PDF | Photosynthesis and cellular respiration are two processes that transform energy and affect concentrations of carbon Dissolved oxygen (DO) levels in various zones of a lake. standing of the relationship between photosynthesis and. The solubility of oxygen, or its ability to dissolve in water, decreases as water Plants and algae produce oxygen during the day as a by-product of photosynthesis. Animals use oxygen in cellular respiration processes to transform digested. Chemical processes. Differences in water temperature and density between layers of water in a lake leads to stratification and seasonal turnover. Dissolved oxygen comes from the atmosphere and from photosynthesis by aquatic plants.
Microbes reduce DO levels in estuaries when they decompose organic matter using oxygen. Animals use oxygen in cellular respiration processes to transform digested organic matter into energy. Due to the shifting balance of physical, chemical and biological processes, DO levels in estuaries vary both seasonally and diurnally daily. Hot, still conditions and periods of high biological activity during summer months can lead to dangerously low DO levels in estuaries.
Highly productive shallow water areas are most likely to become oxygen-depleted at night during the summer when temperature and respirations rates are high, or after a period of cloudy days when the supply of oxygen from photosynthesis is reduced.
Other parts of the Bay, especially the deep channel of the main stem, develop persistent hypoxia or anoxia during the late spring and summer months. Dissolved oxygen levels may remain below the critical threshold for months. This area is referred to as the Bay's "dead zone" where few organisms other than bacteria and Archaea live. Large nutrient inputs are especially problematic for estuaries because they may stimulate algal blooms, which subsequently support high levels of respiration.
In turbid water, this photic light-penetrating zone is often much shallower. The basic reaction of aquatic photosynthesis remains: At equilibrium, the percentage of each gas in the water would be equivalent to the percentage of that gas in the atmosphere — i.
The water will slowly absorb oxygen and other gasses from the atmosphere until it reaches equilibrium at complete saturation What Affects Oxygen Solubility?
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This is true of both atmospheric and hydrostatic pressures. Water at lower altitudes can hold more dissolved oxygen than water at higher altitudes.
As oxygen in the atmosphere is about However, there are several factors that can affect this. 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. 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.
What is the relationship between oxygen and photosynthesis?
As water temperature rises, oxygen solubility decreases. 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.
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. For example, a deep, shaded pool is cooler than a shallow, sunny area. In lakes, temperature can vary with depth, according to the level of solar radiation penetration and mixing characteristics.
Human activities affecting water temperature can include the discharge of cooling water or heated industrial effluents, agriculture and forest harvesting due to effects on shadingurban development that alters the characteristics and path of stormwater runoff, and climate change. Dissolved Oxygen The amount of oxygen that dissolves in water can vary in daily and seasonal patterns, and decreases with higher temperature, salinity, and elevation.
Dissolved oxygen comes from the atmosphere and from photosynthesis by aquatic plants, and is depleted through chemical oxidation and respiration by aquatic animals and microorganisms, especially during the decomposition of plant biomass and other organic material. Surface water, near the water-atmosphere interface and with sufficient light for photosynthesis, is generally saturated or even supersaturated with oxygen.
Deeper water receives oxygen through mixing by wind, currents, and inflows. Mixing and aeration also occur at waterfalls and rapids. Dissolved oxygen can be reduced to very low levels during the winter months when water is trapped under ice.How does temperature affect dissolved oxygen levels