Impact of an Agricultural Point Source on Macroinvertebrate Communities and Water Quality on the Lamoille River

Transcription

1 Impact of an Agricultural Point Source on Macroinvertebrate Communities and Water Quality on the Lamoille River Fundamentals of Ecology 12/2/05

2 Introduction The purpose of this study was to determine if a dairy farm located on the Lamoille River in Johnson has an effect on water quality as well as the chemical characteristics of this stretch of river. Certain agricultural activities have been known to cause negative effects on water quality. Organic and toxic pollutants such as fertilizers, pesticides and other chemicals applied to fields directly adjacent to water body s can wash off and affect the water quality of the surrounding surface waters. Also physical habitat degradation such as increased sediment deposition due to lack of riparian buffer zones can alter the natural habitat of aquatic organisms. The spreading of manure on fields is a practice used by many farms as an alternative to manure pits. Domestic animal waste (manure) contain high levels of both nitrogen and phosphorus. Although these two substances are essential to the lifecycle of plants and animals, slight increases in either by way of anthropogenic practices can severely alter ecosystems of many aquatic environments. Testing rivers chemical characteristics provides insight into the impacts of agricultural runoff. Any changes in a rivers characteristics can affect habitat and water quality.however when doing these tests one must take into consideration other factors that may influence the data including, rain events, types of land use upstream of sampled areas, as well as the size of the farming operation. Page 2 of 20 A study done on the St. Albans Bay Watershed, found that in 1990, 90% of the total phosphorus loading in St Albans bay was as a result of agricultural pollution. As a result of this there has been increased rates of eutrofication due to excess loads of phosphorus resulting from both point and non-point pollution sources. Similar to the St

3 Albans Bay Watershed, the Lamoille River Watershed is adjacent to large amounts of agricultural land, which influence the dynamics of the river. Testing the chemical characteristics and benthic macroinvertabret densities on stretches of river directly adjacent to agricultural lands can provide insight into the impacts that farms have on certain stretches of a river. Macronivertabrets are one of the single best indicators of the ecological integrity of a river. Both type and abundance reflect many physical and chemical characteristics of rivers. Certain species of macroinvertabrets are less tolerant to pollution than others. EPT ( Ephemeroptera, Plecoptera, and Tricoptera) are the most intolerant of pollution, and percentages of these species are the best indicators of water quality. The absence of these keystone species can have a much greater effect on the food chain as a whole. Macroinvertebrates are critical to the food web between aquatic plants, and leave litter, and connect to the upper levels of the food chain by providing food for many fish species in rivers ( Dates, Byrne,1997). In this study density of macroinvertebrates were calculated in order to determine the impact the farm had on this stretch of river. A similar study done using macroinvertabrets was done in tributaries to Lake Tanganyika in East Africa. This study concluded that there certain benthic macroinvertebrates taxa underwent significant changes in abundance related to rapid deforestation of the surrounding watershed. (Swarthout, O Rielly, 2003) In this study a farm was picked that is located on the banks of a stretch of the Lamoille River located between Johnson and Morrisville VT. The farming operation is a small size dairy farm which has a dilapidated appearance. Through investigation of the site, a runoff stream was located that flows into the Lamoille River. The hypothesis of Page 3 of 20

4 this study was that this particular farm stream is affecting both chemical characteristics and water quality downstream of the farm. Materials and Methods Page 4 of 20 First macroinvertebrates were collected from five separate sites along a stretch of the Lamoille River in Johnson, approximately 1 mile up stream of Dogs Head rapids, where Waterman Brook enters the Lamoille. Two sample areas were upstream of the point source, one at the point source ( farm stream), and two below the point source. Samples were collected from consecutive riffle sections in the river. Sample sites were approximately ¼ mile apart from each other with the exception of sites two, and three, which were closer together. Site two was located in the main flow of the river not influenced by the point source, while site three was located closer to the shore and was influenced more by the point source. Refer to figure 1 Site Map for site locations. Four samples of invertebrates were taken from each site, two from high flow sections, and two from low flow sections. Samples were collected by turning over and scrubbing rocks from the river bottom. One person scrubbed the rocks, while the other held the net a few feet down stream in order to collect the insects. The contents of the net were then dumped into a five gallon bucket. Contents of the bucket were poured through the sieve several times in order to ensure that a large majority of the insects were caught in the sieve. The samples were then placed into ball jars and submersed in grain alcohol for preservation. Later in the lab jars of samples from each site were sorted through by insect order; Ephemeroptera, Plecoptera, Tricoptera, Coleoptera, Diptera, and Other. Samples were placed on a white tray that was divided into 12 squares, numbers were selected from a

