Temporal and Spatial Variation in Stable Isotopes of Carbon and Nitrogen in Lake Carl Blackwell, Oklahoma

A survey of stable isotopes of carbon (C) and nitrogen (N) for water, plankton, and sediments and associated limnological parameters was conducted in 2006–2007 in Lake Carl Blackwell, Oklahoma. The effects of time and station were assessed to serve as the basis of further studies that would identify plant sources for consumers and describe the food web of this turbid lake. Samples of water and plankton were taken at four stations along an east to west thalweg; sediments were obtained at four additional stations in coves off the main lake channel. Isotope ratios were obtained for dissolved inorganic carbon (DIC), particulate organic matter (POM), zooplankton, and sediments as well as content of C and N. Time effects were significant in June and July for δ 13 C  DIC , δ 13 C  POM , C:N  POM  and δ 15 N  ZOOPLANKTON , but not for sediments. Station effects were small except for lower %C and %N of sediments in two stations in the lake coves. We conclude that sampling in the summer at the downstream station would be sufficient for an isotope study of the lake. But, it will be necessary to separate algae from detritus and zooplankton, and separate zooplankton and algae taxa to obtain more precise information on plant source and food web transfers in this lake.