decomposition decomposition decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. the process is a part of the nutrient cycle and is essential for recycling the finite matter that occupies physical space in the biosphere. bodies of living organisms begin to decompose shortly after death. animals, such as worms, also help decompose the organic materials. organisms that do this are known as decomposers or detritivores. although no two organisms decompose in the same way, they all undergo the same sequential stages of decomposition. the science which studies decomposition is generally referred to as taphonomy from the greek word taphos, meaning tomb. decomposition can also be a gradual process for organisms that have extended periods of dormancy. stages of death pallor mortis livor mortis algor mortis rigor mortis putrefaction decomposition skeletonization fossilization a rotten apple after it fell from a tree decomposing fallen nurse log in a forest one can differentiate abiotic decomposition from biotic decomposition (biodegradation). the former means "the degradation of a substance by chemical or physical processes", e.g., hydrolysis; the latter means "the metabolic breakdown of materials into simpler components by living organisms", typically by microorganisms. animal decomposition ants eating a dead snake decomposition begins at the moment of death, caused by two factors: 1.) autolysis, the breaking down of tissues by the body's own internal chemicals and enzymes, and 2.) putrefaction, the breakdown of tissues by bacteria. these processes release compounds such as cadaverine and putrescine, that are the chief source of the unmistakably putrid odor of decaying animal tissue. prime decomposers are bacteria or fungi, though larger scavengers also play an important role in decomposition if the body is accessible to insects, mites and other animals. additionally, s oil animals are considered key regulators of decomposition at local scales but their role at larger scales is unresolved. the most important arthropods that are involved in the process include carrion beetles, mites, the flesh-flies (sarcophagidae) and blow-flies (calliphoridae), such as the green bottle flies seen in the summer. in north america, the most important non-insect animals that are typically involved in the process include mammal and bird scavengers, such as coyotes, dogs, wolves, foxes, rats, crows and vultures. some of these scavengers also remove and scatter bones, which they ingest at a later time. aquatic and marine environments have break-down agents that include bacteria, fish, crustaceans, fly larvae and other carrion scavengers. stages of decomposition five general stages are used to describe the process of decomposition in vertebrate animals: fresh, bloat, active decay, advanced decay, and dry/remains. the general stages of decomposition are coupled with two stages of chemical decomposition: autolysis and putrefaction. these two stages contribute to the chemical process of decomposition, which breaks down the main components of the body. with death the microbiome of the living organism collapses and is followed by the necrobiome that undergoes predictable changes over time. fresh among those animals that have a heart, the "fresh" stage begins immediately after the heart stops beating. from the moment of death, the body begins cooling or warming to match the temperature of the ambient environment, during a stage called algor mortis. shortly after death, within three to six hours, the muscular tissues become rigid and incapable of relaxing, during a stage called rigor mortis. since blood is no longer being pumped through the body, gravity causes it to drain to the dependent portions of the body, creating an overall bluish-purple discoloration termed livor mortis or, more commonly, lividity. depending on the position of the body, these parts would vary. for instance, if the person was flat on their back when they died, the blood would collect in the parts that are touching the ground. if the person was hanging, it would collect in their fingertips, toes and earlobes. once the heart stops, the blood can no longer supply oxygen or remove carbon dioxide from the tissues. the resulting decrease in ph and other chemical changes causes cells to lose their structural integrity, bringing about the release of cellular enzymes capable of initiating the breakdown of surrounding cells and tissues. this process is known as autolysis. visible changes caused by decomposition are limited during the fresh stage, although autolysis may cause blisters to appear at the surface of the skin. the small amount of oxygen remaining in the body is quickly depleted by cellular metabolism and aerobic microbes naturally present in respiratory and gastrointestinal tracts, creating an ideal environment for the proliferation of anaerobic organisms. these multiply, consuming the body's carbohydrates, lipids and proteins, to produce a variety of substances including propionic acid, lactic acid, methane, hydrogen sulfide and ammonia. the process of microbial proliferation within a body is referred to as putrefaction and leads to the second stage of decomposition known as bloat. blowflies and flesh flies are the first carrion insects to arrive and they seek a suitable oviposition site. bloat the bloat stage provides the first clear visual sign that microbial proliferation is underway. in this stage, anaerobic metabolism takes place, leading to the accumulation of gases, such as hydrogen sulfide, carbon dioxide, methane and nitrogen. the accumulation of gases within the bodily cavity causes the distention of the abdomen and gives a cadaver its overall bloated appearance. the gases produced also cause natural liquids and liquefying tissues to become frothy. as the pressure of the gases within the body increases, fluids are forced to escape from natural orifices, such as the nose, mouth and anus, and enter the surrounding environment. the buildup of pressure combined with the loss of integrity of the skin may also cause the body to rupture. intestinal anaerobic bacteria transform haemoglobin into sulfhemoglobin and other colored pigments. the associated gases which accumulate within the body at this time aid in the transport of sulfhemoglobin throughout the body via the circulatory and lymphatic systems, giving the body an overall marbled appearance. if insects have access, maggots hatch and begin to feed on the body's tissues. maggot