University of Santo Tomas College of Education INCREASING DISSOLVED OXYGEN LEVEL: A COMPARATIVE STUDY BETWEEN Cabomba aquatica AND Echinodorus amazonicus IN PARTIAL FULFILLMENT OF THE REQUIREMENTS IN NATURAL SCIENCE 106 (ENVIRONMENTAL SCIENCE) ESPIRITU, IVAN KEANU M. GERONIMO, DONN YVES P. MISADOR, PATT KIERWIN C. RANAY, DOMINICK M. TE, CLARISSA J. MARCH 2014 Increasing dissolved oxygen level: A comparative study between Cabomba aquatica and Echinodorus amazonicus Ivan Keanu M. Espiritu, Donn Yves P. Geronimo, Patt Kierwin C. Misador, Dominick M. Ranay and Clarissa J. Te Bachelor of Secondary Education major in Biological Sciences University of Santo Tomas España, Manila ----------------------------------ABSTRACT------------------------------------ Dissolved oxygen (DO) is the relative measure of oxygen gas that is dissolved or carried in a given medium. For an aquatic ecosystem to be able to support life, its DO level should be at least 5 to 7 parts per million (ppm). A lot of factors affect the DO levels of bodies of water, one of which is pollution, which is evident in the country. Two aquarium plants, namely: Cabomba aquatica and Echinodorus amazonicus were experimented using the modified Winkler Method to qualitatively determine which among the two plants release more oxygen through photosynthesis and would be more effective in the rehabilitation of bodies of water. After three trials of laboratory testing, the C. aquatica is found to be more efficient in increasing the DO level of water. Moreover, additional qualitative methods (e.g. colorimetric method) in detecting dissolved oxygen were recommended to give more opportunities in determining the presence of dissolved oxygen.  ---------------------------------------------------KEY WORDS---------------------------------------------------- Dissolved oxygen, Photosynthesis, Cabomba aquatica, Echinodorus amazonicus INTRODUCTION Oxygen is a chemical element with the symbol O and atomic number 8. Oxygen is a member of the chalcogen group – chemical elements belonging to group 16 of the periodic table – and is a highly reactive nonmetal and oxidizing that readily forms compounds (oxides) with most elements. At STP (standard temperature and time), two atoms of the element bind covalently forming dioxygen, a diatomic gas that is colorless, odorless and tasteless; it has a formula of O2. Diatomic oxygen is also what keeps most, if not all organisms alive in our planet. Atmospheric oxygen, though it only constitutes 20.95% of the entire gaseous blanket that covers our planet, is a vital requisite in the propagation and maintenance of life. We humans as well as animals depend on oxygen for normal metabolism of body cells. Whether in terrestrial or aquatic ecosystems, oxygen is a critical limiting factor. Too much would probably burn the entire ecosystem up (a terrestrial ecosystem that is) and too little would kill most of the organisms, making the ecosystem a ghost town. Our planet is composed of 70% water, hence the nickname “The Blue Planet”. These waters cater and serve as a habitat for a numerous number of organisms. From planktons to colossal squids, the Earth’s waters in teeming with life that requires oxygen, like any other aerobic organisms, to live. The main source oxygen in these aquatic ecosystems is through photosynthesis, where the gas is liberated as a by-product of the sugar-making process. Another source would be atmospheric oxygen dissolved in water. Since water, like land, serves as a habitat for a wide array of fauna; its parameters should be monitored and kept at bay especially because water is more easily polluted. Dissolved oxygen is the relative measure of oxygen that is dissolved or carried in a given medium. The concentration of dissolved ecosystem in a given aquatic ecosystem should be at least five (5) to seven (7) ppm (parts per million) in order to support and sustain life. There are many factors that affect the dissolved oxygen level, one of which is pollution. Water pollution is one of the common problems here in our country. The presence of pollutants in a body of water lowers the dissolved oxygen level and therefore suppresses the growth of aerobic organisms such as fish. Many means have been administered in order to “cure” polluted waters and to rehabilitate these ecosystems so that they can once again support life but to no avail. In this research, two (2) aquarium plants, namely: Cabomba aquatica and Echinodorus amazonicus were experimented on to find out which plant liberates more oxygen in the same period of time. One may find these plants in aquariums but because they can both liberate a relatively good