Stream Life at Wolf Trap National Park for the Performing Arts

Courthouse Creek at Wolf Trap National Park for the Performing Arts.

U.S. National Park Service

Key Points

• Stream biota was monitored at Wolf Trap National Park for the Performing Arts in 2022 during the 2019–2022 monitoring cycle.
• Fish Community was poor. Fourteen species of fish were observed across two stream sites. 
• Macroinvertebrate Community was very poor. Thirty-four aquatic macroinvertebrate taxa were observed. 
• Stream Physical Habitat characteristics were marginal or suboptimal. 

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

Stream monitoring locations at Wolf Trap National Park for the Performing Arts.

Scientists working with the National Capital Region Inventory & Monitoring Network (NCRN I&M) monitor the health of fish and macroinvertebrate communities in four streams at Wolf Trap National Park for the Performing Arts. These include Courthouse Creek and Wolf Trap Creek. 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; the proportion of taxa that are sensitive, intermediate, or tolerant to disturbance; as well as comparisons with biological communities expected in environments like Wolf Trap’s. Scientists also collect data on the physical characteristics of these streams to assess the habitat they provide.

Wolf Trap National Park for the Performing Arts falls within the Coastal Plain physiographic province, which consists mostly of layers of sediment primarily eroded from the Appalachian Mountains. This sediment was deposited by river over the Coastal Plain.

Fish Community

Blacknose dace are a highly abundant species in streams at Wolf Trap.

U.S. National Park Service

Fish Index of Biotic Integrity

Both Courthouse Creek and Wolf Trap Creek received a Fish Index of Biotic Integrity (FIBI) score of 2.7 (poor) in 2022. Scores have decreased since the previous monitoring cycle at both streams.

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 the FIBI scores for each stream site.

Figure 1. Fish Index of Biotic Integrity (FIBI) scores for two streams at Wolf Trap. 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 a 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, and stream name on the x-axis, listed from left to right as follows: Courthouse Creek and Wolf Trap Creek. Gray bars indicate data collected in 2012 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

Creek chub was a common fish species at Wolf Trap National Park for the Performing Arts.

U.S. National Park Service

In 2022, 14 species of fish were observed across two stream sites. Fish species richness (the number of different species) increased from 10 in 2012 to 12 in 2022 at Courthouse Creek and decreased from 20 to 13 at Wolf Trap Creek.

Blacknose dace (Rhinichthys atratulus) were the most abundant fish observed overall (506 total individuals) and were found in both stream sites. Other common species include creek chub, longnose dace, and tesselated darter. Central stoneroller, rosyside dace, and common shiner, which are sensitive to environmental degradation, were found at both streams. Swallowtail shiner, another sensitive fish, was also recorded at Wolf Trap Creek.

While blacknose dace populations have remained fairly steady, some sensitive fish, including central stoneroller and rosyside dace, have declined considerably at both streams.

Species Observed at Courthouse Creek

2022 FIBI: 2.7 (poor)

Species	# of Individuals
Blacknose dace (Rhinichthys atratulus)	262
Creek chub (Semotilus atromaculatus)	70
Longnose dace (Rhinichthys cataractae)	45
Tessellated darter (Etheostoma olmstedi)	23
Rosyside dace (Clinostomus funduloides)	8
Common shiner (Luxilus cornutus)	7
Green sunfish (Lepomis cyanellus)	4
Central stoneroller (Campostoma anomalum)	3
American eel (Anguilla rostrata)	2
White sucker (Catostomus commersonii)	2
Pumpkinseed (Lepomis gibbosus)	2
Redbreast sunfish (Lepomis auritus)	1

Species Observed at Wolf Trap Creek

2022 FIBI: 2.7 (poor)

Species	# of Individuals
Blacknose dace (Rhinichthys atratulus)	244
Creek chub (Semotilus atromaculatus)	57
Central stoneroller (Campostoma anomalum)	36
Longnose dace (Rhinichthys cataractae)	28
Common shiner (Luxilus cornutus)	27
White sucker (Catostomus commersonii)	23
Tessellated darter (Etheostoma olmstedi)	20
Green sunfish (Lepomis cyanellus)	17
Rosyside dace (Clinostomus funduloides)	7
Redbreast sunfish (Lepomis auritus)	6
Swallowtail shiner (Notropis procne)	5
Pumpkinseed (Lepomis gibbosus)	4
Bluegill (Lepomis macrochirus)	1

Macroinvertebrate Community

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.

