By Isabelle Groc
7 January 2015
(National Geographic) – In August of 2014, biologists from the Virginia Aquarium and Marine Science Center Stranding Response Team were notified of an unusual sighting in the Elizabeth River, a busy, industrial tributary of the Chesapeake Bay. A 45-foot-long young female sei whale was spotted swimming up the river, far from the deep waters of the Atlantic where the species, listed as endangered, is normally found.
"She was in the wrong place at the wrong time," says the aquarium's research coordinator Susan Barco.
The whale seemed disoriented. Barco and her colleagues followed it for several days in an attempt to protect it from a fatal collision with a ship. Despite these efforts, the whale was found dead a few days later.
A necropsy revealed the animal had swallowed a shard of rigid, black plastic that lacerated its stomach, preventing it from feeding. The weakened whale also had been struck by a ship and suffered a fractured vertebrae. "It was a very long and painful decline," Barco says.
The shard that caused the whale's demise was identified as a broken piece of DVD case. Most likely the marine mammal had swallowed the debris while feeding at the surface.
"It makes me very sad that a piece of plastic that was not disposed of properly ended up killing a whale," she says. "It was a preventable death."
Plastic ingestion is a widespread problem for marine animals, particularly seabirds and turtles, which can easily confuse the debris for food. The indigestible material can obstruct the stomach or intestine, leading to starvation and death. As the amount of sea trash increases, so do the risks to marine life.
To compound the problem, scientists are still trying to fill in the blanks when it comes to the impact of marine debris on cetaceans. A 2014 study found that ingestion of debris has been documented in 56 percent of cetacean species, with rates of ingestion as high as 31 percent in some populations.
"The whales that wash up on the beach are only a small percentage of those that die," says Frances Gulland, a senior scientist with the Marine Mammal Center in Sausalito, California.
Sperm whales are particularly susceptible to plastic debris ingestion, she explains; they mistake debris for squid, their main prey. "Every sperm whale that I have necropsied has had a lot of nets and pieces of plastic" in its stomach, she says.
Gulland encountered her most extreme case in 2008—two male sperm whales stranded along the northern California coast, their stomachs full of pieces of fishing net, rope, and other plastic trash. One animal had a ruptured stomach. The other was emaciated, suggesting that it had been unable to eat. In both cases, the debris proved fatal.
The variety and age of some of the plastic suggested it had accumulated over many years. According to Gulland, who performed the necropsy, one of the whales had at least 400 pounds of debris in its stomach.
"They slowly died of starvation," she says. "It was the first time that I had seen a large whale die from eating garbage debris." [more]