biologically and physically produced traces on shells.

Painting Altamira Cave? Shell tools for ochre-processing in the Upper Palaeolithic in northern Iberia

Much of our knowledge of the symbolic world of Upper Palaeolithic hunter-gatherers is based on the study of the graphic representations found in Western European caves. However, to date, few studies have been conducted on rock art apart from chronological and stylistic characterisation. Altamira Cave (northern Iberia) is characterised by an outstanding rock art ensemble, whose representations cover practically the whole Upper Palaeolithic. The site is equally important for the rich Upper Palaeolithic deposits in the cave entrance, which contain large shell assemblages. Traditionally, the presence of shells in hunter-fisher-gatherer settlements has been interpreted as part of the diet and/or the symbolic world (through the creation of ornaments) of these groups, regardless of their possible use as an instrument. In this paper we utilise use-wear methodology, chemical analysis and analytical experimentation to verify the initial hypothesis that shells in the archaeological deposits of Altamira were used to obtain the ochre powder utilised to produce the magnificent and diverse rock art ensemble in the cave. The results provide new information on the process of obtaining pigments for the realisation of paintings and confirm that the use of shells to obtain ochre was a systematic activity throughout the whole study period. Finally, our conclusions support the explanatory model that highlights the role played by marine resources for Upper Palaeolithic human populations.

Evidence for semi-sessile early juvenile life history in Cretaceous ammonites

Here we present evidence for a semi-sessile early juvenile stage of ammonites. Our hypothesis is based on fossil evidence in early diagenetic limestone concretions discovered in platy limestone deposits of Cenomanian age in the northern state of Coahuila, Mexico. In these locations densely packed post-embryonic shell assemblages were attached to fossilized algal or bacterial mats and preserved in sediments deposited under permanently anoxic bottom conditions. Tiny ammonites, as well as gastropods and byssate pectinid bivalves are abundant and restricted to these mats. They do not occur elsewhere in the sediment. The ammonite hatchlings were apparently unable to escape from mats sinking to the hostile sea floor and must thus have been semi-sessile, similar to the associated gastropods and bivalves.

Dead shell assemblages faithfully record living molluscan assemblages at One Tree Reef

Reef-associated sediments accumulate over time recording the history of biological communities. The agreement between live and dead assemblages has been extensively studied, because discrepancies between the two can reveal taphonomic bias, anthropogenic impact, and/or a decrease in temporal resolution of dead assemblages to centennial scales (i.e., time averaging). Given the potential of sedimentary assemblages to provide temporal perspectives on the history of modern communities, assessments of live-dead agreement in reef mollusk assemblage composition are necessary and timely for understanding rapid environmental change. One Tree Reef (OTR) (southern Great Barrier Reef, Australia) has had very little direct anthropogenic influence over the past four decades, making it a good system for focusing on taphonomic patterns. Live (n=1335) and dead (n=6919) molluscan assemblages were collected from three shallow (6m) carbonate soft-sediment lagoons. Diversity and evenness metrics indicated no significant difference between the live and dead assemblages, and dead assemblage rank order abundance explains 82% of that of the live assemblage. Differences in composition were largely due to sample size, the low probability of sampling rare species and to a lesser degree differences in skeletal durability. Taphonomic factors were responsible for less than 20% of the differences in species composition between live and dead shell assemblages. The live molluscan assemblage sampled was similar to the live assemblage sampled 30years ago. Given that time averaging is approximately 19years in the OTR lagoon, we conclude that the composition of the living assemblage has remained largely unchanged for the last 30years. These findings indicate that dead assemblages preserved in shallow, fully carbonate environments primarily reflect the composition of the original source communities, making them useful to identify recent changes in coral reef areas where anthropogenic impacts are present.

PALEOECOLOGIC SIGNIFICANCE OF MALACOFAUNA, OLDUVAI GORGE, TANZANIA

Abstract The rich record of vertebrate, hominin and archaeological remains recovered from Olduvai Gorge in northern Tanzania stands in stark contrast to the largely unexplored macroinvertebrate record from the region. Here we examine fossil malacofauna from Olduvai Gorge, inclusive of new discoveries and previous reports, and survey their potential as paleoecologic indicators. Recorded for the first time from Olduvai, an assemblage of fossil bivalve shells is attributed by character comparison to modern Chambardia wahlbergi, a freshwater unionid species widespread across Africa. The fossilized shells were localized in Bed III conglomerate channel deposits, with channel geometry exhibiting scour bases and superimposed fill structures with fining upward sequences. The ecology of recent C. wahlbergi combined with sedimentological data indicate the aquatic environment in this region during Olduvai Bed III times can be reconstructed as a periodically desiccated floodplain bordering a river channel or channels with permanent running water and marked seasonal fluctuations. This paleo-environmental setting presents drastic change compared with that of the lower Bed I and Bed II deposits, when an alkaline/saline lake extended over the site and fresh water was restricted to standing groundwater-fed pools with snail species known today to be intermediate hosts for the trematode genera Schistosoma (schistosomiasis) and Fasciola (fascioliasis). This research enhances details of landscape evolution at Olduvai basin and furthers paleoenvironmental interpretations during the time of Bed III deposition.

Factors affecting biodiversity on hermit crab shells

This study explores the abundance, diversity and assemblage structure of epifauna on the shells used by two hermit crab species (Pagurus bernhardus and P. pubescens) in the Arctic (Svalbard and Northern Norway) and investigates the biotic and physical drivers of such patterns. Contrary to our expectations, we found that location (which reflects the variability in environmental conditions and the local species pool of potential colonizers) is a key determinant not only in the cold, ice-scoured, glacier-dominated Arctic shallows of Svalbard but also in boreal Norwegian fjords, where other factors were hypothesized to be more important. Depending on region, shell area and identity were of lesser magnitude, with larger and more irregular shells containing more diverse assemblages. Crab host species also played a role (P. pubescens-inhabited shells supported larger number of individuals and higher diversity than those of P. bernhardus) but this effect might be species or region specific. In this study, no effect of crab gender could be detected. The study indicated that epifaunal assemblages of hermit crab shells are influenced by complex set of factors that interact together to different degree at various locations.

Windward vs. leeward: Inter-site variation in marine resource exploitation on Ebon Atoll, Republic of the Marshall Islands

The variation in windward and leeward marine environments has been linked to distinctions in marine subsistence on large, high volcanic Pacific Islands, but these patterns have not been explored on low coral atolls. We document windward vs. leeward islet site variation in the taxonomic composition of fish bone and mollusc shell assemblages from three archaeological sites at Ebon Atoll, Republic of the Marshall Islands, to elucidate the relationship between local environment, archaeological site type and the taxonomic composition of marine archaeofaunal assemblages. While the representation of taxa at each site was broadly similar in terms of measures of taxonomic heterogeneity (richness, evenness and dominance), chord distance and correspondence analysis reported variation in taxonomic composition at each site. For mollusc shell assemblages, variation in taxonomic abundance indicates the influence of the marine environments adjacent to each site and the relative exposure of these coastlines to heavy surf, wind, waves and extreme weather events. Fish bone assemblages recovered from 6.4mm screens had less inter-site variation in richness, evenness and rank order, but differences were noted in the rank order of fish taxa recovered from selective 3.2mm screening of archaeological deposits when compared between sites. In contrast to patterns for molluscs, variation in the taxonomic composition of fish bone assemblages likely relates to site function, rather than the marine environments adjacent to each site. These trends highlight for the first time the complex range of factors that influenced the prehistoric acquisition of marine resources between leeward and windward islets, and document variation in prehistoric marine subsistence within one atoll.