Stream Life at Antietam National Battlefield

Sharpsburg Creek at Antietam National Battlefield.

U.S. National Park Service

Key Points

• Stream biota was monitored at Antietam in 2022 during the 2019–2022* monitoring cycle.
• Fish Community was good. Four species of fish were observed in Sharpsburg Creek.   
• Macroinvertebrate Community was poor. Eleven benthic (bottom-dwelling) macroinvertebrate taxa were observed. 
• Stream Physical Habitat characteristics were mostly suboptimal. 

*The previous cycle of this periodic (not annual) monitoring occurred 2008-2014.

Stream monitoring at Antietam occurs in Sharpsburg Creek.

Scientists working with the National Capital Region Inventory & Monitoring Network (NCRN I&M) monitor the health of fish and macroinvertebrate communities in Sharpsburg Creek at Antietam National Battlefield. They assess stream fish and macroinvertebrates using the Fish Index of Biotic Integrity and the Benthic Index of Biotic Integrity. These scoring systems take into account the number of taxa; abundance of individuals; and the proportion of taxa that are sensitive, intermediate, or tolerant to disturbance; as well as comparisons with biological communities expected in environments like Antietam's. Scientists also collect data on the physical characteristics of these streams to assess the habitat they provide.

Antietam sits in the Appalachian Mountain region, which consists of ridges of sandstone and valleys of shale and water-soluble limestone. These characteristics form a karst landscape where water sometimes dissolves through the bedrock into subsurface waterways like sinkholes and springs, often distinctively changing the chemistry of the water. The park itself consists of farmland, pastures, woodlots, and limestone forests.

Fish Community

The checkered sculpin is a benthic fish that lives in limestone streams. It has been highly abundant in Sharpsburg Creek across multiple years of monitoring.

Emilio Concari (CC BY NC)

Fish Index of Biotic Integrity

Antietam National Battlefield's Sharpsburg Creek received a Fish Index of Biotic Integrity (FIBI) score of 4.3 (good) in 2022, consistent with the previous monitoring period.

FIBI scores use data such as the abundance of fish that are disturbance tolerant, insect-eating, omnivorous, or benthic to assess stream health. Scores range from 1 to 5, with four possible ratings: very poor (1-1.99), poor (2-2.99), fair (3-3.99), and good (4-4.99). Figure 1 shows FIBI scores for Sharpsburg Creek.

Figure 1. Fish Index of Biotic Integrity (FIBI) scores for Sharpsburg Creek. Scores are measured on a scale of 1 to 5, categorized as: 1–1.99 = very poor, 2–2.99 = poor, 3–3.99 = fair, 4–4.99 = good. Missing bars indicate that the stream was not sampled in that year.

Narrative figure description:

A bar plot showing Fish Index of Biotic Integrity, ranging from 1 to 5, on the y-axis for Sharpsburg Creek. Gray bars indicate data collected in 2013 and white bars indicate data collected in 2022. The background of the bar plots is split into four differently shaded regions based on the FIBI score categories described in the figure caption. 

Species Found

Checkered sculpin (Cottus sp.) were the most abundant fish observed at Sharpsburg Creek (393 individuals), consistent with previous years. Blacknose dace abundance decreased slightly, following a consistent trend since monitoring first began in 2004. Central stoneroller (a sensitive species) and brown trout (a game fish) were recorded for the first time. Fish abundance and species richness both increased from the previous monitoring cycle. Two species were observed in 2013, while four were found in 2022.

Sharpsburg Creek Fish Species

2022 FIBI: 4.3 (good)

Species	# of Individuals Observed
Checkered sculpin (Cottus sp.)	393
Blacknose dace (Rhinichthys atratulus)	37
Brown trout (Salmo trutta)*	6
Central stoneroller (Campostoma anomalum)	1

*Game fish

Macroinvertebrate Community

Amphipods were the most common taxon at Sharpsburg Creek in 2022.

© David H. Funk. / Stroud Water Research Center

Like fish, macroinvertebrates are water quality indicators. Some taxa, such as certain types of dragonflies, worms, and non-biting midges, can tolerate poor environmental conditions. Others, including mayflies, stoneflies, and caddisflies, are more sensitive to higher temperatures and pollution levels.
In addition, macroinvertebrates are a major food source for other aquatic animals. Most fish would not be able to survive without them.

Benthic Index of Biotic Integrity

Sharpsburg Creek received a Benthic Index of Biotic Integrity (BIBI) score of 2 (poor) in 2022, the same as its 2013 score.

Like FIBI, BIBI scores are used to evaluate stream health and take into account the tolerance and abundance of macroinvertebrate taxa, as well as the way each organism feeds and its habitat. BIBI scores range from 1 to 5, with four possible ratings: very poor (1–1.99), poor (2–2.99), fair (3–3.99), and good (4–4.99). Figure 2 shows BIBI scores for Sharpsburg Creek.

Figure 2. Benthic Index of Biotic Integrity (BIBI) scores for Sharpsburg Creek. Scores are measured on a scale of 1 to 5, categorized as: 1–1.99 = very poor, 2–2.99 = poor, 3–3.99 = fair, 4–4.99 = good. Missing bars indicate that the stream was not sampled in that year.

Narrative figure description:

A bar plot showing Benthic Index of Biotic Integrity, ranging from 1 to 5, on the y-axis for Sharpsburg Creek. Gray bars indicate data collected in 2013 and white bars indicate data collected in 2022. The background of the bar plots is split into four differently shaded regions based on the BIBI score categories described in the figure caption. 

