Scientists have learned more about elevated mercury concentrations in Great Salt Lake, and a new report by the U.S. Geological Survey shows that brine shrimp and, in particular, the eared grebes that eat them are being impacted.
Exactly how much lasting damage is being done by mercury contamination will be the subject of another report due out in about nine months that will be coauthored by the U.S. Fish and Wildlife Service.
The new USGS report title is long: "Anthropogenic influences of the input of biogeochemical cycling of nutrients and mercury in Great Salt Lake, Utah, USA." It's published in this month's international journal "Applied Geochemistry."
The report's findings indicate that new pathways, such as sustained high winds, are in effect treating the lake like a mixing bowl, melding mercury present in the water with brine shrimp, where the mercury "bioaccumulates." Many bird species eat the shrimp, but USGS singles out grebes.
The grebes molt for about three to five months around fall and don't fly as a result. While on the lake shores, they dine on the contaminated shrimp. Studies of the birds during that period have revealed an increase of mercury in their livers three times the amount found at other times of the year.
"We found that the composition of isotopes found in brine shrimp change in a consistent manner over the growing season, likely reflecting a change in the type of algae that brine
shrimp were eating," said Dave Naftz, the main author of the USGS report. For an e-mail request of the new USGS report, contact [email protected].
On the phone Naftz explained how an inorganic form of mercury in the lake is actually being transformed into a toxic form. The concerns now include not just global sources of mercury pollution but also the processes that stir up or mix relatively harmless mercury with human-added mercury.
"It's not necessarily the source," Naftz said about the question of cause and effect.
Nathan Darnall, an ecologist with U.S. Fish and Wildlife Service, said mercury can cause numerous problems for birds. Those can include an impact on the neurological system, leading to less attention by adults to their eggs or a reduced responsiveness to predator alarms by ducklings, or a diminishment of their immunity, which can make disease more deadly.
But currently, there is no proof that any of those are happening.
"At this point, I am not aware of any data suggesting that any of the above examples are occurring," he said.
Even if the problems for birds are not documented, debates about the sources for mercury are ongoing.
Last month the Utah Department of Environmental Quality issued what it calls a "Mercury Source Protocol" to provide methods of identifying sources of mercury in lakes and rivers throughout Utah. DEQ's document is the result of fish consumption advisories that began in August 2005. For a look at the whole 90-page report, visit www.deq.utah.gov/docs/Mercury_Source_Protocol_Utah_Apr08.pdf.
The advisories in DEQ's report pointed out how mercury contamination is bioaccumulating up the food chain. Also in 2005 the USGS warned against eating three types of waterfowl living around the lake. As of this time last year, nine counties in Utah were included in "mercury fish advisories, mostly in reservoirs, targeting splake, brown and rainbow trout, channel catfish and large mouth bass."
To a certain extent, mercury is naturally occurring. But human activity releases more mercury into the environment, and then it can become a highly toxic heavy metal that even at low concentrations can affect the central nervous system and the brain, DEQ points out.
So, where is the extra mercury coming from? Depends who you ask or what you read.
Some say power plants. Some generalize and say industry. The national group Sportsmen United for Sensible Mining contends that contamination in the lake is caused by mining operations upwind in Nevada. That group last month released its own report, found at www.sensiblemining.org/documents/sensiblesolutions.pdf, calling for an end to mining's priority status on public lands.
Naftz said mercury is ubiquitous, in the atmosphere everywhere and coming from sources around the world.
"We have global sources of mercury coming into the atmosphere from China," Naftz noted. He also acknowledged regional sources such as industrial activity in Nevada.
One question he raised last week is how much of an effect the combination of naturally existing mercury, such as in areas of southwestern Utah, and human-added mercury are resulting in fish and waterfowl consumption advisories in Utah.
The Utah group Great Salt Lakekeeper isn't waiting for more answers to get involved. Director Jeff Salt is aiding efforts to educate the public about mercury in Utah's watershed and what to do about it, and he would like the state to become even more involved."Our governor and state Legislature really need to step up and recognize the potential risks that mercury compounds can have on our human and wildlife populations and allocate significantly more funds for critical research and monitoring needs," Salt said in a statement. "Our health and economy depend on identifying, controlling and reducing mercury from the environment."
E-mail: [email protected]