Journal of the North Atlantic
P.L. Ascough, M.J. Church, G.T. Cook, Á. Einarsson, T.H. McGovern, A.J. Dugmore, and K.J. Edwards
2014 Special Volume X
1
Introduction
The Viking settlement of the North Atlantic
commenced around AD 800, and was characterized
by rapid expansion of the Norse over a wide
geographical area, including Scotland, the Faroe
Islands, Iceland, and Greenland (e.g., Arge et al.
2005, Dugmore et al. 2005, Sharples and Parker
Pearson 1999, Vésteinsson et al. 2002). In a relatively
short time, settlements were established in a
broad set of ecological and climatic zones, and agriculture
was established in many previously pristine
environments (Dugmore et al. 2005, McGovern et
al. 2007, Vésteinsson 1998). Macro-scale settlement
outcomes varied markedly, from long-term sustainability
in the Faroes and Iceland, to abandonment
of Greenlandic settlements in the mid-15th century
AD (Dugmore et al. 2007a, 2012). This variation
is also evident on smaller geographical scales;
in Iceland, the overall continuity of settlement is
overlain by differences in the history and longevity
of individual farm sites (Dugmore et al. 2007b).
Understanding the mechanisms for this variation is a
key component in the reconstruction of Viking histories
in the North Atlantic, but this aim is frequently
confounded by the complexity of social, economic,
and environmental interactions that influenced the
behavior of inhabitants at a site.
One recurring and crucial research question is:
what economic strategy was in place at a particular
settlement? Understanding economic practices,
particularly in terms of diet and animal husbandry,
is essential to the reconstruction of human–environment
interactions. Over recent years, the utility of
stable isotope analysis in this regard has become increasingly
apparent (e.g., Ambrose 1986; Arneborg
et al. 1999, 2012; Ascough et al. 2012; Barrett and
Richards 2007; Richards and Hedges 1999; Richards
et al. 2006; Schwarcz and Schoeninger 1991). In this
study, we investigate the use of stable isotope ratios
of carbon and nitrogen, expressed as δ13C and δ15N,
as a tool to reconstruct economic practice at early
Viking period sites within the region of Mývatnssveit,
northern Iceland (Fig. 1).
Norse North Atlantic communities used both agricultural
and wild resources to build a broad-spectrum,
effective, and flexible subsistence system that
was initially based on traditional economic knowledge
from the Norse homelands and then adapted
to local settings (Dugmore et al. 2005, 2012). The
agricultural component involved cows, sheep, goats,
pigs, horses, and dogs, plus, where possible, arable
agriculture. The wild component varied but could include
freshwater and marine fish, birds, and marine
mammals. Individual farms generally operated as
part of a multi-farm cooperative system, involving
exchange of materials and products with communal
management of practices, such as upland grazing.
The economic system was not static, but instead
Stable Isotopic (δ13C and δ15N) Characterization of Key Faunal Resources
from Norse Period Settlements in North Iceland
Philippa L. Ascough1,*, Mike J. Church2, Gordon T. Cook1, Árni Einarsson3, Thomas H. McGovern4,
Andrew J. Dugmore5, and Kevin J. Edwards6,7
Abstract - During the Viking Age, Norse peoples established settlements across the North Atlantic, colonizing the pristine
and near-pristine landscapes of the Faroe Islands, Iceland, Greenland, and the short-lived Vinland settlement in Newfoundland.
Current North Atlantic archaeological research themes include efforts to understand human adaptation and impact
in these environments. For example, early Icelandic settlements persisted despite substantial environmental impacts and
climatic change, while the Greenlandic settlements were abandoned ca. AD 1450 in the face of similar environmental degradation.
The Norse settlers utilized both imported domestic livestock and natural fauna, including wild birds and aquatic
resources. The stable isotope ratios of carbon and nitrogen (expressed as δ13C and δ15N) in archaeofaunal bones provide a
powerful tool for the reconstruction of Norse economy and diet. Here we assess the δ13C and δ15N values of faunal and floral
samples from sites in North Iceland within the context of Norse economic strategies. These strategies had a dramatic effect
upon the ecology and environment of the North Atlantic islands, with impacts enduring to the present day.
Viking Settlers of the North Atlantic: An Isotopic Approach
Journal of the North Atlantic
1SUERC, Scottish Enterprise Technology Park, Rankine Avenue, East Kilbride G75 0QF, UK. 2Department of Archaeology,
Durham University, South Road, Durham DH1 3LE, UK. 3 Mývatn Research Station, Skútustaðir, Iceland and Institute of
Biology and Environmental Sciences, University of Iceland, Reykjavik, Iceland. 4Hunter Bioarchaeology Laboratory, Hunter
College CUNY, New York, NY 10021, USA. 5Institute of Geography, School of GeoSciences, University of Edinburgh,
Drummond Street, Edinburgh EH9 8XP, UK. 6Departments of Geography and Environment and Archaeology, University
of Aberdeen, Elphinstone Road, Aberdeen AB24 3UF, UK. 7St. Catherine’s College, University of Oxford, Manor Road,
Oxford OX1 3UJ, UK. *Corresponding author - Philippa.ascough@gla.ac.uk.
2014 Special Volume X:XX–XX
Journal of the North Atlantic
P.L. Ascough, M.J. Church, G.T. Cook, Á. Einarsson, T.H. McGovern, A.J. Dugmore, and K.J. Edwards
2014 Special Volume X
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responded to changing environmental conditions
and social pressures.
Measurements of δ13C and δ15N are a valuable
tool in archaeological palaeodietary reconstruction.
These measurements represent an integration of
δ13C and δ15N isotope values in food consumed over
the time a tissue (e.g., bone collagen) was formed
(Hedges et al. 2007, Hobson and Clark 1992, Tieszen
1978). There is also a diet-tissue offset, meaning
that δ13C and δ15N increase within an organism
with each trophic level up a food chain by typically
≈1–2‰ for δ13C and 3–5‰ for δ15N. An increase in
trophic level has also been observed in the δ15N of
neonatal and suckling animals relative to the tissues
of the mother in both modern and archaeological
populations (e.g., Ascough et al. 2012, Fuller et al.
2006). Although the typical source-consumer δ13C
offset is minimal, it should be noted that the bone
collagen diet-tissue δ13C offset appears to show
species and diet-dependant variations (e.g., Hare et
al. 1991), with a recent survey suggesting an offset
of +3.6‰ for mammalian collagen (Szpak et al.
2012a). If the isotopic values of possible dietary
components are sufficiently different, then the proportion
of each component that was consumed by
an organism can be assessed by analysis of its body
tissues. δ13C and δ15N measurements of archaeological
samples are usually made using bone collagen
and have proved particularly useful in discriminating
between terrestrial and marine components in
the diet of human populations, as there is a large
and consistent difference between both carbon and
nitrogen isotope values in marine and terrestrial
organisms (Arneborg et al. 1999, Richards et al.
2006, Sveinbjörnsdóttir et al. 2010). Commonly,
this approach involves modelling the proportion
of different theoretical dietary components. The
accuracy of such isotope-based diet reconstruction
depends heavily on how accurately the source isotopic
compositions for each resource group represent
the resources actually consumed. Thus, the selection
of appropriate end-member values for such a model
is critical (Dewar and Pfeiffer 2010). Importantly,
both the resources included in the economic strategy
of the inhabitants of the archaeological site and the
isotope values of these resources must be known.
Values of δ13C and δ15N show wide geographical
variation, meaning that the values for a species in
one region cannot necessarily be used in palaeodietary
reconstruction for another region. Geographic
variations occur due to a range of environmental
and anthropogenic variables, summarized in Rubenstein
and Hobson (2004). Terrestrial δ13C decreases
with increasing latitude and increases with altitude
due to temperature effects, while in C3-plant-based
ecosystems, dry habitats are enriched in δ13C compared
to wet habitats due to differences in water-use
efficiency (Lajtha and Marshall 1994). In marine
environments, δ13C decreases with latitude, leading
to northern oceans being enriched in δ13C compared
to southern oceans, and benthic systems are enriched
in δ13C compared to pelagic systems. These effects
Figure 1. Location map of sites mentioned in the text
Journal of the North Atlantic
P.L. Ascough, M.J. Church, G.T. Cook, Á. Einarsson, T.H. McGovern, A.J. Dugmore, and K.J. Edwards
2014 Special Volume X
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are ascribed to temperature differences, surfacewater
CO2 concentration offsets, and differences in
plankton biosynthesis or metabolism (Kelly 2000).
