Grad student sheds light on mercury contamination in fish

There was a statewide advisory on large-mouth bass for mercury, and we thought that seemed kind of overkill because the variation of mercury across the state for a single species is just amazing –- I mean, 10- to 100-fold differences in mercury in the same species, in the same river basin. With all that variation, we thought if we could explain some of that or understand how mercury moves through ecosystems we could get a better idea of areas where you might have high levels of mercury and other areas that are actually safe to eat the fish.

My name is Dana Sackett. I’m a Ph.D. student here at N.C. State working on getting my degree in biology and a minor in environmental toxicology. My project mainly looks at mercury contamination in fish and focuses on the risk to wildlife and people.

Our first step was looking at data that had been collected by the Division of Water Quality, and we took all that data and used different environmental factors that are pretty easy to measure — like ph or just the species of the fish or the area that the lake is in — and came up with a statistical model to explain all that variation in mercury we saw.

And the second project that we’ve done is looking at coal-fired power plants, because they are a main source of mercury. So what we wanted to do is say. Well, next to these coal-fired power plants where you are going to expect to see higher levels of deposition of mercury, does that translate into higher levels in the fish? And what we found was actually really surprising. We found that next to coal-fired power plants there was significantly less mercury than we found in any lakes far away. The reason is that selenium comes out of coal-fired power plants, too, and that’s actually found to negate mercury accumulation in fish.

The next project that we are working on is looking at is pretty much fish size and age and mercury. Size regulations on fish tell a fisherman you can take this fish home and eat it to keep fish populations sustainable. However what we don’t know is are we encouraging fishermen to always take home high mercury fish; older and your typically bigger fish have higher mercury because they just lived longer and so they’ve accumulated it over time.

The main message with the mercury stuff is, It is really important that we understand it well so we can control our risk.

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