View Article Online / Journal Homepage / Table of Contents for this issue JAAS Dynamic Article LinksC< Cite this: J. Anal. At. Spectrom., 2012, 27, 807 www.rsc.org/jaas PAPER Carbon and nitrogen stable isotope ratio analysis of freshwater, brackish and marine fish from Belgian archaeological sites (1st and 2nd millennium AD)† Benjamin T. Fuller,*ab Gundula Muldner,€ c Wim Van Neer,ad Anton Ervyncke and Michael P. Richardsbf Received 12th December 2011, Accepted 12th March 2012 DOI: 10.1039/c2ja10366d Carbon and nitrogen stable isotope ratios were measured in 157 fish bone collagen samples from 15 different archaeological sites in Belgium which ranged in ages from the 3rd to the 18th c. AD. Due to diagenetic contamination of the burial environment, only 63 specimens produced results with suitable C : N ratios (2.9–3.6). The selected bones encompass a wide spectrum of freshwater, brackish, and marine taxa (N ¼ 18), and this is reflected in the d13C results (À28.2& to À12.9%). The freshwater fish have d13C values that range from À28.2& to À20.2&, while the marine fish cluster between À15.4& and À13.0&. Eel, a catadromous species (mostly living in freshwater but migrating into the sea to spawn), plots between À24.1& and À17.7&, and the anadromous fish (living in marine environments but migrating into freshwater to spawn) show a mix of freshwater and marine isotopic signatures. The d15N results also have a large range (7.2& to 16.7&) indicating that these fish were feeding at many different trophic levels in these diverse aquatic environments. The aim of this research is the isotopic characterization of archaeological fish species (ecology, trophic level, migration patterns) and to determine intra-species variation within and between fish populations differing in time and location. Due to the previous lack of archaeological fish isotope data from Northern Europe and Belgium in particular, these results serve as an important ecological backdrop for the future isotopic reconstruction of the diet of human populations dating from the historical period (1st and 2nd millennium AD), where there is zooarchaeological and historical evidence for an increased consumption of marine fish. Published on 05 April 2012. Downloaded by Universiteit Gent 03/07/2015 09:50:01. Introduction from the same or related sites, in terms of location and time period. Most often, the food products measured comprise the d13 Measurement of the stable isotope ratios of carbon ( C) and bones of wild and domestic animals.5–9 However, the isotopic d15 nitrogen ( N) in bone collagen has increasingly become an analyses of fish remains are reported much less frequently. This important method to determine the general types of dietary 1–4 can be linked to the fact that fish skeletal material is often poorly patterns in archaeological human populations. The vast preserved, compared to that from other animals, and to the fact majority of this research has focused on the reconstruction of that the adequate recovery of fish bones at an archaeological site past subsistence patterns by comparing the stable isotope ratios requires sieving, which often was not routinely used on excava- from human bone collagen to those of consumption remains tions until the last decades.10 This is unfortunate as the isotopic analysis of fish remains can provide a more refined picture of the dietary habits of former humans.11–14 Research on fish is espe- a Laboratory of Biodiversity and Evolutionary Genomics, Centre for cially important for isotopic studies of European human pop- Archaeological Sciences, University of Leuven, Ch. Deberiotstraat 32, st nd B-3000 Leuven, Belgium. E-mail: [email protected] ulations dating from the historical period (1 and 2 millennium bDepartment of Human Evolution, Max Planck Institute for Evolutionary AD) where there is evidence for an increased consumption of Anthropology, Deutscher Platz 6, D-04103 Leipzig, Germany marine fish in the diet.15–19 c Department of Archaeology, University of Reading, Whiteknights P.O. In this study, stable isotope ratios of carbon and nitrogen were Box 227, Reading RG6 6AD, UK dRoyal Belgian Institute of Natural Sciences, Vautierstraat 29, B-1000 measured from archaeological freshwater, brackish and marine Brussels, Belgium fish recovered at archaeological sites in Belgium (Fig. 1). The eFlanders Heritage, Koning Albert II-laan 19, box 5, B-1210 Brussels, selected bones encompass a wide spectrum of species that are Belgium regularly found during excavations and that were thus of f Department of Anthropology, University of British Columbia, Vancouver, importance for past human subsistence. The freshwater taxa British Columbia V6T 1Z1, Canada † Electronic supplementary information (ESI) available. See DOI: likely represent fish that were locally captured, and the marine 10.1039/c2ja10366d fish from the inland sites are to be considered imports. The focus This journal is ª The Royal Society of Chemistry 2012 