Chemocline
Encyclopedia
A chemocline is a cline
caused by a strong, vertical chemistry
gradient within a body of water
. A chemocline is analogous to a thermocline
, the border at which warmer and cooler waters meet in an ocean, sea, lake, or other body of water. (In some cases, the thermocline and chemocline coincide.)
Chemoclines most commonly occur where local conditions favor the formations of anoxic bottom water — deep water deficient in oxygen
, where only anaerobic
forms of life can exist. The Black Sea
is the classic example of such a body, though similar bodies of water (classified as meromictic
lakes) exist across the globe. Aerobic
life is restricted to the region above the chemocline, anaerobic below. Photosynthetic forms of anaerobic bacteria
, like green phototrophic and purple sulfur bacteria
, cluster at the chemocline, taking advantage of both the sunlight from above and the hydrogen sulfide
(H2S) produced by the anaerobic bacteria below.
In any body of water in which oxygen-rich surface waters are well-mixed (holomictic
), no chemocline will exist. To cite the most obvious example, the Earth's global ocean has no chemocline.
Cline
Cline, as spelled, is an Irish surname with historical roots in County Roscommon.People bearing the name include:* Catherine Ann Cline , American historian and author* Edward Cline , American screenwriter and director...
caused by a strong, vertical chemistry
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....
gradient within a body of water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
. A chemocline is analogous to a thermocline
Thermocline
A thermocline is a thin but distinct layer in a large body of fluid , in which temperature changes more rapidly with depth than it does in the layers above or below...
, the border at which warmer and cooler waters meet in an ocean, sea, lake, or other body of water. (In some cases, the thermocline and chemocline coincide.)
Chemoclines most commonly occur where local conditions favor the formations of anoxic bottom water — deep water deficient in oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
, where only anaerobic
Anaerobic organism
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present...
forms of life can exist. The Black Sea
Black Sea
The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...
is the classic example of such a body, though similar bodies of water (classified as meromictic
Meromictic
A meromictic lake has layers of water that do not intermix. In ordinary, "holomictic" lakes, at least once each year there is a physical mixing of the surface and the deep waters...
lakes) exist across the globe. Aerobic
Aerobic organism
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.Faculitative anaerobes grow and survive in an oxygenated environment and so do aerotolerant anaerobes.-Glucose:...
life is restricted to the region above the chemocline, anaerobic below. Photosynthetic forms of anaerobic bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
, like green phototrophic and purple sulfur bacteria
Purple sulfur bacteria
The purple sulfur bacteria are a group of Proteobacteria capable of photosynthesis, collectively referred to as purple bacteria. They are anaerobic or microaerophilic, and are often found in hot springs or stagnant water. Unlike plants, algae, and cyanobacteria, they do not use water as their...
, cluster at the chemocline, taking advantage of both the sunlight from above and the hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
(H2S) produced by the anaerobic bacteria below.
In any body of water in which oxygen-rich surface waters are well-mixed (holomictic
Holomictic
Holomictic lakes are lakes, which, at some time during the year, have a uniform temperature and density from top to bottom, allowing the lake waters to completely mix. Holomictic lakes are non-meromictic lakes....
), no chemocline will exist. To cite the most obvious example, the Earth's global ocean has no chemocline.
Types of clines
- ThermoclineThermoclineA thermocline is a thin but distinct layer in a large body of fluid , in which temperature changes more rapidly with depth than it does in the layers above or below...
- A cline based on difference in water temperatureTemperatureTemperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
, - HaloclineHaloclineIn oceanography, a halocline is a subtype of chemocline caused by a strong, vertical salinity gradient within a body of water. Because salinity affects the density of seawater, it can play a role in its vertical stratification...
- A cline based on difference in water salinitySalinitySalinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
, - PycnoclinePycnoclineA pycnocline is the cline or layer where the density gradient is greatest within a body of water. An ocean current is generated by the forces such as breaking waves, terms of temperature and salinity differences, wind, Coriolis effect, and tides caused by the gravitational pull of the Moon and the...
- A cline based on difference in water densityDensityThe mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
.