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The Effect of Mining on the Health of First Order Streams in Boulder County |
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--done w/ 2 colleagues |
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| Abstract |
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| The health of mined and unmined mountain streams west of the city of Boulder was researched during this project. The purpose of this study was to determine if mining had a significant impact on the health of streams located near the towns of Ward, Jamestown, and Nederland in Boulder County. To determine the health of the streams we looked at the number of macroinvertabrates that inhabited each of them, as well as the temperature, pH and the TDS. Certain types of species thrived in polluted streams while others would thrive in clean streams. By doing a chi-square test of the data it was revealed that there was a difference in the health of the two sets of streams (34.6, p-value <0.01). |
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Introduction |
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| Macroinvertebrates are excellent biological indicators of water quality (Manson et. al Internet). Test kits can determine the water quality of an aquatic ecosystem (lakes, ponds, streams, or rivers), however; they can only determine the water quality at that moment in time. Macroinvertebrates, on the other hand, can illustrate the water quality of an area over a long period of time (Ward and Kondratieff 32). |
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| There are three categories of macroinvertebrates defined by their tolerance to pollution. The categories include pollution-sensitive pollution-tolerant" and somewhat pollution-tolerant. Pollution sensitive invertebrates indicate good water quality. Examples of "pollution-sensitive" Macroinvertebrates are stoneflies (Plecoptera), mayflies (Ephemeroptera), riffle beetles (Coleoptera), caddisflies (Trichoptera). Pollution-tolerant" organisms indicate poor water quality and they are leeches and aquatic worms (Planarian). Somewhat pollution-tolerant organisms indicate fair water quality and they include beetle larva and blackfly (Identification Internet, Benthic Internet, and Ward and Kondratieff 33). |
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Any type of human impact can disturb an aquatic macroinvertebrate communities (Insect Book 32). Mining has great potential for environmental damage (Davis et. al 1999) in mountain streams and has serious consequences on aquatic biological communities, such as runoff from abandoned mines (Domagalski 1998) and acid-drainage from coal mines. Several pollutants can affect the structure of the aquatic community, such as suspended solids (Quinn et. al 1992), pH, dissolved oxygen, and trace metals. There is an abundance of research using macroinvertebrates as indicators of water quality in an aquatic ecosystem. This report will only focus on the effect of mines on aquatic communities in mountain streams. |
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| Davis et. al took samples from Bear Butte Creek, Strawberry Creek, and Double Rainbow Creek of the Black Hills in South Dakota. Their data demonstrates the affect on abandoned gold mines on the water quality in the above-mentioned creeks. Their pH values ranged from 6.6 to 9.6 (1999). For an example, the pH value at site 8 (below Double Rainbow Mine) was 8.8, which is considered to be somewhat basic. Another example is that past research indicated the pH values at Park Creek, Lost Glutch, and Headwaters were 9.6, 9.2, and 9.5, respectively. |
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| Rahn et. al also took samples from creeks near the Black Hills, also indicated that most mining problems are associated with abandoned gold mines (1996). Their data illustrated that their pH values ranged from 1.6 to 9.7 (Rahn et. al 1996). For an example, pH values from Strawberry showed a low of 3.12 and a high of 7.71 above the Bear Butte Mine and a low of 6.39 and a high of 9.72 at the mine (Rahn et. al 1996). |
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| Beltman et. al (1999) did a study on the Blackbird Mine in Idaho and their data demonstrated that the mine affected the aquatic communities. The study indicated that the number of mayflies, stoneflies, and other "pollution-sensitive macroinvertebrates were greatly reduced in communities below the mine. Below the mine, the aquatic community was abundant with Chironomids (Beltman et. al 1999). Quinn et. al (1992) did a study on gold mines in six streams in New Zealand. Their study illustrated thatpollution-sensitive organisms (1992) dominated the upstream sites of the streams. |
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| The main objective of this research project was to determine the impact of mining on the water quality of Boulder County?s first order streams. Mining has been an important part of life in the Boulder area since it was settled during the 19th century. This project addresses the health of the small streams that have their headwaters in areas where mining occurred. To assess the relative health of mined and unmined streams, we sought to answer the following questions: |
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| 1.�� What effect do mining wastes have on the number, type, and diversity of the macroinvertebrate populations residing in the streams? What effect do mining wastes have on the temperature, pH, and total dissolved solids of first order streams? |
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| We predicted that the mined communities would have lower pH levels and higher TDS. We also predicted that the macroinvertebrate diversity would be lower in mined streams, and there would be fewer pollution sensitive species. |
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| Methods |
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| We conducted our research during the spring of 2000 at ten different sites in ten first order streams in Boulder County. Five of the streams have mines in their drainages (see maps, sites A-E) and five do not (see maps, sites 6-10). |
