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Topic: Evolutionary responses in aquatic organisms in streams affected by acid mine drainage.

Annotated Bibliography: Agra AR., Guilhermino L., Soares AM., and Barata C. “Genetic costs of tolerance to metals in Daphnia longispina populations historically exposed to a copper mine drainage.” Environ Toxico  Chem. 29.4 (2010): 939-946.

The study was conducted on Daphnia longispina to look at three different microevolutionary aspects of adaptations to pollution, in particular acid mine drainage. The researchers looked at tolerance to Zn and Cu, genetic variability of tolerant traits related to fitness, and fitness costs of tolerance. A control group was studied in a clear stream, free of acid mine drainage, when the test group was studied in a stream affected by acid mine drainage. The results showed that both groups were similarly sensitive to Zn, but only sensitive and resistant lineages to Cu were present in the contaminated stream. They also showed that the tolerance to pollution is ecologically costly.

Bickham J.W., Sandhu S., Hebert P.D., Chikhi L., and Athwal R. “Effects of chemical contaminants on genetic diversity in natural populations: implications for biomonitoring and ecotoxicology.” Mutat Res. 463.1 (2000): 33-51.

This article argues how chemical pollution effects genetic variability in natural populations and how conservation biologists are using this to help conserve population genetics. It goes into the issues surrounding the genetic effects of pollution and summarizes how to address these issues.

Bourret, V., Couture, P., Campbell, P.G.C., and Bernatchez, L. “Evolutionary ecotoxicology of wild yellow perch (Perca flavescens) populations chronically exposed to a polymetallic gradient.” Aquatic Toxicology. 86 (2008): 76-90.

This article looks at wild yellow perch and how the chronic exposure to various metals has affected them as a species over time. They looked at the genetic diversity of yellow perch in two major mine areas in Canada. The researchers sampled water and perch from ten lakes to find a correlation between genetic diversity and metal contamination. The results showed that those populations subject to more contamination had greater genetic diversity than those subject to less contamination. The results also showed that over more than 50 years of metal contamination, the genetic diversity within populations of yellow perch has been severely affected.

Janssens, Thierry K.S., Roelofs, Dick ,and Van Straalen, Nico M. “Molecular mechanisms of heavy metal tolerance and evolution in invertebrates.” Insect Science. 16.1 (2009): 3-18.

This article focuses on various mechanisms within invertebrates that have evolved to cope with higher levels of environmental stress, particularly metal-pollution. It goes into the specifics of the metallothionein system and a study on its function in a species of springtail. The results of the study show that a cis-regulatory change of genes involved in stress response may contribute to the evolution of metal tolerance.

Redell, Lori A., Gall, Wayne K., Ross, Robert M., and Dropkin David S. “Biology of the Caddisfly Oligostomis ocelligera (Trichoptera: Phryganeidae) Inhabiting Acidic Mine Drainage in Pennsylvania.” Northeastern Naturalist. 16.2 (2009): 285-306.

A species of caddisfly (Oligostomis ocelligera) was found in a headwater stream in Pennsylvania that had been affected by acid mine drainage (AMD). The caddisfly was able to maintain a stable population that was free from other aquatic insects. The stream that was sampled had a pH of about 3, which is extremely low for any body of water. More than 350 larvae were found a short distance downstream from the inflow of AMD. The pupae found in the stream were very different from other pupae of the Trichoptera order. They had membranous mandibles and their cases were closed off at the anterior end with a silken mesh. --Wittman.33 (talk) 19:20, 29 September 2014 (UTC)

