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Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance faster than it can be lost or eliminated by catabolism and excretion. Thus, the longer the biological half-life of a Toxin, the greater the risk of chronic poisoning, even if environmental levels of the toxin are not very high. Bioaccumulation, for example in fish, can be predicted by models. Hypothesis for molecular size cutoff criteria for use as bioaccumulation potential indicators are not supported by data. Biotransformation can strongly modify bioaccumulation of chemicals in an organism.
Toxicity induced by metals is associated with bioaccumulation and biomagnification. Storage or uptake of a metal faster than it is metabolized and excreted leads to the accumulation of that metal. The presence of various chemicals and harmful substances in the environment can be analyzed and assessed with a proper knowledge on bioaccumulation helping with chemical control and usage. (2025). 9781784028459 ISBN 9781784028459
An organism can take up chemicals by breathing, absorbing through skin or swallowing. When the concentration of a chemical is higher within the organism compared to its surroundings (air or water), it is referred to as bioconcentration. Biomagnification is another process related to bioaccumulation as the concentration of the chemical or metal increases as it moves up from one trophic level to another. Naturally, the process of bioaccumulation is necessary for an organism to grow and develop; however, the accumulation of harmful substances can also occur.
Strontium-90, part of the Nuclear fallout from , is chemically similar enough to calcium that it is taken up in osteogenesis, where its radiation can cause damage for a long time.
Some animal species use bioaccumulation as a mode of defense: by consuming toxic plants or animal prey, an animal may accumulate the toxin, which then presents a deterrent to a potential predator. One example is the Manduca sexta, which concentrates nicotine to a toxic level in its body as it consumes tobacco plants. Poisoning of small consumers can be passed along the food chain to affect the consumers later in the chain.
Other compounds that are not normally considered toxic can be accumulated to toxic levels in organisms. The classic example is vitamin A, which becomes concentrated in of , e.g. : as a pure carnivore that feeds on other carnivores (seals), they accumulate extremely large amounts of vitamin A in their livers. It was known by the native peoples of the Arctic that the livers of carnivores should not be eaten, but Arctic explorers have suffered hypervitaminosis A from eating the livers of bears; and there has been at least one example of similar poisoning of Xavier Mertz eating husky dog livers. One notable example of this is the expedition of Douglas Mawson, whose exploration companion died from eating the liver of one of their dogs.
Fish are typically assessed for bioaccumulation when they have been exposed to chemicals that are in their aqueous phases. Commonly tested fish species include the Common Carp, rainbow trout, and bluegill sunfish. Generally, fish are exposed to bioconcentration and bioaccumulation of organic chemicals in the environment through lipid layer uptake of water-borne chemicals. In other cases, the fish are exposed through ingestion/digestion of substances or organisms in the aquatic environment which contain the harmful chemicals.
Naturally produced toxins can also bioaccumulate. The marine known as "" can result in local filter-feeding organisms such as and becoming toxic; coral reef fish can be responsible for the poisoning known as ciguatera when they accumulate a toxin called ciguatoxin from reef algae. In some eutrophic aquatic systems, biodilution can occur. This is a decrease in a contaminant with an increase in trophic level, due to higher concentrations of algae and bacteria diluting the concentration of the pollutant.
Wetland acidification can raise the chemical or metal concentrations, which leads to an increased bioavailability in marine plants and freshwater biota. Plants situated there which includes both rooted and submerged plants can be influenced by the bioavailability of metals.
The most common elements studied in turtles are mercury, cadmium, lead, and selenium. Heavy metals are released into rivers, streams, lakes, oceans, and other aquatic environments, and the plants that live in these environments will absorb the metals. Since the levels of trace elements are high in aquatic ecosystems, turtles will naturally consume various trace elements throughout various aquatic environments by eating plants and sediments. Once these substances enter the bloodstream and muscle tissue, they will increase in concentration and will become toxic to the turtles, perhaps causing metabolic, endocrine system, and reproductive failure.
Some marine turtles are used as experimental subjects to analyze bioaccumulation because of their shoreline habitats, which facilitate the collection of blood samples and other data. The turtle species are very diverse and contribute greatly to biodiversity, so many researchers find it valuable to collect data from various species. Freshwater turtles are another model species for investigating bioaccumulation. Due to their relatively limited home-range freshwater turtles can be associated with a particular catchment and its chemical contaminant profile.
In terms of toxic levels of heavy metals, it was observed to decrease egg-hatching rates in the Amazon River turtle, Arrau turtle. In this particular turtle egg, the heavy metals reduce the fat in the eggs and change how water is filtered throughout the embryo; this can affect the survival rate of the turtle egg.
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