amount of oxygen through photosynthesis, they are also good alternatives in raising the dissolved oxygen level of aquatic ecosystems so that they may be able to support life once again. However, the Cabomba aquatica is classified as a class 1 pest which means that it can grow rapidly when left unattended, suppressing the growth of natural flora in an aquatic ecosystem. Nonetheless, the Cabomba plant is still a very good liberator of oxygen due to its uncutinized leaves. The Echinodorus amazonicus, more commonly known as the Amazon sword plant is common in the western hemisphere and can live either totally immersed or half immersed in water. Like the Cabomba plant, the amazon sword plant is also used as an aquarium ornament and is also a good liberator of oxygen. The determination which among the two (2) aquarium plants, namely: Cabomba aquatica and Echinodorus amazonicus is more efficient in liberating more oxygen in tap water in the same time period, can help in raising the dissolved oxygen level thus making the water suitable for aquatic life. Included with this study is the qualitative determination of oxygen in tap water after immersing the two plants in a beaker for one week (setup 1) and another pair of plants in a beaker for three days (setup two). The two beakers were placed in a sunny spot and left undisturbed until the testing day. Results from this study only indicates whether oxygen is present or not and its relative concentration, no exact figures were obtained. REVIEW OF RELATED LITERATURE All living organisms depend upon oxygen in one way or another for their growth and development. Aerobic heterotrophs (i.e. animals) utilize oxygen gas (O2) to sustain their bodily processes. For example, humans breathe in air for their respiration. A decrease in the oxygen concentration would lead to their discomfort and possibly death. However, autotrophs (i.e. photosynthetic plants) yield oxygen gas in the air as by-products of their photosynthesis. Thus, careful monitoring of oxygen concentration in air and also in water, for aquatic organisms, is important. Oxygen is present in aquatic systems as dissolved oxygen (DO). Dissolved oxygen refers to the amount of oxygen contained in water. According to United States Environmental Agency (US EPA) (2012), aquatic systems obtain oxygen from the atmosphere through diffusion and plants as results of photosynthesis. According to Helmenstine (2014), the atmosphere is composed of 78.084% nitrogen gas, 20.9476% oxygen gas and the remainders are trace elements at 15 degrees Celsius (oC) under 101,235 Pascal (Pa). According to Manahan (2010), the solubility of oxygen in water depends upon water temperature, the partial pressure of oxygen in the atmosphere and the salt content of the water. “The solubility of atmospheric oxygen in fresh waters ranges from 14.6 mg/L at O 0C to about 7 mg/L at 35 oC under 1 atm (atmospheric pressure).” (Sawyer, 2003). According to www.michigan.gov (n.d.), the solubility of oxygen increases with decreasing temperature as colder water holds more oxygen. It also increases with decreasing salinity; freshwater holds more oxygen than does saltwater. Both the partial pressure and the degree of saturation of oxygen will change with altitude. Finally, gas solubility decreases as pressure decreases. Thus, the amount of oxygen absorbed in water decreases as altitude increases because of the decrease in relative pressure. The flow or movement of water systems is also an important factor to be considered on how atmospheric oxygen dissolves in water. This is referred to as the reaeration of water that has stumbled over running water. “Cold water that is flowing rapidly tends to carry more dissolved oxygen than warm water that is moving slowly through a pond or swamp. Flowing water tends to dissolve oxygen rapidly, and cold water temperatures help to stabilize oxygen in the water.” (Burton, 2009) Dissolved oxygen concentration in water fluctuates over time with respect to: oxidation-reduction reactions, assimilation of dissolved oxygen in water by aquatic plants; liberation of oxygen as by-products in photosynthesis of plants; and, factors that affect the solubility of oxygen in water described previously. “Accurate data on concentrations of dissolved oxygen (DO) in water are essential for documenting changes to the environment caused by natural phenomena and human activities. Sources of DO in water include atmospheric reaeration and photosynthetic activities of aquatic plants. Many chemical and biological reactions in ground water and surface water depend directly or indirectly on the amount of oxygen present. Dissolved oxygen