(NaturalNews) Present throughout the world's oceans are extremely high levels of mercury that researchers say is a direct result of human activity. Though it occurs naturally, mercury levels in the environment have nearly tripled since the beginning of the Industrial Revolution, according to a new study published in the peer-reviewed journal Nature, mainly from the burning of fossil fuels and the mining of gold.

Scientists from the Woods Hole Oceanographic Institute in Massachusetts found that, generally, mercury is present in both shallow and deep ocean waters. It is typically more concentrated at the surface, they say, as well as at mid-level depths. But in certain areas, it is even being found at great depths, including at 3,300 feet below sea level in the North Atlantic Ocean.

About two-thirds of the world's ocean mercury resides in water that is shallower than 3,300 feet, however, which suggests that toxic sources of mercury have been gradually polluting ocean water for centuries. And over time, this mercury is slowly sinking and spreading, resulting in fish coming into contact with it and absorbing it into their tissue.

"Nobody's attempted to do a more comprehensive overview of all the oceans and get an estimate of total mercury in the surface and some deeper waters before," said David Streets, an energy and environment policy scientist at Argonne National Laboratory in Lemont, Illinois, to Scientific American. Streets was not involved in the study.

Mercury concentrations have risen 340 percent in top 100 meters of ocean water

For their research, scientists collected thousands of water samples during eight separate research "cruises" throughout the North and South Pacific Oceans between 2006 and 2011. They tested water closer to the surface, which had recently come into contact with mercury pollution from both land and air, and compared it to water from lower depths, which is presumably less concentrated with the toxic metal.

Based on this analysis, they determined that the top 100 meters of ocean water have accumulated some 340 percent more mercury from human industry. The total amount of anthropogenic mercury -- that is, mercury originating from human activity -- in the world's oceans is now 290 million moles, with the highest concentrations in the Arctic and North Atlantic Oceans.

"Everywhere on the planet is contaminated with mercury to some extent," stated Carl Lamborg, lead author of the study.

More methylmercury means fish will be less safe to eat

Most existing research on mercury pollution has focused on air concentrations, with little emphasis on what role oceans play in harboring the toxin. But how mercury is contaminating water as well as air says a lot about the safety of seafood, much of which is becoming more toxic as highly toxic methylmercury accumulates in these sea creatures.

According to a separate study, mercury from the air is somehow becoming methylated once it gets into ocean waters. Methylmercury is the most common type of mercury known to harm humans, and oceans appear to be the missing link in what scientists believe is an ever-worsening mercury cycle being perpetuated by industrial pollution.

"Work like this strongly suggests that generational changes have been seen in the oceans' mercury levels -- and if that's the case we would expect them to undergo responses linked to, hopefully, reduced mercury outputs from mankind moving forward," added David Krabbenhoft, a geochemist with the U.S. Geological Survey (USGS) in Wisconsin, as quoted by Scientific American.

"The new data suggest that the problem is actually a bit more tractable. It's a cause for optimism and should make us excited to do something about it because we may actually have an impact."

Sources for this article include:

http://www.huffingtonpost.com

http://www.scientificamerican.com

http://www.nature.com

http://phys.org

http://science.naturalnews.com