Oxygen and hydrogen stable isotope ratios in Mississippi River floodplain invertebrates: Implications for dispersal and food web analysis

Understanding energy fluxes within and between floodplain water bodies, and between rivers and their floodplains is essential for comprehending the dynamics of modern, altered river systems. Floodplain aquatic invertebrates may move between habitats deliberately (through emergence and dispersal) or through passive transport during flooding. This movement may represent a significant flux of energy and an essential food web subsidy. I assessed the usefulness of the stable isotopes of hydrogen and oxygen (D and 18O respectively) for identifying the origins and movements of macroinvertebrates in Mississippi River floodplain water bodies. I sampled water and invertebrates from the Mississippi River, intermittent and permanent floodplain wetlands, and tributaries during 2007 and 2008. Results showed consistent relationships between deltaD and delta18O signatures in invertebrate tissues and their home water bodies. I also investigated whether deltaD and delta 18O could be used as a multivariate "fingerprint" to trace a captured invertebrate back to its environment of origin. Results showed that deltaD can be a useful tracer of the movement of floodplain invertebrates in some cases, although delta18O is likely not suitable for that purpose.