for longer versions of these and other
environment stories, visit www.sciencenews.org
Who should stay
and who could go
By Rachel Ehrenberg
A little human meddling may prevent
the mess of extinctions that can ripple
through disturbed ecosystems.
A new analysis of how perturbations
propagate through a network of organisms reveals that when an ecosystem is
already off-kilter, proactively removing
particular species can halt the cascade
of destruction that may follow. The
approach, described online January 25
in Nature Communications, could help
well-defined areas such as islands deal
with the effects of invasive species.
“At the end of the day, methods based
on inflicting locally controlled damage — despite being damaging — can have
a positive effect on the entire network,”
says study coauthor Adilson Motter of
Northwestern University in Evanston, Ill.
To understand how such tinkering
plays out, Motter, an expert in complex
networks, and his Northwestern colleague
Sagar Sahasrabudhe developed an algo-
rithm that takes into account two classic
ecological models of species interactions.
A food web may collapse
without some species (red)
but get stronger without
others (other colors).
Dispersants persisted after BP spill
chemicals used to break up oil lasted for months in plumes
By Janet Raloff
Nearly 3 million liters (some 771,000
gallons) of a chemical dispersant ejected
into oil and gas from the Deepwater
Horizon oil spill last spring and summer
lingered until at least September, a new
study shows. The chemicals moved in
concert with plumes of oil deep beneath
the Gulf of Mexico’s surface.
David Valentine of the University of
California, Santa Barbara and his col-
leagues periodically sampled plume water
that flowed at depths of 1,000 meters or
more between May and September 2010.
They shipped these samples to chemist
Elizabeth Kujawinski at the Woods Hole
Oceanographic Institution in Massachu-
setts and her colleagues for analysis.
on an active ingredient called DOSS, or
dioctyl sodium sulfosuccinate. DOSS
levels in the plume matched what would
be expected if the dispersants remained
with the oil. That, Kujawinski says, suggests no biodegradation of DOSS — and
shows why remnants of dispersant
applications could be detected up to 300
kilometers from the wellhead and two
months after the last application.
“Corexit is made up of multiple chemicals, so each might have different biodegradation rates,” notes Carys Mitchelmore
of the University of Maryland’s Center for
Environmental Science in Solomons. As
for whether dispersants help degrade oil,
“the jury’s still out,” she says.