Stable isotopic analysis of the Upper Green River in Hart County, Kentucky

Background/Question/Methods

This study was designed to examine the producer-consumer relationships and fluctuation of nutrients in the upper Green River, Kentucky. The Upper Green River is a 7^th order stream and provides habitat for Trichoptera larvae, Pleurocera (aquatic snails), and various mussel species. We hypothesized that the diet of these consumers would include transported organic matter, leaf detritus, and Cladophora, which grows abundantly during the summer and early fall months. We also hypothesized that nitrogen levels would decrease during the duration of this study (June-October), most likely due to the heavy growth of Cladophora. We used nitrogen and carbon isotope analyses to help determine the food sources and trophic level of organisms studied.

Results/Conclusions

Total nitrogen levels were noted to increase through June and peak in July before gradually decreasing through late summer into early fall. There was an inverse correlation between Cladophora and nitrogen levels  Soluble reactive phosphorous levels peaked in August and Ammonia levels peaked in October. Cladophora peaked in August  and then continually declined until October. Podostemum was lowest in August and reached highest concentration October.  Mussels, snails, and Trichoptera shared similar C¹³ ratios with each other and with both Cladophora and terrestrial leaf litter. It is important to know about the diet of Trichoptera and mussels because of their great importance to stream habitats.