Activity 1: Using the Level of Oxygen- Saturation Chart graph Dissolved Oxygen vs. Temperature at 100% saturation. Start by making a 2 column table. Number the first column with temperatures from 0 to 30 C by 5 s. Extend a straight edge from each temperature, across 100% saturation to determine the dissolved oxygen in mg/l.
Activity 2: Given the data below, complete the table using the % saturation chart. Temperature ( C) Dissolved Oxygen (mg/l) % Saturation 15 8 15 12 20 12 18 90 10 110 8 70 10 80 Activity 3: Interpretation of dissolved oxygen and temperature data. Dissolved Oxygen (explanation from Pathfinderscience.net) Dissolved oxygen is the term for atmospheric oxygen that becomes mixed in water and occurs between the water molecules. The presence of oxygen in water is good. Dissolved oxygen is necessary for healthy lakes and rivers. Most aquatic plants and animals need oxygen to survive. Fish will drown in water when the dissolved oxygen levels get too low. The absence of dissolved oxygen in water is a sign of possible pollution. Most dissolved oxygen gets into the water from contatct with the atmosphere. Waves on lakes and slowmoving rivers, water tumbling over riffles or waterfalls on fast- moving rivers mixes oxygen into the water. Anything that increase the surface contact of water and the atmosphere will increase oxygen in the water. Plants and algae also add oxygen to the water through photosynthesis. Because plants need light for photosynthesis, dissolved oxygen levels tend to be highest in the late afternoon and lowest at dawn. Temperature has a very big affect on oxygen levels. In order to determine a Water Quality Index, it is necessary to determine the Percent Saturation. It may seem strange, but cold water holds more dissolved oxygen than warm water. Think about it this way. If you opened two cans of pop and placed one in the refrigerator and left one at room temperature, which do you think would lose its fizz first? In the winter, dissolved oxygen levels are usually higher than in summer. That is why fish kills usually occur in late summer just before dawn. Climate can affect oxygen levels in other ways. During dry seasons water levels decrease and the flow rate or discharge of a river is lower. As the water moves slower, it mixes less with the air; and the dissolved oxygen level goes down. During rainy seasons oxygen levels tend to be higher. The main man-made factor causing dissolved oxygen levels to change in a negative way involves the build-up of organic wastes. Organic wastes are the remains of any living or once-living thing. Leaves, grass clippings, dead plants or animals, and sewage are examples of organic wastes that can lower oxygen levels in water. Organic wastes are decomposed by bacteria which take oxygen out of the water. When people dump organic wastes into lakes and streams it causes dissolved oxygen levels to decrease which can harm the aquatic life. When dissolved oxygen levels get lower, they can cause major changes in the types and amounts of aquatic organisms found living in the water. Species that need high levels of dissolved oxygen such as mayfly nymphs, stonefly nymphs, caddisfly larvae, pike, trout, and bass will move out or die. They will be replaced by organisms such as sludge worms, blackfly larvae, and leeches which can tolerate lower dissolved oxygen levels.
1. What does the data on this graph represent? 2. Identify the variables on the axes: X: Left Y: Right Y: 3. According to the graph how does temperature change through the seasons? 4. According to the graph how does oxygen change through the seasons? 5. Assuming there is no pollution influencing the patterns you described in 4 and 5, why does this make sense? 6. What aspects of this graph make it clear in regards to communicating to a reader?
Activity 4: Interpretation dissolved oxygen and fecal coliform data. Fecal Coliform (explanation from Pathfinderscience.net) Bacteria are single-celled organisms that can only be seen with the aid of a very powerful microscope. Bacteria can be found everywhere- in air, water, soil, even in and on your own body. They can benefit us by recycling wastes, fixing nitrogen helping plants to grow, and by making certain types of food. They may harm us by causing diseases and food spoilage. Bacteria reproduce rapidly if conditions are right for growth. Most bacteria grow best in dark, warm, moist environments with food. Some bacteria form colonies as they multiply which may grow large enough to be seen. By growing and counting colonies of fecal coliform bacteria from a sample of stream water, we can determine approximately how many bacteria were originally present. There are many types of coliform bacteria. Coliform bacteria naturally occur in the human digestive tract and aid in the digestion or breakdown of food. Fecal coliform bacteria are found in the feces of humans and other warm-blooded animals. Fecal coliform bacteria can enter rivers through direct discharge of waste from mammals and birds, from agricultural and storm runoff, and from untreated human sewage. Fecal coliform bacteria are indicator organisms. This means that fecal coliform does not cause disease in humans but it may indicate the presence of other pathogenic bacteria. Fecal coliform bacteria are a type of E. coli bacteria that is not pathogenic; they will NOT make you sick. However, some coliform are pathogenic. Water is tested for fecal coliform because it is a safe, inexpensive way to determine if other, harmful bacteria could be present. If fecal coliform counts are high (over 200 colonies/100 ml of water sample), it is very likely that pathogenic organisms are also present. Diseases and illnesses such as typhoid fever, hepatitis, gastroenteritis, dysentery, and ear infections may result from contact with water having such pathogenic organisms. Fecal coliform like other bacteria can usually be killed by boiling water or by treating it with chlorine. Washing thoroughly with soap after contact with contaminated water can also help prevent infections. Gloves should always be worn when testing for fecal coliform to protect against infection by some of it's disease causing friends.
1. How do fecal coliform counts relate to dissolved oxygen? 2. Why is it more meaningful to graph % saturation of dissolved oxygen rather than the amount in mg/l. Activity 5: Interpreting dissolved oxygen and turbidity data Turbidity (explanation from Pathfinderscience.net) Turbidity refers to how clear the water is. The greater the turbidity, the murkier the water. Turbidity increases when the amount of suspended solids in the water increases. Clay, silt, plankton, industrial wastes and sewage are common suspended solids. High turbidity may be caused by; soil erosion, waste discharge, urban runoff, flooding, dredging operations, channelization, increased flow rates, algae growth, or even too many bottom-feeding fish (such as carp) that stir up bottom sediments. If water becomes too turbid, it loses the ability to support a wide variety of plants and other aquatic organisms. Increased turbidity can affect a stream and the organisms that live in it in many ways. Suspended solids may cause the water color to change. Turbid waters usually become warmer as suspended solids which darken the water absorb heat from sunlight. Warm water holds less oxygen than cold water, so oxygen levels will decrease. Suspended solids reduce the amount of light that can pass through the water. As less light penetrates the water, photosynthesis slows releasing less oxygen into the water. If light is blocked to bottom dwelling plants, they will cease to produce oxygen and will die. As they decompose, bacteria will use up even more oxygen from the water. Suspended solids can clog fish gills, reduce their growth rates, decrease their resistance to disease, and prevent proper egg and larval development. As particles of silt, clay, and other organic materials settle to the bottom, they can suffocate newly hatched larvae. Settling sediments can fill in spaces between rocks which could have been used by aquatic organisms for homes.
1. Describe the relationship in the data between changes in turbidity as it relates to dissolved oxygen. 2. If this relationship were causal, explain the reasons for it. 3. Since other variables could be in part responsible for changes in dissolved oxygen, propose additional analyses that would help determine whether or not high turbidity is the main cause of changes in dissolved oxygen.
Putting it All Together: 1. Teams study watershed map with water quality data attached and revisit Key Question. 2. Teams form conclusions about the streams water quality based on water quality data. 3. Teacher facilitates a whole class dialog that address the Key Question. Note on Land Use and Water Quality: Agriculture may use organic fertilizers that may come from coliform rich manure. Deforestation and development may introduce sediment to the river, increasing turbidity.