Two plots comparing seasonal variability in mussel stable isotope values from the periostracum with measured suspended particulate organic matter, used to reconstruct the isotopic composition of suspended particulate organic matter.
Seasonal variability in mussel stable isotope values from the periostracum (grey) are compared to measured suspended particulate organic matter (SPOM, black) and used to reconstruct the isotopic composition of SPOM (teal). The mussels likely largely dormant during cold winter months are marked by the light grey bars on the background. Thus, the reconstructed SPOM in the late winter months reflects SPOM from both late fall and early spring (teal box and arrow). Credit: Kukolich and Dettman [2021], Figure 9
Source: Geochemistry, Geophysics, Geosystems

Documenting past riverine nutrient conditions, which in turn may reflect excess nitrogen from farms or cities, is difficult because of the limited water chemistry monitoring. Kukolich and Dettman [2021] find that the isotopic composition of shell organic matter in three species of freshwater mussel recorded seasonal variability in chemistry of riverine suspended particulate organic matter. Chronologies developed using oxygen isotopes support a dormant winter season, indicating that most of the shell growth occurs during the warm summer months. This technique can be applied to archived specimens to evaluate past change in riverine water quality.

Citation: Kukolich, S., & Dettman, D. [2021]. Reconstructing seasonal and baseline nitrogen isotope ratios in riverine particulate matter using freshwater mussel shells. Geochemistry, Geophysics, Geosystems, 22, e2020GC009239.

—Branwen Williams, Editor, Geochemistry, Geophysics, Geosystems

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