http://www.eurekalert.org/pub_releases/2006-04/uoc--ass040406.php
Public release date: 4-Apr-2006
Albatross study shows regional differences in ocean contamination
SANTA CRUZ, CA--As long-lived predators at the top of the marine food
chain, albatrosses accumulate toxic contaminants such as PCBs, DDT, and
mercury in their bodies. A new study has found dramatic differences in
contaminant levels between two closely related albatross species that
forage in different areas of the North Pacific. Researchers also found
that levels of PCBs and DDT have increased in both species over the
past ten years.
The differences in contaminant levels between black-footed and Laysan
albatrosses indicate regional differences in the contamination of North
Pacific waters, said Myra Finkelstein, a postdoctoral researcher at the
University of California, Santa Cruz, who led the study.
"The black-footed albatrosses forage mostly in the California Current,
whereas the Laysan albatrosses forage at higher latitudes near Alaska.
So it appears that the California Current system has significantly
higher concentrations of these contaminants," Finkelstein said.
The researchers published their findings in the April issue of the
journal Ecological Applications.
Mercury and organochlorine compounds such as PCBs (polychlorinated
biphenyls), DDT, and related compounds persist in the environment for a
long time and build up in the tissues of animals high on the food
chain. Analysis of blood samples showed that concentrations of these
compounds in black-footed albatrosses were 370 to 460 percent higher
than in Laysan albatrosses.
The two species breed at the same sites in the Hawaiian Islands. But
when they leave their breeding colonies on foraging trips, the
black-footed albatrosses head northeast toward the West Coast of North
America, while Laysan albatrosses head northwest toward the northern
and western regions of the North Pacific.
Black-footed and Laysan albatrosses both consume a mixed diet of squid,
fish, and fish eggs. Finkelstein analyzed nitrogen isotope ratios in
the two species--an indicator of an animal's "trophic level," or how
high it is on the food chain--and found no significant difference.
"Biomagnification means that you get higher concentrations of these
compounds as you go up the food chain, but these species appear to be
feeding at the same trophic level. We saw huge differences in
contaminant levels, which we attribute, at least in part, to the
differences in foraging patterns between the two species," Finkelstein
said.
The high contaminant load in black-footed albatrosses foraging in the
California Current probably reflects the long history of industrial and
agricultural discharges along the West Coast, Finkelstein said. But she
added that the distribution and transport of contaminants in the North
Pacific involves processes that are still not fully understood.
Concentrations of DDE (the main breakdown product of DDT) and PCBs in
both black-footed and Laysan albatrosses were 130 to 360 percent higher
in the samples Finkelstein collected in 2000 and 2001 than in samples
collected by previous researchers in 1991 and 1992. The increases were
much greater in black-footed albatrosses than in Laysan albatrosses,
Finkelstein noted. DDE concentrations, for example, increased 360
percent in black-footed and 170 percent in Laysan albatrosses.
Many countries do not regulate the manufacture and use of PCBs and DDT
as strictly as the United States does now, and these compounds continue
to be released into the marine environment.
"The increases we saw compared with ten years ago probably reflect the
ongoing use of these chemicals in countries that border the Pacific,"
Finkelstein said.
The biggest current threat to albatross populations in the North
Pacific is the longline fishing industry, which kills significant
numbers of both black-footed and Laysan albatrosses. But the
contaminants measured in this study may also take a toll. Comparable
levels of these contaminants in other species, such as herring gulls
and Caspian terns in the Great Lakes region, have been associated with
a variety of adverse effects, including reproductive deformities,
endocrine disruption, and immune system dysfunction.
"It is very difficult to show a cause-and-effect link in a wild
population, but there is evidence of health impacts in other species at
these contaminant levels," Finkelstein said.
Humans are exposed to the same contaminants when they eat seafood, she
added.
"It is important to realize that these contaminants have long-term
effects, and we are only beginning to understand many of the subtle
effects they can have, such as endocrine disruption and effects on the
immune system," she said. "A lot of people think this issue has been
taken care of, but it is still very much a problem."
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