Just three years ago, one small lake in Ireland caused over 182 people to be diagnosed with the often fatal, intestinal parasitic disease, cryptosporidiosis. The disease is caused by the pathogen Cryptosporidium and is most commonly spread by feces digestion. To great dismay of the public, this lake, known as Lough Corrib, was governmentally recognized as safe for drinking and recreational activities for the public. If one small lake was so unknowingly highly concentrated with pathogens, how is the community to trust that the surrounding lakes used for drinking water abstraction and leisure are nontoxic? The academic journal Aquatic Invasions recently débuted a research article in which a team of environmental and health scientists tested Lough Arrow lake in Sligo, Ireland for waterborne parasites. Based on the prior knowledge that zebra mussels are an indicator of the presence of pathogens, the scientists set goals to prove that the size of a zebra mussel does not affect the effectiveness in which it concentrates Cryptosporidium oocysts, Giardia cysts, and microsporidian spores, and, secondly, to examine the existence of pathogens causing intestinal disease in order to determine the risk to the public posed by the lake’s water quality.
The research of the article, titled “Zebra Mussels (Dreissena polymorpha) are Effective Sentinels of Water Quality Irrespective of Their Size,” relies on previous scientific studies that have proven that zebra mussels are valuable indicators of concentration levels and viability of the pathogens Cryptosporidium, Giardia, and microsporidian because of their ability to concentrate the particles of the parasites. After a nominal amount of research, I found that the viability of a pathogen refers to the likelihood that it will persist or be capable of living. This is important knowledge for scientists analyzing bodies of water because if the pathogen has no chance of persisting, then attempting to treat the water or solve runoff issues is time wasted. As mentioned above, the first researched parasite is Cryptosporidium and it can be life threatening. Additionally, it is one of the most well-known and severe sources of waterborne-etiology diarrhea. The parasites Giardia and microporidia are known to pollute bodies of water as a result of wastewater seepage, urban runoff, and agricultural undertakings. The parasites are usually transferred through oocysts, cysts, and spores, respectively. As stated by the article, “it is believed that the ingestion of only ten oocysts can cause a human cryptosporidiosis infection” (Lucy). Thus, depending on the levels measured by the zebra mussels, the water in Lough Arrow can propose a great threat to the dependant community.
Before one can analyze the procedures and results of the zebra mussel research, one has to become familiar with the conditions of the experimenting location. The area selected as the testing location for the project is a small lake used for fishing, drinking water, and wastewater treatment. Lough Arrow is situated in the valley of three surrounding hills and has streams that flow into the body of the lake. Another distinctive aspect of the lake is that it is a designated Special Protection Area for birds, meaning that many species breed and populate the area. In Ireland, zebra mussels are considered an invasive species and were recently first recorded in Lough Arrow in 2003. As a result of the latest influx of zebra mussels, transparency of the lake water has increased; however, despite popular belief, the improved transparency does not reflect an upgrade in water quality. Many lakes in Ireland, including Lough Arrow, are exceptionally susceptible to pollution from agricultural waste and runoff from wastewater treatment plants and septic tanks. Consequently, human health is an important consideration as a result of possible fecal contamination from humans and farm animals. To fairly assess the quality of the lake, six distinct sites on Lough Arrow were chosen to be tested for concentration levels of the three main parasites. Three of the zebra mussel sampling sites were the locations of drinking water plant intake screens, two sites were at the intersection of inflowing streams from wastewater plants and the body of the lake, one site was labeled as low-impact and located close to shore, one of the previous sites was located near a farm with cattle, and the last site was on a filter inside a drinking water plant that extracts water from the lake. The strategically placed testing sites attempt to prove the source of contamination based on varying concentration levels at the different locations.