Edited and commented on: https://en.wikipedia.org/wiki/Acidophiles_in_acid_mine_drainage 3 suggestions: This article could be improved if the author does not try to form an argument for the usage of acidophiles in the Rheidol River, UK. It would also be beneficial if the author presented the information in an unbiased manner; not persuading the reader to believe whether or not acidophiles should have a negative connotation or not, but rather leaving that decision up to the audience. Finally, the author could improve this article by suggesting ways acidophiles could be used to remediate acid mine drainage in streams throughout the world, not just in UK mining operations. --Wittman.33 (talk) 18:50, 29 September 2014 (UTC) Sentence and citation: To grow at low pH, acidophiles must maintain a pH gradient of several pH units across the cellular membrane. [1] [1] Baker-Austin, Craig; Dopson, Mark (2007). "Life in acid: PH homeostasis in acidophiles". Trends in Microbiology 15 (4): 165–71. . --Wittman.33 (talk) 19:20, 29 September 2014 (UTC)

FINAL DRAFT STARTS HERE Evolutionary Effects of Living in Contaminated Conditions: Adaptations to Acid Mine Drainage and Heavy Metal Concentrations By: Jacob Wittman Many organisms exhibit various adaptations to allow them to live in the environment they call home. Organisms have long been adapted to harsh environments like sulfur hot springs and super-saline conditions, but what happens when organisms are exposed to these conditions without being historically adapted? Acid mine drainage exposes organisms to low pH and high heavy metal concentrations. These stressors are being introduced not as slow shifts in water chemistry, but as abrupt severe changes, not allowing evolution to occur at its typical gradual change. Populations subsequently evolve and may develop morphological or physiological adaptations in response to such stressors. Organisms living in mountainous headwater streams are currently facing this today. After mining operations searching for coal and other precious metals and minerals leave a site, weathering of the exposed soil and bedrock gives way to acidic runoff, also known as acid mine drainage. This runoff can have a pH of 2.5, similar to the acids found in the stomachs of many animals, and finds its way to headwater streams where damage begins to occur. The drastic change in pH of the stream has its obvious effects on its inhabitants from the denaturing of proteins to reduced nutrient uptake due to the increase of hydrogen ions. Most aquatic organisms are intolerant to acidic conditions lower than a pH of about 6 (Chadde). Those that are more tolerant are typically found in larger warm-water rivers, not cool mountain streams where acid mine drainage is an issue. Acid mine drainage is the runoff that leaches from abandoned and operational surface mines (Urban, 2012). Pyrite, FeS2, is a common mineral found on sites where precious metals and coal deposits are located. Pyrite and other unwanted soil minerals are left on the abandoned site exposed to the elements where weathering processes occur. The weathering of pyrite is the initial step in the process that leads to an increase in acidity; the main chemical reaction occurring is the oxidation of this mineral (Urban, 2012). Essentially the mineral is transformed from FeS2 to Fe(OH)3, and H2SO4, sulfuric acid. Fe(OH)3, commonly known as yellow-iron oxide, is where acid mine drainage-affected streams receive their yellow-orange coloration and sulfuric acid decreases the pH of the water in the stream. These chemicals and ferric iron ions are mainly responsible for loss of habitat for aquatic organisms (Urban, 2012). The acidity of the water then acts to release heavy metals from minerals in the soil, which is why acid mine drainage-affected streams commonly have high heavy metal concentrations. A water sampling done in an affected stream in New Zealand showed that dissolved aluminum was present as the free ion Al3+, the most toxic aluminum species, which dominated in waters of pH 3.8-4.8 (Waters and Webster-Brown, 2013). In these affected streams, organisms have to cope with high acidity and heavy metal toxicity. Over time these contaminants will affect populations and their corresponding genetics. In streams heavily affected by acid mine drainage, intolerant organisms begin to disappear. They simply do not have the ability to survive in such conditions. Aquatic macro-invertebrates are commonly used to determine the quality of aquatic habitats, due to the easy division into tolerant and intolerant orders. Some common intolerant orders include Plecoptera (stoneflies), Ephemeroptera (mayflies), and Trichoptera (caddisflies). These