Isotopic Landscape Research Articles

Brackish water foraging: isotopic landscapes and dietary reconstruction in Suisun Marsh, Central California

While bone stable isotope signatures of humans foraging in open coastal and fully terrestrial environments have been relatively well documented, the signature of foraging near brackish-water estuaries is less well known. This study examines the Central California isotopic landscape, or isoscape, showing how foods in different ecosystems have distinctive isotopic compositions. We present new bone collagen and apatite stable isotope data from two Late Holocene sites (CA-SOL-11 and CA-SOL-69) near Suisun Marsh, a low salinity brackish water estuary upstream from San Francisco Bay. Faunal remains at the sites include significant numbers of aquatic resources including fish and shellfish, in addition to terrestrial mammals, while paleobotanical remains suggest mainly terrestrial nuts and seeds. Stable isotope data at the population level corroborate this finding and show consumption of significant levels of brackish water nutrients, including both dietary protein and dietary carbohydrates and fats, paired with terrestrial foods. This dietary focus generates a unique brackish-water isotopic signature that is distinct from others in Central California. The documentation of an isoscape with strong regional gradients can be of tremendous help in reconstructing ancient patterns in subsistence, migration, and trade.

Strontium isotopes in tap water from the coterminous USA

Strontium isotope analysis has proven useful in geo‐location investigations of organic and inorganic materials and may complement the region‐of‐origin information provided by hydrogen and oxygen stable isotope analysis. In this study, we analyzed 99 drinking (tap) water samples collected from 95 municipal water systems across the USA to investigate the potential that 87Sr/86Sr can be used to provenance samples from managed hydrological systems. Results from a leaching and exchange experiment demonstrated that non‐ideal storage conditions did not prohibit Sr isotope analysis of previously archived water samples stored in glass. Tap water samples were analyzed via multi‐collector inductively coupled plasma mass spectrometry, which was preceded by a novel, automated, in‐line Sr purification method. Measured tap water 87Sr/86Sr was compared to expected 87Sr/86Sr for collection location, which was predicted using four published isotope landscape (isoscape) models: age of bedrock (bedrock model), age plus major and minor lithology of bedrock (major bedrock model), weathering of Sr from rock (local water model), and surface fluxes within watershed (catchment model). The geologic history of the geographic regions represented by collected tap waters was diverse and we therefore expected significant covariation in measured and modeled 87Sr/86Sr values. Tap water exhibited large ranges in both Sr concentration (0–1.9 mg/L) and 87Sr/86Sr (0.7037–0.7320). Measured tap water 87Sr/86Sr ratios were significantly and positively correlated with predictions based on bedrock and catchment models. However, these bedrock and catchment models explained relatively little of the tap water Sr isotopic variation (∼10% and 17%, respectively), suggesting that the factors affecting drinking water 87Sr/86Sr are complex and more numerous than the variables included in current water models. This could be due to the reliance of some municipal water systems on groundwater, rather than surficial water sources; the natural movement of water across distinct geologic gradients; and/or the managed transport of water from source to point‐of‐use. Although published isoscape models for predicting Sr isotopic variation within the continental USA are reasonable approaches for estimating surface water 87Sr/86Sr, additional efforts are needed to develop a prediction model specifically for tap water 87Sr/86Sr.

Lead and lead isotopes in agricultural soils of Europe – The continental perspective

Abstract Lead isotopes are widely used for age dating, for tracking sources of melts, sediments, Pb products, food and animals and for studying atmospheric Pb contamination. For the first time, a map of a Pb isotope landscape at the continental-scale is presented. Agricultural soil samples (Ap-horizon, 0–20 cm) collected at an average density of 1 site/2500 km2 were analysed for Pb concentration and Pb isotopes (206Pb, 207Pb, 208Pb). Lead concentrations vary from 1.6 to 1309 mg/kg, with a median of 16 mg/kg. Isotopic ratios of 206Pb/207Pb range from 1.116 to 1.727 with a median of 1.202. The new data define the soil geochemical Pb background for European agricultural soil, providing crucial information for geological, environmental and forensic sciences, public health, environmental policy and mineral exploration. The European continental-scale patterns of Pb concentrations and Pb isotopes show a high variability dominated by geology and influenced by climate. Lead concentration anomalies mark most of the known mineralised areas throughout Europe. Some local Pb anomalies have a distinct anthropogenic origin.

