Environment: Deep-sea fish not immune to pollution

New study finds liver damage and tumors in fish living a mile deep off the coast of France

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Even fish living deep in remote oceans are tainted by pollution.

Staff Report

FRISCO — As big and as deep as Earth’s oceans are, they’re still feeling the sting of human-caused pollution. Even a mile down, some fish have liver pathologies, tumors and other types of health problems that are often linked with exposure to toxic chemicals and carcinogens, according to a new study conducted in the Bay of Biscay, off the coast of France.

The study also discovered the first case of a deep water fish species with an “intersex” condition, a blend of male and female sex organs. The sampling was done in an area with no apparent point-source pollution, and appears to reflect general ocean conditions.

“Deep in the ocean one might have thought that the level of contamination and its biological impact would be less,” said Michael Kent, an Oregon State University microbiologist who co-authored the new study. “That may not be the case. The pathological changes we’re seeing are clearly the type associated with exposure to toxins and carcinogens,” said Kent, one of the study’s co-authors.

The researchers did acknowledge that the changes could be caused by naturally occurring compounds in the ocean. Only in-depth follow analysis could show more conclusive links between the diseases found in the deep-sea fish and human-caused pollution.

But Kent also drew a comparison to fish studies done in other places, including the American West. That research also found significant pollution and fish health impacts, including male fish that had been “feminized.”

“In areas ranging from pristine, high mountain lakes of the United States to ocean waters off the coasts of France and Spain, we’ve now found evidence of possible human-caused pollution that’s bad enough to have pathological impacts on fish,” Kent said.

The study was one of the first to look at fish disease deep in the ocean along continental slopes. Previous studies looked at their parasitical fauna, not at internal biological problems such as liver damage. The issues are important, however, since there’s growing interest in these areas as a fisheries resource, as other fisheries on the shallower continental shelf become depleted.

It’s already known that heavy metal contaminants such as mercury, cadmium and lead, and organic contaminants such as PCBs and pesticides can accumulate along the sloping edges of continental shelves, and “intersex” fish that have been discovered elsewhere are also believed to have mutated sex organs caused by “endocrine disrupting chemicals” that can mimic estrogens.

In this study, the health concerns identified were found in black scabbardfish, orange roughy, greater forkbeard and other less-well-known species, and included a wide range of degenerative and inflammatory lesions that indicate a host response to pathogens, as well as natural cell turnover.

The fish that live in these deep water, sloping regions usually grow slowly, live near the seafloor, and mature at a relatively old age. Some can live to be 100 years old. Partly because of that longevity, the fish have the capacity to bioaccumulate toxicants, which the researchers said in their report “may be a significant human health issue if those species are destined for human consumption.”

Organic pollutants in such species may be 10-17 times higher than those found in fish from the continental shelf, the study noted, with the highest level of contaminants in the deepest-dwelling fish.

However, most of those contaminants migrate to the liver and gonads of such fish, which would make their muscle tissue comparatively less toxic, and “generally not high enough for human health concern,” the researchers wrote.

The corresponding author on this study was Stephen Feist at the Centre for Environment, Fisheries and Aquaculture Science in Weymouth, England.

In the previous research done in the American West, scientists found toxic contamination from pesticides, the burning of fossil fuels, agriculture, industrial operations and other sources, which primarily found their way into high mountain lakes through air pollution. Pesticide pollution, in particular, was pervasive.

Together, the two studies suggest that fish from some of the most remote parts of the planet, from high mountains to deep ocean, may be impacted by toxicants, Kent said.

The findings have been published in Marine Environmental Research, by scientists from Oregon State University; the Centre for Environment, Fisheries and Aquaculture Science in the United Kingdom; and other agencies. It was supported by the European Union.

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