is necessary in aquatic systems for the survival and growth of many aquatic organisms.” (water.usgs.gov, n.d.) According to Water Action Volunteers (2006), Different aquatic organisms have different oxygen needs. Trout and stoneflies, for example, require high dissolved oxygen levels. Trout need water with at least 6 mg/L D.O. Warm water fish like bass and bluegills survive nicely at 5 mg/L D.O. and some organisms like carp and bloodworms can survive on less than 1 mg/L D.O. The oxygen demand of aquatic plants and cold-blooded animals also varies with water temperature. A trout uses five times more oxygen while resting at 80˚F (26.7˚C.) than at 40˚ F (4.4˚C). Thus, dissolved oxygen plays a vital role in the sustainability of aquatic life. Since an adequate supply of oxygen is necessary to support life in a body of water, a determination of the amount of oxygen provides a means of assessing the quality of the water with respect to sustaining life. The methods that are most commonly used to measure dissolved oxygen (DO) can be done qualitatively or quantitatively. Qualitative methods can provide rough and rapid measurement and are often used for detecting dissolved oxygen based from colors. This kind of method can be easily used by non-professional operators. Qualitative determination may include the use of colorimetric method or using the modified Winkler method. Both methods require that the samples must be collected and processed without contact with air. It is because oxygen can easily diffuse into water sample during handling and altering the concentration of dissolved oxygen. (Katznelson, 2004) In colorimetric method, the sample fluid is sucked into an ampoule under vacuum (an ampoule is a sealed glass tube with an easy-to-break tip. Use of the ampoule involves breaking of the tip). Chemical reagents that are present in the ampoule in excess interact with oxygen to form a colored product (that absorbs light at a visible wavelength). The intensity of the color, which is proportional to the oxygen concentration in that sample, is compared to a series of tubes with color intensities that reflect known concentrations of dissolved oxygen and are expressed in units of mg/l (Katznelson, 2004). While in Winkler method, it is based on the oxidizing property of dissolved oxygen or the tendency of free oxygen to attach to certain ions (Katznelson, 2004). A standard chemical method to determine the amount of oxygen dissolved in a water sample is a modification of the Winkler Method. In this method, the precisely measured amounts of chemicals (reagents) are added to a water sample until a color change is achieved. A color change indicates that there is a presence of dissolved oxygen in the water sample (Behar, 1996). The Winkler test is used to determine the level of dissolved oxygen in water samples and to estimate the biological activity in the water sample. An excess of Manganese (II) salt, iodide (I-) and hydroxide (OH-) ions are added to a water sample causing a white precipitate of Mn(OH)2 to form. This precipitate is then oxidized by the dissolved oxygen in the water sample into a brown Manganese precipitate. In the next step, a strong acid is added to acidify the solution. The brown precipitates then convert the iodide ion (I-) to Iodine. The amount of dissolved oxygen is directly proportional to the free Iodine in the solution. (Katznelson, 2004) Oxygen gas dissolves freely in fresh water. Thus, oxygen from the atmosphere as well as that produced as a by-product of photosynthesis may increase the dissolved oxygen concentration in water. The distribution of dissolved oxygen (DO) within an aquatic environment may vary horizontally or vertically and with time. Its distribution is dependent upon atmospheric contact, biological activity of both plants and aquatic animals, wave and current actions, thermal phenomena, waste inputs and other factors. Dissolved oxygen may show fluctuations. Photosynthesis contributes to an increase in dissolved oxygen levels during the day. When the demand for oxygen is high and oxygen production from photosynthesis is not occurring dissolved oxygen can be low. But it can be replenished with the help from the aquatic plants that can rapidly photosynthesize like the Cabomba aquatica and Echinodorus amazonicus. Cabomba aquatica is commonly known as the Cabomba plant. Below is the detailed systematics for the classification of C. aquatica: Kingdom: Plantae Order: Nymphaeales Family: Nymphaeaceae Subfamily: Cabomboideae Genus: Cabomba Species: Cabomba aquatica Table 1.1 Cabomba aquatica The organisms under the family Nymphaeaceae, where Cabomba belongs, are