Oxygen and Carbon Isotopic Data from Wellington Creek, Lorain County, Ohio

Oxygen isotopic values have been obtained from microsamples of the
aragonitic freshwater bivalves Sphaerium striatinum (Pisidiidae) and
Anodonta grandis (Unionidae) alive from Wellington Creek, Ohio. To
test whether these organisms secrete their shell in isotopic
equilibrium, the delta 18O values of shell aragonite are compared to
ambient water temperature and delta 18O values monitored for > 1
year. These bivalves were chosen for study because they are abundant
in surface sediments and cores from Lake Erie where they represent a
source of information on the environmental history of the lake. The
observed mean values are -5.54% for A. grandis and -6.16% for
S. striatinum. The mean delta 18O value expected for bivalve
aragonite if equilibrium precipitation is occurring during May-August
in Wellington Creek is -5.69%. The similarity between measured and
predicted isotopic values for both species suggests that they are
useful sources of paleoenvironmental data. Overall, the isotopic
values for both species reflects less than one half of the calculated
range of potential biogenic aragonite values for the stream and omits
recording evaporative conditions associated with ponded water. Bivalve
delta 18O and delta 13C data co-vary. The delta 13C data are highly
negative and values could reflect 12C enrichment of dissolved organic
carbon from organic matter oxidation and/or ingestion of food carbon.

This work was part of the project: Stable Isotopic Composition of
Biogenic Carbonate from Lake Erie Drainage.

URL for CSUOHIO/CESTP metadata:
"http://www.csuohio.edu/cestp/dataproj/metadata/isotopes.htm"