Are elevated levels of mercury in the American dipper due to run-of-river dams?

November 01, 2017

A study published in Environmental Toxicology and Chemistry used American dippers to determine if run-of-river (RoR) dams altered food webs and mercury levels at 13 stream sites in British Columbia.

Run-of-river dams are deemed "green energy" because they produce lower greenhouse gas emissions, have lower water storage, barrier size, extent of flooding and water level fluctuations than conventional hydropower facilities. They divert part of a stream through turbines before returning it to the stream downriver. The impact this process has on the ecosystem is unknown, particularly with regards to the production of methylmercury as a result of the dam and the disruption of natural flows. RoR dams can cause a spike in methylmercury in two ways - they can form small reservoirs, called headponds, which flood soil and create slow-flowing, low-oxygen environments; or they can create higher temperatures in the stream as a result of the reduced flow conditions when portions of the stream are diverted to the turbines.

American dippers are river birds that live along fast-moving mountain streams and are considered an excellent indicator of stream quality. While some populations migrate up and down the mountain streams, they are strictly aquatic feeding on underwater insects and salmon eggs and fry that can accumulate methylmercury and biomagnify it up the food chain. All of that combined makes the American dipper a suitable indicator of stream quality and contaminant exposure.

Author Veronica Silverthorn and her colleagues sampled American dipper blood and feathers in coastal British Columbia to assess the bird's diet and mercury levels. The blood samples showed birds on regulated streams were feeding more in the run-of-river headponds, but there were no significant differences in mercury levels between dippers at run-of-river regulated streams compared with those at unregulated streams. Overall, dippers had higher mercury levels than most other songbirds tested in western North America, which may be due to more atmospheric deposition of mercury in snow at these high elevations. Silverthorn notes that future studies should "monitor mercury concentrations of the entire food-web before and after the RoR regulation, both upstream and downstream of the intake since there is high potential for methylmercury production in these systems that may change over time."
-end-


Society of Environmental Toxicology and Chemistry

Related Mercury Articles from Brightsurf:

Mercury's 400 C heat may help it make its own ice
Despite Mercury's 400 C daytime heat, there is ice at its caps, and now a study shows how that Vulcan scorch probably helps the planet closest to the sun make some of that ice.

New potential cause of Minamata mercury poisoning identified
One of the world's most horrific environmental disasters--the 1950 and 60s mercury poisoning in Minamata, Japan--may have been caused by a previously unstudied form of mercury discharged directly from a chemical factory, research by the University of Saskatchewan (USask) has found.

New nanomaterial to replace mercury
Ultraviolet light is used to kill bacteria and viruses, but UV lamps contain toxic mercury.

Wildfire ash could trap mercury
In the summers of 2017 and 2018, heat waves and drought conditions spawned hundreds of wildfires in the western US and in November, two more devastating wildfires broke out in California, scorching thousands of acres of forest, destroying homes and even claiming lives.

Removing toxic mercury from contaminated water
Water which has been contaminated with mercury and other toxic heavy metals is a major cause of environmental damage and health problems worldwide.

Fish can detox too -- but not so well, when it comes to mercury
By examining the tissues at a subcellular level, the researchers discovered yelloweye rockfish were able to immobilize several potentially toxic elements within their liver tissues (cadmium, lead, and arsenic) thus preventing them from interacting with sensitive parts of the cell.

Chemists disproved the universal nature of the mercury test
The mercury test of catalysts that has been used and considered universal for 100 years, turned out to be ambiguous.

Mercury rising: Are the fish we eat toxic?
Canadian researchers say industrial sea fishing may be exposing people in coastal and island nations to excessively high levels of mercury.

New estimates of Mercury's thin, dense crust
Michael Sori, a planetary scientist at the University of Arizona, used careful mathematical calculations to determine the density of Mercury's crust, which is thinner than anyone thought.

Understanding Mercury's magnetic tail
Theoretical physicists used simulations to explain the unusual readings collected in 2009 by the Mercury Surface, Space Environment, Geochemistry, and Ranging mission.

Read More: Mercury News and Mercury Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.