Bear Brook: Strong Evidence of Pollution
Part of the Young Naturalist Awards Curriculum Collection.
Introduction
While pursuing my Soil and Water Conservation merit badge for the Boy Scouts, I had to identify possible areas of pollution and erosion in my town. During my exploration last year, I identified Bear Brook as one of the locations in my community that is possibly a polluted stream. I became interested because this brook flows on the outskirts of the residential development in which I live. I decided to find out whether or not Bear Brook is able to sustain healthy organisms.
On October 11, 2009, I walked approximately three-quarters of a mile from my home to the point where Bear Brook crosses under Southfield Road in West Windsor Township, New Jersey. On this balmy autumn day, I took a closer look at the stream while walking along its banks. Downstream from the bridge, I noted the discharge pipe from the nearby housing development that emits runoff from a storm sewer. I had read, "The release of acidifying substances through human activities has caused widespread acidification of freshwater systems … with consequent reductions in species diversity and ecological functioning in many regions" (Driscoll et al. 2001). Although a "No Dumping" sign was posted near the brook, I saw an old tire in the stream.
The stream was approximately 20 feet across and at its deepest point approximately four feet in depth. I saw no evidence of fish or any other type of life at first glance. There was no vegetation in the stream itself, but the area abutting the water had a preponderance of pokeweed (Phytolacca americana) and mature silver maple trees (Acer saccharinum). While attaining my Boy Scout Forestry merit badge this past summer, I learned that vegetation is important for the health of streams. "Forest cover is important, too, in determining how much water infiltrates … and how much runs off the surface to nearby streams. Wise watershed management can help ensure adequate quantities of water at the right times and guarantee that water quality is good." (Boy Scouts of America 2005.)
My follow-up trip was on November 1 at 11:45 a.m. We loaded my grandfather's Jeep with the tools needed to determine whether Bear Brook is a healthy stream and whether it supports life or not. When I arrived at the stream, I found it to be swollen and running faster than on my previous trip. This was due to four days of rain that had left the water a discolored muddy brown. Initially, the water depth in this area would have been between 30 to 60 centimeters. The depth of the water now was approximately 120 to 180 centimeters. At this point I could not safely enter the stream.
I took my first sample from the bank of the brook. I proceeded upstream above the bridge to try to find areas where it would be safe to enter the stream and collect samples. The stream bank was muddy and slippery, and on one occasion I lost my footing and slipped into the murky water. Luckily, I was wearing hip boots at the time.
In order to determine whether Bear Brook supports life, I hypothesized that because of the runoff from the nearby housing development as well as a drainage ditch from nearby soccer fields, and the trash in the stream, I would find the stream to be unhealthy. My research shows that three indicators used to identify a healthy stream are pH, the types of macroinvertebrates present, and the absence of coliform bacteria (Maryland Department of Natural Resources).
In order to identify the organisms present, I used a chart from the Maryland Department of Natural Resources' online database. The database also identifies which organisms are pollution-sensitive, moderately pollution-sensitive, or pollution-tolerant. Pollution-sensitive organisms such as the mayfly, stonefly, caddisfly, and gilled snails have a multiplication factor of 3. Moderately pollution-sensitive organisms such as the cranefly, dragonfly, clams, and mussels have a multiplication factor of 2, and pollution-tolerant organisms such as the blackfly, aquatic worms, midge larvae, and pouch snails have a multiplication factor of 1. The multiplication factor is based on the importance of that group of organisms. A stream with 22 or more is excellent, 17 to 22 is good, 11 to 16 is fair, and under 11 is poor.
I believed I would find the pH of the stream to be more acidic because I saw no signs of life in the brook. As I viewed the rocks in the stream, I thought I might discover some invertebrates that were at least pollution-tolerant. Regarding the presence of coliform bacteria, I thought I would find some, but I was not sure. The independent variable for my testing was the portion of the stream after the discharge pipe, because I wanted to see if this drainage site affected the brook negatively. The dependent variable I used for pH testing was the pH factor. For the macroinvertebrate sampling, the dependent variable was the number of specimens. In testing for coliform bacteria, the dependent variable was the number and types of bacteria in each colony.
Materials and Methods
In order to test the pH of the water, I acquired pH paper and color chart. I took three samples at all three locations and tested the water with pH paper. As pH is measured on a scale of 0 to 14, with 0 being high acidic and 14 highly alkaline, a pH of 7 is neutral. Most organisms can tolerate a pH close to 7.
I also needed tweezers, a magnifying glass, strainers and buckets to collect and identify the specimens. I lifted rocks from the stream and examined the underside of them, carefully picking off any organisms with my tweezers. Using an identification chart for macroinvertebrates, I was able to identify the specimens that I had accumulated.
To collect samples for bacterial testing, I used containers purchased from a nearby medical supply store. The coliform bacterial testing was to be continued at my high school science lab after school, with the supervision of my biology teacher. At school I placed the samples on three separate petri dishes containing nutrient agar, a substance that promotes bacterial growth. I placed these dishes into an incubator at 37°C for two days. After the petri dishes were retrieved from the incubator, I took a photograph of each and also drew sketches of them. I placed a small sample of each colony under a microscope and observed. I made notes on the sketches and drew the bacteria I saw. I repeated this procedure on two other days.
