Human-caused mercury pollution has been found by researchers in the Mariana Trench in the Pacific Ocean, the deepest point on Earth. Two independent studies presented at the Goldschmidt Geochemistry Conference showed how a toxic form of mercury is accumulating in animals, fish, and crustaceans in the deepest point of the ocean indicating that pollution is much more widespread than what has been expected.
Much of the mercury introduced into the oceans comes from human activities, such as when coal or oil are burned and during industrial processes like mining and manufacturing.
“Some water pollution actually starts as air pollution, which settles into Waterways and Oceans”
How does toxic mercury get into fish – The Mercury Cycle. Credit: WHOI
As in this case, the mercury is coming from the atmosphere. The teams of scientists identified human-derived methylmercury at depths points around 36,000 feet. This is a toxic form of mercury that easily accumulates in some animals, fish, and crustaceans living in the trench located in the Western Pacific Ocean.
When mercury gets into the ocean, tiny microbes change it into methylmercury. From there it gets into the food web — a small amount of mercury is ingested by species and then it repeats the cycle by a larger species. The mercury becomes more concentrated in marine organisms and is leading to harmful concentrations of mercury as it rises in the food chain becoming dangerous on the human diet.
The submersible “Deep Sea Warrior”, used by Ruoyu Sun’s team. Credit: Ruoyu Sun and IDSSE-CAS
They were able to present unequivocal mercury isotope evidence that the mercury in the trench fauna originates exclusively from methylmercury from the upper ocean.
“We can tell this because of the distinctive isotopic fingerprint which stamps it as coming from the upper ocean.”
Dr. Joel Blum of the University of Michigan determined the methylmercury in the animals fell on the ocean surface from the rain in the atmosphere. They were able to conclude this, because of the “isotopic composition” from the ocean floor, matched the reading from mercury found in animals living at depths of around 1,300 – 2,000 feet in the Central Pacific.
“This better understanding of the origin of mercury in the deepest reaches of the ocean will aid in modeling the fate of mercury in the atmosphere and oceans.”
Hadal snailfish Notoliparis kermadecensis at 7000m in the Kermadec Trench off New Zealand as sampled by Joel Blum’s team. Credit: Alan Jamieson
It looks complicated, but the experts still believe that there is time to fix the problem. In a report Launched by a London Professor, Edward Kosier called Stopping Ocean Plastics: An Agenda for Action, he claims caps on plastic waste and stamping out waste mismanagement by the top 10 polluting countries could cut ocean plastics by 77%.
“The global magnitude of the problem means it needs to be on the agendas of international leaders such as the G20 summits, UN Assembly and World Economic Forum.”
The Mariana Trench or Marianas Trench is located in the western Pacific Ocean about 200 kilometers (124 mi) east of the Mariana Islands; it is the deepest oceanic trench on Earth. It is crescent-shaped and measures about 2,550 km (1,580 mi) in length and 69 km (43 mi) in width. The maximum known depth is 10,984 metres (36,037 ft) (± 25 metres [82 ft]) (6.825 miles) at the southern end of a small slot-shaped valley in its floor known as the Challenger Deep. However, some unrepeated measurements place the deepest portion at 11,034 metres (36,201 ft). By comparison: if Mount Everest were placed into the trench at this point, its peak would still be over two kilometres (1.2 mi) under water.
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