Taxa Found

In 2022, 11 benthic (bottom-dwelling) macroinvertebrate taxa were observed in Sharpsburg Creek, consistent with the previous two monitoring cycles (2013 and 2006). Gammarus (amphipods), which have an intermediate sensitivity to environmental disturbance, was the most commonly identified taxon by far, accounting for nearly 84% of macroinvertebrates recorded at the stream. Gammarus similarly dominated the stream in 2013.

Macroinvertebrate taxa richness at Sharpsburg Creek has remained consistent. The five most common macroinvertebrate taxa all have an intermediate sensitivity level to environmental disturbance.

Sharpsburg Creek Top 5 Most Common Macroinvertebrate Taxa

Table shows five most common taxa of 11 total found
2022 BIBI: 2 (poor)

Taxon	% of Total Individuals
Gammarus	83.9
Optioservus	9.0
Baetis	2.4
Simulium	0.9
Tanytarsus	0.9

Stream Physical Habitat Monitoring

Observations of stream physical habitat are gathered at the same location and time as macroinvertebrate monitoring in spring and fish monitoring in late summer. The physical habitat characteristics fall into two broad categories: solid substrates (stream bed materials), and stream flow and depth.

Solid Substrates

• Embeddedness of substrates: higher embeddedness = less available habitat for small fish, macroinvertebrates, and periphyton (small surface-growing organisms)
• Epifaunal substrate: the amount and variety of hard materials that can be used as habitat
• Instream habitat quality: higher values = greater variety of habitat and substrate particle sizes

Stream Flow and Depth

• Pool quality: diversity of slow- and still-water habitats. Higher scores = more optimal habitat
• Riffle quality: depth and complexity of riffles (shallow flows disrupted by substrate)
• Water velocity and depth: higher scores indicate greater variety of water speeds and depths

All characteristics except embeddedness of substrates are measured on a scale of 0–20, with 20 being the most optimal habitat conditions. Embeddedness is measured as a percent.

NCRN I&M no longer reports index scores for stream physical habitat but instead provides data on individual measures. These, along with FIBI and BIBI, provide a comprehensive view of stream quality. Other stream physical habitat characteristics observed but not reported here include the quantity of woody debris and root wads in the stream, stream bank stability, percent of channel shaded, distance from nearest road (remoteness), and land cover composition (percent urban, forested, and agricultural land).

Stream habitat quality characteristics at Sharpsburg Creek ranged from suboptimal to optimal (Figure 3). All characteristics aside from epifaunal substrate improved from the previous monitoring cycle.

Figure 3. Stream physical habitat characteristics of Sharpsburg Creek in 2013 and 2022. Epifaunal substrate, instream habitat, pool quality, riffle quality, and velocity/depth are all measured on a scale of 0–20, categorized as: 0–5 = poor, 6–10 = marginal, 11–15 = suboptimal, 16–20 = optimal.

Narrative figure description:

Bar plot showing stream physical habitat quality scores, ranging from 0–20, on the y-axis for Sharpsburg Creek. Stream physical habitat quality characteristics are listed on the x-axis from left to right as follows: epifaunal substrate, instream habitat, pool quality, riffle quality, velocity/depth. Gray bars indicate data collected in 2013 and white bars indicate data collected in 2022. The background of the bar plots is split into four differently shaded regions based on the habitat quality score categories described in the figure caption. 

Embeddedness, which is closely related to epifaunal substrate, is a measure of habitat availability. Embeddedness increased at Sharpsburg Creek between 2013 and 2022, indicating lower habitat availability (Figure 4).

Figure 4. Embeddedness at Sharpsburg Creek in 2013 and 2022. Embeddedness is a percent; values above 55% indicate less available habitat and poor habitat quality.

Narrative figure description:

A bar plot showing embeddedness as a percent at Sharpsburg Creek in Antietam National Battlefield, with 0 percent at the top of the y-axis and 100 percent at the bottom. The bottom region of the graph is shaded red to represent values of 55% or more embedded, which indicate poor stream quality. Values below 55% are considered minimally impaired. Gray bars indicate data collected in 2013 and white bars indicate data collected in 2022. 

Conclusions: Increase in Fish Biodiversity and Abundance, FIBI and BIBI Consistent

Antietam’s Sharpsburg Creek received a FIBI score of 4.3 (good) in 2022, the same as its 2013 score. Although FIBI did not change, the monitoring team observed higher fish abundance and species richness compared to the previous monitoring period, including the appearance of six brown trout, a game species, and one central stoneroller, a species that is sensitive to environmental degradation.

Like FIBI, BIBI at Sharpsburg Creek was consistent with the 2013 score. Community composition (the taxa that make up the macroinvertebrate community) was similar between the past two monitoring cycles, which span nine years.

Stream habitat quality at Sharpsburg Creek is generally in fair condition, improving across all metrics aside from epifaunal substrate and embeddedness.

Learn More about the National Park Service's Inventory & Monitoring Efforts

To help protect natural resources ranging from bird populations to forest health to water quality, National Park Service scientists perform ecological Inventory & Monitoring (I&M) work in parks across the country. The National Capital Region Network, Inventory & Monitoring program (NCRN I&M) serves national parks in the greater Washington, DC area. Visit the NCRN stream biota monitoring webpage to learn more. Previous cycles of fish, macroinvertebrate, and stream physical habitat monitoring were reported in 2015.