Terrestrial plant tissue δ15N varies according to the
method of nitrogen fixation, the influence of anthropogenically
and naturally added fertilizers, land-use
practices resulting in differential loss of 14N, and the
enrichment of wet habitats in δ15N relative to dry habitats
(Kelly 2000). Marine δ15N geographic patterns
are less well understood, although δ15N in northern
oceans appears more enriched compared to southern
oceans (Kelly 2000). In addition to the above variables,
the isotope values of any resource (e.g., cattle)
at a single location will show considerable variability
due to factors such as individual feeding preferences,
age, sex, or illness (Bocherens and Drucker 2003,
Hobson 1999, Hobson and Schwartz 1986).
This paper compiles stable isotope (δ13C and
δ15N) values for a range of resources available to early
Norse settlements in northern Iceland, within the
region of Mývatnssveit, surrounding Lake Mývatn
(Fig. 1, Table 1). These data include both domestic
animals and wild resources from four archaeological
sites: Undir Sandmúla (McGovern 2005), Sveigakot
(Vésteinsson 2002), Hofstaðir (Lucas 2010), and
Hrísheimar (Edvardsson and McGovern 2007).
The region has been the focus of an international
research effort to investigate human–environment
interaction over the past twenty years (McGovern
et al. 2007). The dataset presented here includes the
first investigation of archaeological bird bone δ13C
and δ15N for the study region. This inclusion is significant,
given the extensive evidence for exploitation
of bird populations surrounding Mývatn by the
Norse inhabitants of Mývatnssveit (McGovern et
al. 2007). In addition, analysis of bird remains from
archaeological and paleontological contexts have
contributed significantly to a better understanding
of the ecology of a number of bird species (e.g.,
Chamberlain et al. 2005, Emslie and Patterson 2007,
Fox-Dobbs et al. 2006), and so the results may have
value beyond archaeological investigations.
The aim of the research is firstly to compile a new
and more comprehensive assessment of the isotope
values and their ranges for resources used in the
Norse economy of the study area. Secondly, it aims
to investigate the potential for using isotope analysis
of archaeofaunal remains in informing researchers
about animal husbandry practices in the study
area. Animal husbandry is a key component within
North Atlantic archaeology, but little research has
addressed the direct reconstruction of animal diet
through stable isotope analysis. This paper therefore
assesses the isotopic values of archaeofauna from
sites in Mývatnssveit (Table 1) to determine whether
it is possible to use these data to detect differences
in husbandry practices in differing environments
and between sites of differing status or function. In
omnivores, such as pigs, both δ13C and δ15N can vary
significantly between animals obtaining nutrients
through free-range pannage versus those that are
stalled and fed upon domestic waste including animal
protein. This difference is particularly evident
if the domestic waste includes marine or freshwater
resources. In herbivores, δ13C values tend to show
less variability in areas where plant communities are
dominated by C3 vegetation (as in Iceland). However,
plant δ15N values can vary widely, depending
upon local environment. Of particular interest to the
current study is that long-term intensive use of animal
manure distinctly raises plant δ15N values relative
to unmanured areas (Bogaard et al. 2007; Bol et
al. 2005; Commisso and Nelson 2006, 2007; Fraser
et al. 2011; Kanstrup et al. 2011, 2012). This elevation
is considerable and has been shown to be as high
as 10‰ in cereal grains (Kanstrup et al. 2012). High
δ15N values in domestic animals may therefore indicate
enhancement of production via manuring practices
or feeding of stalled animals over winter. It is
important to note that natural variation in plant δ15N
values can also be considerable, and baseline values
are required. For this reason, the data presented here
also include values of modern vegetation from zones
unaffected by modern agriculture in Mývatnssveit.
Methods
Sample material
Modern sample material. Stable isotope values
used in this study represent the δ13C and δ15N of
Table 1. Site descriptions from which material was obtained for
analysis in this study.
Site Description
Mývatn A highland lake basin in the interior of North
Iceland
Haganes Area adjacent to the Mývatn shoreline
Kálfaströnd Area adjacent to the Mývatn shoreline
Seljahjallagil Gorge located ~5 km south east of Mývatn
Framengjar A large wetland area directly to the south of
Mývatn
Hrúteyjarnes An island within Mývatn
Undir Sandmúla Archaeological site. Indeterminate-status
Norse period farmstead
Sveigakot Archaeological site. Low-status Norse period
farmstead
Hofstaðir Archaeological site. High-status Norse period
farmstead
Hrísheimar Archaeological site. Indeterminate-status
Norse period farmstead
Journal of the North Atlantic
P.L. Ascough, M.J. Church, G.T. Cook, Á. Einarsson, T.H. McGovern, A.J. Dugmore, and K.J. Edwards
2014 Special Volume X
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both modern and archaeological biota from Mývatnssveit.
These values include a range of new
analyses and previously published measurements.
Modern vegetation was obtained from four locations
close to Mývatn (Haganes, Kálfaströnd, Framengjar,
and Hrúteyjarnes) and from two locations ≈5 km
from the lake in the vicinity of the archaeological
site of Sveigakot (Sveigakot and Seljahjallagil; see
Fig. 1). At Framengjar and Hrúteyjarnes, multiple
vegetation samples were collected along a short
transect to assess isotope variability in terrestrial
plants at these locations in more detail. Leaves were
sampled from living vegetation, air-dried at 30 °C,
and then freeze-dried. Samples were stored in precleaned
glass vials or plastic bags prior to subsequent
analysis. Living biota from within and around
Mývatn, including freshwater fish, were obtained as
described in Ascough et al. (2010). Wildfowl were
procured from local gyrfalcon (Falco rusticolus)
nests, or from gillnets in Lake Mývatn. Some were
collected as roadkill adjacent to Mývatn as soon as
practical after death. Full sample details are given in
Table 2.
Archaeofaunal sample material. The dataset of
Norse period archaeofauna included in this study
were obtained from four sites of varying status in the
Mývatnssveit region. Broadly, Hofstaðir is interpreted
as a high-status farm, while specialist activities,
such as industry, appear to have taken place at the
farms of Hrísheimar and Undir Sandmúla. Finally,
Sveigakot represents a lower-status farm site. The
holdings at Hofstaðir, Hrísheimar, and Sveigakot are
located at 250–350 m above sea level (asl), while
the territory of Undir Sandmúla is located slightly
higher, at ≈400 m asl. All samples retrieved date
to the 9th to 11th centuries AD. The age of samples
obtained was established through a combination
of tephrochronology and radiocarbon (14C) dating.
Archaeofaunal samples included in the dataset are
the bones of domesticated mammals (cow, sheep,
goat, pig, horse, and dog) and wild species (birds
and freshwater fish). These materials were obtained
during excavations for two main projects: the Leverhulme
Trust-funded “Landscapes circum-landnám”
(Edwards et al. 2004) and the NSF-funded “Long
Term Human Ecodynamics in the Norse North
Atlantic: cases of sustainability, survival, and collapse”
(McGovern 2011). Full sample details are
given in Table 3.
Laboratory methods
Pretreatment of dried vegetation involved homogenization
of each sample by grinding using an
agate mortar and pestle. A sub-sample (≈2–3 mg)
of the ground material was then taken for analysis.
