In a piece of welcome news for seafood lovers, a Stony Brook-led research team has found declining levels of mercury in bluefin tuna caught in the North Atlantic over the past decade. Mercury is a neurotoxin harmful to humans, and tuna provide more mercury to humans than any other source.
A study led by Stony Brook University’s School of Marine and Atmospheric Sciences (SoMAS) and published in Environmental Science & Technology provides a new data set, the largest of its kind, of mercury concentrations in Atlantic bluefin tuna. The data demonstrate that, while tissue concentrations were higher than in most other fish species, there has been a consistent decline in mercury concentrations in these tuna over time, regardless of age of the fish.
The rate of decline parallels the declines – over the same time period — of mercury emissions, mercury levels in North Atlantic air, and mercury concentrations in North Atlantic seawater. Authors of the study include Stony Brook’s Cheng-Shiuan Lee, a Ph.D student in chemical/biological oceanography, and Nicholas S. Fisher, Distinguished Professor & Director, Consortium for Inter-Disciplinary Environmental Research at SoMAS.
According Fisher, the finding appears to indicate that changes in mercury levels in fish tissue respond in real time to changes in mercury loadings into the ocean. The study suggests that mercury levels may be improving as a result of declining coal use, reducing emissions that drift over the Atlantic.
The researchers measured mercury concentrations from the tissue of 1,292 bluefin tuna caught between 2004 and 2012. Some of the key findings:
- Over the eight-year period, mercury levels in the fish fell 19 percent.
- Mercury concentrations were generally high, and were highest in the largest, oldest fish; no differences were noted between males and females.
- Mercury in the air over the North Atlantic fell 20 percent from 2001 to 2009.
- Global levels of mercury emissions have fallen 2.8 percent a year from 1990 to 2007.
The study was supported in part by a grant from the Gelfond Fund for Mercury Research & Outreach.