Agriculture Operations Can Impact the Water Quality of Nearby Streams

This is my first year of conducting research through the New Hampshire Academy of Science. My research was focused on analyzing the impact of agricultural runoff on water quality. I wrote my summary paper last August, and it was accepted for submission to the AJAS conference in October. I am so glad to have the opportunity to showcase my research this February, and look forward to seeing the research of my peers.

According to the Environmental Protection Agency, agriculture operations in the United States are the leading cause of water quality issues in streams and rivers (EPA, 2021). These widespread issues include presence of coliform bacteria due to manure runoff, the rise of sediment levels due to soil erosion, and the removal of dissolved oxygen due to excess nutrients from runoff containing phosphates and nitrates (EPA, 2021). It is important to study the impacts of agriculture on water quality to advance research in the field, and to inform views and policies relating to agricultural operations.

In Peacham, Vermont, there is a small stream called the South Peacham Brook. Along the length of the brook are four farms with thin riparian buffers between themselves and the waterway. Due to the positioning of the South Peacham Brook between diverse agricultural operations and its lack of former testing, this brook was chosen as the focus of this study.

Experimental Design

The hypothesis of this study was that water quality would be worse downstream of the farms. The objective of this study was to determine which bacteria and fungi were present in the South Peacham Brook.

Methods

Three sites, labeled Site A, Site B, and Site C were tested along the South Peacham Brook: Site A was upstream of the four farms, Site B was downstream of two farms, and Site C was downstream of the four farms. Sites were tested on five dates for dissolved oxygen, nitratrates, phosphates, pH, total dissolved solids, temperature and turbidity. Water samples were taken on three dates, and pipetted onto Endo Agar, Lysogeny Broth (LB) and Yeast Peptone Dextrose (YPD) plates, and the plates were incubated. Colonies on the Endo Agar plates were counted after two days of incubation to determine Coliform Forming Units (cfus), and colonies on the LB and YPD plates were resteraked for isolation after one day of incubation and incubated for another day. Colonies were also restreaked onto Macconkey plates, to determine their gram status. To identify bacteria and fungi, PCR was used to amplify the 16S gene. Gel electrophoresis was used to ensure that PCR was successful. Purified DNA was sent to a lab to be sequenced. Sequencing chromatograms were observed using FinchTV, and the sequences were entered into NCBI Blast to be matched with bacteria and fungi with similar matches.

Results

Dissolved oxygen, phosphate and turbidity levels were recorded at constant levels on each testing date. Dissolved oxygen was consistently between 6-8 ppm, phosphate levels were consistently less than 10 ppm, and turbidity levels were consistently below 5 NTU except on two dates where Sites A and B were 6 NTU, which were considered outliers. Mean nitrate levels increased from 0.11 ± 0.03 ppm to 0.38 ± 0.13 ppm from Site A to Site C. Site A had a mean water temperature of 23.0 ± 1.1℃, Site B had a mean water temperature of 16.0 ± 0.9℃ and Site C had a mean water temperature of 16.1 ± 1.0℃. Site A had a mean pH of 7.90 ± 0.16, Site B had a mean pH of 7.77 ± 0.13 and Site C had a mean pH of 7.75 ± 0.13. Total dissolved solids concentrations increased from 76 ± 2 ppm to 216 ± 5 ppm from Site A to Site C. 7 types of bacteria were identified: Hafnia alvei, Acinetobacter haemolyticus, Acinetobacter calcoaceticus, Kurthia gibsonii, Enterobacter cloacae, Lelliottia amnigena and a bacteria of the Bacillus genus.

Discussion

Nitrate, total dissolved solid and coliform bacteria levels, which increased from Site A to Site C, suggest that the farms did have a slight impact on the water quality of the South Peacham Brook. However, overall water quality still remained in the healthy range. No readings violated the Vermont Department of Conservation’s standards for water quality except for temperature readings at Site A, which were expected to be higher because of the site’s positioning at the edge of a pond.

The bacteria Hafnia alvei (Hafnia alvei, 2020), Lelliottia amnigena (Lelliottia amnigena, 2020) and Enterobacter Cloacae (Enterobacter cloacae, 2020) were identified to be in the enterobacterales order, whose bacteria are likely to originate in the gastrointestinal tract of humans or animals. If these bacteria were found at Sites B and C and not at A, it could indicate that the farms introduced fecal coliform bacteria into the South Peacham Brook. However, since these bacteria were found at Sites A and B, it does not suggest that farms had an impact on coliform presence in the brook.

As for the bacteria’s implications on the health of the people who use the South Peacham Brook, Hafnia alvei (Hafnia alvei, 2020), Acinetobacter haemolyticus (Bai et al., 2020), Acinetobacter calcoaceticus (Pal and Kale, 1981), and Enterobacter cloacae (Enterobacter cloacae, 2020) are all widely recognized as human pathogens. However, they are in low enough concentrations that they do not pose a serious threat to those who use the brook for recreation.

In the future, more sites should be tested and more bacteria and fungi identified, to yield a more comprehensive analysis.