Project Type


Publication Date


Department or Program

Biological Sciences


College of Arts and Sciences

Faculty Mentor #1

Tomba, Abbie


Freshwater ecosystems are some of the most biodiverse on the planet, but they are threatened due to human actions resulting in habitat loss, pollution, and nutrient runoff. Macroinvertebrates can be used to measure the health of a freshwater system because different taxa have different tolerances to pollutants. However, the relationship between nutrient runoff and macroinvertebrates remains understudied. Accokeek Creek and Aquia Creek are two tidal freshwater streams in Stafford, VA. Accokeek Creeks drains a watershed containing the Crow’s Nest Natural Area Preserve and minimal development. Aquia Creek’s watershed is largely suburban. The objectives of this study were a) to examine differences in macroinvertebrate diversity between Accokeek and Aquia Creeks and b) to investigate the relationship between nutrient concentration and macroinvertebrate community assemblage. Because we expected nutrient levels to be higher in Aquia Creek, we hypothesized that Accokeek Creek would have higher macroinvertebrate biodiversity than Aquia Creek. In late spring 2021, habitat data and three macroinvertebrate samples were taken from six Accokeek sites and four Aquia sites. Two water samples and one sediment sample were collected from each Accokeek and Aquia site for nitrogen and phosphorus testing. A total of 1,874 macroinvertebrates across 25 taxa were identified with the most common taxa being Oligochaeta (n=954), Chironomidae (n=314), and Hydrobiidae (n=191). Shannon Diversity was significantly higher in Aquia Creek (1.418±0.096 mean±SE, n=10) than in Accokeek Creek (0.939±0.099, t(20)= -3.4, p=0.003, n=12). Orthophosphate levels were significantly higher in Aquia Creek (0.154mg/L±0.012) than in Accokeek Creek (0.065mg/L±0.008), t(20)= -6.3, p<0.0001). Based on these results, our hypothesis was not supported. A positive relationship was found between orthophosphate level and Shannon Diversity [R2 =0.25, p=0.0104], which may be explained by increased vegetation associated with elevated orthophosphate levels. Further analysis will be done to examine the relationship between biodiversity and nutrient levels in the late summer months.

Included in

Biology Commons