Wendy Choi Mr. Cook Ib Biology (period 3) 3 Oct

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Wendy Choi Mr. Cook IB Biology (Period 3) 3 Oct 2008

Research Article – Biomagnifications

Subjects:

Water pollution, Research, Lakes, Fish

Author(s):

Kidd, Karen A, Schindler, David W, Muir, Derek C G, Lockhart, W Lyle, Hesslein, Raymond H

Publication title:

Science. Washington: Jul 1995. pg. 240, 3 pgs

ISSN:

00368075

Text Word Count 2186

1. What is the hypothesis of the work? The high concentrations of toxaphene in fishes from subarctic Lake Laberge in Canada's Yukon Territory resulted from the biomagnification of point sources. Since the stable delta sup 15 N values in fish represent the integral of several months of feeding, which provides a continuous measure of trophic position. It is also demonstrated that delta sup 15 N in lake trout muscle is correlated with food-chain length across a large number of lakes and thus the hypothesis that delta sup 15 N would be directly correlated with contaminant concentrations in individuals varying in trophic position. 2. What did the researcher do to try to prove the hypothesis? What conclusions did the researcher reach? This group of researchers based their research on a routine survey of contaminants in fishes from Yukon lakes in 1991, which reveals that the lake trout (Salvelinus namaycush) and the burbot (Lota lota) from Lake Laberge were contaminated with toxaphene and other lipophilic contaminants much higher than same species from other subarctic and arctic lakes and rivers. Despite Canada and the United States’ discontinued use of toxaphene as a piscicide and pesticide in the early 1980s, it is still used by Eurasians and Central Americans with longrange atmospheric transport to subarctic and arctic regions, thus causing an elevated concentration of toxaphene in upper-trophic-level biota from the Arctic, far away from its original source. To prove their point after their basic background research, they drew large-volume water samples from six lakes on the Yukon River system and sup 210 Pb-dated sediment core slices from Laberge, Fox, and Kusawa lakes were used as back-up measures for toxaphene inputs from atmospheric or point sources. “The total toxaphene concentration in Laberge water (23 pg liter sup -1 ) was within the range found for five other lakes in southern Yukon [12 to 27 pg liter sup -1 (20)]. Surface and maximum fluxes of toxaphene in the sediment cores were

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comparable in all three lakes, similar to those found in other arctic cores and orders of magnitude lower than values found in temperate lakes previously treated with toxaphene (Table 1) (21). We thus dismissed the hypothesis that Laberge received elevated inputs of toxaphene from point sources,” concluding that high concentrations of toxaphene in fishes from Laberge resulted entirely from the biomagnification of atmospheric inputs. The stable nitrogen isotope ratios (delta sup 15N) were thus calculated with the equation: delta sup 15 N = [( sup 15 N/ sup 14 N sub sample / sup 15 N/ sup 14 N sub atmos. nitrogen ) - 1] X 1000, which provides for an index of trophic level for freshwater organisms.

3. Make some personal observations. Were there flaws in any part of the design or conclusions? In this experiment, which is largely based on the accuracy of water samples collected as well as the amount of sup 210 Pb-dated sediment core slices added. For the fact that the researchers did not specify the method of collecting the water or details in the instruments to be used in measuring the amount of each reactor in the experiment, one cannot identify possible flaws throughout the process. However, human mistakes are inevitable; thus, there are no specification on how many times each trial is repeated or how many people have been at the site to observe the sample as it first reacted. Generally speaking though, this experiment is well designed and aims to observe the few lakes that it has under suspicion and does— at the end— finds a definite cause to the high concentrations of toxaphene in fishes from subarctic Lake Laberge in Canada's Yukon Territory, which resulted entirely from the biomagnifications of atmospheric inputs. Despite its success, I personally do not agree that the word “entirely” should be used because there is always room for improvement and there may be other not-yet-identified causes of high toxaphene concentrations in the Laberge.