Bone samples of modern organisms were de-fatted
prior to collagen extraction with 2:1 (v/v) chloroform/
methanol solution, followed by sonication for
60 minutes. The extraction was repeated until the
solvent remained clear. Collagen was extracted from
bone samples according to a modified Longin (1971)
method. The sample surface was cleaned by abrasion
with a Dremmel® tool, after which the bone was
crushed and placed in 1M HCl at room temperature
(≈20 °C). The bone was left in the HCl for up to 96
hours, after which dissolution of the bone mineral
component was complete. The solution was then decanted,
and the collagen washed in reverse-osmosis
water. The collagen was placed in reverse-osmosis
water and the solution pH adjusted to 3.0 by addition
of 0.5 M HCl. The collagen was solubilized by
gentle heating at ≈80 ºC. After cooling, the resulting
solution was filtered through Whatman GF/A
glass-fiber paper and then freeze-dried to recover
the collagen. A sub-sample (≈0.5–1 mg) of the dried
collagen was transferred into tin capsules for measurement
of elemental abundance and stable isotope
ratios.
Sample elemental abundances of %C and %N, to
calculate CN ratios, were measured using a Costech
elemental analyser (EA) (Milan, Italy) and fitted
with a zero-blank auto-sampler. Vegetation samples
were measured at the University of St. Andrews
Facility for Earth and Environmental Analysis, and
bone collagen samples were measured at the Scottish
Universities Environmental Research Centre. The
sample CN ratio was used to screen collagen samples
for purity; samples with ratios of 2.9–3.6 were
included in the dataset (cf. DeNiro 1985). Following
combustion in the EA, the δ13C and δ15N of vegetation
samples was measured using a ThermoFinnegan
Deltaplus XL, and the δ13C and δ15N of collagen was
measured using a Thermo Fisher Scientific Delta V
Advantage isotope ratio mass spectrometer (IRMS)
(Thermo FisherScientific Inc. GmbH, Bremen, Germany).
The EA and IRMS were linked via a ConFlo
III (Werner et al. 1999). Isotope values thus obtained
are reported as per mil (‰) deviations from the
VPDB and AIR international standards for δ13C and
δ15N. Samples were measured with a mix of appropriate
laboratory standards and blanks, from which
measurement precision (1σ) for δ13C was determined
to be better than ± 0.2‰, and measurement precision
(1σ) for δ15N was better than ± 0.3‰. Statistical differences
in isotope values between archaeological
sites for each archaeofaunal species were assessed
using one-way analysis of variance (ANOVA) and
post hoc Tukey tests.
Journal of the North Atlantic
P.L. Ascough, M.J. Church, G.T. Cook, Á. Einarsson, T.H. McGovern, A.J. Dugmore, and K.J. Edwards
2014 Special Volume X
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Table 2. Stable isotope measurements of modern samples from Mývatnssveit. Previously published measurements: *Ascough et al. 2010,
**Ascough et al. 2011. Modern terrestrial vegetation δ13C values are also given corrected for the Suess effect (i.e., -1.57‰; Feng and Epstein
1995, Keeling 1979, Keeling et al. 1979, McCarroll and Loader 2004, McCarroll et al. 2009).
Suess-
Sample corrected
ID location Latin name Common name Habitat; dietary preference δ13C δ13C δ15N C/N
SUERC- Haganes Poa sp. Grass Temperate grassland -28.3 -26.7 1.3 37
19798*
SUERC- Kálfaströnd Poa sp. Grass Temperate grassland -29.1 -27.5 2.6 23
19799*
StA-1 Sveigakot Poa sp. Grass Temperate grassland -28.2 -26.6 -6.3 33
StA-2* Seljahjallagil Poa sp. Grass Temperate grassland -28.5 -26.9 -9.1 25
StA-3* Seljahjallagil Equisetum arvense Field horsetail Meadow -26.9 -25.3 -2.6 19
StA-4 Kálfaströnd Equisetum arvense Field horsetail Meadow -29.2 -27.6 1.4 17
StA-5 Framengjar Carex rostrata Bottle sedge Wet meadows, Carr -27.8 -26.2 -0.9 24
StA-6 Framengjar Vaccinium uliginosum Bog bilberry Heaths, blanket bog -30.1 -28.5 -5.5 29
StA-7 Framengjar Carex lyngbyei Lyngbye’s sedge Wetlands, brackish water -27.8 -26.2 -0.9 26
StA-8 Framengjar Salix phylicifolia Tea-leaved willow Damp/freshwater zones -29.0 -27.4 -4.3 28
StA-9 Framengjar Betula nana Dwarf birch Heaths, bogs -29.4 -27.8 -4.9 22
StA-10 Framengjar Potentilla palustris Marsh cinquefoil Marsh, stream/lake banks -27.5 -25.9 1.1 21
StA-11 Framengjar Salix lanata Woolly willow Meadow, streamside -28.4 -26.8 -4.1 26
StA-12 Framengjar Empetrum nigrum Crowberry Heathland -28.9 -27.3 -6.2 77
StA-13 Framengjar Bartsia alpina Alpine bartsia Pastures and flushes -29.4 -27.8 -3.6 25
StA-14 Framengjar Galium verum Lady's bedstraw Meadows and pastures -27.0 -25.4 -0.8 18
StA-15 Hrúteyjarnes Geranium sp. Geranium Meadows, woodlands -30.2 -28.6 0.4 16
StA-16 Hrúteyjarnes Geum rivale Water avens Wet meadow, bog, riparian zones -29.0 -27.4 1.7 19
StA-17 Hrúteyjarnes Salix phylicifolia Tea-leaved willow Damp/freshwater zones -28.0 -26.4 2.3 17
StA-18 Hrúteyjarnes Erysimum hieraciifolium Wallflower Open damp grasslands -30.6 -29.0 1.8 9
StA-19 Hrúteyjarnes Angelica archangelica Angelica Stream/lake shorelines -30.9 -29.3 2.1 11
StA-20 Hrúteyjarnes Geranium sp. Geranium Meadows, woodlands -28.8 -27.2 4.0 12
StA-21 Hrúteyjarnes Geum rivale Water avens Wet meadow, bog, riparian zones -30.9 -29.3 1.5 14
StA-22 Hrúteyjarnes Angelica archangelica Angelica Stream/lake shorelines -29.3 -27.7 3.9 8
StA-23 Hrúteyjarnes Salix phylicifolia Tea-leaved willow Damp and freshwater zones -27.1 -25.5 3.9 15
StA-24 Hrúteyjarnes Geum rivale Water avens Wet meadow, bog, riparian zones -31.6 -30.0 1.9 16
StA-25 Hrúteyjarnes Salix phylicifolia Tea-leaved willow Damp and freshwater zones -29.1 -27.5 3.4 18
StA-26 Hrúteyjarnes Geranium sp. Geranium Meadows, woodlands -26.9 -25.3 2.1 14
StA-27 Hrúteyjarnes Angelica archangelica Angelica Stream and lake shorelines -29.5 -27.9 3.7 12
StA-28 Hrúteyjarnes Geum rivale Water avens Wet meadow, bog, riparian zones -29.1 -27.5 1.7 16
StA-29 Hrúteyjarnes Salix phylicifolia Tea-leaved willow Damp and freshwater zones -28.7 -27.1 4.8 20
StA-30 Hrúteyjarnes Geranium sp. Geranium Meadows, woodlands -28.8 -27.2 3.6 13
StA-31 Hrúteyjarnes Geum rivale Water avens Wet meadow, bog, riparian zones -30.9 -29.3 2.6 16
StA-32 Hrúteyjarnes Salix phylicifolia Tea-leaved willow Damp and freshwater zones -30.5 -28.9 5.0 16
StA-33 Hrúteyjarnes Salix phylicifolia Tea-leaved willow Damp and freshwater zones -30.5 -28.9 6.5 17
StA-34 Hrúteyjarnes Salix phylicifolia Tea-leaved willow Damp and freshwater zones -30.8 -29.2 4.1 17
StA-35 Hrúteyjarnes Salix phylicifolia Tea-leaved willow Damp and freshwater zones -31.3 -29.7 4.6 17
StA-36 Hrúteyjarnes Geranium sp. Geranium Meadows, woodlands -30.6 -29.0 3.0 12
SUERC- Mývatn Salvelinus alpinus Arctic char Fresh and/or marine waters; -14.0 - 5.8 7.0
19788* insectivore/piscivore
SUERC- Mývatn Gasterosteus aculeatus Three-spined Fresh and/or marine waters; -13.4 - 5.4 4.6
19789* stickleback benthic insectivore
SUERC- Mývatn Tanytarsus gracilentus Chironomid midge Freshwater -14.4 - 0.5 -
19791*
SUERC- Mývatn Tanytarsus gracilentus Chironomid larvae Freshwater, benthic detritivore -11.8 - -1.7 -
19792*
SUERC- Mývatn - Bulk zooplankton Freshwater pelagic; heterotrophic -17.7 - 1.5 -
19793*
SUERC- Mývatn Daphnia longispina Zooplankton Freshwater pelagic ; algae and -17.0 - 1.2 7.2
27076** organic detritus
SUERC- Mývatn Apatania zonella Caddisfly larvae Freshwater benthic; algae and -19.0 - -0.9 6.6
27072** detritus
SUERC- Mývatn Simulium vittatum Blackfly larvae Freshwater, benthic detritivore -15.4 - 1.2 5.1
27062**
SUERC- Mývatn Tanytarsus gracilentus Chironomid larvae Freshwater, benthic detritivore -15.8 - 6.1 5.1
27070**
SUERC- Mývatn Tanytarsus gracilentus Chironomid larvae Freshwater, benthic detritivore -19.3 - 0.7 -
27071**
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P.L. Ascough, M.J. Church, G.T. Cook, Á. Einarsson, T.H. McGovern, A.J. Dugmore, and K.J. Edwards
2014 Special Volume X
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Table 2, continued.