aquatic, rhizomatous herbs. “Cabomba grows in ponds, lakes and quiet streams. It is generally rooted in water 1–3 m deep (down to 6 m deep water clarity permitting) but can continue to grow free-floating if uprooted. It does well in both cool and warm waters but does not tolerate overly warm water (above 30 °C). Cabomba prefers slightly acidic to neutral water (pH 6–7) and alkaline waters (pH >8) are not conducive to its growth. Cabomba needs fine substrates that provide sufficient nutrients for healthy growth. Cabomba, or fanwort, is a fully submerged aquatic plant, originally introduced into Australia as an aquarium plant.” (Mackey, 2013) “Cabomba is an aggressive invader of native freshwater systems. It out competes native freshwater plants and presumably has a negative impact on native fish and aquatic invertebrates. Dense infestations impede aquatic recreational activities and the risk of drowning from entanglement is a danger to swimmers. Cabomba is a popular aquarium plant. However, if released into natural waterways, its rapid growth allows it to dominate native vegetation and obstruct creeks and wetlands, lakes and dams. Recent research indicates Cabomba adversely affects water quality by imparting color and taints. This increases the cost of treating potable water and impairs the sustainable use of drinking water storages. Broken Cabomba stems can interfere with water infrastructure by blocking water intake pipes.” (The State of Queensland Department of Agriculture, Fisheries and Forestry, 2013) Like Cabomba aquatica, Echinodorus amazonicus is also an aquarium plants. It is commonly known as the Amazon Sword plant. Below is the detailed systematics for the classification of E. amazonicus: Kingdom: Plantae Order: Alismatales Family: Alismataceae Genus: Echinodorus Species: Echinodorus amazonicus Table 1.2 Echinodorus amazonicus The organisms under the order Alistamales are monocotyledons. The organisms under the family Alismataceae, where E. amazonicus belongs, are aquatic, rhizomatous herbs. “This species prefers softer water and needs carbon dioxide (CO2) fertilization to look its best. Old leaves that shed frequently and new "glassy" looking yellowish leaf buds is a sign that it is suffering from bad lighting or iron deficiency and liquid fertilizer should be added. The related Echinodorus bleheri is a related sword also often called Amazon that tolerates slightly harder water.” (Aquahobby, 2011) “Echinodorus bleheri does well even in poorly illuminated aquariums, as it grows towards the light.” (Tropica, n.d.) Cabomba aquatica and Echinodorus amazonicus are autotrophs. These are organisms that are capable of producing their own food to sustain life. Autotrophs make use of inorganic compounds to synthesize organic compounds. This process is referred to as photosynthesis. Below is the balanced equation for the process of photosynthesis in plants: 6 CO2 + 7 H2O C6H12O6 + 6 O2 According to Caraco (2006), the chemical changes induced by organisms can alter habitat quality and the availability of resources to other organisms. Of the many chemical changes engineered by organisms, perhaps the most important are the past and present effects of organisms on oxygen levels in the atmosphere, soils and aquatic ecosystems. In addition to habitat considerations, the presence of oxygen determines the extent to which some organic compounds are decomposed or preserved, and chemical processes at the oxic-anoxic interface can strongly influence the cycling of limiting nutrients for autotrophic and heterotrophic production, including nitrogen, phosphorus, and iron. Hydrological and physical features strongly influence external inputs of both oxygen and organic carbon. However, organisms can also influence these transfers substantially both by modifying the hydrological and physical features of a system and by directly transferring organic carbon or oxygen, or both, across habitat or even ecosystem boundaries. Vascular plants are diverse group of organisms that dominate the shallows of many lakes, rivers, and estuaries. They act as “hot spots” of metabolism and serve as habitat for animals. Vascular aquatic plants that are completely submersed can transfer organic material within the confines of the aquatic ecosystem. Plants with floating or emergent leaves, on the other hand, can transfer substantial amounts of organic carbon to the aquatic ecosystem from leaves whose photosynthesis occurs in the overlying atmosphere. Aquatic plants, through their production, consumption and transport of oxygen, can generate strong oxygen gradients in space and time and be engineers of redox-related biogeochemical