The purpose of the experiment is to determine the variable conditions in which microorganisms are most common in the Duck Pond. The problem we are trying to solve is what conditions are most likely to support the population growth of freshwater microorganisms. Our hypothesis is that microorganisms will be most abundant in areas with closest to neutral pH, high levels of phosphorous, and high levels of plant life, whose temperatures are higher. We decided upon this topic because we are interested in both water and microbiology and the duck pond affords a chance to study them in depth. By performing this experiment, we plan to demonstrate what conditions are most likely to support life in the duck pond, which may be used in the future to determine the effects of pollution.
Much research has been done on the effects of certain conditions on microorganisms for the express purpose of determining when pollution begins to adversely affect the ecosystem. As Bruce J. Russell states in 'Life in a Drop of Pond Water', "Without bacteria, no fish, no frogs, no birds, no pretty pond lilies, cattails or sedges would survive. The simple fact is that microorganisms create the ecological foundation for life on planet Earth - a foundation that supports humans and all over living things." (Russell 2002) Bacteria and other microorganisms are surprisingly resilient; considering how many places they can be found. Microbial ecologists have revealed that Earth’s ecosystems harbor an enormous diversity of microbial species that may even surpass the number of known plant and animal species (Nold and Zwart 1998). As Francis H. Chapelle says, "it's little wonder that microorganisms display such astonishing diversity." (Chapelle p.32, 2001)
First, the general environment that is being investigated must be described. A pond is a body of water usually smaller than a lake, encircled by vegetation, and generally shallow enough for sunlight to reach the bottom. Algae, which are very small plant-like organisms, provide the base of the food chain in ponds. Algae release oxygen, which are necessary for fish and other aquatic organisms. However, when algae becomes excessive from an overabundance of nutrients, the decaying algae can decrease oxygen levels to a point at which plants and animals die. The problem with fertilizers is that they encourage too many algae to grow. When the algae die, their decomposition by aerobic bacteria takes oxygen out of the water, thus killing many fish or other life that relies on dissolved oxygen in the water. The amount of dissolved oxygen is an important indicator of water quality. (www.lalc.k12.ca.us 2002) Excessive nutrients can result from agricultural processes, runoff from fertilized lawns and fields, and septic tanks. (www.epa.gov 2002)
Each of the factors previously listed comprises the organism’s environment, so the effects of each need to be individually analyzed.
pH, a measure of acidity in water, is very important to most forms of life. It effects many chemical and biological processes. Most aquatic animals prefer a range of 6.5 to 8.0. Anything outside of this range is most likely caused by mine drawings and industrial wastes. (www.beesinc.org 2002)
Phosphorus is an essential nutrient for plant growth and for metabolic reactions in plants and animals. There is a delicate balance between plants and animals for phosphorous. It has been determined that is excess levels of phosphorous exist, sediment bacteria absorb the phosphorous as polyphosphate granules (Khoshmanish et Al. 2002). If animals develop phosphorus fixation as a result of this and consume too much, algae will die (www.biologic.de 2002). It is estimated that the increase in net phosphorous storage in terrestrial and freshwater ecosystems to be at least 75% greater than preindustrial levels of storage (Bennet 112). If there is too much phosphorus, plant life may choke out living animals. (www.beesinc.org 2002)
Dissolved oxygen measures the presence of oxygen gas molecules in water. Oxygen is essential to keep organisms living, to sustain species reproduction, and for many chemicals processes that happen in water. Water with higher dissolved oxygen is generally considered healthy, and more capable of supporting a variety of lives. Warm water can hold less dissolved oxygen than cool water. The amount of oxygen consumed by all of the biological processes is called biochemical oxygen demand (BOD). If the amount of oxygen that is consumed is greater than the amount produced by photosynthesis or by diffusion from the surrounding air, dissolved oxygen levels decline, and the ecosystem suffers. Bacteria often processes oxygen, taking raw nitrogen gas transforming it into usable biological nitrogen (www.beesinc.org 2002).
Temperature affects the rate of many of the waterway’s biological and chemical processes and the amount of oxygen gas that can dissolve in the water. Organisms can only live and reproduce within a certain temperature range. It also affects the rate of photosynthesis of plants and the rate of decomposition. Therefore, ‘heat pollution’ is created when factories or other industrial centers use water to cool machinery, then dump it into ground water, cause high temperature fluxes which kill off local organisms. (www.beesinc.org 2002)
Though there is great diversity in species of bacteria, they all fall into four recognizable basic categories based on shape. These shapes are Coccus (round), Coccobacillus (oblong), Bacillus (pill-shaped), and Spilillum (spiral shaped) (Lundy 2002).