Suess-
Sample corrected
ID location Latin name Common name Habitat; dietary preference δ13C δ13C δ15N C/N
SUERC- Mývatn Tanytarsus gracilentus Chironomid larvae Freshwater, benthic detritivore -16.1 - 0.4 5.2
27068**
SUERC- Mývatn Tanytarsus gracilentus Chironomid larvae Freshwater, benthic detritivore -13.7 - 1.7 5.1
27069**
SUERC- Mývatn Radix peregra Mollusc Freshwater benthic; algae and -22.6 - 5.5 5.6
27082** detritus
SUERC- Mývatn Radix peregra Mollusc Freshwater benthic; algae and -15.7 - 3.6 5.0
27086** detritus
SUERC- Mývatn Radix peregra Mollusc Freshwater benthic; algae and -13.4 - 0.5 6.7
27081** detritus
SUERC- Mývatn - Detritus Lake benthic detritus -16.4 - -0.5 -
19797*
SUERC- Mývatn - Detritus Lake benthic detritus -17. 5 - -1.9 -
27059**
SUERC- Mývatn - Detritus Lake benthic detritus -18.3 - -0.4 -
27056**
SUERC- Mývatn - Detritus Lake benthic detritus -17.7 - -3.1 6.6
27057**
SUERC- Mývatn - Detritus Lake benthic detritus -16.5 - -2 -
27058**
SUERC- Mývatn - Detritus Lake benthic detritus -19.2 - 6.3 -
27060**
SUERC- Mývatn - Detritus Lake benthic detritus -17.4 - -2.1 -
27061**
SUERC- Mývatn Cladophora spp. Green algae Freshwater aquatic plant -14.8 - -1.3 8.7
27067**
SUERC- Mývatn Cladophora spp. Green algae Freshwater aquatic plant -10.1 - 3.4 16.7
27066**
SUERC- Mývatn Myriophyllum Alternate water- Freshwater aquatic plant -10.2 - -1.3 -
19800* alterniflorum milfoil
SUERC- Mývatn Potamogeton perfoliatus Perfoliate pondweed Freshwater aquatic plant -12.5 - 0.8 -
19801*
SUERC- Mývatn Potamogeton filiformis Slender-leaved Freshwater aquatic plant -16.9 - 2 26.6
27079** pondweed
SUERC- Mývatn Potamogeton filiformis Slender-leaved Freshwater aquatic plant -12.1 - -16 17.1
27080** pondweed
SUERC- Mývatn Potamogeton filiformis Slender-leaved Freshwater aquatic plant -13.1 - -4.3 17.8
27077** pondweed
SUERC- Mývatn Potamogeton filiformis Slender-leaved Freshwater aquatic plant -11.9 - -2.5 25.2
27078** pondweed
StA-37 Mývatn Melanitta nigra Common scoter Inland/coastal waters; aquatic -7.9 - 5.4 3.4
invertebrates, fish, vegetation
StA-38 Mývatn Anas penelope Wigeon Freshwater/coastal wetlands; -11.0 - 1.3 3.2
herbivorous
StA-39 Mývatn Numenius phaeopus Whimbrel Freshwater/coastal wetlands; -12.6 - 9.8 3.5
invertebrates, fish
StA-41 Mývatn Sterna paradisaea Arctic tern Coastal zone (may breed on -17.1 - 11.1 2.9
inland water); piscivorous
StA-42 Mývatn Podiceps auritus Slavonian grebe Inland/coastal waters; fish and -10.6 - 8.0 3.2
invertebrates
StA-44 Mývatn Podiceps auritus Slavonian grebe Inland/coastal waters; fish and -12.2 - 7.7 3.3
invertebrates
StA-45 Mývatn Podiceps auritus Slavonian grebe Inland/coastal waters; fish and -13.1 - 10.5 3.1
invertebrates
StA-46 Mývatn Podiceps auritus Slavonian grebe Inland/coastal waters; fish and -9.8 - 8.0 3.3
invertebrates
StA-47 Mývatn Aythya fuligula Tufted duck Lakes, rivers, estuaries: -23.2 - 16.4 3.5
Omnivorous
StA-49 Mývatn Anas crecca Teal Lake, marsh and river systems -20.6 - 5.4 3.5
StA-51 Mývatn Bucephala islandica Barrow’s goldeneye Inland/coastal waters; aquatic -13.4 - 5.2 2.9
insects, crustaceans and vegetation
StA-52 Mývatn Podiceps auritus Slavonian grebe Inland/coastal waters; fish and -14.6 - 10.4 3.0
invertebrates
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Table 3. Stable isotope measurements of archaeological samples from Mývatnssveit. †Ascough et al. 2007, *Ascough et al. 2010, §Ascough
et al. 2012. xNeonatal animal.