activity, typically confined to natural orifices, and masses under the skin, causes the skin to slip, and hair to detach from the skin. maggot feeding, and the accumulation of gases within the body, eventually leads to post-mortem skin ruptures which will then further allow purging of gases and fluids into the surrounding environment. ruptures in the skin allow oxygen to re-enter the body and provide more surface area for the development of fly larvae and the activity of aerobic microorganisms. the purging of gases and fluids results in the strong distinctive odors associated with decay. active decay active decay is characterized by the period of greatest mass loss. this loss occurs as a result of both the voracious feeding of maggots and the purging of decomposition fluids into the surrounding environment. the purged fluids accumulate around the body and create a cadaver decomposition island (cdi). liquefaction of tissues and disintegration become apparent during this time and strong odors persist. the end of active decay is signaled by the migration of maggots away from the body to pupate. advanced decay decomposition is largely inhibited during advanced decay due to the loss of readily available cadaveric material. insect activity is also reduced during this stage. when the carcass is located on soil, the area surrounding it will show evidence of vegetation death. the cdi surrounding the carcass will display an increase in soil carbon and nutrients such as phosphorus, potassium, calcium and magnesium; changes in ph; and a significant increase in soil nitrogen. dry/remains during the dry/remains stage, the resurgence of plant growth around the cdi may occur and is a sign that the nutrients present in the surrounding soil have not yet returned to their normal levels. as the ecosystem recovers from the disturbance, the cdi moves into the dry/remains stage, which is characterized by a decrease in the intensity of the disturbance and an increase in the amount of plant growth around the affected area. this is a sign that the nutrients and other ecological resources present in the surrounding soil have not yet returned to their normal levels. during this stage, it is important to monitor the ecosystem for any signs of continued disturbance or ecological stress. the resurgence of plant growth is a positive sign, but it may take several years for the ecosystem to fully recover and return to its pre-disturbance state. all that remains of the cadaver at this stage is dry skin, cartilage, and bones, which will become dry and bleached if exposed to the elements. if all soft tissue is removed from the cadaver, it is referred to as completely skeletonized, but if only portions of the bones are exposed, it is referred to as partially skeletonized. pig carcass in the different stages of decomposition: fresh > bloat > active decay > advanced decay > dry remains factors affecting decomposition of bodies exposure to the elements a dead body that has been exposed to the open elements, such as water and air, will decompose more quickly and attract much more insect activity than a body that is buried or confined in special protective gear or artifacts. this is due, in part, to the limited number of insects that can penetrate a coffin and the lower temperatures under the soil. the rate and manner of decomposition in an animal body are strongly affected by several factors. in roughly descending degrees of importance, they are: temperature; the availability of oxygen; prior embalming; cause of death; burial, depth of burial, and soil type; access by scavengers; trauma, including wounds and crushing blows; humidity, or wetness; rainfall; body size and weight; composition; clothing; the surface on which the body rests; foods/objects inside the specimen's digestive tract (bacon compared to lettuce). the speed at which decomposition occurs varies greatly. factors such as temperature, humidity, and the season of death all determine how fast a fresh body will skeletonize or mummify. a basic guide for the effect of environment on decomposition is given as casper's law (or ratio): if all other factors are equal, then, when there is free access of air a body decomposes twice as fast as if immersed in water and eight times faster than if buried in the earth. ultimately, the rate of bacterial decomposition acting on the tissue will depend upon the temperature of the surroundings. colder temperatures decrease the rate of decomposition while warmer temperatures increase it. a dry body will not decompose efficiently. moisture helps the growth of microorganisms that decompose the organic matter, but too much moisture could lead to anaerobic conditions slowing down the decomposition process. the most important variable is the body's accessibility to insects, particularly flies. on the surface in tropical areas, invertebrates alone can easily reduce a fully fleshed corpse to clean bones in under two weeks. the skeleton itself is not permanent; acids in soils can reduce it to unrecognizable components. this is one reason given for the lack of human remains found in the wreckage of the titanic, even in parts of the ship considered inaccessible to scavengers. freshly skeletonized bone is often called "green" bone and has a characteristic greasy feel. under certain conditions (normally cool, damp soil), bodies may undergo saponification and develop a waxy substance called adipocere, caused by the action of soil chemicals on the body's proteins and fats. the formation of adipocere slows decomposition by inhibiting the bacteria that cause putrefaction. in extremely dry or cold conditions, the normal process of decomposition is halted – by either lack of moisture or temperature controls on bacterial and enzymatic action – causing the body to be preserved as a mummy. frozen mummies commonly restart the decomposition process when thawed (see ötzi the iceman), whilst heat-desiccated mummies remain so unless exposed to moisture. the bodies of newborns who never ingested food are an important exception to the normal process of decomposition. they lack the internal microbial flora that produces much of decomposition and quite commonly mummify if kept in even moderately dry conditions. anaerobic vs aerobic aerobic decomposition takes place in the presence of oxygen. this is most common to occur in nature. living organisms that use oxygen to survive feed on the body. anaerobic decomposition takes place in the absence