A Study of Diatom Periphyton Communities on the Moss Genus Fontinalis in Three Headwater Streams in Central Pennsylvania

During June and July 2015 we sampled three headwater streams (Henstep, Little Weikert and Coral Run) that flow down the north slope of Penns Creek Mountain (Bald Eagle State Forest, western Union/Snyder counties), each in a separate cut along the ridgetop. The streams drain a perched water table underlain by impervious sandstone and are approximately two meters wide and wadeable. Throughout the reaches studied the streams are shaded by a mixed forest of hemlock and birch with a substrate of small boulders, cobble, and sand. Because of the uniform geology and land use, the chemical and physical properties of the streams are very similar. Conductivity (19.4-31.9 µs/cm) and buffering capacity are very low (63-313 µeq/L), and pH rarely exceeds 6. The prominent producers in each stream are mosses, the most abundant of which are species of Fontinalis. Mosses submerged in the streams, partially submerged, or on the stream bank were collected at each sample site. Biofilms were removed chemically without scraping. Diatoms were cleaned by a standard method using HCl and H2O2, identified to species, and counted using a JEOL 6010 SEM. We investigated the diatom communities associated with Fontinalis in each of the streams to determine the similarity of those communities on the same substrate in different streams. Our preliminary results suggest that there is not a moss periphyton diatom community. The metrics differed from stream to stream. The communities had 26-39 species in a count of 300 valves. The Pollution Tolerance Index values ranged from 2.261 to 2.745, Shannon Diversity was 2.218 to 3.116 and Evenness ranged from 0.68 to 0.85. The most surprising results had to do with the dominant taxa in the moss periphyton community of each stream. Eolimna minima was the dominant taxon on Henstep mosses while Fragilariaforma virescens dominated in moss periphyton of Little Weikert. Both of these streams had similar features including levels of discharge. Coral Run, a smaller stream had Eunotia minor as the dominant species in moss periphyton. Thus, the moss diatom communities are made up of different dominant taxa that appear to be undetermined and stochastic in occurrence