Human pollution found in carcasses of fish in the deepest part of the globe

(CN) — It was announced that the rotten meat of fish that lived in waters contaminated with mercury, an element harmful to the human nervous system, sank, introducing toxic pollutants into the furthest trenches on Earth. Monday according to research.

Mercury is a naturally occurring metallic element that is liquid at room temperature. Every year more than 2,000 metric tons are emitted from human activities such as burning fossil fuels and are present in soil, air and water.

Microorganisms convert some of the inorganic mercury that falls from the atmosphere into methylmercury. Methylmercury is a highly toxic organic form that accumulates in fish and poses a danger to humans and wildlife.

According to the report, high exposure to all forms of mercury can cause nerve damage, lung damage, skin rashes, and kidney abnormalities, in addition to nerve damage. Centers for Disease Control and Prevention..

How did this neurotoxin reach the most inaccessible caves in the deep sea, including the 36,000-foot-deep Mariana Trench in the Pacific Northwest?

According to a study published Monday in the minutes of the National Academy of Sciences, it began with coal-fired power plants, cement plants, incinerators, mines, and other operations that expel toxins into the atmosphere.

University of Michigan researcher Joel Bloom analyzed some mercury from “natural” outbreaks, according to an analysis of carcasses (also known as carrion) and crustaceans called amphipods collected in two trenches in the Pacific Ocean. It comes from the source, but most of it is due to human activity. A statement issued with the study.

“Mercury, which we believe was once in the stratosphere, is now in the deepest trenches on Earth,” said Blum, an environmental geochemist and lead author of research. “It was widely believed that anthropogenic mercury was primarily confined to the upper 1,000 meters of the ocean, but some of these deep-sea trench mercury are of natural origin, but most of them can be of human origin. Activities that turned out to be high. “

Researchers have been able to identify mercury samples of various origins based on the ratio of isotopes with unique chemical characteristics. Studies have shown that the isotopes of mercury found in amphipods in deep-sea caves are consistent with isotopes of fish that feed near sea level at a depth of about 500 meters.

“We investigated the trench biome because it lives in the deepest and most remote areas of the globe. Mercury there is almost exclusively from geological origin, a deep-sea volcanic source. I expected it to be, “says Blum. “Our most amazing discovery was the discovery of mercury in organisms from deep-sea trenches, showing evidence from the sunlit surface zones of the ocean.”

According to study co-author Jeffrey Drazen, an oceanographer at the University of Hawaii, samples were collected at a depth of 32,800 feet in the Mariana Trench southwest of Guam and the Kermadec Trench in the Pacific Ocean in northeastern New Zealand.

“These samples were difficult to obtain due to the deep trenches and high pressure,” said Drazen. “Trench is part of the least studied ecosystem on the planet, and the Mariana snailfish was just discovered in 2014.”

At this June conference, coordinated by both Bloom’s team and researchers led by Chinese scientists, independent findings show that human or anthropogenic activity promoted the presence of mercury in deep-sea organisms. Shown.

A China-led study published in Nature Communications on July 7 found that mercury latched on organic matter such as fecal material and dead plankton and continuously sank from sea level to the sea floor.

A study led by Blum found that the sinking meat of fish that lived near mercury-contaminated sea levels carried most of the toxins detected in deep-sea trenches.

“The importance of carrion to dig into the web is consistent with observations of submarine communities of fish and amphipods that depend on carrion for nutrition in other deep-sea regions,” the study said. “The subsidence of corpses as a delivery mechanism provides a means of increasing the efficiency of Hg (mercury) biopumps to the deep sea floor in ultra-deep sea environments and perhaps deep sea environments.”

Blum said the findings are important information for policy makers seeking to understand the correlation between global mercury emissions and mercury in seafood.

“Yes, we eat fish caught in shallow water, not from deep-sea trenches,” Blum said. “But to be able to model future changes in the ocean near the surface, we need to understand the circulation of mercury through the ocean.”

In the large emerging economies of China and India, new coal-fired power plants come online weekly, releasing high levels of mercury into the atmosphere and an unknown amount of mercury into the ocean.

Studies show that North America and Europe have reduced emissions of toxic substances.

As long as mercury is being released from anthropogenic sources, Drazen said the element will continue to be brought into the ocean by rainfall, river spills, and wind-blown dust.

“Deep-sea trenches have been regarded as unspoiled ecosystems unpolluted by human activity,” Drazen said. “But recent research has found traces of anthropogenic lead, carbon-14 from nuclear tests, and persistent organic pollutants such as PCBs from organisms that live even in the deepest parts of the ocean, known as the hadal zone. It was. “

Researchers did not immediately respond to requests for further comment on the study entitled “Mercury isotopes identify marine mercury near the surface of deep-sea trench biomes.”