Oxygen saturation or dissolved oxygen (DO) is a relative measure of the amount of 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...

 that is dissolve

Dissolution (chemistry)

Dissolution is the process by which a solid, liquid or gas forms a solution in a solvent. In solids this can be explained as the breakdown of the crystal lattice into individual ions, atoms or molecules and their transport into the solvent. For liquids and gases, the molecules must be compatible...

d or carried in a given medium. It can be measured with a dissolved oxygen probe such as an oxygen sensor

Oxygen sensor

An oxygen sensor, or lambda sensor, is an electronic device that measures the proportion of oxygen in the gas or liquid being analyzed. It was developed by the Robert Bosch GmbH company during the late 1960s under the supervision of Dr. Günter Bauman...

 or an optode

Optode

An optode or optrode is an optical sensor device that optically measures a specific substance usually with the aid of a chemical transducer.-Construction:...

 in liquid media, usually water.

It has particular significance in medicine

Oxygenation (medical)

Oxygenation occurs when oxygen molecules enter the tissues of the body. For example, blood is oxygenated in the lungs, where oxygen molecules travel from the air and into the blood...

 and environmental science

Oxygenation (environmental)

Environmental oxygenation can be important to the sustainability of a particular ecosystem. Insufficient oxygen may occur in bodies of water such as ponds and rivers, tending to suppress the presence of aerobic organisms such as fish...

.

Oxygen saturation in medicine

In medicine

Medicine

Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

, oxygen saturation refers to oxygenation, or when 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...

 molecules enter the tissues

Tissue (biology)

Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

 of the body. In this case blood

Blood

Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

 is oxygenated in the lung

Lung

The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

s, where oxygen molecules travel from the air and into the blood. Oxygen saturation, or O2 sats measure the percentage of hemoglobin binding sites in the bloodstream occupied by oxygen.
Fish, invertebrates, plants, and aerobic bacteria all require oxygen for respiration. Blood is also vital to the body system.
The optimal levels in an estuary for Dissolved Oxygen (DO) is higher than 6 ppm. Fish prefer it this way.

Environmental oxygen saturation

Oxygen saturation in the environment generally refers to the amount of oxygen dissolved in the soil or bodies of water. Environmental oxygenation can be important to the sustainability

Sustainability

Sustainability is the capacity to endure. For humans, sustainability is the long-term maintenance of well being, which has environmental, economic, and social dimensions, and encompasses the concept of union, an interdependent relationship and mutual responsible position with all living and non...

 of a particular ecosystem

Ecosystem

An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

. Insufficient oxygen (environmental hypoxia

Hypoxia (environmental)

Hypoxia, or oxygen depletion, is a phenomenon that occurs in aquatic environments as dissolved oxygen becomes reduced in concentration to a point where it becomes detrimental to aquatic organisms living in the system...

) may occur in bodies of water such as pond

Pond

A pond is a body of standing water, either natural or man-made, that is usually smaller than a lake. A wide variety of man-made bodies of water are classified as ponds, including water gardens, water features and koi ponds; all designed for aesthetic ornamentation as landscape or architectural...

s and river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

s, tending to suppress the presence of aerobic organism

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:...

s such as fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

. Deoxygenation increases the relative population of anaerobic organism

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...

s such as plants and some 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...

, resulting in fish kill

Fish kill

The term fish kill, known also as fish die-off and as fish mortality, is a localized die-off of fish populations which may also be associated with more generalised mortality of aquatic life...

s and other adverse events. The net effect is to alter the balance of nature

Balance of nature

The balance of nature is a theory that says that ecological systems are usually in a stable equilibrium , which is to say that a small change in some particular parameter will be corrected by some negative feedback that will bring the parameter back to its original "point of balance" with the rest...

 by increasing the concentration of anaerobic over aerobic species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

.