Nitrogen isotopes in tooth enamel record diet and trophic level enrichment: Results from a controlled feeding experiment

Nitrogen isotope ratios (?15N) are a well-established tool for investigating the dietary and trophic behavior of animals in terrestrial marine food webs. To date, ?15N values fossils have primarily been measured collagen extracted from bone or dentin, which is susceptible to degradation rarely preserved deep time (>100,000 years). In contrast, tooth enamel organic matter protected diagenetic alteration by mineral structure hydroxyapatite thus often over geological time. However, due low nitrogen content (<0.01 %) enamel, measurement its isotopic composition has prevented analytical limitations traditional methods. Here, we present novel application oxidation-denitrification method that allows (?15Nenamel). This involves oxidation enamel-bound nitrate followed bacterial conversion N2O, requires ?100 times less than approaches. demonstrate ?15Nenamel record diet behavior, conducted controlled feeding experiment with rats guinea pigs (n = 37). We determined concentration (x? 5.0 ± 1.0 nmol/mg) sufficient analyses ?5 mg untreated powder. The reflects an enrichment (?15Nenamel-diet) ca. 2–4‰. differ significantly between groups clearly shift pre-experimental experimental diet. small sample size required (?5 mg) this permits size-limited, diagenetically robust and, as such it represents promising new proxy reconstructing webs ecology extant extinct taxa.