Reconstructing Seasonal and Baseline Nitrogen Isotope Ratios in Riverine Particulate Matter Using Freshwater Mussel Shells
Affiliation
Department of Geosciences, University of ArizonaIssue Date
2021-03-19
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American Geophysical Union (AGU)Citation
Kukolich, S., & Dettman, D. Reconstructing seasonal and baseline nitrogen isotope ratios in riverine particulate matter using freshwater mussel shells. Geochemistry, Geophysics, Geosystems, e2020GC009239.Rights
© 2021. American Geophysical Union. All Rights Reserved.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
We present a timeline of the carbon, nitrogen, and oxygen stable isotope compositions of 10 unionid mussel shells across three species–Threeridge (Amblema plicata), Ebonyshell (Reginaia ebenus), and Pimpleback (Cyclonaias pustulosa)—collected live in 2011 from the Tennessee River near Paducah, Kentucky, USA. Inorganic aragonite δ18O profiles were compared to a predicted shell δ18O time series that was based on water temperature and isotopic composition. Shell growth was assumed to stop below ∼12°C. Profiles of inorganic δ18O and δ13C were then used to establish relationships between shell growth and calendar dates. Because shell growth is faster during warmer months and therefore easy to sample, assignment of calendar years to individual growth increments was validated using the interannual changes in the predicted minimum δ18O value of summer shell. Mussel shell periostracum and carbonate‐bound organic matter (CBOM) samples were then assigned calendar dates based on their location along shell growth axes and compared to measurements of δ13C and δ15N of suspended particulate organic matter (SPOM)–the mussels' food source–during shell growth (1997–2006). Mussel shell periostracum and CBOM faithfully recorded seasonal variability in δ15N and δ13C values of SPOM, after accounting for the time difference between SPOM consumption and deposition of shell organics due to the gradual turnover of mantle tissue. This demonstrates that unionid shell geochemistry could be used to document changes in riverine environment, runoff, and nutrient cycles across a spectrum of time scales, from historical to archeological to Quaternary.Note
6 month embargo; first published: 14 February 2021ISSN
1525-2027EISSN
1525-2027Version
Final published versionae974a485f413a2113503eed53cd6c53
10.1029/2020gc009239