Ecological death is the inability of an

organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...

to function in an

ecological Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ...

context, leading to

death Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...

.Scott, G.R., and K.A. Sloman. 2004. The effects of environmental pollutants on complex fish behavior: integrating behavioural and physiological indicators of toxicity. Aquatic Toxicology 68:369-392. This term can be used in many fields of

biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...

to describe any

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

. In the context of

aquatic toxicology Aquatic toxicology is the study of the effects of manufactured chemicals and other anthropogenic and natural materials and activities on aquatic organisms at various levels of organization, from subcellular through individual organisms to communit ...

, a toxic chemical, or

toxicant A toxicant is any toxic substance, whether man-made or naturally occurring. By contrast, a toxin is a poison produced naturally by an organism (e.g. plant, animal, insect). The different types of toxicants can be found in the air, soil, water, or ...

, directly affects an aquatic organism but does not immediately kill it; instead it impairs an organism's normal ecological functions which then lead to death or lack of

offspring In biology, offspring are the young creation of living organisms, produced either by a single organism or, in the case of sexual reproduction, two organisms. Collective offspring may be known as a brood or progeny in a more general way. This ca ...

. The toxicant makes the organism unable to function ecologically in some way, even though it does not suffer obviously from the toxicant. Ecological death may be caused by sublethal toxicological effects that can be behavioral, physiological, biochemical, or

histological Histology, also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures vis ...

.Rand, G.M. (Ed). Fundamentals of Aquatic Toxicology: Effects, Environmental Fate, and Risk Assessment. 2nd Ed. Florida: CRC Press, 1995.

Types of sublethal effects causing ecological death

Sublethal effects consist of any effects of an organism caused by a

that do not include death. These effects are generally not observed well in a shorter

acute toxicity Acute toxicity describes the adverse effects of a substance that result either from a single exposure or from multiple exposures in a short period of time (usually less than 24 hours). To be described as ''acute'' toxicity, the adverse effect ...

test. A longer,

chronic toxicity Chronic toxicity, the development of adverse effects as a result of long term exposure to a contaminant or other stressor, is an important aspect of aquatic toxicology. Adverse effects associated with chronic toxicity can be directly lethal but are ...

test will allow enough time for these effects to appear in an organism and for them to lead to ecological death.

Behavioral effects

Toxicant A toxicant is any toxic substance, whether man-made or naturally occurring. By contrast, a toxin is a poison produced naturally by an organism (e.g. plant, animal, insect). The different types of toxicants can be found in the air, soil, water, or ...

s can affect an organism's behavior, which with aquatic organisms, may impact their ability to swim, feed or avoid predators. The impacted behavior can lead to an organism's death because it may starve or get eaten by predators. Toxicants may affect behavior by impacting the sensory systems which organisms depend on to collect information about their environment or by impacting an organism's motivation to properly respond to sensory cues. If an organism is unable to use sensory cues effectively, they may be unable to respond to early warning signs of predation risk. Toxicants can also affect later stages of predation by impacting an organism's ability to respond to predators or follow through with escape strategies.

Physiological effects

s can affect an organism's

physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...

which may impact its growth, reproduction, and/or development. If an organism does not grow correctly and is undersize or has growth defects, it will be more likely to be eaten by predators. If an organism's reproduction is impaired, it may not directly die, but it will be unable to pass on its genes to the population. The organism will no longer be representative in the population's gene pool.

Biochemical effects

s can alter the enzymes or

ions An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

present in an organism. If this alteration does not directly cause death, but impacts the behavior or physiology of the organism, it can also lead to ecological death.

Histological effects

s can alter an organism's tissues. If this alteration does not directly cause death, but impacts the behavior or physiology of the organism, it can also lead to ecological death.

Toxicant examples leading to ecological death

DDT

An effect caused by

DDT Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochloride. Originally developed as an insecticide, it became infamous for its environmental impacts. ...

is shell thinning in bird eggs, leading to the death of the chick. Once DDT has been accumulated by an adult bird, it is metabolized into the form DDE which is both stable and toxic.U.S. Dept. of Interior, National Biological Service. “Environmental Contaminants”. Status and Trends of the Nation’s Biological Resources. Dept. of Interior, National Biological Service: Washington, DC. 1998. 15 May 2013. Once in the form of DDE, the chemical impacts the metabolism of calcium in adult female birds’ shell glands, ultimately causing a decrease in eggshell thickness. At high concentrations of DDT, the eggshells will no longer be able to support the incubating parents’ weight and will lead to the death of the unborn chick. This is an example of physiological and biochemical sublethal effects leading to ecological death of the chick.