Measurement ID Sample location Context No. Latin name Common name δ13C δ15N C/N
StA-133 Hofstaðir 4 Aythyinae Diving duck -12.6 6.1 3.0
StA-134 Hofstaðir 8 Anas platyrhynchos Mallard -11.9 5.1 3.3
StA-135 Hofstaðir 4 Anas platyrhynchos Mallard -11.6 7.0 2.9
StA-136 Hofstaðir 1144 Aythyinae Diving duck -9.7 5.8 3.0
StA-138 Hofstaðir 6h Cepphus sp. Guillemot -15.9 8.7 3.3
StA-139 Hofstaðir 4a Laridae (family) Gull -16.6 7.1 3.1
StA-140 Hofstaðir 4a Lagopus sp. Ptarmigan -20.0 -4.9 3.4
StA-141 Hofstaðir 4a Phalacrocorax carbo Cormorant -12.0 5.4 3.3
StA-142 Hofstaðir 5a Alle alle Little Auk -21.0 5.2 2.9
StA-143 Hofstaðir 16 Aythyinae sp. Diving duck -15.0 13.9 2.9
StA-144 Hofstaðir 4 Aythyinae sp. Diving duck -13.1 4.8 2.9
SUERC-3429*x Hofstaðir 7a Bos taurus Cow -21.0 5.9 3.1
SUERC-3431*x Hofstaðir 6d Bos taurus Cow -20.3 1.6 3.1
SUERC-3433* Hofstaðir 6g Bos taurus Cow -20.9 3.8 3.3
SUERC-6393§ Hofstaðir 62 Bos taurus Cow -21.2 -0.1 3.2
SUERC-6397§ Hofstaðir 159 Bos taurus Cow -21.3 -0.1 3.2
SUERC-6398§ Hofstaðir 159 Bos taurus Cow -21.4 0.6 3.1
SUERC-6399§ Hofstaðir 159 Bos taurus Cow -21.4 -0.2 3.2
SUERC-8618† Hofstaðir 6N Bos taurus Cow -21.2 1.4 3.2
SUERC-8619†x Hofstaðir 6N Bos taurus Cow -21.0 2.6 3.3
SUERC-8623† Hofstaðir 6N Bos taurus Cow -21.2 0.1 3.1
SUERC-8624† Hofstaðir 6N Bos taurus Cow -21.4 -0.2 3.3
GU-14804§ Hofstaðir 1495 Bos taurus Cow -21.5 0.2 3.5
SUERC-8353§ Hofstaðir 233 Ovicaprine Sheep/Goat -21.7 0.7 3.4
SUERC-8354§ Hofstaðir 254 Ovicaprine Sheep/Goat -21.3 1.1 3.2
SUERC-8360§ Hofstaðir 170 Ovicaprine Sheep/Goat -21.4 1.3 3.2
SUERC-11541§ Hofstaðir 760 Ovicaprine Sheep/Goat -21.3 0.4 3.6
SUERC-11547§ Hofstaðir 170 Ovicaprine Sheep/Goat -21.4 1.8 3.4
GU-15267§x Hofstaðir 6M Ovicaprine Sheep/Goat -21.3 4.0 3.1
GU-15268§x Hofstaðir 6M Ovicaprine Sheep/Goat -21.5 2.5 3.1
GU-15269§ Hofstaðir 6M Ovicaprine Sheep/Goat -21.0 0.5 3.1
GU-15270§ Hofstaðir 6M Ovicaprine Sheep/Goat -20.9 1.6 3.1
GU-15271§ Hofstaðir 6M Ovicaprine Sheep/Goat -20.8 1.2 3.1
GU-15272§ Hofstaðir 6M Ovicaprine Sheep/Goat -21.0 0.2 3.1
SUERC-8356§ Hofstaðir 254 Ovis aries Sheep -21.8 0.1 3.3
SUERC-11542§ Hofstaðir 4480 Ovis aries Sheep -20.9 0.6 3.4
SUERC-11546§ Hofstaðir 1480 Ovis aries Sheep -21.0 1.1 3.3
GU-14805§ Hofstaðir 1166 Ovis aries Sheep -21.5 1.4 3.3
SUERC-11540* Hofstaðir 219/470 Salmo trutta Brown trout -12.2 6.8 3.5
SUERC-11539* Hofstaðir 219/470 Salvelinus alpinus Arctic char -12.5 5.7 3.4
SUERC-3430* Hofstaðir 7a Sus scrofa Domestic pig -21.0 4.6 3.4
SUERC-3432* Hofstaðir 6d Sus scrofa Domestic pig -21.5 0.5 3.5
SUERC-3438* Hofstaðir 6g Sus scrofa Domestic pig -19.8 3.7 3.2
SUERC-8355† Hofstaðir 254 Sus scrofa Domestic pig -16.9 7.4 3.2
GU-15273§x Hofstaðir 6N Sus scrofa Domestic pig -21.7 4.4 3.3
GU-15274§x Hofstaðir 6N Sus scrofa Domestic pig -21.2 0.9 3.3
GU-15275§ Hofstaðir 6N Sus scrofa Domestic pig -21.3 1.8 3.3
GU-15276§ Hofstaðir 6N Sus scrofa Domestic pig -18.9 6.6 3.4
GU-15277§ Hofstaðir 6N Sus scrofa Domestic pig -21.5 0.3 3.1
GU-15278§ Hofstaðir 6N Sus scrofa Domestic pig -21.3 3.1 3.3
StA-150 Hrísheimar 45 Anas crecca Teal -23.6 3.6 3.4
StA-154 Hrísheimar 384 Anser sp. Goose -10.4 4.9 3.0
SUERC-3445§x Hrísheimar 60 Bos taurus Cow -20.9 1.5 3.2
SUERC-3446*x Hrísheimar 2 Bos taurus Cow -21.4 1.0 3.1
SUERC-6431† Hrísheimar 45 Bos taurus Cow -21.7 -0.4 3.2
SUERC-6432† Hrísheimar 45 Bos taurus Cow -21.6 1.5 3.2
SUERC-6433† Hrísheimar 45 Bos taurus Cow -21.8 0.0 3.2
SUERC-6437† Hrísheimar 45 Bos taurus Cow -20.9 1.8 3.2
GU-14807§ Hrísheimar 429 Bos taurus Cow -20.4 3.1 3.4
GU-14808§ Hrísheimar 429 Bos taurus Cow -21.6 2.3 3.3
GU-14809§ Hrísheimar 429 Ovis aries Sheep -21.0 1.6 3.4
GU-15286§ Hrísheimar 3 Ovis aries Sheep -21.2 -0.5 3.3
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Table 3, continued.
Measurement ID Sample location Context No. Latin name Common name δ13C δ15N C/N
GU-15287§ Hrísheimar 3 Ovis aries Sheep -21.0 0.9 3.3
GU-15288§ Hrísheimar 3 Ovis aries Sheep -21.3 0.6 3.4
GU-15289§ Hrísheimar 3 Ovis aries Sheep -21.1 1.6 3.2
GU-15290§ Hrísheimar 3 Ovis aries Sheep -22.0 1.7 3.6
GU-15291§ Hrísheimar 3 Ovis aries Sheep -21.2 -0.2 3.3
GU-15292§ Hrísheimar 3 Ovis aries Sheep -21.2 0.6 3.2
GU-15293§ Hrísheimar 3 Ovis aries Sheep -21.3 -1.5 3.3
GU-15294§ Hrísheimar 3 Ovis aries Sheep -21.6 0.3 3.4
SUERC-9045† Hrísheimar 45 Salvelinus alpinus Arctic char -15.9 6.0 3.1
SUERC-9049† Hrísheimar 45 Salvelinus alpinus Arctic char -16.0 5.7 3.3
SUERC-9050† Hrísheimar 45 Salvelinus alpinus Arctic char -15.5 5.6 3.2
SUERC-9051† Hrísheimar 45 Salvelinus alpinus Arctic char -15.9 5.8 3.2
SUERC-3440* Hrísheimar 3 Sus scrofa Domestic pig -21.3 0.1 3.1
SUERC-3442* Hrísheimar 2 Sus scrofa Domestic pig -20.1 1.3 3.1
GU-14806§ Hrísheimar 429 Sus scrofa Domestic pig -20.6 3.9 3.5
GU-15279§x Hrísheimar 3 Sus scrofa Domestic pig -22.5 -1.2 3.4
GU-15280§x Hrísheimar 3 Sus scrofa Domestic pig -22.2 -0.7 3.5
GU-15281§x Hrísheimar 3 Sus scrofa Domestic pig -21.8 0.0 3.3
GU-15282§ Hrísheimar 3 Sus scrofa Domestic pig -22.2 -0.4 3.5
GU-15283§ Hrísheimar 3 Sus scrofa Domestic pig -22.0 -0.5 3.3
GU-15284§ Hrísheimar 3 Sus scrofa Domestic pig -21.3 0.1 3.2
GU-15285§ Hrísheimar 3 Sus scrofa Domestic pig -21.9 -0.6 3.3
StA-155 Sveigakot 27 Aythyinae Diving duck -20.5 -2.7 2.9
StA-156 Sveigakot 58 Gavia immer Great Northern diver -14.5 14.2 3.4
StA-158 Sveigakot 55 Podiceps auritus Slavonian grebe -17.0 11.3 3.1
StA-159 Sveigakot 4 Podiceps auritus Slavonian grebe -11.9 11.1 3.0
StA-160 Sveigakot 2 Anser sp. Goose -13.5 14.1 2.9
StA-161 Sveigakot 54 Anatidae Ducks, geese, swans (family) -13.8 8.6 2.9
StA-162 Sveigakot 2 Aythyinae Diving duck -12.2 4.2 2.9
StA-163 Sveigakot 1437 Laridae (family) Gull -15.6 15.0 3.1
StA-164 Sveigakot 55 Gavia stellata Red throated diver -13.6 12.6 3.1
GUsi-1312 Sveigakot 2859 Bos taurus Cow -21.5 2.7 3.3
GU-15461§ Sveigakot 55 Bos taurus Cow -21.5 1.2 3.2
GU-15462§ Sveigakot 55 Bos taurus Cow -21.3 0.2 3.3
GU-15463§ Sveigakot 55 Bos taurus Cow -22.1 0.3 3.3
GU-15464§ Sveigakot 55 Bos taurus Cow -21.3 0.9 3.3
GU-15465§x Sveigakot 55 Bos taurus Cow -20.9 2.3 3.4
GU-15466§x Sveigakot 55 Bos taurus Cow -21.2 2.1 3.5
GU-15467§ Sveigakot 55 Ovicaprine Sheep/Goat -21.1 0.0 3.3
GU-15468§ Sveigakot 55 Ovicaprine Sheep/Goat -21.1 -0.6 3.4
GU-15469§ Sveigakot 55 Ovicaprine Sheep/Goat -21.1 0.3 3.3
GU-15470§ Sveigakot 55 Ovicaprine Sheep/Goat -21.5 0.4 3.6
