Bioaccumulation

Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism.^[1] 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 toxic substance, the greater the risk of chronic poisoning, even if environmental levels of the toxin are not very high.^[2] Bioaccumulation, for example in fish, can be predicted by models.^[3][4] Hypothesis for molecular size cutoff criteria for use as bioaccumulation potential indicators are not supported by data.^[5] Biotransformation can strongly modify bioaccumulation of chemicals in an organism.^[6]

Toxicity induced by metals is associated with bioaccumulation and biomagnification.^[7] Storage or uptake of a metal faster than it is metabolized and excreted leads to the accumulation of that metal.^[8] 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.^[9]

An organism can take up chemicals by breathing, absorbing through skin or swallowing.^[7] When the concentration of a chemical is higher within the organism compared to its surroundings (air or water), it is referred to as bioconcentration.^[1] 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.^[1] Naturally, the process of bioaccumulation is necessary for an organism to grow and develop; however, accumulation of harmful substances can also occur.^[7]

Examples

Terrestrial examples

An example of poisoning in the workplace can be seen from the phrase "mad as a hatter" (18th and 19th century England). Mercury was used in stiffening the felt used to make hats involved. This forms organic species such as methylmercury, which is lipid-soluble (fat-soluble), and tends to accumulate in the brain, resulting in mercury poisoning. Other lipid-soluble poisons include tetraethyllead compounds (the lead in leaded petrol), and DDT. These compounds are stored in the body fat, and when the fatty tissues are used for energy, the compounds are released and cause acute poisoning.^{[citation needed]}

Strontium-90, part of the fallout from atomic bombs, is chemically similar enough to calcium that it is taken up in forming bones, where its radiation can cause damage for a long time.^{[citation needed]}

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 tobacco hornworm, 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 livers of carnivores, e.g. polar bears: 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 Antarctic explorers eating husky dog livers. One notable example of this is the expedition of Sir Douglas Mawson, whose exploration companion died from eating the liver of one of their dogs.

Aquatic examples

Coastal fish (such as the smooth toadfish) and seabirds (such as the Atlantic puffin) are often monitored for heavy metal bioaccumulation. Methylmercury gets into freshwater systems through industrial emissions and rain. As its concentration increases up the food web, it can reach dangerous levels for both fish and the humans who rely on fish as a food source.^[10]

Fish are typically assessed for bioaccumulation when they have been exposed to chemicals that are in their aqueous phases.^[11] Commonly tested fish species include the common carp, rainbow trout, and bluegill sunfish.^[11] Generally, fish are exposed to bioconcentration and bioaccumulation of organic chemicals in the environment through lipid layer uptake of water-borne chemicals.^[11] In other cases, the fish are exposed through ingestion/digestion of substances or organisms in the aquatic environment which contain the harmful chemicals.^[11]

Naturally produced toxins can also bioaccumulate. The marine algal blooms known as "red tides" can result in local filter-feeding organisms such as mussels and oysters 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 to dilute the concentration of the pollutant.^{[citation needed]}

Wetland acidification can raise the chemical or metal concentrations, which leads to an increased bioavailability in marine plants and freshwater biota.^[12] Plants situated there which includes both rooted and submerged plants can be influenced by the bioavailability of metals.^[12]

Studies of turtles as model species

Bioaccumulation in turtles occurs when synthetic organic contaminants (i.e., PFAS), heavy metals, or high levels of trace elements enter a singular organism, potentially affecting their health. Although there are ongoing studies of bioaccumulation in turtles, factors like pollution, climate change, and shifting landscape can affect the amounts of these toxins in the ecosystem.^[13]

The most common elements studied in turtles are mercury, cadmium, argon^{[dubious ]}, 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.^[14] 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.^[15]

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.^[14] 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.^[16] Due to their relatively limited home-range freshwater turtles can be associated with a particular catchment and its chemical contaminant profile.