In order to compare concentrations of human waterborne parasites in different bodies of water without boundaries set by the age and density of zebra mussels or varying environmental factors, the team of researchers created an experiment testing the hypothesis that zebra mussels are an effective portrayal of the concentration of contamination in water regardless of their size. To test this hypothesis, the team first collected zebra mussel samples by using divers to remove them from the six testing sites by hand. Next, each sample was labeled with its site of origin and stored on the boat. The samples were then cleaned and organized into three main size intervals. The ranges selected were 11-15 mm, 16-20 mm, and 21-25 mm. The fourth step was to blend, or homogenize, each mussel with its shell. The resulting homogenates were then sedimented by gravity overnight and the top settlement was collected in a tube and centrifuged- the use of a machine to cause centrifugal force in order to separate substances of different densities. The liquid material resulting from the centrifugation was then discarded and the remaining material was stored in an ethanol substance. The next step was to wash the matter of its alcohol by the process of centrifugation and divide it into two parts. Each part was tested using the fluorescence in situ hybridization technique, known as FISH. Simply stated, FISH uses fluorescent probes to identify species-specific sequences of rRNA that reveal the type of pathogens. The final step to determining the existence and concentration of parasites from zebra mussels was to examine each sample blindly using a high powered microscope to identify and count the pathogens found. Though the actual procedure for the experiment is extensively more complex and involved, these simplistic steps allow enough insight for a student to gain the basics of the experiment and recognize the credibility and tediousness of the research.
After testing various sizes, ages, and densities of zebra mussels, the results of the experiment show that the concentration of pathogens in the mussels were unchanged by the size of the mussel, but the quantity of pathogens did vary with the pathogen species. Contamination from fecal matter was found at all three drinking water plants, and all of the pathogens were equally represented at each plant with about the same number of potential pathogens at each plant. A human source of contamination was evident at the drinking water plant screen because of the presence of Cryptosporidium; however, there were no pathogens found in the filter inside of the drinking water treatment plant. At the sites where the stream from the wastewater treatment plant intersected with the lake body, a higher concentration of pathogens was found closer to the intersection, where as the amount of pathogens decreased toward the middle of the lake body. Since zebra mussels are stationary creatures, this data is especially important because it clearly shows the concentrations of pathogens based on location, which helps analyzers can determine the source of contamination and how to manage water quality.
Based on the research published and peer reviewed in the Aquatic Invasion journal, it has been tested and supported with clear data that zebra mussels are efficient indicators of water contamination by human waterborne pathogens and the size of the zebra mussel is not a factor when comparing concentrations from different bodies of water. Also, because of the high levels of Cryptosporidium oocysts, Giardia cysts, and microsporidian spores found in the Lough Arrow lake, it is risky for humans to use the water for drinking or recreational purposes.
http://www.aquaticinvasions.net/2010/AI_2010_5_1_Lucy_etal.pdf
The research of the article, titled “Zebra Mussels (Dreissena polymorpha) are Effective Sentinels of Water Quality Irrespective of Their Size,” relies on previous scientific studies that have proven that zebra mussels are valuable indicators of concentration levels and viability of the pathogens Cryptosporidium, Giardia, and microsporidian because of their ability to concentrate the particles of the parasites. After a nominal amount of research, I found that the viability of a pathogen refers to the likelihood that it will persist or be capable of living. This is important knowledge for scientists analyzing bodies of water because if the pathogen has no chance of persisting, then attempting to treat the water or solve runoff issues is time wasted. As mentioned above, the first researched parasite is Cryptosporidium and it can be life threatening. Additionally, it is one of the most well-known and severe sources of waterborne-etiology diarrhea. The parasites Giardia and microporidia are known to pollute bodies of water as a result of wastewater seepage, urban runoff, and agricultural undertakings. The parasites are usually transferred through oocysts, cysts, and spores, respectively. As stated by the article, “it is believed that the ingestion of only ten oocysts can cause a human cryptosporidiosis infection” (Lucy). Thus, depending on the levels measured by the zebra mussels, the water in Lough Arrow can propose a great threat to the dependant community.
