Compound‐specific amino acid δ¹⁵N values in archaeological shell: Assessing diagenetic integrity and potential for isotopic baseline reconstruction

Abstract

Overall, this new data indicates that the CSI-AA analysis of fossil shell represents a promising new approach to determining isotopic baselines in coastal paleo-ecosystems.

Back to the future? Late Holocene marine food web structure in a warm climatic phase as a predictor of trophodynamics in a warmer South‐Western Atlantic Ocean

“…Our interpretation of the results reported here relies partially in two major assumptions about the isotope baseline: (a) that the organic matrix of mollusc shells records the changes in the isotopic baseline of the ecosystem throughout time (Casey & Post, ; Hill et al, ; Misarti et al, ), and (b) that benthic and pelagic primary producers contributed equally to the nitrogen and carbon pool fuelling the food web in the Beagle Channel (Riccialdelli et al, ). Both assumptions provide the rationale for correcting changes throughout time in the isotopic baseline by averaging the stable isotope ratios in the shells of one species of grazer (limpet) and one species of suspension feeder (mussel).…”

“…Our interpretation of the results reported here relies partially in two major assumptions about the isotope baseline: (a) that the organic matrix of mollusc shells records the changes in the isotopic baseline of the ecosystem throughout time (Casey & Post, 2011;Hill et al, 2006;Misarti et al, 2017), and (b) that benthic and pelagic primary producers contributed equally to the nitrogen and carbon pool fuelling the food web in the Beagle Channel (Riccialdelli et al, 2017).…”

“…The stable isotope ratios of modern and ancient organisms cannot be compared directly, because temporal variations in the isotopic baseline may exist (Casey & Post, 2011). Nonetheless, the proteins that make up the organic matrix of mollusc shells can become encased within mineral crystals and preserved, hence offering a material suitable to reconstruct the changes in the isotopic baseline (Casey & Post, 2011;Drago et al, 2017;Misarti, Gier, Finney, Barnes, & McCarthy, 2017;Vales et al, 2017;Zenteno, Borella, et al, 2015). Accordingly, values of δ 13 C and δ 15 N of limpets and mussels…”

“…The stable isotope ratios of modern and ancient organisms cannot be compared directly, because temporal variations in the isotopic baseline may exist (Casey & Post, ). Nonetheless, the proteins that make up the organic matrix of mollusc shells can become encased within mineral crystals and preserved, hence offering a material suitable to reconstruct the changes in the isotopic baseline (Casey & Post, ; Drago et al, ; Misarti, Gier, Finney, Barnes, & McCarthy, ; Vales et al, ; Zenteno, Borella, et al, ). Accordingly, values of δ 13 C and δ 15 N of limpets and mussels were compared independently using General Linear Models (GLM) as run in IBM SPSS Statistics (Version 23.0.0.2 for Mac) with two fixed factors (species and period) to assess the temporal variation of the δ 13 C and δ 15 N values in shells and, when necessary, correct for any isotopic baseline shift between the two periods considered.…”

Paired bulk organic and individual amino acid δ15N analyses of bivalve shell periostracum: A paleoceanographic proxy for water source variability and nitrogen cycling processes

“…In addition, bivalve shells offer the opportunity to extend absolutely dated, via crossdating methods (Black et al, 2016;Black et al, 2019), records of  15 N at the base of the food web well back beyond the instrumental record at a high resolution scale due to the fact that many of these shells grow in annual or sub-annual increments. Because they are relatively immobile suspension feeders, bivalves have been identified as particularly useful in recording changes in baseline  15 N (assuming no change in the diet of the clams) and nitrogen cycling in ecosystems through time (Post, 2002;Jennings and Warr, 2003;O'Donnell et al, 2003;Vokhshoori and McCarthy, 2014;Darrow et al, 2017;Misarti et al, 2017). Such records have been identified as crucial in understanding ecosystem scale food web dynamics (Casey and Post, 2011).…”