Amino Acid d13C Analysis of Ancient Marine Consumers Quantifies Environmental Change in a Nearshore Ecosystem through the Late Holocene

Summary

This is an abstract from the "Advances in Interdisciplinary Isotopic Research" session, at the 84th annual meeting of the Society for American Archaeology.

Kelp forests are some of the most biodiverse and ubiquitous temperate marine ecosystems. Here, we employ d13C analysis of individual essential amino acids (EAA) from ancient top consumers to evaluate the dynamics of southern California kelp forests across a period of rapid cultural change and accelerating human impacts (~3500 ybp – present). We analyzed sea otter (Enhydra lutris) and sheephead (Semicossyphus pulcher) bone collagen sourced from late Holocene archaeological sites on two southern California islands. We also characterized d13CEAA profiles for modern marine producer groups as baseline values for comparison: kelps, green algae, red algae, and offshore particulate organic matter. We used linear discriminant analysis (LDA) and Bayesian isotope mixing models (MixSIAR) to classify consumers according to their reliance on different producers. Results showed that over 75% of ancient sea otters and sheephead EAA were derived from kelp, indicating that these consumers were feeding in ecosystems driven by kelp production. In combination with bulk tissue analysis and ongoing d13CEAA analysis of modern samples, these findings suggest that, at these sites, kelp forests were more extensive in the late Holocene than they are today. Our study demonstrates the application of d13CEAA analysis in integrating historical ecological information and modern conservation biology.

This Resource is Part of the Following Collections

• Advances in Interdisciplinary Isotopic Research   •
• Society for American Archaeology 84th Annual Meeting, Albuquerque, NM (2019)

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Record Identifiers

Abstract Id(s): 26046