Open AccessReconstructing Seasonal and Baseline Nitrogen Isotope Ratios in Riverine Particulate Matter Using Freshwater Mussel Shells
Author(s) -
Kukolich Stephanie,
Dettman David
Publication year - 2021
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2020gc009239
Subject(s) - mussel , aragonite , isotopes of nitrogen , organic matter , oceanography , stable isotope ratio , particulates , δ13c , carbonate , environmental chemistry , δ15n , environmental science , geology , nitrogen , ecology , calcite , mineralogy , chemistry , biology , physics , organic chemistry , quantum mechanics
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 δ 18 O profiles were compared to a predicted shell δ 18 O time series that was based on water temperature and isotopic composition. Shell growth was assumed to stop below ∼12°C. Profiles of inorganic δ 18 O and δ 13 C 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 δ 18 O 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 δ 13 C and δ 15 N 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 δ 15 N and δ 13 C 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.