Figure 2. Scanning electron photomicrographs of the dominant species in the study. A) Diatoma mesodon, B) Fragiliaforma virescens, C) Planothidium frequentissimum, D) Eunotia minor, E) Nupela lapidosa, and F) Sellophora seminulum.

A Study of Diatom Communities in Five Headwater Streams in Central Pennsylvania Amir Alwali, Brian Rothbard, Grace O’Malley, Dylan Kutz and Jack R. Holt

Department of Biology, Susquehanna University, Selinsgrove, PA 17870

Abstract 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 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. Because of the uniform conditions of the streams and the size of the streams, we expected that the communities would be relatively depauperate and dominated by one or two common taxa. We find, however, that the diatom communities show high scores for Shannon Diversity (SDI; 2.6-3.2), SDI evenness (0.75-0.85) and taxa richness (35-52 taxa in 600 valves). In general, the dominant morphological classifications are eunotids and monoraphids, most of which are pollution intolerant. Though many taxa co-occur in the streams, dominant taxa (>10%) seem to vary stream to stream. Diversity and water quality indices identify all five streams as having high water quality with very speciose communities; however, despite the similarities of the streams, particular members of the communities vary in occurrence and importance such that the Bray-Curtis similarity indices describe communities whose average similarity is only 42.5% (15.0-66.8). Thus, there is not a defined diatom community for these headwater streams that are adjacent to each other and whose abiotic parameters are quite similar.

Introduction • Diatoms, a dominant group of algae and major component of stream biofilm

communities, are used to evaluate water quality (Werner 1977). • Diatoms are hypersensitive towards their environments (Pan et al. 1996), and,

therefore are good biological indicators (Stevenson et al. 2008) of water quality. • The purpose of this study is to use diatom periphyton in in the assessment of five

headwater streams and to define a headwater stream diatom community.

Site Description Five headwater streams drain a perched water table on the north slope of Penns Creek Mountain (western Union/Snyder counties). The rock is impervious sandstone and the streams have a substrate that ranges from small boulders and cobbles to sand. The streams can be accessed by Hunter Road on the ridge top and are in Bald Eagle State Forest (Figure 1) with a mixed canopy mainly of hemlock and birch. Each stream is about 2m wide with mixed riffles, runs and pools, rarely more than 0.5m deep.

Figure 1: Map of the collection sites on the five headwater streams.

Methods • Field collections of active biofilms were made at the marked sites (see Figure 1). • Stones were collected and placed in containers. • Samples were returned to the lab and cleaned using the following procedure:

• Hypochlorite and detergent plus heating and ultrasonication • Concentrated Potassium Permanganate • Concentrated Hydrochloric Acid • Concentrated (30%) Hydrogen Peroxide

• Diatom ID confirmed by JEOL JSM 6010LV SEM. • Counts performed using the JEOL JSM 6010LV, 2 plugs, each of 300 valves. • Pollution Tolerance Index (PTI) calculated according to Stephenson et al. (2008). • Shannon Diversity (natural log) and Shannon Evenness (SDI & SDE, respectively) • Trophic Diatom Index (TDI) and Generic Diatom Index (GDI) calculated

according to Kelly (2013) • Bray-Curtis Proportional Similarity (BCI) comparisons generated according to

Bloom (1981). • Water at each site was monitored on a weekly basis for 8 weeks (June-July) using

a YSI 556 Multimeter (recorded temperature, conductivity, oxygen concentration and pH) and a Secchi Tube to measure turbidity.

• Water was collected for alkalinity and some was filtered in the laboratory and frozen in whirl-pacs for future chemical analysis.

Results Table 1. A composite list of the 84 species of diatoms found on stones at the headwater

streams: Little Weikert Run, Green Gap, Lick Run, Coral Run and Henstep (see Figure 1). The following table compares the relative abundance of taxa at each study site from counts of at least 600 valves. Note that relative abundance is color-coded according to three categories: dominant (>10%), common (1-10%) and rare (<1%). See key at right.

A B C

D E F

Conclusions • Collected and identified 84 different diatom species from all collection sites (Table 1). • Of the taxa found, only 6 had >10% occurrence (Table 1 and Figure 2). • pH and conductivity were quite similar across all of the stream sites, but alkalinity

was more variable (Table 2). • Diatom-derived metrics generally showed that the communities came from streams

with high water quality (Table 3), but Green Gap appeared to have the lowest water quality of the five streams (e.g. elevated TDI and depressed PTI scores).

• The Proportional Bray-Curtis Similarity scores (Table 4) were relatively low given the physical/chemical similarities between the sites (Table 1). These results suggest that although the streams are very close together (within 10km), there is not a defined diatom community for these headwater streams.

Acknowledgments This research was supported in part by the Foundation for Pennsylvania Watersheds, the Degenstein Foundation, the Susquehanna River Heartland Coalition for Environmental Studies and Susquehanna University.

References available upon request.

PARAMETER L WEIKERT GREEN GAP LICK CORAL RUN HENSTEP pH 5.4 ± 0.6 6.1 ± 0.2 5.6 ± 0.5 5.6 ± 0.6 5.0 ± 0.5 Conductivity (µs/cm) 19.4 ± 7.8 31.9 ± 13.7 22.7 ± 9.9 24.6 ± 9.0 22.5 ± 5.9 Alkalinity (µeq/L) 63.0 ± 13.6 313.3 ± 60.5 197 ± 35.0 208.9 ± 55.0 75.7 ± 17.3

METRIC L WEIKERT GREEN GAP LICK CORAL RUN HENSTEP PTI 2.83 / 4.00 2.35 / 4.00 2.61 / 4.00 2.77 / 4.00 2.92 / 4.00 SDI 2.66 / 3.56 3.00 / 3.89 3.13 / 3.95 3.20 / 3.76 3.00 / 3.83 SDE 0.75 / 1.00 0.77 / 1.00 0.79 / 1.00 0.86 / 1.00 0.78 / 1.00 TDI 21.09 / 100 57.50 / 100 33.57 / 100 31.41 / 100 30.45 / 100 GDI 17.78 / 20 16.35 / 20 17.44 / 20 17.82 / 20 17.76 / 20

Table 2. Table of important descriptive parameters for each of the streams. Values given are mean ±1 SD.

Table 3. Diatom-derived metrics describing each of the streams. The first number in each cell is the metric followed by the maximum value for that metric.

Table 4. A Proportional Bray-Curtis Similarity Index table comparing percent similarity between diatom communities of all five streams. Only one pair (Lick-Henstep) had high overlap. The others had moderate to low overlap. Little Weikert-Green Gap had only 15% similarity though they were neighboring streams.

X L WEIKERT GRN GAP LICK CORAL HENSTEPL WEIKERT 80-100 VERY HIGH OVERLAPGRN GAP 15.0 60-80 HIGH OVERLAPLICK 28.3 42.3 40-60 MODERATE OVERLAPCORAL 39.2 46.0 50.9 20-40 LOW OVERLAPHENSTEP 37.2 40.6 66.8 58.8 0-20 VERY LOW OVERLAP

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