Seabird satellite tracking validates the use of latitudinal isoscapes to depict predators' foraging areas in the Southern Ocean

Stable isotopes are increasingly being used to trace wildlife movements. A fundamental prerequisite of animal isotopic tracking is a good knowledge of spatial isotopic variations in the environment. Few accessible reference maps of the isotopic landscape ("isoscapes") are available for marine predators. Here, we validate for the first time an isotopic gradient for higher trophic levels by using a unique combination of a large number of satellite-tracks and subsequent blood plasma isotopic signatures from a wide-ranging oceanic predator. The plasma δ(13)C and δ(15)N values of wandering albatrosses (n = 45) were highly and positively correlated to the Southern Ocean latitudes at which the satellite-tracked individuals foraged. The well-defined latitudinal baseline carbon isoscapes in the Southern Ocean is thus reflected in the tissue of consumers, but with a positive shift due to the cumulative effect of a slight (13)C-enrichment at each trophic level. The data allowed us to estimate the carbon isotopic position of the main oceanic fronts in the area, and thus to delineate robust isoscapes of the main foraging zones for top predators. The plasma δ(13)C and δ(15)N values were positively and linearly correlated, thus suggesting that latitudinal isoscapes also occur for δ(15)N at the base of the food web in oceanic waters of the Southern Ocean. The combination of device deployments with sampling of relevant tissues for isotopic analysis appears to be a powerful tool for investigating consumers' isoscapes at various spatio-temporal scales.

Stable isotope analysis reveals habitat partitioning among marine mammals off the NW African coast and unique trophic niches for two globally threatened species

Stable isotope abundances of carbon (δ 13 C) and nitrogen (δ 15 N) in the bone of 13 species of marine mammals from the northwest coast of Africa were investigated to assess their positions in the local trophic web and their preferred habitats. Also, samples of primary producers and potential prey species from the study area were collected to characterise the local isotopic landscape. This characterisation indicated that δ 13 C values increased from offshore to nearshore and that δ 15 N was a good proxy for trophic level. Therefore, the most coastal species were Monachus monachus and Sousa teuszii, whereas the most pelagic were Physeter macrocephalus and Balaenoptera acutoros- trata. δ 15 N values indicated that marine mammals located at the lowest trophic level were B. acu- torostrata, Stenella coeruleoalba and Delphinus sp., and those occupying the highest trophic level were M. monachus and P. macrocephalus. The trophic level of Orcinus orca was similar to that of M. monachus, suggesting that O. orca preys on fish. Conservation of coastal and threatened species (M. monachus and S. teuszii) off NW Africa should be a priority because these species, as the main apex predators, cannot be replaced by other marine mammals.

Isoscapes: Spatial Pattern in Isotopic Biogeochemistry

Isotope ratios of actively cycled elements vary as a function of the biogeochemical processes in which they participate and the conditions under which those processes occur. The resultant spatiotemporal distribution of isotopes in environmental materials can be predicted using models of isotope-fractionating processes and data describing environmental conditions across space and time, and it has been termed an isoscape, or isotopic landscape. Analysis of isoscapes and comparison of isoscape predictions with observational data have been used to test biogeochemical models, calculate aerially integrated biogeochemical fluxes based on isotope mass balance, and determine spatial connectivity in biogeochemical, ecological, and anthropological systems. Isoscape models of varying quality are available for stable H, C, N, and O isotopes in a range of Earth surface systems, but significant opportunities exist to refine our understanding of biogeochemical cycles and our ability to predict isoscapes through the development of more mechanistic and more comprehensive isoscape models.

The evolution of the chemical isotopes as an analog of biological evolution

A comparison is made between a biological adaptive landscape and the chemical isotopic landscape defined with three dimensions: the number of protons, the number of neutrons, and the stability of each isotopic nucleus. The courses of both biological and elemental evolution have been stochastic, leading from the simple to the complex; this is in agreement with statistical thermodynamic predictions. Analogs of mutation and natural selection occur in elementary evolution. The isotopic landscape can be assumed to have an a priori existence; at least the general features of the biological adaptive landscape also have an a priori existence. Both landscapes were occupied by spontaneous processes, analogous to diffusion.