Primary productivity and spatial structure of phytolithic growth in streams in the Great Smoky Mountains National Park,Tennessee

The purpose of this study was to examine the primary production rates of phytolithic communities found in the major different habitats of streams and determine the effects of physical and chemical parameters associated with each habitat on periphyton community spatial structure. The project was designed to study natural, intact communities within stream systems.A comparative analysis was made of phytolithic communities found in Camel Hump and Husky Branch streams in the Great Smoky Mountains National Park. Camel Hump flows through virgin forest area and Husky Branch flows through an area logged approximately 60 y ago. The effects of logging on Husky Branch stream and the surrounding watershed are discussed.Seasonal data were collected from July, 1981 through May, 1982 from fast flow, slow flow and pool areas within each stream. An incubation chamber designed for use in lotic systems was used for in situ measurements of ¹⁴C uptake. Rock samples collected at each site were used as substrates for community structure observations utilizing a scanning electron microscope.The algal communities of Camel Hump and Husky Branch streams were found to be predominantly composed of diatoms. The dominant genera in the fast, slow and pool areas included Achnanthes, Eunotia, Meridion, Navicula and Gomphonema. Fast flow areas were dominated by diatom species growing in a prostrate position. Slow flow areas were more densely populated by diatoms than the fast flow areas. Diatoms in the slow flow areas appeared mainly in prostrate position with a few stalked forms present. Pool area communities were less densely packed than slow flow areas and contained stalked and chain formations of diatoms.Results indicate that the physical and chemical parameters associated with each habitat affect the primary production rates and community structure found at the experimental sites. Measurements of carbon assimilation and chlorophyll a concentration were significantly greater in habitats of higher current velocity and light availability. Cell densities tend to increase with a decrease in current velocity. Habitats of high density showed a decrease in diversity and evenness. Correlations between productivity in the various habitats of each stream and other parameters measured in the study are discussed.