5 random numbers list, which told what squares would be sampled from. Once the 3 random sample squares were picked, insects were identified by the use of a microscope and placed into separate jars based on order. There were five separate jars: jar one Plecoptera and Ephemeroptera, jar two Tricoptera, jar three Coleoptera, jar four Diptera, and jar five Other. This was done for each of the five site samples. Later percentages of EPT ( Ephemeroptera, Plecoptera, and Tricoptera), EP( Ephemeroptera and Plecoptera) were calculated by taking the total number of EPT and dividing it by the total number of insects found at a given site. The same technique was used to calculate the percentage of EP. Water sampling for chemical characteristics was also done. First, temperature, dissolved oxygen, and conductivity was measured in the field at each of the five sites with the use of dissolved oxygen and conductivity meters. At later dates, two separate sets of water samples were taken from the river and taken back to the lab for chemical analysis. The first set of samples were taken from three sites, one from upstream, one from point source, and one from downstream. The second set of samples were taken later from five sites along the stretch of river; two from upstream, one from point source, and two from downstream of point source. The reason that only three samples were taken first, was as a result of the river being near flood stage and certain sites were inaccessible. In the lab tests were done to measure ph, alkalinity, total hardness, phosphates, and nitrates. All lab tests were done with in twenty-four hours of obtaining the water samples. ph was calculated by using a ph meter which was calibrated to a ph of 7.00(neutral), by using a ph 7.0 buffer solutions. Page 5 of 20

6 Page 6 of 20 Total Hardness and Alkalinity were calculated by way of titration and the use of different indicator solutions (EDTA, and 0.02 Sulfuric Acid). In each test a 50 ml sample was used, and the #ml of titrant added was recorded. Later calculations were done to convert the #ml of titrant added into mg/l CaCO 3 and mg/l Alkalinity Nitrates were measured by the use of a Hach kit. First the Hach kit was calibrated to measure medium range nitrate/nitrogen which is measured by 400 nm wavelength. Second a twenty-five ml container was filled with deionized and a second container was filled with twenty-five ml of sample water. A nitrogen powder pillow was added to both samples and they had to be shaken for one minute. The deionized water sample was placed in the kit first (to zero out the device) for five minutes and then the twenty-five ml water sample was placed in the Hach kit for five minutes. The reason for this is the reaction time for testing the nitrogen levels is five minutes. Phosphates were measured in the same way as nitrates, with the use of the Hach kit. A phosphate powder pillow was added to the water sample, and the sample was placed in the Hach kit for a reaction time of phosphates. Data was then recorded. Results Slightly downstream of the point source %EP drops significantly. %EPT also drops from upstream two (site2) to downstream two (site 5). Amounts of Coleoptera increase significantly from upstream one ( site 1) to downstream two ( site 5). Also percent of Other decrease significantly downstream of point source. In the first set of samples taken during high-water there was no major difference in the chemical characteristics of all sites sampled. There was only a slight difference in the point source in hardness and alkalinity. In the second set of samples, there was no

7 difference in ph in all of the sampled sites. For upstream one, and downstream one and two, there was no difference in hardness or alkalinity. Both hardness and alkalinity were lower at upstream one, compared to all other sampled sites. Also hardness and alkalinity were lower in the samples taken from the point source. Phosphate levels were the same throughout all Lamoille River samples, but were significantly higher in the point source sample. Nitrate levels were non existent from the point source downstream. In comparing the two data sets, phosphate levels were much higher in the second set of samples, while nitrate levels fluctuated. Both ph and hardness was also higher in the second set of samples, and alkalinity was lower overall in the second set of samples. The high water stages appeared to dilute the first set of samples and may have caused discrepancies between sites. Also upstream one is located within close proximity to Waterman Brook appeared to effect the results of the chemical characteristics, resulting from the fact that the two water body s were not completely mixed at this point. The table shows other chemical characteristics ( Dissolved 0 2, conductivity, and temperature) of the water that were measured. The biggest difference was in conductivity, which is the lowest in the point source, by almost 100mµ. Also oxygen levels in the point source are lower than that of the Lamoille. There is not much difference in temperature which ranges from C. Some visual observations were also made, including that of algae growth on the river bottom. (Figures 10 and 11) There is a difference in the color of the algae growing in the section of the river influenced by the point source, compared to that of the algae growing in the main flow of the river. The alga nearer the point source is brown in color, while the main flow algae is green in color. Also there was a difference in the clarity of Page 7 of 20

