New Diseases, Dolphins, other marine mammals weakened by pollution, scientists say toxins Harming Marine Life

April 15, AP – The dead sea otters arrived at Melissa Miller’s Santa Cruz, California, lab with bright-yellow eyes and gums, their livers destroyed.

One by one, Miller, a marine-wildlife veterinarian, eliminated the potential causes of death until “the last thing I was left with seemed so implausible that I thought I was going crazy.”

The otters had been poisoned by a “nasty toxin” called microcystin, which is produced by cyanobacteria, or blue-green algae. Such toxins can appear when human sewage and fertilizers run into lakes and rivers, adding nutrients that spur the growth of algae “superblooms,” Miller said.

But sea otters stick to the ocean, never entering the polluted lakes and rivers where these blooms occur.

“I said, OK, we have to figure out how the otters are getting into this,” said Miller, of the California Department of Fish and Wildlife and the University of California, Davis.

Miller’s sleuthing led her to California’s Pinto Lake (map), a water body about 2.5 miles (4 kilometers) from the ocean and so prone to superblooms that Miller said “it’ll blow your mind—it looks like fluorescent green paint.”

Sure enough, she found that Pinto Lake eventually drains into the Pacific Ocean—close to where the dead otters were found in 2007.

Later experiments revealed the algae’s toxins can live for long periods of time in shellfish—otters’ main diet. Toxins from the polluted lake were traveling downstream into the ocean, Miller concluded, where they were getting into shellfish and killing otters. (See pictures of threatened marine species.)

Of course, the toll that some types of water pollution take on marine mammals has long been documented. For example, cancer-causing chemicals called PCBs and pesticides like DDT are known to accumulate in marine mammals’ fatty tissues and cause serious harm.

But scientists are just now beginning to understand how these and other toxins in the water are spurring the resurgence of some diseases and the creation of others, largely by weakening animals’ immune systems. And with more development and pollution in coastal areas, the problem appears to be accelerating.

“Currently there is a general belief that infectious diseases stop where the land and the water meet,” said Stephanie Venn-Watson, a veterinarian and director of the One Health Medicine and Research Program, which is part of the National Marine Mammal Foundation (NMMF).

But recent research is showing that such diseases don’t discriminate—and the ocean provides “lots of opportunities” for viruses and bacteria to blossom, Venn-Watson said.

Even more worrisome, experts say, is that these organisms could eventually make their way back to land—and to us.

Because people eat shellfish harvested where the land meets the sea, the sea otters may be serving as an “early warning system” for human health risks, Miller said.

Diseased Dolphins

Along Florida’s Indian River Lagoon (map) one day last spring, the water looked smooth and clean, the mangroves lush.

But Gregory Bossart knows otherwise.

Since 2003, the Georgia Aquarium’s chief veterinarian has been monitoring the health of more than 280 bottlenose dolphins that live along this 170-mile (275-kilometer) stretch of eastern Florida near Fort Pierce, about halfway between Orlando and Fort Lauderdale.

A large team helps him collect a suite of samples from the dolphins, which are catalogued by their dorsal fins.

The prognosis is worrisome: Many of the studied dolphins are sick, suffering from newly described and resurgent diseases that could be triggered by human activities—especially pollution.

Though the process isn’t fully understood, pollution and other environmental stressors may be changing the environment here in a way that’s favorable for the growth of such diseases, many of which are opportunistic.

As a heavily used recreation area, the Indian River Lagoon has extremely high levels of mercury, mostly due to vehicle exhaust from boats and cars. Coal-fired power plants as far away as China also contribute to mercury pollution in the state.

This toxic metal has been found in dolphins at 20 times the level permitted in human food by the U.S. government.

That exposure could be linked to new papilloma and herpes viruses that have appeared in Indian River dolphins in the last 30 years. The viruses manifest as grisly tumors, sometimes on the dolphins’ genitals.

During some recent years, another rare fungal disease called lobomycosis—found only in people and dolphins—has arisen in “epidemic proportions” among Indian River dolphins, Bossart said.

While it’s unknown what caused lobomycosis, the diseased animals share a “profoundly” suppressed immune system, he said, likely caused by the dolphins’ constant exposure to environmental stressors like mercury. (Also see “Dolphin-Baby Die-Off in Gulf Puzzles Scientists.”)

Toxic Wake-up Call

Just up the coast, in southern Georgia, marine scientist Lori Schwacke and colleagues have made similar findings in a population of bottlenose dolphins.

Schwacke, of the U.S. National Oceanic and Atmospheric Administration, has found “extreme” chemical concentrations in dolphins living in a coastal area highly contaminated by pollution from a former plastics facility.

The chemical, called PCB, is a chemical byproduct of some industrial processes that can linger in the environment for decades. (Read more about marine pollution.)

In one recent study of the coastal dolphin population, Schwacke and colleagues found that 26 percent of sampled dolphins in the research area had anemia and decreased immunity.

“The severity of the effects suggests that the PCB mixture to which the Georgia dolphins were exposed has substantial toxic potential,” according to a 2011 study led by Schwacke and published in the journal Proceedings of the Royal Society B.

Associated press writer for human rights observers – contributed to this report.

Category: Environment