Developmental effects of turtles

Toxic concentrations in turtle eggs may damage the developmental process of the turtle. For example, in the Australian freshwater short-neck turtle (Emydura macquarii macquarii), environmental PFAS concentrations were bioaccumulated by the mother and then offloaded into their eggs that impacted developmental metabolic processes and fat stores.^[17] Furthermore, there is evidence PFAS impacted the gut microbiome in exposed turtles.^[18]

In terms of toxic levels of heavy metals, it was observed to decrease egg-hatching rates in the Amazon River turtle, Podocnemis expansa.^[15] 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.^[15]

See also

• Biomagnification (magnification of toxins with increasing trophic level)
• Chelation therapy
• Drug accumulation ratio
• Environmental impact of pesticides
• International POPs Elimination Network
• Persistent organic pollutants
• Phytoremediation (removal of pollutants by bioaccumulation in plants)

References

1. Alexander (1999). "Bioaccumulation, bioconcentration, biomagnification". Environmental Geology. Encyclopedia of Earth Science. pp. 43–44. doi:10.1007/1-4020-4494-1_31. ISBN 978-0-412-74050-3.
2. Bryan, G. W.; Waldichuk, M.; Pentreath, R. J.; Darracott, Ann (1979). "Bioaccumulation of Marine Pollutants [and Discussion]". Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 286 (1015): 483–505. JSTOR 2418066.
3. Stadnicka, Julita; Schirmer, Kristin; Ashauer, Roman (2012). "Predicting Concentrations of Organic Chemicals in Fish by Using Toxicokinetic Models". Environmental Science & Technology. 46 (6): 3273–3280. Bibcode:2012EnST...46.3273S. doi:10.1021/es2043728. PMC 3308199. PMID 22324398.
4. Otero-Muras, I.; Franco-Uría, A.; Alonso, A.A.; Balsa-Canto, E. (2010). "Dynamic multi-compartmental modelling of metal bioaccumulation in fish: Identifiability implications". Environmental Modelling & Software. 25 (3): 344–353. doi:10.1016/j.envsoft.2009.08.009.
5. Arnot, Jon A.; Arnot, Michelle; MacKay, Donald; Couillard, Yves; MacDonald, Drew; Bonnell, Mark; Doyle, Pat (2007). "Molecular Size Cut-Off Criteria for Screening Bioaccumulation Potential: Fact or Fiction?". Integrated Environmental Assessment and Management. 6 (2009): 210–224. doi:10.1897/IEAM_2009-051.1. PMID 19919169.
6. Ashauer, Roman; Hintermeister, Anita; o'Connor, Isabel; Elumelu, Maline; Hollender, Juliane; Escher, Beate I. (2012). "Significance of Xenobiotic Metabolism for Bioaccumulation Kinetics of Organic Chemicals in Gammarus pulex". Environmental Science & Technology. 46 (6): 3498–3508. Bibcode:2012EnST...46.3498A. doi:10.1021/es204611h. PMC 3308200. PMID 22321051.
7. Blowes, D. W.; Ptacek, C. J.; Jambor, J. L.; Weisener, C. G. (1 January 2003), Holland, Heinrich D.; Turekian, Karl K. (eds.), "9.05 - The Geochemistry of Acid Mine Drainage", Treatise on Geochemistry, Oxford: Pergamon, pp. 149–204, doi:10.1016/b0-08-043751-6/09137-4, ISBN 978-0-08-043751-4, retrieved 17 February 2021
8. Gaion A, Sartori D, Scuderi A, Fattorini D (2014). "Bioaccumulation and biotransformation of arsenic compounds in Hediste diversicolor (Muller 1776) after exposure to spiked sediments". Environmental Science and Pollution Research. 21 (9): 5952–5959. doi:10.1007/s11356-014-2538-z. PMID 24458939. S2CID 12568097.
9. Philip Wexler, ed. (2014). Encyclopedia of toxicology (Third ed.). London. ISBN 978-1-78402-845-9. OCLC 878141491.{{cite book}}: CS1 maint: location missing publisher (link)