hot spots. Aquatic plants provide oxygen to aquatic environments. METHODOLOGY Materials In this study, the necessary materials were set in order to perform the qualitative determination of the dissolved oxygen level in water. The glasswares and the reagents used were provided by the University of Santo Tomas Laboratory Equipment and Supplies Office in the College of Education. The glasswares that were prepared for the experiment include six (6) 1000 mL beakers, eighteen (18) test tubes, two (2) test tube racks, and two (2) 250 mL beakers. The procedure also required the use of reagents specifically, 40% Manganese sulfate (MnSO4), alkaline–iodine solution and concentrated phosphoric acid (H3PO4) to react with the water sample. The three (3) 50 mL syringe was purchased in a drug store while the plastic wrap (was bought in a grocery store. The sample water that was used for the qualitative testing of dissolved oxygen originated from the two (2) sets of the prepared water samples containing a tap water with a different kind of aquatic plant soaked in each set. The tap water came from the normal faucet in the laboratory. The two aquatic plants namely, Echinodorus amazonicus and Cabomba aquatica were purchased in a pet shop. Sample preparation The water sample was collected directly from the faucet. The 1000 mL of tap water was placed in each three (3) 1000 mL beaker and was labeled with A, B and C. The weight of the two (2) aquatic plants respectively, Cabomba aquatica and Echinodorus amazonicus were obtained using a platform balance. The first aquatic plant (Cabomba aquatica) was placed in beaker B and the second plant (Echinodorus amazonicus) was placed in beaker C while beaker A was left without a plant to serve as a control set-up. The beakers were covered with a plastic wrap and had been placed outside the laboratory to let the first set-up be exposed to sunlight for one week. The procedure was repeated using the same tap water and aquatic plants and placed under the same place were the first set-up was placed but this time, the second set-up had been exposed to sunlight for two days only. Determination of Dissolved Oxygen Level The modified Winkler Method was used to qualitatively determine the presence of dissolved oxygen in the water sample. The water samples were obtained and were brought back to the laboratory. Two set-ups of water samples were made and each set-up had three beakers: Beaker A (without plant, control), Beaker B (with Cabomba aquatica) and Beaker C (Echinodorus amazonicus). Schematic Diagram of the Procedure In a 50 mL syringe with a removed plunger, a few small pieces of stones were placed inside it and the plunger was then pushed until it reached the other end. When the syringe needle was ready, 10 mL of 40% MnSO4 solution was drawn and the syringe was held in a vertical position with the needle pointing upward. Afterwards, the needle was totally immersed into the water sample and an 8 mL of it was drawn. A 0.5 mL of alkaline iodine solution was also drawn. Then, the syringe was held in a horizontal position and was slowly rotated to allow the contents to be mixed. The syringe containing the water sample solution was laid on the table for five minutes to enable the precipitate to absorb the dissolved oxygen in the sample. With the syringe still in horizontal position, a 0.5 mL of concentrated H3PO4 was drawn and was rotated to be mixed with the solution. The solution was then transferred into a test tube and was covered well. The solution was observed and the results that were gathered in the beaker A served as the basis for comparing the amount of dissolved oxygen in the other water samples in Beaker B and beaker C. The procedures were repeated but this time, the sample water with the plants submerged was used. The same procedure was also done to the second set-up and the color intensity produced by the reactions were collected and used. In every step of the method make sure that the syringe must be submerged just below the surface of the water to prevent the penetration of unwanted particles present in the air that may interfere with the results. RESULTS AND DISCUSSION There are several methods to determine the dissolved oxygen concentration in water systems. In this study, the qualitative determination was used through the modified Winkler Method. The dissolved oxygen in the water sample is "fixed" by adding a series of reagents that form an acid compound that results in a color change. The color change coincides with the dissolved oxygen concentration in the sample. Table 2 – Content of the Water Sample Beaker A Beaker B Beaker C 1000 mL tap water 1000 mL