Standard Salinity Profile - Windows to the Universe
RELATIONSHIP BETWEEN OCEAN DEPTH AND SEA FLOOR AGE IN THE NORTH ATLANTIC AND THE HISTORY OF CONTINENTAL. What is the relationship between DO and ocean depth? The shallow water at the surface conatins a lot of disloved oxygen because the water moves, there is. In general the relationship between dissolved oxygen and nitrate is complex. While in areas of water mass formation, especially in the Arctic.
The aeration of water can be caused by wind creating wavesrapids, waterfalls, ground water discharge or other forms of running water. Man-made causes of aeration vary from an aquarium air pump to a hand-turned waterwheel to a large dam.
Dissolved oxygen is also produced as a waste product of photosynthesis from phytoplankton, algae, seaweed and other aquatic plants 8. Dissolved Oxygen from Photosynthesis Dissolved oxygen can enter the water as a byproduct of photosynthesis. While most photosynthesis takes place at the surface by shallow water plants and algaea large portion of the process takes place underwater by seaweed, sub-surface algae and phytoplankton.
Light can penetrate water, though the depth that it can reach varies due to dissolved solids and other light-scattering elements present in the water.
In clear water, there is no longer enough light for photosynthesis to occur beyond m, and aquatic plants no longer grow. 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? 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.
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. 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 same schlieren can be observed when hot air rises off the tarmac at airports or desert roads and is the cause of mirages. Other water bodies[ edit ] Thermoclines can also be observed in lakes. In colder climates, this leads to a phenomenon called stratification. During the summer, warm water, which is less dense, will sit on top of colder, denser, deeper water with a thermocline separating them.
The warm layer is called the epilimnion and the cold layer is called the hypolimnion. Because the warm water is exposed to the sun during the day, a stable system exists and very little mixing of warm water and cold water occurs, particularly in calm weather. One result of this stability is that as the summer wears on, there is less and less oxygen below the thermocline as the water below the thermocline never circulates to the surface and organisms in the water deplete the available oxygen.
As winter approaches, the temperature of the surface water will drop as nighttime cooling dominates heat transfer. A point is reached where the density of the cooling surface water becomes greater than the density of the deep water and overturning begins as the dense surface water moves down under the influence of gravity.
Thermocline - Wikipedia
This process is aided by wind or any other process currents for example that agitates the water. This effect also occurs in Arctic and Antarctic waters, bringing water to the surface which, although low in oxygen, is higher in nutrients than the original surface water. This enriching of surface nutrients may produce blooms of phytoplanktonmaking these areas productive.
During this transition, a thermal bar may develop.
- Dissolved Oxygen
- What is the relationship between DO and ocean depth?
Waves can occur on the thermocline, causing the depth of the thermocline as measured at a single location to oscillate usually as a form of seiche. Alternately, the waves may be induced by flow over a raised bottom, producing a thermocline wave which does not change with time, but varies in depth as one moves into or against the flow.
Atmosphere[ edit ] The lower atmosphere also typically contains a boundary between two distinct regions the troposphere and stratospherebut that boundary the tropopause displays quite different behavior. However, atmospheric thermoclines, or inversionscan occur, e.
The coldest air is next to the ground, with air temperature increasing with height.