Search results
Results From The WOW.Com Content Network
Anoxic waters are areas of sea water, fresh water, or groundwater that are depleted of dissolved oxygen. The US Geological Survey defines anoxic groundwater as those with dissolved oxygen concentration of less than 0.5 milligrams per litre. [1] Anoxic waters can be contrasted with hypoxic waters, which are low (but not lacking) in dissolved ...
In 2021, the low-oxygenated waters caused a mass-kill event of freshwater drum fish species (also known as sheepshead fish). [49] Water from the lake is also used for human drinking. [50] Water from the lake has been said to acquire a pervasive odor and discoloration when the dead zone is active in the late summer months. [51]
In dimictic, eutrophic lakes, the hypolimnion is often anoxic throughout a majority of the stratified period. [6] However, hypolimnetic oxygen concentrations are replenished in the fall and early winter in many temperate lakes, as lake turnover allows mixing of oxic surface waters and anoxic bottom waters. [7]
While it is mainly lakes that are meromictic, the world's largest meromictic basin is the Black Sea. The deep waters below 50 m (160 ft) do not mix with the upper layers that receive oxygen from the atmosphere. As a result, over 90% of the deeper Black Sea volume is anoxic water. The Caspian Sea is anoxic below 100 m (330 ft).
Sulfur-reducing bacteria are common in anoxic layers of soda lakes. These reduce sulfate and organic sulfur from dead cells into sulfide (S 2−). Anoxic layers of soda lakes are therefore often rich in sulfide. As opposed to neutral lakes, the high pH prohibits the release of hydrogen sulfide (H 2 S) in gas form.
The exaerobic zone is found at the boundary of anoxic and hypoxic zones. Hypoxia can occur throughout the water column and also at high altitudes as well as near sediments on the bottom. It usually extends throughout 20–50% of the water column, but depends on the water depth and location of pycnoclines (rapid changes in water density with depth).
An anoxic event describes a period wherein large expanses of Earth's oceans were depleted of dissolved oxygen (O 2), creating toxic, euxinic (anoxic and sulfidic) waters. [1] Although anoxic events have not happened for millions of years, the geologic record shows that they happened many times in the past.
Meromictic lakes are poorly mixed and anoxic bodies of water with strong vertical stratification. [1] While meromictic lakes are frequently categorized as bodies of water with the potential for euxinic conditions, many do not exhibit euxinia. Meromictic lakes are infamous for limnic eruptions. [46]