tap water 1000 mL tap water No aquatic plant With Cabomba aquatica (23g) With Amazon Sword plant (23 g) For the first step in the procedure is the incorporation of water with the 40% MnSO4 that produced Mn(OH)2. The Mn(OH)2 will then react with the oxygen wherein two possible reactions occur: Mn(OH)2 + 2H2O + 2O2 → 4Mn(OH)3 which will produce a brownish inorganic oxide suspended in the water sample with the aquatic plants, or Mn(OH)2 + O2 → 4MnO(OH)3 + 2H2O which will also produce a brown solution. The addition of the alkaline-iodine solution is added to react with the Mn2+ ions and OH- salt with Mn. The Mn(OH)3 precipitate formed was then dissolved with the concentrated H3PO4 while the MnO(OH) precipitate will react with the iodide ions from the alkaline iodide solution: 6H+ + Mn(OH) (s) + 2I- → 2Mn2+ + I2 + 4H2O. The I2 produced in the desired reaction will be equivalent to the amount of dissolved oxygen in the water sample. Table 3.1 – Aquatic Plants Submerged for ONE WEEK (February 7 – 14, 2014) Beaker A Beaker B Beaker C Trial 1 Clear, transparent Turbid light yellow-brown Turbid lighter yellow-brown Trial 2 Clear, transparent Turbid light yellow-brown Turbid lighter yellow-brown Trial 3 Clear, transparent Turbid light yellow-brown Turbid lighter yellow-brown The set-up immersed for 7 days: Beaker A, as expected yielded a negative results; it did not have a brown precipitate or a brown coloration of the solution. Beaker B which has the Cabomba aquatica gave positive results by having a brown precipitate and brown coloration of the solution, same as the Beaker C which has the Echinodorus amazonicus. The only difference in the results is the color intensity of the two solutions; Beaker B has a darker intensity compared to Beaker C, meaning that the Cabomba aquatica yielded a relatively more amount of dissolved oxygen. Table 3.2 – Aquatic Plants Submerged for TWO DAYS (February 12 – 14, 2014) Beaker A Beaker B Beaker C Trial 1 Clear, transparent Turbid light yellow-brown Turbid faint yellow-brown Trial 2 Clear, transparent Turbid light yellow-brown Turbid faint yellow-brown Trial 3 Clear, transparent Turbid light yellow- brown Turbid faint yellow-brown For the setup immersed for 2 days, Beaker A, also yielded negative results, it did not have a brown precipitate or a brown coloration of the solution. Beaker B which has the Cabomba aquatica gave positive results by having a brown precipitate and brown coloration of the solution, same as the Beaker C which has the Echinodorus amazonicus. The only difference in the results is the color intensity of the two solutions; Beaker C has a lighter color intensity compared to Beaker B, meaning that the Cabomba aquatica in Beaker B yielded a relatively more amount of dissolved oxygen than the Echinodorus amazonicus in Beaker C. Visual Interpretation of the Color Intensity of the Solution Beaker A Beaker B Beaker C The overall results, based from the data gathered shows that a relative amount of dissolved oxygen is liberated by the aquatic plants on the tap water, characterized by the brown precipitate and brown coloration of the solution. Among the two aquatic plants used, the Cabomba aquatica liberated more dissolved oxygen than the Echinodorus amazonicus characterized by the former with a darker brown intensity compared to that of the latter. The oxygen liberated was a result of the photosynthesis of the plants as they are exposed to light, one week for the first soaking and 2 days for the second soaking. The amount of time the plants are immersed also contributed to the yield of results as having a longer time of being immersed liberated more dissolved oxygen than being immersed for a short duration of 2 days. For the control, or the beaker without the aquatic plants showed negative results indicating the absence of dissolved oxygen in tap water. CONCLUSION Based from the data obtained in our results, it can be said that a relative amount of oxygen is liberated by both plant specimens, namely: Cabomba aquatica and Echinodorus amazonicus. The presence of oxygen in water is characterized by the brown precipitate and coloration of the solution. The oxygen liberated and tested for is the by-product of the photosynthesis of the two plant specimens. We therefore conclude that the longer we soak the C. aquatica and the E. amazonicus in water, the more oxygen they would liberate, dissolving in the water. The test results also indicate that the C. aquatica liberated more oxygen than the E. amazonicus. Because of this, it can also be said that the C. aquatica and the E. amazonicus are not just pests in different bodies of water but they can also be used