A Study of Diatom Communities at 5 Small Headwater Streams in Central Pennsylvania during Summer of 2017

Elaine Langone Center, Terrace Room

The diatom communities at 5 headwater streams that flow through Bald Eagle State Park on Penns Creek Mountain were examined. From June to August of 2017, weekly water samples were collected at Little Weikert Run, Coral Run, Green Gap Run, Lick Run, and Henstep Run. The surrounding geology and land use of each stream are extremely similar, resulting in very low variability in the chemical and physical properties of the streams. Conductivity remained low (17-26 %m/cm); buffering capacity ranged from 50 to 200 %eq/L, and pH rarely exceeded 6.00. Biofilms were collected from headwater cobbles, and diatoms were removed chemically. Cleaned diatom valves were counted and identified to species using a JEOL 6010 LV Scanning Electron Microscope (SEM). The number of species found in 300 valves ranged from 30 to 35, and the Shannon Diversity index ranged 2.2-3.1. The Pollution Tolerant Index (PTI) of the streams did not exceed 3, which falls in the relatively pollution intolerant range. Generic Diatom Index (GDI), the European equivalent to PTI, ranged from 16 to 18, which also falls in the pollution intolerant range. The Trophic Diatom Index (TDI) supports the oligotrophic nature of the sites with values that ranged 19-39. Despite the similar measurements and metrics, the diatom community similarity generated by the Proportional Bray-Curtis Similarity algorithm showed very low to low overlap (0-39%) between the majority of the stream comparisons, and moderate overlap in taxa (40-59%) between Lick Run and Green Gap Run, Lick Run and Coral Run, and Coral Run and Henstep Run. Although the players (diatom taxa) vary from stream to stream, the stories defined by diatom metrics remain the same for these small headwater streams.