Diazinon

An effect caused by

diazinon Diazinon (IUPAC name: ''O'',''O''-Diethyl ''O''- -methyl-6-(propan-2-yl)pyrimidin-2-ylphosphorothioate, INN - Dimpylate), a colorless to dark brown liquid, is a thiophosphoric acid ester developed in 1952 by Ciba-Geigy, a Swiss chemical company ...

is a decrease in response to predator cues in

Chinook salmon The Chinook salmon (''Oncorhynchus tshawytscha'') is the largest and most valuable species of Pacific salmon in North America, as well as the largest in the genus '' Oncorhynchus''. Its common name is derived from the Chinookan peoples. Other ...

(''Oncorhynchus tshawytscha''). Diazinon, an organopesticide, was exposed to juvenile Chinook salmon for two hours at 1 and 10 μg/L, and these concentrations were enough to eliminate the behavioral responses of the fish to predator chemical cues.Scholz, N.L., Truelove, N.K., French, B.L., Berejikian, B.A., Quinn, T.P., Casillas, E., Collier, T.K. 2000. Diazinon disrupts antipredator and homing behaviors in Chinook salmon (Oncorhynchus tshawytschaI). Can. J. Fish. Aquat. Sci. 57: 1911-1918. If the fish cannot recognize that a predator is nearby, it is likely to be eaten. This is an example of a behavioral sublethal effect leading to ecological death.

Pentachlorophenol

An effect caused by pentachlorophenol is a decrease in response to predator attacks in

guppies The guppy (), also known as millionfish and rainbow fish, is one of the world's most widely distributed tropical fish and one of the most popular freshwater aquarium fish species. It is a member of the family Poeciliidae and, like almost all ...

(''Poecilia reticula''). Pentachlorophenol was exposed to juvenile guppies at 500 and 700 μg/L, and both concentrations decreased the guppies’ reactions to predators.Brown, J.A., Johansen, P.H., Colgan, P.W., Mathers, R.A. 1985. Changes in the predator-avoidance behavior of juvenile guppies (Poecilia reticulata) exposed to pentachlorophenol. Can. J. Zool. 63: 2001-2005. The predators did not have to strike as frequently, did not have to pursue as frequently, or have to pursue the guppies as long as guppies that had not been exposed to these levels of pentachlorophenol. The guppies that were exposed to this chemical were more likely to be eaten due to their slower responses. This is another example of a behavioral sublethal effect that leads to ecological death.

Copper

An effect caused by

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

is impacting the

salmon Salmon () is the common name for several commercially important species of euryhaline ray-finned fish from the family Salmonidae, which are native to tributaries of the North Atlantic (genus ''Salmo'') and North Pacific (genus '' Oncorhy ...

olfactory system The olfactory system, or sense of smell, is the sensory system used for smelling ( olfaction). Olfaction is one of the special senses, that have directly associated specific organs. Most mammals and reptiles have a main olfactory system and an ...

. The olfactory system is used to gather important information about one's environment. In the case of salmon, olfactory cues can gather information about habitat quality, predators, mates and more.Baldwin, D.H., Sandahl, J.F., Labenia, J.S., Scholz, N.L. 2003. Sublethal effects of copper on Coho Salmon: Impacts on nonoverlapping receptor pathways in the peripheral olfactory nervous system. Environ. Tox. and Chem. 22(10):2266-2274. Salmon can detect distinct copper gradients using their olfactory system, and use this information to avoid

contaminated Contamination is the presence of a constituent, impurity, or some other undesirable element that spoils, corrupts, infects, makes unfit, or makes inferior a material, physical body, natural environment, workplace, etc. Types of contamination ...

waters. However, when salmon are affected by copper, the olfactory system can be impacted in a matter of minutes. If the fish is no longer able to gather environmental information, it may be at risk for predation or unable to find resources for survival. This is an example of a physiological sublethal effect leading to ecological death.

References

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Types of sublethal effects causing ecological death

Behavioral effects

Physiological effects

Biochemical effects

Histological effects

Toxicant examples leading to ecological death

DDT

Diazinon

Pentachlorophenol

Copper

References

See also