Yung_alpaca's interactive graph and data of "Relationship Between Temperature and Dissolved Oxygen Concentration in Water" is a scatter chart, showing. Chart showing the inverse relation between temperature and dissolved oxygen. As this chart shows, the concentration of dissolved oxygen in. Find the correlation between water temperature and dissolved oxygen. manipulating the data using the MS Excel correlation, formula and chart functions .
If oxygen is present, a brownish-orange cloud of precipitate or floc will appear. When this floc has settle to the bottom, mix the sample by turning it upside down several times and let it settle again. Add 2 mL of concentrated sulfuric acid via a pipette held just above the surface of the sample. Carefully stopper and invert several times to dissolve the floc.
At this point, the sample is "fixed" and can be stored for up to 8 hours if kept in a cool, dark place. As an added precaution, squirt distilled water along the stopper, and cap the bottle with aluminum foil and a rubber band during the storage period.
In a glass flask, titrate mL of the sample with sodium thiosulfate to a pale straw color. Titrate by slowly dropping titrant solution from a calibrated pipette into the flask and continually stirring or swirling the sample water.
Add 2 mL of starch solution so a blue color forms. Continue slowly titrating until the sample turns clear. As this experiment reaches the endpoint, it will take only one drop of the titrant to eliminate the blue color. Be especially careful that each drop is fully mixed into the sample before adding the next. It is sometimes helpful to hold the flask up to a white sheet of paper to check for absence of the blue color.
Aquatic respiration and decomposition lower DO concentrations, while rapid aeration and photosynthesis can contribute to supersaturation. During the process of photosynthesis, oxygen is produced as a waste product.
Dissolved Oxygen by the Winkler Method
In addition, the equalization of water is a slow process except in highly agitated or aerated situations. Supersaturation of water can be caused by rapid aeration from a dam. Unlike small rapids and waves, the water flowing over a dam or waterfall traps and carries air with it, which is then plunged into the water.
As water temperature rises, oxygen solubility decreases.
Water Quality Indicators: Temperature and Dissolved Oxygen
But if there is no wind to move the equilibration along, the lake will still contain that initial 9. Typical Dissolved Oxygen Levels Dissolved oxygen concentrations can fluctuate daily and seasonally.
Dissolved oxygen concentrations are constantly affected by diffusion and aeration, photosynthesis, respiration and decomposition. In freshwater systems such as lakes, rivers and streams, dissolved oxygen concentrations will vary by season, location and water depth. Dissolved oxygen levels often stratify in the winter and summer, turning over in the spring and fall as lake temperatures align. In rivers and streams, dissolved oxygen concentrations are dependent on temperature. Saltwater holds less oxygen than freshwater, so oceanic DO concentrations tend to be lower than those of freshwater.
World Ocean Atlas ; photo credit: Examples of Freshwater Organisms and Dissolved Oxygen Requirements Minimum dissolved oxygen requirements of freshwater fish Coldwater fish like trout and salmon are most affected by low dissolved oxygen levels The mean DO level for adult salmonids is 6.
Water's the Matter--Lesson Presentation: Dissolved Oxygen
The mean DO levels should remain near 5. The freshwater fish most tolerant to DO levels include fathead minnows and northern pike. Northern pike can survive at dissolved oxygen concentrations as low as 0. If all the oxygen at their water level gets used up, bacteria will start using nitrate to decompose organic matter, a process known as denitrification.
If organic matter accumulates faster than it decomposes, sediment at the bottom of a lake simply becomes enriched by the organic material. This does not mean that saltwater fish can live without dissolved oxygen completely. The red hake is also extremely sensitive to dissolved oxygen levels, abandoning its preferred habitat near the seafloor if concentrations fall below 4.
The dissolved oxygen requirements of open-ocean and deep-ocean fish are a bit harder to track, but there have been some studies in the area.
