What is anoxic water ?!

Anoxic Water

Oxygen in water?

• Just like the air in the atmosphere contains various types of gases and components, water bodies not only consist of h2o molecules but also a percentage of gases.

• The atmosphere contains about 26% oxygen, while a water body usually contains only about 0.009% oxygen.

How does oxygen enter a water body?

A) Diffusion : oxygen particles move from high to low concentrations.

B) Aeration: a water body that is moving and crashing into rocks for example creates more surface area allowing more oxygen to enter.

C)Waste Products of aquatic plants.

How much dissolved oxygen do organisms need?

• Cold water organisms require a minimum DO (dissolved oxygen) level of at least 6.0 mg/L.

• In Warm water organisms if the DO level drops below 4.0-5.0 mg/L, the organisms will become stressed and erratic behavior is induced.

Causes of Anoxic Water

• Temperature:  The lower the temperature, the higher the amount of dissolved oxygen in a body of water;  the opposite is also true.
• Altitude: As altitude increases, the atmospheric pressure decreases.  Thus, the amount of oxygen diffused into the water decreases.

• Organic material: Organic material comes from parts of trees and plants that fall into a body of water. 

• Algae growth:  A large algae population will create stressful conditions for some aquatic organisms.

Human Caused Anoxic Conditions

• Dams :Dams slow the flow of water, reducing the amount of aeration and increasing the temperature. 

• Human Wastes :Besides creating a health hazard, human waste carries with it a large amount of oxygen consuming bacteria.

• Fertilizers :Poor farming practices result in large amounts of fertilizer being washed into rivers and lakes.  This creates algae blooms and large growths of other plants.

Daily and Seasonal Anoxic Cycles

• The temperature of a body of water directly affects the amount of dissolved oxygen it can hold. Thus, bodies of water are more vulnerable to anoxic conditions during warmest period of the day and during the summer months.

• Organisms have adapted a variety of mechanisms to live within anoxic sediment.

A) Some organisms are able to pump oxygen from higher water levels down.

B) some organsisms have developed specific hemoglobins for low oxygen environments.

C) Symbiotic relationships with anaerobic bacteria.

Geographical locations of Anoxic Basins (DEAD ZONES )

• Some possible solutions are :-

1- Farmers should build two-stage drainage ditches which would decrease the amount of fertilizer reaching the waters

2- Conserve water at home to reduce the volume of waste water that must be treated.

3- Always take your household/lawn chemicals to a recycling center, not in the trash or down your drain.

NOW CLAAPPP

Solutions to this condition

Mass Extinction Due To Anoxic Events

• Aquatic organisms, just like all other organisms, depend on oxygen for survival.
• The lack of oxygen causes species that are known to live in an area to be endangered.
• If the problem of decreased DO level is not solved, mass extinctions of aquatic organisms will occur.

areas of the Chesapeake bay

The gulf of mexico

So What is Anoxic Water ??

Biological Adaptations of Organisms to Anoxic Water

Dead zones are low-oxygen, or hypoxic, areas in the world’s oceans and lakes. there are 150 of them so far

examples of dead zones include:

• Anoxic waters are areas of sea water, fresh water or groundwater that are depleted of dissolved oxygen.

• This condition is generally found in areas that have restricted water exchange.

Areas of the black sea

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• Daily cycles are also influenced by the activity of photosynthetic organisms.

Alaa Khader, Bassma Alcharfli, and Yasmeen Shebli