Dolphins studied for pollution's impacts

Geneticists have found that the dolphin genome and the human genome are basically the same

February 4, 1999
Web posted at: 1:30 PM EST

By Environmental News Network staff

Scientists conducting gene-mapping studies are comparing human chromosomes to those of dolphins and finding that the two share many similarities. This may lead to increased understanding of how bioaccumulated pollutants are or will be affecting us.

Biologists have been observing sporadic die-offs, diseased and emaciated animals and reduced reproductive success among marine mammals for some time. What they don't know is what is causing the ever-increasing mortality.

"Right now, we know next to nothing about the genetics of dolphins and whales," said Texas A&M University scientist Dr. David Busbee.

What geneticists have found is that the dolphin genome and the human genome are basically homologous -- the same. "It's just that there are a few chromosomal rearrangements that have changed the way the genetic material is put together," Busbee says.

Marine mammals are exposed to the same pollutants that humans are. Because dolphins are so close genetically, they may be able to tell us how well they are tolerating exposure to environmental toxins and possibly even how they handle them and what genetic systems either let them tolerate or handle the toxins.

The danger these synthetic compounds pose are summed up in the three Bs: biopersistent, bioamplification and biogenerational.

They are biopersistent because some of them don't break down for hundreds of years. Bioamplification means that the higher up the food chain, the more vulnerable we are to them. They pose more of a problem for whales and humans than, say, amoebas. Perhaps the most frightening aspect is biogenerational, meaning mammals can pass up to 30 percent of the compounds they're storing on to the next generation through the placental barrier and mother's milk.

Busbee has been studying a group of dolphins stranded on the shores of the Matagordo Bay, Texas. The dolphins, when examined, had a toxicity equivalency quotient that was 1,000 times higher than the minimum level that would cause birth defects in rats.

To Busbee, it's important to answer the question 'Why did they die?' and to determine whether dolphins are the equivalent to the proverbial canary in the mine, signaling us that there are too many toxins being released into the environment.

"We don't know why these animals died, and we think it's important to find out why these animals have declined significantly," Busbee said.

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