GU-15471§ Sveigakot 55 Ovicaprine Sheep/Goat -21.3 0.0 3.3
GU-15472§ Sveigakot 55 Ovicaprine Sheep/Goat -21.1 -0.3 3.3
GUsi-1316 Sveigakot 2859 Ovis aries Sheep -21.8 0.5 3.4
GUsi-1317 Sveigakot 2859 Ovis aries Sheep -21.2 1.2 3.2
GUsi-1318 Sveigakot 2859 Ovis aries Sheep -21.9 1.4 3.6
GUsi-1319 Sveigakot 2859 Ovis aries Sheep -21.3 1.2 3.3
GUsi-1314 Sveigakot 2859 Sus scrofa Domestic pig -21.6 5.0 3.6
GU-15473§ Sveigakot 55 Sus scrofa Domestic pig -19.8 3.0 3.5
GU-15474 Sveigakot 55 Sus scrofa Domestic pig -21.3 0.2 3.3
GU-15475 Sveigakot 55 Sus scrofa Domestic pig -17.8 8.7 3.4
GU-15476x Sveigakot 55 Sus scrofa Domestic pig -21.3 2.0 3.5
GU-15477 Sveigakot 55 Sus scrofa Domestic pig -20.4 3.3 3.4
GU-15478 Sveigakot 55 Sus scrofa Domestic pig -21.5 3.0 3.3
SUERC-11548 Undir Sandmúla 2 Bos taurus Cow -21.6 2.1 3.4
SUERC-11549 Undir Sandmúla 2 Bos taurus Cow -21.6 0.1 3.6
GU-14803§ Undir Sandmúla 2 Capra hircus Goat -21.4 -1.0 3.3
GU-14799§ Undir Sandmúla 2 Ovicaprine Sheep/Goat -21.3 -1.3 3.3
GU-14800§ Undir Sandmúla 2 Ovicaprine Sheep/Goat -21.4 -0.2 3.5
GU-14801§ Undir Sandmúla 2 Ovicaprine Sheep/Goat -21.3 -0.8 3.5
GU-14802§ Undir Sandmúla 2 Ovicaprine Sheep/Goat -21.5 -1.0 3.6
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Results and Interpretations
Modern vegetation and biota from Mývatnssveit
Modern terrestrial vegetation. The raw δ13C values
of modern terrestrial vegetation were adjusted
by +1.57‰ (Feng and Epstein 1995, McCarroll and
Loader 2004, McCarroll et al. 2009) to account for
the decrease in atmospheric δ13C since ca. AD 1880
due to human burning of fossil fuels (the Suess effect;
Keeling 1979, Keeling et al. 1979)). The corrected
δ13C values ranged from -30.0 to -25.3‰, and
the δ15N values ranged from -9.0 to +6.5‰ (Table
2, Fig. 2). These values accord with previous measurements
by Wang and Wooller (2006) and Gratton
et al. (2008) of plant δ15N values for a range of locations
in Iceland. The δ13C values of all sites falls
within the same broad range. In contrast, the δ15N
values of samples from Haganes, Kálfaströnd, and
Hrúteyjarnes (+0.4 to +6.5‰; average = +2.9‰)
is higher than that of samples from Framengjar,
Sveigakot, and Seljahjallagil (−9.0 to +1.1‰; average
= -3.7‰). The sampling sites of Hrúteyjarnes
and Framengjar in particular were selected due to the
lack of modern grazing animals at these locations,
meaning that the elevated δ15N values at Hrúteyjarnes
are unlikely to be due to the effect of manuring
via these species. An alternative explanation for
higher plant δ15N values at Haganes, Kálfaströnd,
and Hrúteyjarnes is higher δ15N of bioavailable soil
nitrogen (as NH4
+ or NO3
-) at these sites. One potential
source is the transportation of nitrogen from the
lake to the shore in the bodies of chironomids (nonbiting
midges). Gratton et al. (2008) estimated that,
on average, 17 kg N ha-1 d-1 (kilograms of nitrogen
per hectare, per day) were transported from Lake
Mývatn to the terrestrial environment in this way,
and that midge abundances decreased logarithmically
with distance from shore. In contrast to our results,
Gratton et al. (2008) did not find elevated δ15N
values in plants close to Mývatn. A further potential
source of elevated plant δ15N values close to the lake
is that of guano from nesting bird populations. Bird
guano has been shown to elevate plant δ15N values
considerably in experimental studies (Szpak et al.
2012b).
The results of stable isotope measurements on
modern vegetation show that there is a wide range
Figure 2. Modern vegetation samples from Mývatnssveit. Bars represent 1σ measurement precision (i.e., ± 0.2‰ for δ13C
and ± 0.3‰ for δ15N). δ13C values are given corrected for the Suess effect (i.e., -1.57‰; Feng and Epstein 1995, Keeling
1979, Keeling et al. 1979, McCarroll and Loader 2004, McCarroll et al. 2009).
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in Einarsson et al. 2004, where the trophic pathways
from detritus up to waterfowl and fish are illustrated.
The overall δ13C value of modern freshwater biota
is higher than that of terrestrial plants, meaning that
the δ13C values of fish and birds obtaining carbon
from the lake will generally be higher than that
of terrestrial herbivores (cf. Ascough et al. 2012).
In contrast, the δ15N values of aquatic plants and
invertebrates are within the range of that represented
in terrestrial vegetation samples. Excluding an
extreme δ15N value of -16‰ (discussed in Ascough
et al. 2011), the δ15N value range is -4.3 to +6.1‰.
Thus, the δ15N of organisms consuming freshwater
resources will overlap with that of organisms consuming
terrestrial plants in Mývatnssveit (Ascough
et al. 2012). An important point concerning the δ13C
and δ15N values of modern freshwater biota is that
values for both these isotopes show large variability
within the lake. This variation may therefore be
reflected in the δ13C and δ15N values of organisms
consuming lake biota.
The δ13C values of modern bird bones from
around Mývatn ranged from -23.2 to -7.9‰, and the
δ15N values for these samples ranged from +1.3 to
+16.4‰ (Table 2, Fig. 3). The very wide range in
these values reflects the broad diet of the sampled
in δ13C and δ15N values in plants in the Mývatn area.
While δ13C is variable at all sites, δ15N values appear
to differ significantly between locations. The expected
δ15N values of modern herbivores consuming
plants exclusively from Framengjar, Sveigakot, and
Seljahjallagil would therefore be ≈0–2‰, whereas
the expected δ15N values of animals consuming
plants at Haganes, Kálfaströnd, and Hrúteyjarnes
would be ≈6–8‰. These values are based on the
average δ15N value of plants at these locations,
meaning that the actual range in animal δ15N values
at any location is likely to be larger than the values
quoted above. Despite this, the overall δ15N value of
a population at Hrúteyjarnes, for example, would be
expected to be higher than an equivalent population
at Framengjar.
Modern freshwater biota and birds. The range in
δ13C and δ15N values within modern freshwater biota
in Mývatn, with respect to internal spatial lake variability,
is discussed in detail in Ascough et al. (2011).
However, the overall δ13C and δ15N values of lake
biota also have relevance for the isotope values of
wild resources (freshwater fish and birds) that were
exploited by the Norse inhabitants of Mývatnssveit.
