A Study of Diatom Communities in Five Headwater Streams in Central Pennsylvania
Start Date
13-11-2015 8:00 PM
End Date
13-11-2015 9:59 PM
Description
During June and July 2015 we have sampled five headwater streams 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, hydrology, 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. Stones with intact biofilms are were collected at each sample site, and biofilms were removed chemically, utilizing a standard method of HCL and H2O2. Diatoms were identified to species and counted using a JEOL 6010 SEM. Because of the size of the streams, we anticipated the communities to be relatively depauperate and primarily inhabited by one or two dominant taxa. Furthermore, we expected the streams that were similar in physical/chemical parameters to have similar diatom communities on similar substrates. Contrary to expectations, the diatom communities were quite speciose (35-52 taxa in a count of 600 valves). Although the communities were similar in measures of diversity [e.g. Shannon Diversity (2.6-3.2) and SDI evenness (0.75-0.85)], the Bray-Curtis similarity index described quite dissimilar communities; with a 42.5% average similarity (15.0-66.8). In general, the dominant morphological classifications were eunotids and monoraphids, most of which are pollution intolerant. Although co-occurrence of taxa among the streams is high, universal dominant taxa (>10%) were not present. Our results indicate that there is no particular headwater stream epilithic diatom community and that the occurrences of particular taxa are driven by stochastic processes.
Type
Poster
Language
eng
A Study of Diatom Communities in Five Headwater Streams in Central Pennsylvania
Elaine Langone Center, Terrace Room
During June and July 2015 we have sampled five headwater streams 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, hydrology, 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. Stones with intact biofilms are were collected at each sample site, and biofilms were removed chemically, utilizing a standard method of HCL and H2O2. Diatoms were identified to species and counted using a JEOL 6010 SEM. Because of the size of the streams, we anticipated the communities to be relatively depauperate and primarily inhabited by one or two dominant taxa. Furthermore, we expected the streams that were similar in physical/chemical parameters to have similar diatom communities on similar substrates. Contrary to expectations, the diatom communities were quite speciose (35-52 taxa in a count of 600 valves). Although the communities were similar in measures of diversity [e.g. Shannon Diversity (2.6-3.2) and SDI evenness (0.75-0.85)], the Bray-Curtis similarity index described quite dissimilar communities; with a 42.5% average similarity (15.0-66.8). In general, the dominant morphological classifications were eunotids and monoraphids, most of which are pollution intolerant. Although co-occurrence of taxa among the streams is high, universal dominant taxa (>10%) were not present. Our results indicate that there is no particular headwater stream epilithic diatom community and that the occurrences of particular taxa are driven by stochastic processes.