Billfish swim in areas with a minimum of 3. Likewise, white sharks are also limited in dive depths due to dissolved oxygen levels above 1. Tracked swordfish show a preference for shallow water during the day, basking in oxygenated water 7. Albacore tuna live in mid-ocean levels, and require a minimum of 2. Many tropical saltwater fish, including clown fish, angel fish and groupers require higher levels of DO, such as those surrounding coral reefs.
Coral reefs are found in the euphotic zone where light penetrates the water — usually not deeper than 70 m. Crustaceans such as crabs and lobsters are benthic bottom-dwelling organisms, but still require minimum levels of dissolved oxygen. Consequences of Unusual DO Levels If dissolved oxygen concentrations drop below a certain level, fish mortality rates will rise. In the ocean, coastal fish begin to avoid areas where DO is below 3. It can be species-based or a water-wide mortality.
Fish kills can occur for a number of reasons, but low dissolved oxygen is often a factor. Dissolved oxygen depletion is the most common cause of fish kills When a body of water is overproductive, the oxygen in the water may get used up faster than it can be replenished. This occurs when a body of water is overstocked with organisms or if there is a large algal bloom die-off. Fish kills are more common in eutrophic lakes: High levels of nutrients fuel algae blooms, which can initially boost dissolved oxygen levels.
But more algae means more plant respiration, drawing on DO, and when the algae die, bacterial decomposition spikes, using up most or all of the dissolved oxygen available.
This creates an anoxic, or oxygen-depleted, environment where fish and other organisms cannot survive. They occur when the water is covered by ice, and so cannot receive oxygen by diffusion from the atmosphere. If the ice is then covered by snow, photosynthesis also cannot occur, and the algae will depend entirely on respiration or die off. In these situations, fish, plants and decomposition are all using up the dissolved oxygen, and it cannot be replenished, resulting in a winter fish kill.
Gas Bubble Disease Sockeye salmon with gas bubble disease Just as low dissolved oxygen can cause problems, so too can high concentrations. Extended periods of supersaturation can occur in highly aerated waters, often near hydropower dams and waterfalls, or due to excessive photosynthetic activity.
This is often coupled with higher water temperatures, which also affects saturation. Dead Zones A dead zone is an area of water with little to no dissolved oxygen present. They are so named because aquatic organisms cannot survive there. They can occur in large lakes and rivers as well, but are more well known in the oceanic context. Hypoxic and anoxic zones around the world photo credit: NASA These zones are usually a result of a fertilizer-fueled algae and phytoplankton growth boom.
These anoxic conditions are usually stratified, occurring only in the lower layers of the water. Naturally occurring hypoxic low oxygen conditions are not considered dead zones. Such naturally occurring zones frequently occur in deep lake basins and lower ocean levels due to water column stratification.
Dissolved Oxygen and Water Column Stratification Stratification separates a body of water into layers. This layering can be based on temperature or dissolved substances namely salt and oxygen with both factors often playing a role. The stratification of water has been commonly studied in lakes, though it also occurs in the ocean.
It can also occur in rivers if pools are deep enough and in estuaries where there is a significant division between freshwater and saltwater sources. Lake Stratification Lake stratification The uppermost layer of a lake, known as the epilimnion, is exposed to solar radiation and contact with the atmosphere, keeping it warmer. Within this upper layer, algae and phytoplankton engage in photosynthesis. The exact levels of DO vary depending on the temperature of the water, the amount of photosynthesis occurring and the quantity of dissolved oxygen used for respiration by aquatic life.
Below the epilimnion is the metalimnion, a transitional layer that fluctuates in thickness and temperature. Here, two different outcomes can occur. This means that the dissolved oxygen level will be higher in the metalimnion than in the epilimnion.The Effects of Salinity and Temperature on Dissolved Oxygen
The next layer is the hypolimnion. If the hypolimnion is deep enough to never mix with the upper layers, it is known as the monimolimnion. The hypolimnion is separated from the upper layers by the chemocline or halocline.