8 the water, which can be seen on (Figure 12 and 13). Another observation that was made is that of riparian buffer zones along the sampling area. Larger buffer area located on the banks of the river where sites two, three, and four are located, and there is less of a buffer zone near site five(figure 14). Also when the second sets of samples were taken manure was being spread on the field. Discussion Page 8 of 20 The most significant evidence found that supports the hypothesis is the macroinvertebrate data. In particular with percentages of EP which drop significantly downstream of the point source. The fact that % EP drops shows evidence of lower water quality downstream of the point source. Major groups of macroinvertabrets are assigned number values from 0-10 based on there tolerance to pollution, 0 being the most intolerant, and 10 be most tolerant of pollution(dates, Byrne,1997). Ephemeroptera has a value of 2 and Plecoptera has a value of 1. Out of all the macroinvertabrets sampled these two orders of insects are the most intolerant of pollution. In healthy stream in New England, percentage of Plecoptera and Ephemeroptera usually make up 25-50% of the macro-invertabret community. Based on this fact, the data shows that over all the %EP is on the low side, and is extremely low at both sites downstream of the point source. Next is the %EPT, which declined significantly downstream of site two. Taking into consideration that Waterman Brook may have affected results from site one, there is a significant decline in %EPT downstream of site two. As a result of this, the lower percentage of EPT connected to the fact that Tricoptera is more pollution tolerant shows more evidence of lower water quality downstream of the point source. Tricoptera has a tolerance value of 3 which makes then more pollution tolerant than both Ephemeroptera

9 and Plecoptera. From site one to site five the numbers of Diptera and Coleoptera more than doubled in size. Both Diptera and Coleoptera are the most pollution tolerant out of all the sampled orders with a pollution tolerance value of 4. Higher percentages of these are found it indicates lower water quality. Although there is evidence of the point source effecting water quality ( macroinvertebrates ), it could also be due to a number of other factors. There was a noticeable change in habitat at site five compared to that of the other sampled areas. Bottom composition of site five was comprised more of smaller cobbles, and sand, which is a less suitable habitat for certain macroinvertabrets (EPT). This change in habitat could be natural, or it could be as a result of erosion and runoff caused by the farm. Referring back to Figure 14 and Figure 1 there is less riparian buffer zone along the banks were sample site five is located, and more of a buffer zone near site four. This could mean that the lower percentages of EP and EPT downstream of the point source, particularly site five, is a combination of both the farm stream, as well as direct runoff from the farm field itself. The presence of the farms on the banks of rivers can result in physical habitat degradation, which include; flow alteration, and silt, sand and sediment deposition that can fill niches in rocks were organisms could live. Also site five s proximity to VT RT15 may have had an effect on the habitat In terms of the chemical analysis of the water with the exception of Nitrates, there is no noticeable difference between the samples taken upstream of the point source compared to those sites downstream of the point source. One interesting thing to note is that of the phosphorus levels coming out of the farm stream. Levels of phosphorus flowing from the farm stream were considerably higher (.26mg/LPO4) than that of the Page 9 of 20

10 Lamoille River(.02mg/LPO4). This is most likely do to the fact that liquid manure was being spread on the field during the time the second water samples were taken. Manure is known to contain high levels of organic nutrients such as phosphorus. Although drainage from manured land may be washed into a stream during wet weather, in general, pollution from this source in rivers is unlikely to be considerable since the flow of the stream carry s these substances farther downstream to a larger water body like a lake ( Klein,1972). This explains the lower levels of phosphates found throughout the Lamoille river itself. It is possible that larger pools located farther downstream, may have higher phosphorus levels resulting runoff from the farm that has accumulated in the pools. Although there is no criteria established for phosphorus concentration in water, to control eutrofication, the EPA recommends that total phosphate should not exceed.05mg/l in a stream were it a lake or reservoir, and should not exceed.1mg/l in streams that do not discharge directly into lakes or reservoirs(usgs,2005). In the case of this farm phosphorus levels are far exceeding the recommended 0.1mg/LPO4. During the course of sampling the water visual observations were made of the algae growth on the bottom of the river. It appeared that the algae growing in the water influenced by the point source was brown in color, while the algae growing in all other parts of the sampled areas was green. It is a known fact that increased in certain nutrients like nitrogen and phosphorus can cause increases in certain types of algae. Based on the observation of this algae growth, one could hypothesize that the difference in algae type is as a result of the point source. Page 10 of 20

