Abstract
The shells of marine invertebrates can serve as high-resolution records of oceanographic and atmospheric change through time. In particular, oxygen and carbon isotope analyses of nearshore marine calcifiers that grow by accretion over their lifespans provide seasonal records of environmental and oceanographic conditions. Archaeological shell middens generated by Indigenous communities along the Northeast Pacific coast contain shells harvested over multiple seasons for millennia. These shell middens, as well as analyses of archival and modern shells, have the potential to provide multi-site, seasonal archives of nearshore conditions throughout the Holocene. A significant volume of oxygen and carbon isotope data from archaeological shells exists, yet is separately published in archaeological, geochemical, and paleoceanographic journals and has not been comprehensively analyzed to examine oceanographic change over time. Here, we compiled a database of previously published oxygen and carbon isotope data from archaeological, archival, and modern marine molluscs from the North American coast of the Northeast Pacific (32° N to 50° N). This database includes oxygen and carbon isotope data from over 550 modern, archaeological, and sub-fossil shells from 8880 years before present (BP) to the present, from which there are 4,845 total δ13C and 5,071 total δ18O measurements. Shell dating and sampling strategies vary among studies (1–118 samples per shell) and vary significantly by journal discipline. Data are from various bivalves and gastropod species, with Mytilus spp. being the most commonly analyzed taxon. This novel database can be used to investigate changes in nearshore sea surface conditions including warm-cool oscillations, heat waves, and upwelling intensity, and provides nearshore calcite δ13C and δ18O values that can be compared to the vast collections of offshore foraminifera calcite δ13C and δ18O data from marine sediment cores. By utilizing previously published geochemical data from midden and museum shells rather than sampling new specimens, future scientific research can reduce or omit the alteration or destruction of culturally valued specimens and sites. The data set is publicly available through PANGAEA at https://doi.org/10.1594/PANGAEA.932671 (Palmer et al., 2021).
Highlights
Introduction1.1 Nearshore records of environmental changeAnalysis of past climatic and oceanographic change is critical for understanding scales of natural variability in marine systems and is essential to predict outcomes of modern climate change
Analysis of past climatic and oceanographic change is critical for understanding scales of natural variability in marine systems and is essential to predict outcomes of modern climate change
In the Northeast Pacific, the abundance of previously published data on archaeological, archival, and modern specimens allows for exploration of oceanographic and climate change through the Holocene
Summary
1.1 Nearshore records of environmental changeAnalysis of past climatic and oceanographic change is critical for understanding scales of natural variability in marine systems and is essential to predict outcomes of modern climate change. We lack similar continuous records of nearshore environments, preventing quantification of past oceanographic changes in these systems. Shell material from nearshore marine molluscs are archives of the environment in which these organisms lived, and shifts in oxygen and carbon isotope ratios indicate changes in sea surface temperature, salinity, and upwelling (Andrus, 2011). Such archives can provide insight into the role of nearshore marine molluscs in ecosystems and 45 as resources for human communities. In the coastal Northeast Pacific, an abundance of sub-fossil marine mollusc shells are found in archaeological middens, which have been analyzed to provide environmental proxies and to understand historical food sources and trading routes (Rick et al, 2006a; Braje et al, 2012; Eerkens et al, 2013)
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