Mercury concentrations in oceans have tripled since the Industrial Revolution, according to a new study, and humans may be to blame. Mercury is a toxin produced naturally, as well as being a by-product of industrial production of several products, including cement and burning of charcoal.
Woods Hole Oceanographic Institution (WHOI) investigators researched the concentration and effects of bioavailable mercury - forms which can be absorbed by animals, and also humans. Working with the group were researchers from Wright State University, the Royal Netherlands Institute for Sea Research, and the Observatoire Midi-Pyréneés in France. Investigators took part in 12 sampling cruises over the course of eight years, collecting data for the study.
"If we want to regulate the mercury emissions into the environment and in the food we eat, then we should first know how much is there and how much human activity is adding every year," WHOI marine chemist Carl Lamborg said.
Few studies had been previously undertaken to study concentration of mercury in the world's oceans. This was the first major investigation ever performed of mercury levels in pollution.
Researchers looked at the distribution of phosphate in the world's oceans. This material behaves in a similar manner to mercury in water systems. It is also better studied than the toxic element. They then examined water samples taken from 3,300 feet beneath the surface of the water, measuring the ratio of mercury to phosphate. The water at these depths has not been in contact with the atmosphere since the beginning of the industrial revolution, allowing researchers a way to compare concentrations of mercury before and after widespread industrialization.
The North Atlantic showed the greatest concentration of mercury. Surface waters in the region sink quickly, carrying pollutants to great depths. In the northwest Pacific Ocean, where circulation is much slower, the ratio of mercury to phosphate was lower. This provides further evidence increased levels of the toxin were due to human production.
The investigation revealed there could be between 60,000 to 80,000 tons of mercury in the global ocean.
"The trouble is, we don't know what it all means for fish and marine mammals. It likely means some fish also contain at least three times more mercury than 150 years ago, but it could be more," Lamborg said.
Study of the prevalence of the toxin can aid officials in establishing mercury warnings for the public, warning people of tainted seafood. The research could also play a role in the creation of international treaties regulating the release of the toxic element into the environment.
Study of mercury in the world's oceans was published in the journal Nature.