orders typically are the first to disappear when contaminants enter an aquatic habitat. However, a species of Trichoptera, Oligostomis ocelligera, was found in a degraded headwater stream in Pennsylvania that was severely impacted by acid mine drainage (Redell et al, 2009). The larvae were observed in high quantity and were able to sustain a large population. This could have been due to the lack of competition from other macro-invertebrates, or the population in this stream has become adapted to living in this type of environment. The stream had a very low pH, 2.58–3.13, high concentrations of sulfate, 542 mg/L, and high concentrations of heavy metals: iron, manganese, and aluminum (Redell et al, 2009). It is not clear as to how Oligostomis ocelligera is able to live in such conditions, as the species is generally poorly studied, other than basic life history details. However, there are physiological adaptations that other invertebrates use to cope with stressors associated with acid mine drainage that Oligostomis ocelligera may be using as well. Macro-invertebrates, and any other organisms, are subject to acute stressors throughout their lives. This could include daily fluctuations in temperature or dissolved oxygen levels or seasonal fluctuations in salinity due to rock salt usage on roads. They do this using physiological acclimatization, which is a form of phenotypic plasticity, where an organism can adjust its metabolism in a short-term response to environmental stressors (Bickham et al, 2000). This would allow an organism to survive a relatively short-lived condition. However, chronic stressors that do not fluctuate daily or seasonally are much harder to cope with simply because they do not go away. Genetic adaptation can occur as a result of these conditions, allowing an increase in fitness in those whose genotypes have better constitutive or plastic responses toward adverse environmental conditions (Bickham et al, 2000). This would increase the frequency of the genes responsible and place negative selection on the deleterious genes among the population. In response to high heavy metal concentrations a Dipteran species, Chironomus riparius, of the midge family, Chironomidae, has evolved to become tolerant to Cadmium toxicity in aquatic environments. Altered life histories, increased Cd excretion, and sustained growth under Cd exposure is evidence that shows that Chironomus riparius exhibits genetically based heavy metal tolerance (Bickham et al, 2000). This species of Chironomidae, as well as other aquatic macro-invertebrates could have developed this tolerance over a short period of time if: life cycles are short and a large quantity of offspring are produced, as well as enough genetic diversity in the population. Aquatic macro-invertebrates typically exhibit these qualities making this sped-up evolution possible. Populations can evolve this tolerance by altering the structure of proteins or by altering the amount of protein that is produced (Janssens et al, 2009). So essentially Chironomus riparius was able to adapt physiologically by developing the ability to increase its secretion of Cadmium from its system. However, some populations do not respond as well and consequently become negatively affected by contaminants they are exposed to. The presence of contaminants, like heavy metals and hydrogen ions, impact organisms in various ways. Toxicity can occur at a level that organisms cannot cope with and they become eliminated from the system. Alternatively, if genetic variability in the ability to cope with said contaminants is present in the population, the contaminants could only affect a certain portion of individuals, leaving only a proportion of the original population alive. This would create a bottleneck effect and decrease genetic variability in the affected population. In Canada, a study examined genetic diversity in wild yellow perch along various heavy metal concentration gradients in lakes polluted by mining operations. Researchers wanted to determine as to what effect metal contamination had on evolutionary responses among populations of yellow perch. Along the gradient, genetic diversity over all loci was negatively correlated with liver cadmium contamination (Bourret et al, 2008). Researchers could infer that cadmium contamination was decreasing overall genetic diversity in these populations through demographic bottlenecks or metal-induced selection (Bourret et al, 2008). Additionally, there was a negative correlation observed between copper contamination and genetic diversity. The genetic effect was observed at a single locus (Pfla L1), thus allowing the researchers to hypothesize that copper contamination