Gulls exposed to oil pollution are found to have smaller red spots on their bills than their healthy counterparts, thanks to lower levels of a key enzyme in their blood.
Getty Images
In the wake of a massive oil spill from the tanker Prestige, poisoned seagulls displayed smaller red spots on their beaks than healthy birds, according to a new study.
The finding could open the way for the birds, fish and lizards to be used as signposts for a host of environmental ills.
The dark story of the Prestige began in November 2002, when the ship tore in half off the coast of northwestern Spain, spilling some 63,000 tons of oil into the Atlantic Ocean. The Spanish and French coasts were mired in a thick muck of heavy fuel oil. Thousands of sea birds perished, and local fishing fleets were grounded for months.
Today the cleanup crews are long gone, but scientists are still tallying the environmental damage.
In 2004 Cristobal Perez of the University of Vigo in Spain and a team of researchers tested 27 adult yellow-legged gulls (Larus michahellis) from isolated colonies off the coast of Galicia, Spain.
In a study published today in the journal Biology Letters, they found a distinct pattern among birds that had been sickened, but not killed by the spill: The more oil they were exposed to, the smaller the red spots on their beaks were.
Gulls' red spots are a big part of reproduction. The size of the spots figures prominently in courtship and competition for mates, and gull chicks peck at them to induce their parents to regurgitate food for them. Loss or diminution of the spots could endanger gulls' ability to procreate.
The spots are made of brightly-colored chemicals called carotenoids. Many species of birds, fish, and lizards use them to create yellow, orange and red hues on their bodies that are attractive to potential mates.
"The degradation of polycyclic aromatic hydrocarbons (PAHs) in oil produced oxidative stress, which damages tissue. Besides being commonly used as colorants, carotenoids can protect tissues from oxidative damage," Perez wrote in an email to Discovery News.
The team surmised that gulls that consumed large amounts of oil had to divert the reddish compounds away from their spots to wash poisons from their bodies.
The finding raises an intriguing possibility. Any animals that use carotenoids to anoint their bodies may be useful as color-coded indicators of environmental pollution.
"These color traits may be a really good way to do environmental monitoring," Geoffrey Hill of Auburn University said. "If we see a population-wide drop in coloring, we can suspect something bad is going on."
Animals stressed by any number of pollutants -- whether oil, heavy metals or polychlorinated biphenyls (PCBs), for example -- should show signs of fading colors, making them excellent early-warning signs of contamination in the environment.
"It's going to be more like a canary in a coal mine sort of thing," Hill said. "You can look across a population and follow up with more detailed monitoring in areas that look like they have problems."
Tags: Birds, Disaster Recovery, Oceans, Petroleum, Pollution
comments ( )