I decided to take three samples from three different locations for each of the three indicators of stream health. Location 1 was upstream of Southfield Road, Location 2 was upstream from the discharge pipe, and Location 3 was downstream from the discharge pipe.
Results
pH
At Location 1, upstream from the bridge, I took my first water samples. Results for this area were 6.2, 6.2, and 6.2. I proceeded downstream to Location 2, above the discharge pipe, where I was able to enter the stream with my wading boots to take samples. These were 6.55, 6.3, and 6.3. Then I proceeded to Location 3, downstream of the discharge pipe, where there was no water coming out of the pipe. Samples there were 6.2, 6.0, and 6.0. I also took samples of tap water from my home, which has a consistent pH of 7.2 that is controlled by the water company.
The results show that Bear Brook is not favorable to species that cannot tolerate acidic conditions. "Some (creatures) cannot live in water that has any acid in it. Many of the chemicals and nutrients that enter the stream through runoff change the pH of the water." (Maryland Department of Natural Resources).
Invertebrates
At Location 1, I was able to pull out six rocks just before the riffle. Attached to the bottoms of the rocks I found 12 midge larvae, one pouch snail, and one black fly. I used tweezers and a magnifying glass to get a better look to identify the specimens. I entered the data on my table and carefully returned the samples. At Location 2 I lifted a rotten log from the stream bottom and found one midge larva. This I listed it on my table. At Location 3, I found no invertebrates, rocks, or logs. I scooped up the silt and sand from the bottom of the stream and ran it through a strainer, carefully looking for any life, and found none. This was indicated in my journal.
Coliform Bacteria
Above the Southfield Road bridge, I found a location where I could safely retrieve water samples, which I collected in a sterile container. I marked this sample 1B. Upstream of the discharge pipe I collected a water sample into a sterile container and marked it 2B. Downstream of the discharge pipe, I gathered my third sample of water into a sterile container, marking it 3B.
The next phase was the lab work. I spent four days after school at my school's science laboratory. On Day 1 I took three petri dishes of nutrient agar and streaked the water samples from each location on the petri dishes using sterile loops. Then I placed them in an incubator at 37°C. On Day 2, I retrieved Dish 1 and saw there were two large colonies in this sample. I used a toothpick to put a piece of the colony from each petri dish on the slide of the microscope and placed a drop of bromothymol blue solution on top in order to view it better. The smaller of the two samples did not contain much bacteria at less than 400X. The larger of the two contained a lot of bacteria.
On Day 3, the first part of the procedure was repeated from incubator to microscope. This time I chose to work with the two colonies in Dish 3 from Location 3 because the largest one seemed to be growing fuzz (possibly fungi). It contained a huge amount of bacteria at 400X but no fungi. The smaller colony had a lot of bacteria at 400X, but many were in clusters and few moved.
My final testing of coliform bacteria, on Day 4, was on the sample from Dish 2 from Location 2. It showed six colonies. Two of the round colonies at 100X had large substances that were brown and most likely were fungi. The other round colony did not have any fungi and virtually no bacteria. The additional three colonies at 400X had no moving bacteria, and all were clumped together. I think the bacteria may have died when this sample was preserved in the freezer.
Discussion
The pH results for Bear Brook were all acidic. With regard to the macroinvertebrates found, the presence of a pouch snail (Physa virgata) generally indicates nutrient-enriched conditions and poor water quality (MacDonald 1990). The black fly (Simulium sp.) breeds in enriched streams such as sewage areas and around beaver dams. Deposits of eggs are made on rocks and water plants in the streams (Ohio State University Extension). Midge larvae (Chironomus sp.), also called bloodworms because of their color, can tolerate very low oxygen levels and are often found in very large numbers in sludge at the bottom of stagnant ponds. The organic pollutants that this species thrives on originate from domestic sewage, urban runoff and farm wastes, with domestic sewage being preferred (MacLeod 2006). Using the Maryland Department of Natural Resources' chart, I was able to determine from the kinds of invertebrates present in the stream what the general quality of the water would be. Bear Brook registered a 3, which is a poor rating, as is any score below 11.
The coliform bacteria results in the area showed that there were fungi before the discharge pipe, and no fungi after the discharge pipe, which indicates that the increase of pollutants after the discharge pipe killed the fungi.
Conclusion
My hypothesis was that I believed Bear Brook to be an unhealthy stream as a result of the emission of drainage water from a pipe coming a nearby residential development, runoff from a drainage ditch near soccer fields, and trash in the stream. I was correct in my hypothesis. Remediation of the pollution problem at Bear Brook should start with a settling basin for the water being drained from the development. One way I can help is to volunteer to eliminate the trash in the stream with my fellow Scouts.
I wish that the pH paper I used had a more precise range so I could have gotten more accurate readings. I think that my coliform bacteria experiment dragged on for too long, and the bacteria may have been frozen rather than preserved in the lab. I believe this problem impacted my final lab data.
If I were to conduct my project again, I would take samples from a larger section of the stream. If time permitted, I would compare not only more sections of the stream itself but branches of the stream that flow into other waterways. I would have taken samples where Bear Brook enters the Millstone River to determine if there is a change in water quality in the river before and after the point that the stream enters the river.
Bibliography
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