Tuesday, May 27, 2008
282

δ D and δ18O as tracers of macroinvertebrate origins and movements in large river floodplain water bodies

David J. Myers1, Matt R. Whiles1, and Gw Whitledge2. (1) Department of Zoology and Center for Ecology, Southern Illinois University, Carbondale, IL 62901-6501, (2) Department of Zoology, Fisheries and Illinois Aquaculture Center, Southern Illinois University, Carbondale, IL 62901-6511

The stable isotope of hydrogen (D) is a useful tool for discriminating between terrestrial and aquatic contributions to aquatic food webs. δD has also been used in migration studies of terrestrial organisms, and has been proposed for use as a natural marker for assessing fish movement between water bodies with distinct δD signatures. Stable oxygen isotope ratios (δ18O) have proven useful as natural markers in freshwater bivalve shells and in paleoenvironmental studies. We assessed the usefulness of δD and δ18O for identifying the origins and movements of macroinvertebrates in Mississippi River floodplain water bodies. We sampled water and invertebrates from the Mississippi River, intermittent and permanent floodplain wetlands, and tributaries in the summer of 2007. Results showed consistent relationships between δD and δ18O signatures in invertebrate tissues and their home water bodies. Results also showed no significant difference in δ18O ratios of invertebrates with open or closed respiratory systems. Further development of hydrogen and oxygen stable isotopes as tools for assessing the origins of invertebrates will help in quantifying the relative inputs of different habitat types in large river systems to main channel food webs, and may also prove useful for analyses of freshwater food webs in general.


Web Page: Stable Isotopes, Large River Floodplains, Mississippi River

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