Before one can analyze the procedures and results of the zebra mussel research, one has to become familiar with the conditions of the experimenting location. The area selected as the testing location for the project is a small lake used for fishing, drinking water, and wastewater treatment. Lough Arrow is situated in the valley of three surrounding hills and has streams that flow into the body of the lake. Another distinctive aspect of the lake is that it is a designated Special Protection Area for birds, meaning that many species breed and populate the area. In Ireland, zebra mussels are considered an invasive species and were recently first recorded in Lough Arrow in 2003. As a result of the latest influx of zebra mussels, transparency of the lake water has increased; however, despite popular belief, the improved transparency does not reflect an upgrade in water quality. Many lakes in Ireland, including Lough Arrow, are exceptionally susceptible to pollution from agricultural waste and runoff from wastewater treatment plants and septic tanks. Consequently, human health is an important consideration as a result of possible fecal contamination from humans and farm animals. To fairly assess the quality of the lake, six distinct sites on Lough Arrow were chosen to be tested for concentration levels of the three main parasites. Three of the zebra mussel sampling sites were the locations of drinking water plant intake screens, two sites were at the intersection of inflowing streams from wastewater plants and the body of the lake, one site was labeled as low-impact and located close to shore, one of the previous sites was located near a farm with cattle, and the last site was on a filter inside a drinking water plant that extracts water from the lake. The strategically placed testing sites attempt to prove the source of contamination based on varying concentration levels at the different locations.
In order to compare concentrations of human waterborne parasites in different bodies of water without boundaries set by the age and density of zebra mussels or varying environmental factors, the team of researchers created an experiment testing the hypothesis that zebra mussels are an effective portrayal of the concentration of contamination in water regardless of their size. To test this hypothesis, the team first collected zebra mussel samples by using divers to remove them from the six testing sites by hand. Next, each sample was labeled with its site of origin and stored on the boat. The samples were then cleaned and organized into three main size intervals. The ranges selected were 11-15 mm, 16-20 mm, and 21-25 mm. The fourth step was to blend, or homogenize, each mussel with its shell. The resulting homogenates were then sedimented by gravity overnight and the top settlement was collected in a tube and centrifuged- the use of a machine to cause centrifugal force in order to separate substances of different densities. The liquid material resulting from the centrifugation was then discarded and the remaining material was stored in an ethanol substance. The next step was to wash the matter of its alcohol by the process of centrifugation and divide it into two parts. Each part was tested using the fluorescence in situ hybridization technique, known as FISH. Simply stated, FISH uses fluorescent probes to identify species-specific sequences of rRNA that reveal the type of pathogens. The final step to determining the existence and concentration of parasites from zebra mussels was to examine each sample blindly using a high powered microscope to identify and count the pathogens found. Though the actual procedure for the experiment is extensively more complex and involved, these simplistic steps allow enough insight for a student to gain the basics of the experiment and recognize the credibility and tediousness of the research.
After testing various sizes, ages, and densities of zebra mussels, the results of the experiment show that the concentration of pathogens in the mussels were unchanged by the size of the mussel, but the quantity of pathogens did vary with the pathogen species. Contamination from fecal matter was found at all three drinking water plants, and all of the pathogens were equally represented at each plant with about the same number of potential pathogens at each plant. A human source of contamination was evident at the drinking water plant screen because of the presence of Cryptosporidium; however, there were no pathogens found in the filter inside of the drinking water treatment plant. At the sites where the stream from the wastewater treatment plant intersected with the lake body, a higher concentration of pathogens was found closer to the intersection, where as the amount of pathogens decreased toward the middle of the lake body. Since zebra mussels are stationary creatures, this data is especially important because it clearly shows the concentrations of pathogens based on location, which helps analyzers can determine the source of contamination and how to manage water quality.
Based on the research published and peer reviewed in the Aquatic Invasion journal, it has been tested and supported with clear data that zebra mussels are efficient indicators of water contamination by human waterborne pathogens and the size of the zebra mussel is not a factor when comparing concentrations from different bodies of water. Also, because of the high levels of Cryptosporidium oocysts, Giardia cysts, and microsporidian spores found in the Lough Arrow lake, it is risky for humans to use the water for drinking or recreational purposes.
http://www.aquaticinvasions.net/2010/AI_2010_5_1_Lucy_etal.pdf
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