The range in isotope values for individual species
fits the established food web of Mývatn presented
Figure 3. Modern and archaeofaunal bird bone collagen isotope values for archaeofaunal samples from Mývatnssveit. Bars
represent 1σ measurement precision (i.e., ± 0.2‰ for δ 13C and ± 0.3‰ for δ 15N).
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a factor that should be considered before applying
these data within the context of a palaeodietary baseline.
Archaeological biota from Mývatnssveit
Cows: inter-site comparison. The δ13C values
of archaeofaunal cow samples ranged from -22.1 to
-20.3‰ (Table 3, Fig. 4). Excluding neonatal cattle,
there is a barely significant difference between
cattle δ13C values at the four sites (ANOVA: P =
0.4659). Although values from Undir Sandmúla appear
slightly lower than those from the other sites,
the significance of this offset is difficult to assess
owing to the small sample size at Undir Sandmúla
(2 animals) relative to other locations. Although
the majority of the vegetation–cow-bone offsets are
reasonably explained by a trophic effect, it should be
borne in mind in future work that some higher cow
δ13C values could indicate the deliberate feeding of
cattle with fish bones, a practice that is documented
in Icelandic historical records.
The δ15N values of neonatal cattle were not
higher than that of adult animals, with the exception
birds. While some species have a diet of terrestrial
material (e.g., the whimbrel), the majority of other
species incorporate freshwater and marine resources
in their diets. The broad range in freshwater biota
δ13C and δ15N values discussed above is hence represented
in the δ13C and δ15N values of bird tissues. In
addition, some birds represented in the sample group
are piscivorous (Slavonian grebe), and hence will be
at higher trophic levels than other species. In addition,
most are migratory, spending part of the year
in marine environments. This life history means that
the δ13C and δ15N values of their tissues represent
an integration of many different dietary resources
from a variety of locations. One important point
here regards differences in tissue turnover rates; the
isotopic values of tissues with rapid turnover (e.g.,
muscle) reflect recent diet, whereas tissues with
slower turnover (e.g., bone collagen) reflect longerterm
dietary averages (Hobson and Clark 1992).
Therefore, the bone collagen δ13C and δ15N values
of migratory birds measured in this study may not
exactly reflect the values of the tissues consumed by
humans exploiting these birds as a dietary resource,
Figure 4. Bos taurus (cow) bone collagen isotope values for archaeofaunal samples from Mývatnssveit. Bars represent 1σ
measurement precision (i.e., ± 0.2‰ for δ 13C and ± 0.3‰ for δ 15N).
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of SUERC-3429 (δ15N = +5.9); this result is in contrast
to the effective trophic level increase observed
in neonates and suckling animals relative to the
adult mother in previous studies (e.g., Ascough et
al. 2012, Fuller et al. 2006). There is no statistically
significant difference in the δ15N of non-neonatal
cattle between the four sites (ANOVA: P = 0.52737).
However the range of δ15N values of cows at Sveigakot,
Undir Sandmúla, and Hrísheimar (2.5‰, 2.0‰,
and 3.5‰, respectively) is lower that that of cows at
Hofstaðir (4‰). The farm holdings of Hofstaðir and
Sveigakot (Thomson and Simpson 2007) are shown
on Figure 1. It is possible that the larger range in
δ15N values at Hofstaðir may reflect the larger size
of the potential area available for grazing of animals
at this site, incorporating zones with more-varied
vegetation δ15N values.
Ovicaprine: inter-site comparison. In some
instances, it was possible to identify samples within
the ovicaprine group to species (Ovis aries or
Capra hircus) on an archaeozoological basis. Where
further identification was possible, there was no
apparent difference between the isotope values of
these species and the larger group of indeterminate
ovicaprines. The range of δ13C values in ovicaprine
samples was -22.0 to -20.8‰ (Table 3, Fig. 5).
This range is not different from the range of δ13C
values in cattle samples, and there is no significant
difference in ovicaprine δ13C values between sites
(ANOVA: P = 0.73311). The δ15N values of the ovicaprine
sample group ranged from -1.5 to +4.0‰.
The two highest values belonged to two identified
neonatal animals (GU-15267 and GU-15268), resulting
from the trophic offset between neonates and
mothers discussed above. Exclusion of these values
from the dataset gives a maximum δ15N value of
+1.8‰. The average δ15N value of the archaeofaunal
ovicaprine bones is hence lower than that of the
cattle bones. If neonatal animals are excluded, the
average cattle δ15N value is +1.0‰, versus an average
of +0.4‰ for ovicaprines. This finding could
be the result of a physiological difference between
cattle and ovicaprines, although we are not aware of
any studies that demonstrate that such a difference
results in a δ15N offset between the two groups of
the kind observed here. An alternative explanation
is that there was a variation in the average δ15N
value of material consumed by cattle versus that of
ovicaprines. Such a dietary difference between the
two groups could be the result of food selection by
the organisms directly, or a difference in the type of
food to which ovicaprines and cattle had access as
a result of human control. The findings may therefore
be suggestive of different husbandry practices
Figure 5. Ovicaprine (sheep/goat) bone collagen isotope values for archaeofaunal samples from Mývatnssveit. Bars represent
1σ measurement precision (i.e., ± 0.2‰ for δ 13C and ± 0.3‰ for δ 15N).
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ed. This result is potentially a function of site status,
with greater access to herds grazing in a variety of
different vegetation catchments or a wider range of
fodder sources procured by the inhabitants of the site
Pigs: inter-site comparison. The δ13C values
of pig bone samples from the archaeofaunal sites
ranged from -22.5 to -16.9‰, and the δ15N values of
these samples covers a range of -1.2 to +8.7‰ (Table
3, Fig. 6). There are significant differences between
sites for non-neonatal animals for both δ13C (ANOVA
P = 0.29374) and δ15N (ANOVA P = 0.03839).
The broad range in isotope values at all three sites
(Sveigakot, Hrísheimar, and Hofstaðir) from which
pig bones were obtained, is likely to reflect a mixed
and variable range of husbandry practices. Their diet
clearly included a variety of resources and was not
restricted to terrestrial material. The most distinctive
difference between the sites is between the samples
from Hrísheimar and those from Sveigakot and Hofstaðir.
At Hrísheimar, the δ13C and δ15N values in the
majority of sampled pig bones falls within a narrow
range that is characteristic of animals existing on a
diet of terrestrial vegetation. Thus, the δ13C of pigs
at Hrísheimar is significantly lower than those at
Sveigakot (ANOVA, Tukey posthoc P = 0.4425)
and Hofstaðir (ANOVA, Tukey posthoc P =0.3067),
while there is no difference in δ13C between pigs from
Sveigakot and Hofstaðir (ANOVA, Tukey posthoc
between species, such as grazing of cattle and ovicaprines
in different areas of the region. Specialization
in husbandry practices between species has
also been used to explain similar dietary differences
between domestic animal species expressed in isotopic
values in previous archaeofaunal studies (e.g.,
Fuller et al. 2012a). The range of ovicaprine δ15N
values shows these animals did not frequently consume
plants with the high δ15N values observed at
Haganes, Kálfaströnd, and Hrúteyjarnes. This finding
argues against grazing of ovicaprines in intensively
manured areas or zones of high natural plant
δ15N values.
The δ15N of non-neonatal ovicaprines from
Undir Sandmúla are significantly lower than animals
from Hofstaðir (ANOVA, Tukey posthoc: P =
0.0003), Hrísheimar (ANOVA, Tukey posthoc: P =
0.0079), and Sveigakot (ANOVA, Tukey posthoc:
P = 0.0152). Values from Sveigakot are significantly
lower than values from Hofstaðir (ANOVA, Tukey
posthoc: P = 0.3489). It seems likely this difference
is a function of the rangeland areas of sheep and goats
at Undir Sandmúla, where plant δ 15N values are low
in modern vegetation samples. Simlarly, δ15N values
are also lower in animals from Sveigakot, though to
a lesser extent. As observed in the cattle bones, the
range in δ15N values at Hofstaðir is larger than at
other sites, even when neonatal animals are exclud-
Figure 6. Sus scrofa (pig) bone collagen isotope values for archaeofaunal samples from Mývatnssveit. Bars represent 1σ
measurement precision (i.e., ± 0.2‰ for δ 13C and ± 0.3‰ for δ 15N).
