Tracking Mercury from Ore to Organisms

Amelia Barrales: Hello and welcome to a sneak preview of our "Western Region - Evening Public Lecture" for June 25th. I'm Amelia Barrales and today we have in the USGS Western Ecological Research Center Tom Suchanek. Well, Tom, summer's here and people will be doing some camping and fishing, I'm sure, which brings us to your talk, "Tracking Mercury from Ore to Organism". Thank you for giving us a glimpse of what is to come in your talk.

Tom Suchanek: Amelia, it'll be a pleasure to join you. I'm looking forward to Thursday evening's talk. As you know, this is the culmination of about 15 years worth of work by about 45 scientists from UC Davis and other universities around the country. As you also know, this is the final release of the publication in the Ecological Applications journal of about 17 papers that culminates the work that we've done at Clear Lake. So, it will be a good summary of what we've done.

Amelia Barrales: I wanted to know, first off, when did mercury contamination become a problem in Clear Lake?

Tom Suchanek: That's an interesting question.00:58

The mining operations at Clear Lake started in the 1800s, about 1865 with a sulfur mine. So, they decided to convert it from a sulfur mine into a mercury mine about 1873. Concentration of mercury just jumped exponentially around 1927, which is exactly the time that they started the open-pit mining, and they actually dumped the tailings of the mine right into the lake. It was about a hundred metric tons of mercury that they deposited into the lake from this dumping. And that's really when the mercury started to become a problem was about 1927.

Amelia Barrales: How does the mercury concentration in Clear Lake compare with that of other lakes and reservoirs in California?

Tom Suchanek: Well, again, Clear Lake is an unusual place and that it has an enormous amount of mercury being dumped into it. It's probably one of the most mercury-contaminated lakes in the world. However, the mercury concentration in the fish really is pretty comparable to many other water bodies in the state.01:58

There's about 25 or 24 other water bodies in the state of California that have fish consumption advisories in them and most of those water bodies have mercury concentrations in fish tissue—and that is the fillet, the part that we eat—of about 2 parts per million. And that's not as high as we might expect based on the amount of mercury that's being dumped into the lake.

There are other places in California where there are much higher concentrations because they're very different water bodies. They can go up to 6 or 7 or 8 parts per million, which is extremely high. So, all in all, Clear Lake is pretty comparable to many others, but in reality, that is still too high to allow unregulated fish consumption.

Amelia Barrales: If there is so much mercury entering Clear Lake from the abandoned mine, why don't the fish have higher mercury concentrations than they do?

Tom Suchanek: Well, that's an easy question, but it's a complex answer, unfortunately. And that's, hopefully, what I wish to get into on Thursday evening.

Amelia Barrales: Are there human consumption advisories for eating fish from Clear Lake?03:00

Tom Suchanek: There are. The California Department of Fish and Game first announced human consumption advisories in about 1985 and they've been revised a couple of times. But the regulation states mdash; if you look in the back of your California Department of Fish and Game manual that they'd give you when you get your fishing license, it lists Clear Lake and the number of other water bodies in there.

And for Clear Lake, it states that if you're a pregnant woman or a nursing mother or a child, you really shouldn't be eating any of the top predatory fish in the lake, like largemouth bass or like catfish. If you're not one of those types of humans, maybe a grown male, for instance, you probably shouldn't be eating more than about one pound per month of that same type of fish.

Amelia Barrales: Thank you so much, Tom. We look forward to hearing more by the end of the week.

Tom Suchanek: My pleasure. We'll look forward to seeing you on Thursday.

Amelia Barrales: If you're interested in learning more about Tom's upcoming lecture, interview any of our previous lectures, please visit our USGS Evening Public Lecture Series website, at online.wr.usgs.gov/calendar.04:06

His video will be available online at the end of the month for viewing. Thank you for your interest in our Western Region Evening Public Lecture Series. This is a production of the U.S. Geological Survey, Department of Interior.