Land Animals Could Pick Up Methylmercury From The Sea | Chemical & Engineering News
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Web Date: April 27, 2015

Land Animals Could Pick Up Methylmercury From The Sea

Environment: Analysis of Arctic lichens shows that the ocean may be an important source of the toxic compound worldwide
Department: Science & Technology | Collection: Life Sciences
News Channels: Environmental SCENE, Analytical SCENE
Keywords: mercury, methylmercury, Arctic, caribou, lichens
The open ocean transfers toxic methylmercury into lichens, a favorite wintertime food of caribou in the Arctic.
Credit: Martin Fortier/ArcticNet
Photo of a caribou eating lichen along a coast in Norway.
The open ocean transfers toxic methylmercury into lichens, a favorite wintertime food of caribou in the Arctic.
Credit: Martin Fortier/ArcticNet

People and animals in the Arctic have some of the highest levels of methylmercury in their tissues in the world. Environmental scientists have long known that the neurotoxic compound readily moves through aquatic food chains, accumulating in apex predators. But now researchers report for the first time that the ocean might pump methylmercury into terrestrial food webs via lichens growing near Arctic coastlines (Environ. Sci. Technol. 2015, DOI: 10.1021/acs.est.5b00347).

Mercury emitted into the atmosphere from industrial sources such as coal plants is mostly inorganic and not as harmful as methylmercury, which is an organic form. However, when inorganic mercury is deposited into lakes and oceans, aquatic bacteria transform it into methylmercury.

A 2012 Canadian government report showed that not much was known about how mercury moves through the terrestrial food web, says Kyra St. Pierre, an environmental science graduate student at the University of Alberta. Earlier studies that tested lichens growing on Arctic coasts found high levels of total mercury but didn’t determine if any was methylmercury. Because lichens make up 77% of the wintertime diet of caribou, a popular source of meat for aboriginal people, St. Pierre and her team wanted to know whether the mercury was coming from the ocean and how much was methylmercury.

They picked two islands in the Arctic Ocean as their testing sites. Devon Island is locked in ice for most of the year, which eliminates any possible mercury inputs from the ocean. But neighboring Bathurst Island is next to several areas of year-round open water. The team sampled lichens and soil along a path running from the coast to 24 km inland on each island.

The researchers used inductively coupled plasma mass spectrometry to measure levels of total mercury, methylmercury, and elements associated with the marine environment, such as sodium. The scientists found a median concentration of 4.27 ppb methylmercury in the lichens—about 100 times as much as in underlying soil. On ice-bound Devon Island, the levels of mercury were the same no matter where the samples were collected. But on Bathurst Island, lichens within 10 km of the coast had 10 times as much methylmercury and sodium as the lichens growing inland.

“The results show that the closer you get to the open sea, the higher the methylmercury and sodium levels you have,” says Lars-Eric Heimbürger, a chemical oceanographer at the University of Bremen, in Germany. “That’s evidence that the mercury in coastal lichens must be coming out of the ocean.” The study is important because it confirms previous findings showing methylmercury can escape from the ocean, and the data link the oceanic mercury to caribou, a local food source in the Arctic, he says.

Elsie M. Sunderland, a marine chemist at Harvard University, says the study challenges the common dogma that terrestrial food webs are usually not contaminated with methylmercury.

This is probably not an Arctic-only phenomenon, St. Pierre says: The transfer of methylmercury from marine waters into terrestrial food webs is likely occurring on coasts worldwide.

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Herman Rutner (April 29, 2015 4:42 PM)
Hi Elsie, your work is commendable in identifying transfer of Me Hg from oceans to land vegetation. Let's also focus on man made sources apart of unavoidable volcanic and other natural events. E.g. dental amalgam still in millions of mouths and foolishly still approved by ADA, shed amalgam from millions in tooth brushing, cremation creating volatile mercury (outlawed in some European countries), numerous toxic and radioactive metals including Hg from coal burning power plants, etc....all ultimately winding up in the oceans as runoff and from atmospheric pollution and entering the food chain via plankton into larger fishes like tuna and swordfish. A partial dietary remedy is eating sulfur containing foods like eggs along with fish to neutralize the Hg as less toxic sulfur complexes like insoluble HgS, a natural soil mineral. Years ago US diner owners were savvy in serving sandwiches of boiled eggs and sardines or tuna.
Ronald W. Gumbs (April 29, 2015 9:05 PM)

"Mercury exposure has been associated with autoimmune disease, scleroderma, autism, Alzheimer's disease, and Parkinson's disease. While mercury may directly cause these diseases, it may also trigger or exacerbate current but unrecognized conditions, such as genetic factors. It has been reported that autistic children have been exposed to elevated mercury and they have an atypical mercury metabolism. The dysfunctions mercury causes in the immune, sensory, neurological, motor, and behavioral systems are similar to those found in autism." Reproduced from Clinical Aspects of Mercury Neurotoxicity by David Wallace, Elizabeth Lienenmann, and Amber N. Hood, page 253, in Clinical Neurotoxicology, Syndromes, Substances, Environments, edited by Michael R. Dobbs, MD, Saunders Elsevier, Philadelphia, PA

Mercury levels are found to be elevated in the blood of patients with Alzheimer's disease. In one study, mercury was found to be more than twofold higher in the blood of patients with Alzheimer's disease than in the control group. Blood mercury levels of the individuals with Alzheimer's disease were found to be 2.64 ± 0.38 μg/L, while the control group that consisted of individuals without any psychiatric disorders levels was 1.09 ± 0.12 μg/L.[27] Postmortem brain tissue from patients with Alzheimer's disease shows elevated levels of mercury.

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