had only a local effect on this gene (Bourret et al, 2008). It is unclear as to how metal contamination is affecting the genes in populations of yellow perch; researchers were simply searching for a correlation between the two. However, it is known that contamination can cause population reduction by the effects of somatic and heritable mutations along with physical impacts of toxicity. These drivers would inevitably lead to a decrease in genetic diversity merely through the loss of individuals representing the gene pool. Genetic diversity is of major concern to conservation biologists and wild yellow perch are not the only organisms whose genetic diversity and structure has been affected by contaminants from mine drainage. A population of Daphnia longispina has been subject to drainage from a copper mine for over 50 years. Because of this, Daphnia longispina has suffered major changes in genetic makeup. The presence of copper and other metal contaminants increases the rate of mutation in affected organisms. Upon initial exposure, the increased rate of mutation may cause an immediate increase in population genetic diversity (Agra et al, 2010). However, since the majority of mutations accumulate and are deleterious, increased mortality and/or a decreased reproduction rates can occur (Agra et al, 2010). A study compared genetic diversity between two different populations of Daphnia longispina. One population has been subject to chronic acid mine drainage from a copper mine, and one that had not. It has been observed that acid mine drainage and metal contamination can decrease genetic diversity, but no difference in diversity was seen in this species. It is not known why this population of Daphnia did not follow other trends of loss. This could be due to the extended period of time this species had been exposed to the drainage. The initial contamination may have caused a decrease in genetic diversity, but over time selection and mutation events could have re-diversified the genetics of this population. Aquatic populations exposed to acid mine drainage, and the heavy metal concentrations that follows, typically experience negative effects. These could be in the form of a loss in genetic diversity or a loss in total population numbers all together. Streams and lakes severely impacted by acid mine drainage are commonly void of any life whatsoever. Even those that are the most tolerant do not appear since the conditions are so harsh. However, some species have evolved to live in these acidic and metal contaminated habitats through physiological or morphological adaptations. As minerals present at abandoned mines continue to weather, the buffer capacity of these streams will be reduced and unaltered aquatic habitats downstream will become affected as well. In order to conserve the genetic diversity and species diversity of these aquatic organisms, much work needs to be done in order to reduce the effects of acid mine drainage. Currently liming and the construction of wetlands at or near the mine are done to counteract the acidity and encourage the precipitation of heavy metals. The continuation of these efforts will help conserve the aquatic habitat not yet affected by acid mine drainage. References Agra AR., Guilhermino L., Soares AM., and Barata C. (2010). “Genetic costs of tolerance to metals in Daphnia longispina populations historically exposed to a copper mine drainage.” Environ Toxico Chem. 29.4: 939-946. Bickham J.W., Sandhu S., Hebert P.D., Chikhi L., and Athwal R. (2000). “Effects of chemical contaminants on genetic diversity in natural populations: implications for biomonitoring and ecotoxicology.” Mutat Res. 463.1: 33-51. Bourret, V., Couture, P., Campbell, P.G.C., and Bernatchez, L. (2008). “Evolutionary ecotoxicology of wild yellow perch (Perca flavescens) populations chronically exposed to a polymetallic gradient.” Aquatic Toxicology. 86:76-90. Chadde, J. S. Macroinvertebrates as Bioindicators of Stream Health. Janssens, Thierry K.S., Roelofs, Dick ,and Van Straalen, Nico M. (2009). “Molecular mechanisms of heavy metal tolerance and evolution in invertebrates.” Insect Science. 16.1: 3-18. Redell, Lori A., Gall, Wayne K., Ross, Robert M., and Dropkin David S. (2009). “Biology of the Caddisfly Oligostomis ocelligera (Trichoptera: Phryganeidae) Inhabiting Acidic Mine Drainage in Pennsylvania.” Northeastern Naturalist. 16.2: 285-306. Urban, A. (2012, Spring). How Acid Mine Drainage Has Affected the Greater Susquehanna Waters, A. S., & Webster-Brown, J. G. (2013). Assessing aluminium toxicity in streams affected by acid mine drainage. Water Science & Technology, 67(8): 1764-1772.Wittman.33 (talk) 01:02, 17 November 2014 (UTC)