Objective Statement

An investigational, comparative approach has been adopted in research to assess the feasibility of using stable isotope ratios to detect the influence of confined animal waste on the aquatic food web of stream ecosystems.

Stable Isotope Techniques and Design

Organic materials contain naturally occurring stable isotopes that form distinct "signatures" that can be used to trace the flow of organic matter through ecosystems. The first step of this research is to determine the stable isotope signatures of animal waste from local poultry or livestock operations. Then an intensive sampling approach will be followed to attempt to differentiate isotopic signatures of consumers collected from impacted and reference stream food webs within a region. The sampling will be conducted in streams of the Ozark Mountains of northwest Arkansas. This comparative process will suggest if organic matter and nutrients from animal waste enter the stream food web.

Expected Results and Benefits

The results of this comparative investigation should provide a sufficient indication if stable isotope ratios may serve as a feasible analytical technique to determine the relative influence of animal waste on the aquatic food webs in streams. One of two potential overall findings are likely to result from this preliminary research:

(1) No isotopic differentiation between systems. If the isotopic composition of biotic materials sampled from an animal waste impacted food web is not distinct from that sampled from a reference food web, then we will conclude that stable isotope techniques are not a feasible method to detect influences of animal waste on aquatic food webs in streams of this region. This would be an efficient expenditure of funds prior to engaging in detailed studies requiring substantial funding. In addition, these preliminary results may suggest ecological trends unrelated to animal use that could be pursued in future studies on aquatic food web dynamics.

(2) Distinct isotopic differentiation between systems. If the isotopic composition of biotic materials is distinct between impacted and reference systems, and if the difference represents a shift toward the signature of animal waste in the impacted systems, then it is likely that animal waste enters the stream food webs in this region and that stable isotope techniques are a feasible method to detect influences of animal waste on aquatic food webs. These preliminary results would be a significant scientific finding and would provide strong justification and background to warrant additional studies.

 Return to Tom Kwak's home page.

 Return to North Carolina Cooperative Fish and Wildlife Research Unit home page.

 Return to Department of Biology home page.