J. Anal. At. Spectrom., 2012, 27, 807–820 | 807 View Article Online Fig. 1 Map of Belgium with the main river basins and the sites sampled in this study (1: Antwerpen, 2: Dendermonde, 3: Ename, 4: Gent, 5: Ieper, 6: Londerzeel, 7: Mechelen, 8: Raversijde, 9: Tongeren, 10: Tournai). of this research is the assessment of the species’ isotopic char- stable isotope ratios are used to determine the trophic level or the acteristics (determined by their ecology, place in the foodchain, type of protein in the diet of an organism.1–4 With each stepwise etc.) and of intra-species variation (both within populations and increase in the food chain, d15N values increase by 3–5& relative between populations differing in time and/or location). This will to the diet21,22 and a recent literature review23 has placed this Published on 05 April 2012. Downloaded by Universiteit Gent 03/07/2015 09:50:01. lead to a better understanding of the aquatic isotopic ecology value at 3.6 Æ 1.3&. This phenomenon is known as the ‘trophic during the historical period in Belgium. In this way, the isotopic level effect’, and due to the large number of steps in aquatic food results of this study will be of great value for the more accurate chains, d15N values can become very elevated in higher trophic determination of human diets during historical times in north- level fish, or in birds and mammals consuming aquatic western Europe, which is an area of active research. resources.24 However, for a more detailed discussion of the complexities and uncertainties associated with nitrogen isotope Stable isotope ratios and diet ratios and how they can be used as trophic discrimination factors see ref. 25–27. Carbon and nitrogen stable isotope compositions are measured In aquatic ecosystems d13C and d15N measurements can also be as the ratios of the heavier isotope to the lighter isotopes (13C/12C used to determine the origin of species inhabiting freshwater, or 15N/14N) and are reported in standard delta (d) notation as brackish, and marine environments.17,28 The two most important parts per thousand (per mil, &) relative to internationally primary producers in marine ecosystems are microalgae defined standards for carbon (Vienna Pee Dee Belemnite, VPDB) (phytoplankton) and macroalgae (kelps and seaweeds) and these and nitrogen (Ambient Inhalable Reservoir, AIR).1 Bone are isotopically distinct. Phytoplankton have higher d13C values collagen is the most abundant protein in skeletal remains and it is compared to kelps and seaweeds,29 and the contribution of kelp- routinely analyzed for its carbon (d13C) and nitrogen (d15N) derived carbon to nearshore detrital foodwebs can be consider- stable isotope ratios, since it is usually all that remains of the able in marine ecosystems and has a significant impact on organic tissues of an organism after burial.3,4 The stable isotope consumer d13C values.30–32 As a result, organisms living in near- ratios reflect the protein portion of the averaged diet of an shore and benthic environments generally have 13C- and 15N- organism during the period of bone growth.20 In terrestrial enriched results compared to species living in offshore and environments, carbon stable isotope ratios are useful to distin- pelagic environments.29,33 The isotopic composition of marine 34–36 guish between C3 (most vegetables, fruits, nuts, wheat, and species also varies with respect to latitude. This is again due barley) and C4 (esp. sugarcane, sorghum, maize and millet) to the isotopic values of the primary producers, with species from plants or animals/humans consuming these plants.1–4 Nitrogen higher latitudes having lower d15N values compared to species 808 | J. Anal. At. Spectrom., 2012, 27, 807–820 This journal is ª The Royal Society of Chemistry 2012 View Article Online from the middle latitudes that display elevated d15N values.36 The sampling procedure for the recovery of the fish bone involves wet analysis of stable isotope ratios in aquatic environments is sieving of sediment over a series of sieves of 4, 2 and 1 mm mesh complex and for detailed reviews see ref. 10,17,23 and 37. size, which ensures the recovery of even the smallest fish remains. Identification of the fish bones was carried out by comparison to st the extensive modern reference collection housed at the Royal Importance of fish in the human diet: the case of 1 and Belgian Institute of Natural Sciences. The taxonomy was recor- nd 2 millennium Belgium ded and when the bone was sufficiently well preserved, the cor- On the territory of what is now Belgium, human dietary patterns responding fish length was also established. This was done by have undergone a marked evolution during the historical period direct comparison with modern fish skeletons of known body (i.e. the first two millennia AD). A diachronic comparison of length. The reconstructed fish lengths are expressed as centi- archaeozoological assemblages of a large number of sites shows metres standard length (cm SL), i.e.