10. "Mercury: What it does to humans and what humans need to do about it". IISD Experimental Lakes Area. 23 September 2017. Retrieved 6 July 2020.
11. Alan., Hoke, Robert. Review of laboratory-based terrestrial bioaccumulation assessment approaches for organic chemicals : current status and future possibilities. OCLC 942770368.{{cite book}}: CS1 maint: multiple names: authors list (link)
12. Albers, Peter H.; Camardese, Michael B. (1993). "Effects of acidification on metal accumulation by aquatic plants and invertebrates. 1. Constructed wetlands". Environmental Toxicology and Chemistry. 12 (6): 959–967. doi:10.1002/etc.5620120602.
13. Franke, Christian; Studinger, Gabriele; Berger, Georgia; Böhling, Stella; Bruckmann, Ursula; Cohors-Fresenborg, Dieter; Jöhncke, Ulrich (October 1994). "The assessment of bioaccumulation". Chemosphere. 29 (7): 1501–1514. Bibcode:1994Chmsp..29.1501F. doi:10.1016/0045-6535(94)90281-X.
14. Dias de Farias, Daniel Solon; Rossi, Silmara; da Costa Bomfim, Aline; Lima Fragoso, Ana Bernadete; Santos-Neto, Elitieri Batista; José de Lima Silva, Flávio; Lailson-Brito, José; Navoni, Julio Alejandro; Gavilan, Simone Almeida; Souza do Amaral, Viviane (1 July 2022). "Bioaccumulation of total mercury, copper, cadmium, silver, and selenium in green turtles (Chelonia mydas) stranded along the Potiguar Basin, northeastern Brazil". Chemosphere. 299: 134331. Bibcode:2022Chmsp.299m4331D. doi:10.1016/j.chemosphere.2022.134331. ISSN 0045-6535. PMID 35339524. S2CID 247638704.
15. Frossard, Alexandra; Coppo, Gabriel Carvalho; Lourenço, Amanda Toledo; Heringer, Otávio Arruda; Chippari-Gomes, Adriana Regina (1 May 2021). "Metal bioaccumulation and its genotoxic effects on eggs and hatchlings of giant Amazon river turtle (Podocnemis expansa)". Ecotoxicology. 30 (4): 643–657. doi:10.1007/s10646-021-02384-8. ISSN 1573-3017. PMID 33754232. S2CID 232315423.
16. Beale, David J.; Hillyer, Katie; Nilsson, Sandra; Limpus, Duncan; Bose, Utpal; Broadbent, James A.; Vardy, Suzanne (1 February 2022). "Bioaccumulation and metabolic response of PFAS mixtures in wild-caught freshwater turtles (Emydura macquarii macquarii) using omics-based ecosurveillance techniques". Science of the Total Environment. 806 (Pt 3): 151264. Bibcode:2022ScTEn.806o1264B. doi:10.1016/j.scitotenv.2021.151264. ISSN 0048-9697. PMID 34715216.
17. Beale, David J.; Nilsson, Sandra; Bose, Utpal; Bourne, Nicholas; Stockwell, Sally; Broadbent, James A.; Gonzalez-Astudillo, Viviana; Braun, Christoph; Baddiley, Brenda; Limpus, Duncan; Walsh, Tom; Vardy, Suzanne (15 April 2022). "Bioaccumulation and impact of maternal PFAS offloading on egg biochemistry from wild-caught freshwater turtles (Emydura macquarii macquarii)". Science of the Total Environment. 817: 153019. Bibcode:2022ScTEn.817o3019B. doi:10.1016/j.scitotenv.2022.153019. ISSN 0048-9697. PMID 35026273.
18. Beale, David J.; Bissett, Andrew; Nilsson, Sandra; Bose, Utpal; Nelis, Joost Laurus Dinant; Nahar, Akhikun; Smith, Matthew; Gonzalez-Astudillo, Viviana; Braun, Christoph; Baddiley, Brenda; Vardy, Suzanne (10 September 2022). "Perturbation of the gut microbiome in wild-caught freshwater turtles (Emydura macquarii macquarii) exposed to elevated PFAS levels". Science of the Total Environment. 838 (Pt 3): 156324. Bibcode:2022ScTEn.838o6324B. doi:10.1016/j.scitotenv.2022.156324. ISSN 0048-9697. PMID 35654195. S2CID 249213966.

External links

• Bioaccumulation & Biotransformation