Diatom Community Analysis of Penns Creek Mountain Headwater Streams, a Study in Community Similarity

Elaine Langone Center, Terrace Room

Penns Creek Mountain, located in northcentral Pennsylvania, gives rise to a series of streams that are fed by a perched water table and continue to flow throughout the year. For the past four years, we have studied five of the streams that flow down the north side of the ridge and feed Penns Creek. Of the streams studied, Lick Run and Coral Run appear to be most similar regarding physical, geological, and chemical characteristics. During summer 2018 we focused on these two streams to study diatom community diversity between similar streams and diversity between biofilm communities within the same streams 100 meters apart, which we called Lick up, Lick down, Coral up, and Coral down. We used Green Gap, another of the headwater streams which has been studied for four years for comparison. The temperature over the past four summers averaged 12.72°C-13.20°C. The conductivity averaged 19.26µs/cm (18.16-21.17), and the percent oxygen saturation has remained at or above 100% saturation at all locations (117.54%-121.14%). The pH has been stable overall at all locations (6.33-6.58), while alkalinity averaged at 200.27µeq/L (x ̅=177.33-237.34µeq/L). Diatom biofilm was collected from stones at each site and then chemically processed to clean the diatom frustules for observation and enumeration with a JEOL 6010 LV scanning electron microscope. Diatom communities at all sites over this summer had an average species richness of 24 taxa (20-30). The Bray-Curtis similarity index indicated a moderate overlap (43-59%) between the Lick and Coral locations and low to moderate overlap (35-50%) with the Green Gap site. Despite the Bray-Curtis results, the sites display the same two dominant taxa (Achnanthidium deflexum and Nupela lapidosa). Though the particular members of the diatom community varied, metrics such as the Sedimentation index range of 0.67-8.67% (SED, x ̅=3.65%), Shannon Diversity Index range of 1.80-3.09 (SDI x ̅=2.38), Shannon Evenness range of 57-81% (SE x ̅=71.48%), Pollution Tolerance Index range of 2.66-3.34 (PTI x ̅=2.98), and the Generic Diatom Index range of 16.59-19.15 (GDI, x ̅=17.66) all are consistent with a stream of high-water quality