Journal of the North Atlantic
P.L. Ascough, M.J. Church, G.T. Cook, Á. Einarsson, T.H. McGovern, A.J. Dugmore, and K.J. Edwards
2014 Special Volume X
14
group (Ascough et al. 2007, 2010). The δ13C range
for freshwater fish overlaps with that of previous
values for archaeofaunal marine fish bone collagen
(Atlantic cod from Norse and medieval period sites
in northern Scotland; Russell et al. 2011), but the
δ15N is several per mill lower than average cod bone
values from Russell et al. (2011) and other studies
(e.g., Barrett et al. 2011). The δ13C and δ15N values
of fish from freshwater systems show great site-specific
variation on geographic scales; for example,
Fuller et al. (2012b) found δ13C values of -20.3
to -28.2‰ for freshwater fish in Belgium, while
Grupe et al. (2009) measured δ13C values of -11.7 to
-27.4‰ for non-marine species in a brackish fjord
in northern Germany. In these studies, the average
δ15N of freshwater fish bone collagen was several per
mill higher than that of modern or archaeofaunal fish
from Mývatn.
The δ13C values of archaeofaunal bird bone samples
from sites in Mývatnssveit were -23.6 to -9.7‰
(Table 3, Fig. 3). This range is approximately equivalent
to that of the sample of modern bird bones,
and similarly reflects the range in diet of the species
represented. The lowest δ13C values indicate a diet
containing more terrestrial resources, while higher
values denote increasing amounts of freshwater and/
or marine material in the diet. This pattern is also reflected
in the δ15N values of the samples, which range
from -4.9 to +15.2‰. If the resources consumed by
the birds were simply terrestrial and marine in origin,
a positive linear correlation between δ13C and
δ15N values in the sample group would be expected.
This is not the case, due to the confounding influence
of freshwater resources in the diet of the birds. As
discussed above, the isotope values for freshwater
resources in the lake are highly variable. The isotope
values of waterfowl in the region therefore incorporate
varying proportions of terrestrial, marine,
and freshwater food, whereas the isotope values for
freshwater resources cover a very large range. This
variability is apparent in both archaeological and
modern bird samples and has implications for palaeodietary
reconstructions of omnivorous organisms
such as humans. Along with consumption of waterfowl
themselves, exploitation of waterfowl populations
by Norse populations around Mývatnssveit involved
the collection of large quantities of waterfowl
eggs (McGovern et al. 2006, 2007). Egg production
by a bird uses nutrients obtained in the diet, and it
is likely that the large variation in isotope values
reflected in the bone collagen of samples analyzed
in this study would be reflected in the δ13C and δ15N
values of eggs consumed by human populations.
P = 0.9842). Similarly, the δ15N of pigs at Hrísheimar
is significantly lower than those at Sveigakot
(ANOVA, Tukey posthoc P = 0.058) and Hofstaðir
(ANOVA, Tukey posthoc P = 0.0716), while there is
no difference in δ13C between pigs from Sveigakot
and Hofstaðir (ANOVA, Tukey posthoc P = 0.957).
These results suggest that animal protein or non-terrestrial
resources did not feature significantly in the
diet of pigs from Hrísheimar, which have isotope
values consistent with free-range pannage of plant
material with low δ15N values (such as in the modern
vegetation sampled at Framengjar, Sveigakot, and
Seljahjallagil). This finding could be a function of
the early landnám date of the Hrísheimar midden
layers, as previous research has suggested the use
of free-range pannage pig husbandry as a means of
clearing woodland (Dugmore et al. 2005; McGovern
et al. 2006, 2007). In contrast, pig bone samples at
Sveigakot and Hofstaðir show significantly higher
δ13C and δ15N values that covers a wider range between
animals. Clearly, non-plant material featured
more heavily in the diet of pigs at these sites, which
included a mix of terrestrial, freshwater, and (potentially)
marine material. Animals with δ13C values
characteristic of terrestrial herbivores but with high
δ15N values could represent free-range pannage on
vegetation that had high δ15N values. Alternatively,
these values could represent the inclusion of terrestrial
animal protein in the diet of these pigs. Unfortunately,
these two possibilities are not readily discriminated
with bulk δ13C and δ15N values, although
analysis of the isotopic values of amino acids may
be a method that can shed further insight (e.g., Choy
et al. 2010) and could be a possible focus for future
work. However, where pig bone collagen δ13C values
are also elevated suggests inclusion of freshwater or
marine protein in the diet. Potential sources of this
material include fish-processing waste, fish bones,
and bird eggs. The presence of freshwater protein in
the diet of pigs from Mývatnssveit is also evidenced
in 14C dating, which has revealed a freshwater 14C
reservoir effect in the bones of pig samples from
these sites (Ascough et al. 2010, 2012). The range
of pig husbandry practices represented at Sveigakot
and Hofstaðir is therefore characteristic of a varied
strategy, including some animals that were fed upon
domestic waste, potentially while styed.
Wild species
The isotope values of archaeofaunal freshwater
fish (δ13C from -12.2 to -16.0‰, δ15N from 5.6 to
6.8‰) are within the range of modern fish from Mývatn
(δ13C from -13.4 to -14.0‰, δ15N from +5.4 to
+5.8‰), although there is some variation within the
Journal of the North Atlantic
P.L. Ascough, M.J. Church, G.T. Cook, Á. Einarsson, T.H. McGovern, A.J. Dugmore, and K.J. Edwards
2014 Special Volume X
15
Conclusions
The research presented here compiles isotope
values for Norse economic resources in Mývatnssveit,
representing the most comprehensive suite of
archaeofaunal δ13C and δ15N measurements for sites
in the region and anywhere in Iceland. The analyses
emphasize the wide range in isotope values of resources
used by the Norse settlers of Mývatnssveit.
As previously noted, there is separation between the
δ13C values of terrestrial and freshwater resources,
but considerable overlap between the δ15N values
of these groups (Ascough et al. 2012). This overlap
means that paleodietary reconstruction of individuals
in the region based solely on δ13C and δ15N values
will always be problematic.
The results provide information that is useful
to reconstructing animal husbandry practices in
the study area. While herbivore bone δ13C and δ15N
are unlikely to reveal subtle husbandry differences
(e.g., small-scale differences in grazing areas or in
the duration of over-winter stalling), it is clear that
with sufficiently large datasets, differences and similarities
between isotope values at individual sites
begin to emerge. In particular, δ13C and δ15N measurements
of pig bone enable detailed investigation
of husbandry in the region as these animals are omnivores
and consume a potential range of resources
with large separation in terms of isotope values (e.g.,
terrestrial versus marine material). Within the dataset
represented here, quite marked differences in pig
husbandry are apparent between a relatively small
number of sites.
Finally, the work highlights methodological
“best practice” in the application of stable isotope
analysis for archaeological research. Variation in
animal management practices, rather than animals
having unrestricted access to a landscape, means
that particular isotopic patterns at a site could arise
from a range of practices. Therefore, careful research
design is required and the results need to be
placed within a secure archaeological, chronological,
and palaeoenvironmental framework.
Acknowledgments
This research was supported by funding from the
Leverhulme Trust (“Landscape circum-landnám” Programme
Award: grant number F/00 152/F), US National
Science Foundation (grant number 0732327 “IPY: Long
Term Human Ecodynamics in the Norse North Atlantic:
Cases of sustainability, survival, and collapse” awarded
by the Office of Polar Programs Arctic Social Sciences
International Polar Year program 2007–2010), the Carnegie
Trust for the Universities of Scotland, and the Royal
Scottish Geographical Society. Thanks are due to Olafur K.
Nielsen, Institute of Natural History, Iceland, for providing
some of the bird samples from the Lake Mývatn area.
We would also like to thank Ian Lawson and Katy Roucoux
for help gathering the modern vegetation samples; Kerry
Sayle, Helen Hastie, and Elaine Dunbar for stable isotope
support at SUERC; and to three reviewers of the original
submission for their helpful and constructive comments.
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