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| Over a three-week period, we tested each site once. We recorded water temperature, pH, and total dissolved solids (TDS) at each site. We also collected macroinvertebrate samples at each site. We stood on the upstream side of the net and used our feet to agitate the stream bed cobbles for 20-30 seconds, allowing the macroinvertebrates to drift into the net. We took two net loads at each site, placed them in sample pans, and identified them by scientific order. For the purpose of analysis, the macroinvertebrate order and number data from all five mined sites were combined to form a community sample, as was the data from the undisturbed sites. |
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| We used t-tests to assess whether or not the average temperature, pH, and TDS measurements for the mined and undisturbed streams differed significantly. We calculated the species richness and Shannon diversity for each community, and we compared the two communities using the percent similarity figure and a Chi-square contingency table test. |
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Results |
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Water Temperature |
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| The average water temperature of the unmined streams was slightly colder than that of the mined streams (see Figure 1). However, the difference was not significant (t=1.978, df= 8, p=0.8). |
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Figure 1 |
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pH |
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| The mined and unmined streams had slightly different pH levels (see Figure 2) although the difference was not significant (t=0.835, df=8, p=0.42). |
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Figure 2 |
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| Total Dissolved Solids (TDS) |
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| Each stream demonstrated a wide range of TDS measurements. Overall, the averages (see Figure 3) did not vary significantly (t=1.42, df=8, p=0). |
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Figure 3 |
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| Macroinvertebrates |
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As seen in Figure 4, the unmined streams are dominated by round-bodied mayflies (Ephemeroptera), caddisflies (Trichoptera), and stoneflies (Plecoptera). On the other hand, Figure 5 illustrates that mined streams are dominated by chironomids. Both types of streams had a similar number of flat-bodied mayflies (Ephemeroptera), black flies (Simulidae), and planaria. The Shannon value for the mined streams is 0.717 and is 0.709 for the unmined streams. The percent similarity between the two types of streams is 62%. The chi-square contingency table test showed that the macroinvertebrate communities in the two different stream types differed significantly (df=4, chi-square=34.6, p<0.01). |
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Figure 4 |
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Figure 5 |
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| Discussion |
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| We found that there is a significant difference between the macroinvertebrate communities of streams near mined areas and streams undisturbed by mining. The largest difference was noted in the total Ephemeroptera abundance. Ephemeroptera are pollution sensitive invertebrates whose presence indicates good water quality (Identification Internet and Benthic Internet). There were 52% fewer mayflies in the mined samples than in the unmined samples. There was also a marked difference in Chironomid abundance, with 75% more Chironomids at mined sites. Although the macroinvertebrate data indicated that there is decreased water quality in streams affected by mining, the abiotic data we collected did not provide any explanation for the cause of the decrease, for there were no significant differences between the average temperatures, pH, or TDS of the two community types. We were surprised to find no difference in the pH results; low pH values have often been cited as a water quality problem in areas located downstream from abandoned mines (Rahn et al. 1996). |
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| We suspect that the presence of heavy metals in the sediment load of the mined streams is responsible for the decrease in water quality indicated by the macroinvertebrate data. Leakage from old mine deposits can lead to elevated levels of copper, zinc, lead, and cadmium (Malmqvist and Hoffsten 1999). According to Clements (1994), these metal levels are the highest during the spring runoff season. Mayflies have been found to be highly sensitive to heavy metals and total mayfly abundance is usually a reliable indicator of heavy metal contamination (Clements and Kiffney 1995; Clements et al. 2000). Moderate metal pollution can reduce Ephemeroptera abundance by as much as 75% (Clements et al. 2000). In contrast, Richardson and Kiffney (2000) found that Chironomid densities showed no significant decrease with increased heavy metal concentration. We believe that testing our sites for heavy metal presence would reveal that higher concentrations of lead, copper, and zinc at the mined sites are the cause of the decrease in water quality. |
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The largest source of error was in the identification of the macroinvertebrates. We used several different illustrated keys to help us classify them, but there were definitely some individuals for which we had to make a tough choice at he end. Also, site 7 was located just downstream from a large, rusty culvert that was coated with algae, which we reasoned could have had some effect on the macroinvertebrates found there. Our study would have been more conclusive if we could have determined whether or not heavy metal concentrations varied significantly between communities, but we were unable to procure the proper test kits for the collection of metals data. To improve this project, we would suggest conducting tests of the same streams at different times of year. While our results showed no significant difference in the pH of the two communities, repeated testing might turn up different results due to time of year or stream flow characteristics. |
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