Larval midges in the Chironomidae family, which includes the genera Diamesa and Polypedilum, the most abundant macroinvertebrate taxa at Wolf Trap National Park for the Performing Arts.

© David H. Funk. / Stroud Water Research Center

Benthic Index of Biotic Integrity

Benthic Index of Biotic Integrity (BIBI) at Courthouse Creek and Wolf Trap Creek was very poor. BIBI at both streams declined between 2012 and 2022.

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 the BIBI scores for each stream site.

Figure 2. Benthic Index of Biotic Integrity (BIBI) scores for two streams at Wolf Trap. 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.

Narrative figure description

A bar plot showing Benthic Index of Biotic Integrity, ranging from 1 to 5, on the y-axis, and stream name on the x-axis, listed from left to right as follows: Courthouse Creek and Wolf Trap Creek. Gray bars indicate data collected in 2012 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, 34 benthic (bottom-dwelling) macroinvertebrate taxa were observed across two stream sites. Diamesa (tolerant non-biting midges) was the most commonly identified taxon at the park, accounting for 26.9% of all macroinvertebrates recorded. All of the most common taxa at the two streams were intermediate or tolerant of environmental disturbance.

Diamesa were more dominant at Courthouse Creek than Wolf Trap Creek, where the most common taxon was a different type of non-biting midge called Polypedilum. The relative abundance of Diamesa, Polypedilum, and Orthocladius (another non-biting midge) increased considerably.

Courthouse Creek Top 5 Most Common Macroinvertebrate Taxa

Table shows five most common taxa of 25 total found
2022 BIBI: 1.57 (very poor)

Taxon	% of Total Individuals
Diamesa	46.0
Polypedilum	11.1
Cricotopus	9.5
Orthocladius	9.5
Cladotanytarsus	3.7

Wolf Trap Creek Top 5 Most Common Macroinvertebrate Taxa

Table shows five most common taxa of 19 total found
2022 BIBI: 1.45 (very poor)

Taxon	% of Total Individuals
Polypediulum	29.6
Orthocladius	27.4
Cricotopus	8.4
Tvetenia	8.4
Diamesa	6.7

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 physical habitat characteristics varied at the park (Figure 3). Wolf Trap Creek generally had higher habitat quality scores than Courthouse Creek. Scores at both streams declined since 2012 in almost every characteristic (aside from epifaunal substrate quality and velocity and depth diversity at Courthouse Creek).

Embeddedness, a measure of habitat availability that is closely related to epifaunal substrate, remained the same at both streams (Figure 4). Embeddedness was below 55%, indicating sufficient habitat availability for most fish and insects.

Figure 3. Stream physical habitat characteristics of Wolf Trap streams in 2010 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

Two bar plots showing stream physical habitat quality scores, ranging from 0–20, on the y-axis for Courthouse Creek and Wolf Trap 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 2012 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. 

Figure 4. Embeddedness at Wolf Trap streams in 2012 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 Wolf Trap streams, 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. Streams are listed on the x-axis as follows: Courthouse Creek, Wolf Trap Creek. Gray bars indicate data collected in 2012 and white bars indicate data collected in 2022. 

Conclusions: Poor Fish and Macroinvertebrate Communities, Stream Physical Habitat Characteristics Vary

Declining FIBI and BIBI scores at both Courthouse Creek and Wolf Trap Creek may indicate poor stream quality. Sensitive fish were found at both sites, but the abundance of some sensitive species declined considerably. Stream phyiscal habitat scores varied. Wolf Trap Creek scored higher than Courthouse Creek in stream flow and depth characteristics, and both sites had sufficient habitat availability according to embeddedness values.

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 2012–2015.