11 Conclusion In conclusion, based on the macroinvertebrate data there is also evidence shows lower water quality downstream of the farm stream (point source), there is not enough data to confirm that this is as a result of the farm stream itself. Another hypothesis is that the lower water quality found at site five is a result of the entire farm itself, including the farm stream as well as direct field runoff and bank erosion. Further tests would need to be done farther downstream of site five in order make more definite conclusions. Based on the chemical analysis that was done of the river, there is no change in the chemical characteristics from upstream to downstream. As a result of this the farm has no effect on the chemical characteristics of this particular stretch of river. However, there are significant levels of phosphorus coming out of the farm stream which may have an affect on other areas farther downstream. Like with the macroinvertebrates, further testing would have to be done in order to better assess the impacts of this farm on the river. Also if future tests are done, they should be scheduled around manure spreading times, and at different times of the year based on crop cover of the fields. Page 11 of 20

12 Site Map Figure 1 Figure 1 shows sample site locations of macro-invertebrates and Chemical Characteristics Page 12 of 20

13 Macroinvertebrate Data Site Site2 Site3( point source) Site 4 Site 5 Sample Squares 1,3,12 3,6,9 10,7,4 7,12,11 8,6,7 Ephimeroptera Plecoptera Tricoptera Diptera Coleoptera Other Totals %EPT 76.70% 84.60% 73.10% 76% 55.70% %EP 28% 30.70% 30.00% 21.00% 12.00% Figure 2 : Table 1 %EP 35% 30% 25% Upstream 1 28% Upstream % Point Source 30.00% Percentage 20% 15% Downstream % Site 1 Site 2 Site 3 Site 4 Site 5 10% Downstream % 5% 0% Site Figure 3: Graph 1 Page 13 of 20

14 % EPT 90.00% Percentage 80.00% 70.00% 60.00% 50.00% 40.00% 30.00% Upstream 1 Upstream % 84.60% Point Source 73.10% Downstream1 76% Site 1 Site 2 Site 3 Point Source Site 4 Site 5 Downstream2, 55.70% 20.00% 10.00% 0.00% Site Figure 4: Graph 2 Page 14 of 20

15 Oct.17,2005 Chemical Characteristics high water flows Phosphates Nitrate ph Hardness Alkalinity units of measure (mg/l) (mg/l) (mg/lcaco3) (mg/l) Upstream of Farm Farm Stream(Point Source) Downstream of Farm Nov. 3,2005 normal water flows Phosphates Nitrate ph Hardness Alkalinity units of measure (mg/l) (mg/l) (mg/lcaco3) (mg/l) Upstream Upstream Point Source Downstream Downstream Figure 5:Table 2 Physical Characteristics Dissolved Temperature Conductivity Oxygen units (mg/lo2) Site Site Point source Site Site Air temperature 28.4 Figure 6: Table 3 Page 15 of 20

16 Nitrate(mg/L) first samples Nitrate 0.8 mg/l Upstream of Farm Farm Stream(Point Source) Downstream of Farm Site Figure 7:Graph 3 Nitrate(mg/L) second samples Nitrate 0.8 mg/l Upstream 1 Upstream 2 Point Source Downstream 1 Downstream 2 Site Figure 8: Graph 4 Page 16 of 20

17 Phosphates second samples mg/l 0.15 Phosphates Upstream 1 Upstream 2 Point Source Downstream 1 Downstream 2 Site Figure 9: Graph 5 Page 17 of 20

18 Figure 10 and 11: Difference in algae growth brown vs. green Figures 12 and 13: difference in water clarity resulting from point source Page 18 of 20

19 Figure 14: Buffer zones site five is located to the left of the field. There are more trees acting as buffers near site four, notice the buffer zone at the far end of the field Page 19 of 20

20 References 1. Living Water: Using Benthic Macroinvertebrates and Habitat to asses your Rivers Health, The River Watch Network. By Geoff Dates and Jack Byrne, Testing the Waters: Chemical and Physical Vital Signs of a River, The River Watch Network by Sharon Behar and contributing authors Geoff Dates and Jack Byrne, St. Albans Bay Rural Clean Water Program: Final Report, United States Department of Agriculture and Vermont Water Resources Research. Submitted by Vermont RCWP Coordinating committee, May River Pollution 2. Causes and Effects, London Butterworths, by Louis Klien with chapters by J.R. Erichsen Jones, H.A. Hawkes, and A.L. Downing 5. Impact of deforestation on benthic macroinvertebrate communities in tributaries of Lake Tanganyika, East Africa. By Robert F. Swarthout and Catherine O Reilly, Nov The Biology of Polluted Waters, University of Toronto Press, by H.B.N. Hynes General Information on Phosphorus. By USGS, 2005 bcn.boulder.co.us/basin/data/nutrients/info/tp.html Page 20 of 20