Melanoma Observed in Wild Fish Populations for the First Time

 For the first time in recorded history, melanoma skin cancer has been observed in a wild fish population.  A recent study conducted by researchers at Newcastle University and the Australian Institute of Marine Science has shown that up to 15% of fish in the studied population of coral trout suffer from dark skin lesions that are nearly identical to skin lesions found on fish that were given melanoma in a laboratory.  Of the 136 fish sampled from the population, 20 of them were found to suffer from melanoma.  However, Dr. Michael Sweet of Newcastle University claims that 15% may be a conservative estimate, saying, “Once the cancer spreads further you would expect the fish to become quite sick, becoming less active and possibly feeding less, hence less likely to be caught.  This suggests the actual percentage affected by the cancer is likely to be higher than observed in this study.

The coral trout is a species of fish found throughout Australia and the west Pacific.  Researchers collected their samples from two particular locations in the southern Great Barrier Reef Marine Park – Heron Island and One Tree Island.  Once they had ruled out factors like microbial pathogens and marine pollution, researchers determined that the cause of the cancer was most likely UV radiation.  After considering the fact that the Great Barrier Reef lies almost directly below the world’s largest hole in the ozone layer, this diagnosis makes quite a bit of sense.  Ozone helps shield the earth from UV rays, meaning organisms that live below a hole in the ozone layer are at a greater risk of being harmed by UV radiation.

The full implications of these findings may not be entirely clear until radiation-induced disease is studied in other species and in other parts of the world.  However, these results do raise the issue of our environmental hubris and just how far-reaching the consequences of our actions may be.  Holes in the ozone layer are largely caused by manmade chemical agents.  Many substances that we use every day, including aerosol sprays and refrigerants, produce chlorofluorocarbons that release chlorine atoms into the stratosphere.  In cold temperatures, these chlorine atoms can begin a destructive chain reaction that converts ozone to oxygen, creating large gaps in the ozone layer that allow UV radiation to reach the surface of the earth.  Scientists also claim that climate change may exacerbate the existing problem of ozone depletion; greenhouse gases trap heat at the surface of the atmosphere and keep the stratosphere at colder temperatures, creating an environment that facilitates ozone-to-oxygen conversion.  With decreasing ozone protection comes greater exposure to UV radiation, and as this study on coral trout may suggest, a growing number of wild populations that are affected by cancers and other radiation-induced diseases.

The world needs to see further research into new diseases affecting wild populations before we can make any big assumptions regarding future trends.  However, it looks like there’s quite a bit of evidence pointing to the conclusion that human activity and production are leading directly to serious health problems in species that have no way of defending themselves against an increasingly dangerous environment.  The authors of the study note that “the increase in reports of novel diseases in a wide range of ecosystems, both terrestrial and marine, has been linked to many factors including exposure to novel pathogens and changes in the global climate.”  While disheartening, this information is absolutely vital to the future protection and conservation of the planet’s incredibly diverse ecosystems.  The discovery of a cancer previously unknown to affect wild fish populations could suggest a growing trend of new diseases in other species, threatening the biodiversity of the planet.  The more we know about the way our drastically changing environment is affecting wild species, the more we can do to stop a potentially catastrophic series of wild epidemics.  For now, it looks like it’s time to continue to keep the car in the garage and to cut down on hairspray.  Our marine-dwelling friends may depend on it.

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