The presence of microorganisms themselves can be indicative of a healthy environment. The presence of algae such as Navicula and Cocconeis indicates clean water. On the other hand, algae such as Euglena, Spirogyra, and Nitzschia indicate polluted water. (Chapelle p. 32, 2001)
Materials and Methods
In our experimental design, we will be testing four variables of pH, temperature, phosphorous levels and plant life by testing the samples and/or taking measurements in the field. We selected these variables based on their relevance to the topic and the ease with which we can measure them. We are not measuring current, for example, because the process would be difficult and expensive. Statistically, the results will prove accurate as long as we take enough measurements and samples. We were advised that the more variables we have and the more times we test them, the more accurate our results will be. Five distinct locations will be chosen as testing sites. To ensure that the class collects accurate data, we will keep records of our own data to ensure that they were in collusion.
A representation of the pond locations.
Materials used will be primarily for testing and observation. We will use collection tubes to collect the samples and microscopes to observe them and count microorganisms. Temperature will be gauged with a thermometer. Phosphorous and pH levels will be gauged using specialized chemical tests, and plant life will identified by counting the number of specimens in each grid. The class will be asked to use similar methods to gauge the variety of variables to be tested.
Measurements from each site will be taken for a nonconsecutive period of seven days, starting on the 23 of October and spanning until mid-November. The measurements will be taken between noon and 5:00. The data will be analyzed at the end of each week, so that a completed data table will be produced at the end of the period. This can be shortened to allow for time constrictions.
Oct. 23 Oct. 26 Oct. 28 Nov. 1
Nov. 3 Nov. 8 Nov. 12 Nov. 13 Nov. 15
Attached are the graphs of all pertinent data from the experiment.
Discussion and Conclusions
Hypothesis #1: Count is High when Temperature is High is Rejected
The histogram shows cells were most prolific at temperatures near the average of 10 degrees Celsius. This suggests that the organisms do not flourish in temperatures unusually high or low for the season. The unseasonable warmth on day 3 precipitated the massive count drop of day 4. There is no correlation shown between count and temperature.
Hypothesis #2: Count is High when pH is near or at 7 is Rejected
During three of the seven tested days, the average pH level approached or exceeded 7, the pH of pure water. All three of these days experienced a drop in organism count or precipitated a drop. This suggests that pond water is naturally basic and any alteration to this balance causes organism loss. The natural balance (where organism count was highest) was 6.7 pH. There is no clear correlation.
Hypothesis #3: Count is High when Plant Life is Abundant is Rejected
This hypothesis was immediately rejected because the p-value was over .05. In addition, plants surrounding the test sites were shown to actually decrease microorganism count in the pond water. This can be explained by two factors; one, the plants take up necessary resources and nutrients the organisms need to survive, and two, the carbon dioxide released by the plants causes the immediate area to become acidic, which has already been shown to decrease organism count.
Hypothesis #4: Count is High when Phosphorous is High has Failed to be Rejected
True to prediction, the charts show a clear and striking positive correlation between phosphorous and cell count. The phosphorous level at each site was directly related to how many organisms existed in that site. This result was obtained because green algae were counted as organisms, and research has shown that green algae produce phosphorous in a natural process.
This project tests environmental factors, many of which can be changed by human influence. By studying how small changes in environment can effect populations, we can more readily determine the effects of sources of freshwater pollutants. Thus, this topic is relevant both to current environmental and anti-pollution research. Further research could be made to investigate the effects of specific industrial pollutants.
Chapelle, Francis H., Ground-Water Microbiology and Geochemistry. John Wiley &
Sons Inc., New York, New York. 200“EPA-Lakes and Ponds” Online. http://www.epa.gov/maia/html/lakes.html 9/26/02
Geiszler-Jones, Amy. “Ponds, Scum, Bacteria Usually Helpful”. Online.
Kemp P., Sherr B., Sherr E., Cole J., eds. Handbook of Methods in Acquatic Microbial Ecology. Boca Raton FL: CRC Press, Inc 1993
“Microoraganisms”. Online. http://www.lalc.k12.ca.us/target/units/river/tour/micr.html
Russell, Bruce J., “A Drop of Life”. Online.
“Water Monitoring”. Online. http://www.beesinc.org/resource/currenha/watmonit.html.
Lundy, Dan. ‘Bacteria Shapes and Sizes.’ Online. http://dl.clackamas.cc.or.us/ 10/10/02
Bennett, Elena M. “Human Impact on Erodable Phosphorus and Eutrophication: A Global Perspective.” Bioscience March 2002: 112-122.
Nold, Stephen C. and Zwart, Gabriel. “Patterns and Governing Forces in Aquatic Microbial Communities.” Aquatic Ecology 32 (1998): 17-35.
Khoshmanish, Aazam, Hart, Barry T., Duncan, Anabelle, and Beckett, Ron. “Luxury Uptake of Phosphorous by Sediment Bacteria.” Water Research 36 (2002): 774-778
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