Deep sea fish showing adverse effects of pollution

Societyforscience.org reports, 19th April 2015: “Far below the ocean’s surface is a dark, mysterious world. There, it’s too deep for the sun’s rays to penetrate. Very few people have seen this world. Even fewer have studied the health of its inhabitants — oddly named fish such as the greater forkbeard, black scabbardfish and orange roughy.

This odd fish is a black scabbardfish (Aphanopus carbo). It is one of several deep-water species with health problems that may be related to pollution.

This odd fish is a black scabbardfish (Aphanopus carbo). It is one of several deep-water species with health problems that may be related to pollution.

“Though hidden, these strange creatures still are part of our world. After all, people eat these and other deep-sea species. Now, a study finds some of these fish appear to be falling ill and that pollution may be the culprit. If true, eating these fish could expose people to the same pollution.

“Changes in the internal organs of deep-sea fish resemble those seen in shallow-water fish exposed to human pollutants. These pollutants include heavy metals and industrial chemicals, such as PCBs.

“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,” says Michael Kent. He’s an expert on fish disease who works at Oregon State University in Corvallis.

His team’s new study could not confirm what caused the inflammation, liver damage and other problems seen in fish netted deep in the Atlantic Ocean. However, Kent notes, the types of harm seen in these deep-sea fish resemble what’s usually seen in animals exposed to cancer-causing pollutants and other toxic chemicals.

His group described the evidence of disease in these fish in the May 2015 issue of Marine Environmental Research.

As a fish pathologist, Stephen Feist studies diseases in fish. Also an author of the new study, he works at the Centre for Environment, Fisheries and Aquaculture Science in Weymouth, England. By understanding what ails fish, he hopes to protect others from a similar fate. And the subtle impacts seen in the fish surveyed as part of the new study left him disturbed.

His research team examined the livers and gonads (reproductive organs) of fish caught in the Bay of Biscay. This area of the Atlantic is about 250 kilometers (155 miles) west of France. Fish here inhabited underwater slopes jutting out from the edge of the European continent. They lived at depths from 700 meters (2,300 feet) to 1,400 meters. The fish looked fine to the unaided eye. But under a microscope, a different picture emerged. The researchers saw changes in some fish that appeared to be early stages of tumour formation.

“A wide variety of inflammatory and degenerative lesions were found in all species examined,” the team reports. Inflammation is one way the body responds to injury. It’s not a healthy sign. Similarly, degenerative changes signal injury to a tissue from disease or trauma.

None of the fish had visible tumours. But the researchers did see telltale signs that tumours may be starting to develop. These showed up when the scientists looked at cells in the fishes’ livers.

The researchers turned up one fish with what scientists call “intersex characteristics.” This means it showed signs of being both male and female. Only females should make eggs. But one of the male fish also was developing eggs.

Certain chemical pollutants can trigger such changes by mimicking or altering the action of the body’s hormones, important signalling agents. Such hormone-like pollutants are known as endocrine disrupters. That is because these pollutants alter the normal action of the hormonal — or endocrine — system.

Feist says scientists would need to catch many more deep-water fish with this condition before they could say whether intersex fish are common in the deep sea. But such changes have become common in the fish of many polluted rivers and lakes.

If pollution is causing the ailments showing up in deep-sea fish, eating those fish could transfer the pollutants to the diner. And that could be us. Indeed, overfishing of coastal waters has encouraged many fleets to begin fishing deeper waters.

And deep-sea fish may become a sort of accidental magnet for pollutants, notes Brett Lyons. Like Feist, he works at the Centre for Environment, Fisheries and Aquaculture Science. However, Lyons was not involved in the study. Lyons studies how chemical pollutants harm animals. Deep-water fish tend to live longer than those near the surface. This gives them longer to “accumulate more chemical pollutants,” he explains. And that, he notes, “is important to know if we start targeting these fish as a food [for people].”

Right now, Lyons says, biologists “know lots about how pollution impacts the marine life on our beaches or close to the coast, but very little about how it may harm those animals living in the very deepest parts of our oceans.” And that’s what makes the study so potentially important, he says. Feist and his team emphasize that while the fish problems they describe look like pollution poisoning, they can’t be sure. The same changes also might be caused by naturally occurring poisons in the ocean. One type, known as microcystins, are toxins produced by algae.

Scientists would have to analyse chemicals in the fish before knowing for sure if human pollution was behind the animals’ health problems. Feist and his team hope to do that soon.

Source: Societyforscience.org, 19th April 2015. For the full text, see https://student.societyforscience.org/article/deep-sea-fish-show-signs-exposure-pollution


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