for sustaining life and in fact can be beneficial in rehabilitating different bodies of water. Biologically speaking, the dissolved oxygen is absolutely essential for the survival of all aerobic aquatic organisms such as fish, crabs and even zooplanktons. Moreover, dissolved oxygen level affects a vast number of other water indicators, not only biochemical but esthetic ones like the odor, clarity and taste. Consequently, oxygen is perhaps the most well-established indicator of water quality. The researchers recommend that the test samples should be exposed to the sun at a longer period of time to liberate more oxygen and gain more accurate results. The researchers also suggest using different types of indicator of dissolved oxygen concentration for acquiring an accurate data about the sample. Furthermore, additional qualitative methods (e.g. colorimetric method) in detecting dissolved oxygen are also commended to give more opportunities in determining the presence of dissolved oxygen. BIBLIOGRAPHY Burton, L.D. (2009). Fish and wildlife: principles of zoology and ecology (3rded.). Clifton Park, NY: Delmar, Cengage Learning. Bruckner, M. Z. (2013). The Winkler Method - Measuring Dissolved Oxygen. Retrieved March 9, 2014, from http://serc.carleton.edu/microbelife/research_methods/environ_sampling/oxygen.html Caraco, N. et al. (2006). Vascular plants as engineers of oxygen in aquatic systems. Bioscience, vol. 53, no. 3. McLean, VA: American Institute of Biological Sciences. Dagmang, N. (2011). Experiment 9 Results and Discussion Report: Redox Titration: Winkler Method for Dissolved Oxygen Determination. Retrieved March 9, 2014, from http://www.scribd.com/doc/51635425/Experiment-9-Results-and-Discussion-Report-Redox-Titration-Winkler-Method-for-Dissolved-Oxygen-Determination DeVere, B. L. (2009). Fish & wildlife: Principles of Zoology and Ecology. Clifton Park, NY: Delmar, Cengage Learning. Helmenstine, A. M. (2014). What is the chemical composition of air? Retrieved March 06, 2014 from http://chemistry.about.com/od/chemistryfaqs/f/aircomposition.htm Judd, W. S. et al. (2008). Plant Systematics: A phylogenetic approach (3rd ed). Sunderland, Mass.: Sinauer Associates. Katznelson, R. (2004). Dissolved Oxygen Measurement Principles and Methods. The Clean Water Team Guidance Compendium for Watershed Monitoring and Assessment, California: California State Water Resources Control Board Manahan, S. E. (2010). Environmental Chemistry. Boca Raton: Taylor & Francis. Sawyer, C. N., McCarty, P. L., & Parkin, G. F. (2003). Chemistry for environmental engineering and science (5th ed). Boston: McGraw-Hill. Williams, I. (2001). Environmental Chemistry: A modular approach. Chichester: John Wiley & Sons. ACKNOWLEDGEMENT We would like to express our deepest and sincerest gratitude to all the people who helped us to come up with our very own study especially to our research adviser and NS106 Environmental Science professor, Assistant Professor Rosario R. Cabusao for patiently guiding us in our research—thank you for evaluating our work by sharing with us your significant suggestions and comments and for all the support, encouragement and genuine concern she gave to us; to our laboratory technician, Mr. Ronald Balbin and Mr. Ramon Bayson, for being at our aid with the materials needed for the study; to the whole 3rd Year Secondary Education-Biological Sciences majors namely: Paolo, Dayan, Angela, Koko, Gemina, Johanna, Luisa, Anne and Marian for always being there to uplift our spirit while we are doing this study; to our parents who loved and supported us in everything that we did and the encouragement they gave us to accomplish this study; and most of all, to God who gave us the wisdom and persistence to finish this study. APPENDICES: Plants used: C. aquatica and E. amazonicus Three 1000 mL beakers (A, B and C) filled with tap water Plants were submerged in water and covered with plastic wrap. Two setups were prepared. Setup 1 was exposed to sunlight for one week and setup 2 for two days. Two setups were prepared with three beakers each. Experimentation Results of Trial 2 Results of Trial 1 Comparison of results: Topmost syringe contains water from controlled setup (A), middle syringe contains water from beaker with C. aquatica (B), and bottom syringe contains water from beaker with E. amazonicus (C). Brown coloration of solution indicates the presence of O2. Intensity of the color dictates concentration of O2 in water. Reagents: 40% MnSO4, Alkaline-iodine solution & H3PO4 (from left to right) Members of Group 1 presenting the research paper to Class 3BSM and Asst. Prof. Rosario Cabusao last March 10, 2014.