[h=1]Mercury levels drop in Atlantic bluefin tuna[/h] [h=2]Study shows 19-percent improvement in just 8 years.[/h]
Scott K. Johnson - Dec 6, 2016 4:24 pm UTC
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A recent study led by Stony Brook University?s
Cheng-Shiuan Lee took advantage of an archive of Atlantic bluefin tuna tissue samples from fish caught between 2004 and 2012 to find out whether mercury levels are improving as regulations and declining coal use reduce North American emissions that drift over the Atlantic.
The researchers analyzed almost 1,300 samples from 9- to 14-year-old fish, each of which were measured, weighed, and examined when they were caught. The fish were caught on commercial boats working the waters of the Gulf of Maine and Gulf of St. Lawrence, mainly, but these tuna travel pretty widely. Older and bigger fish tend to contain more mercury, so the researchers compared fish of the same age over time?all the 9-year-old fish caught each year, for example.
The results showed just how effectively mercury gets concentrated in these apex predators. Tissue samples contained as much as
100 million times the concentration of mercury in seawater. But each age group showed a consistent pattern of declining mercury concentrations?a drop of about 19 percent between 2004 and 2012. Because of the age of the fish, that actually represents changes in the Atlantic Ocean going back to about 1990...
