WHOI biologists used mathematical
models to predict the effect on penguins of climate change and the
resulting loss of sea ice. The research indicates that if climate
change continues to melt sea ice at predicted rates, the median population
size of a large emperor penguin colony in Terre Adelie, Antarctica,
likely will shrink from its present size of 3,000 to only 400 breeding
pairs by the end of the century. (Chris Linder, Woods Hole Oceanographic Institution)
Emperor penguins, which delighted audiences of the
Academy Award-winning documentary March of the Penguins, could be sliding on
the path toward extinction—the victims of climate change.
The key threat to the penguins is
diminishing sea ice, an essential platform on which the tall, tuxedoed birds
breed, feed, and molt. The ice also serves as a grazing ground for krill, tiny
crustaceans that thrive on algae growing on the underside of the ice. Krill, in
turn, provide food for fish, seals, whales, and penguins.
Stephanie Jenouvrier and Hal
Caswell, biologists at Woods Hole Oceanographic Institution, developed
mathematical models that project the penguins’ population growth and decline
based on observations of the birds’ mating, breeding, and feeding behaviors and
birth and mortality rates. The models used data collected over 43 years by
French scientists studying the large emperor penguin colony in Terre Adelie,
Antarctica.
Jenouvrier and Caswell coupled
their population dynamics models with projections of Antarctic climate change
and resulting loss of sea ice—working with scientists from the National Center
for Atmospheric Research and the National Snow and Ice Data Center and from
Expeditions Polaires Francaises and Institut Paul Emile Victor in France. Their
results predicted what would happen to the penguin population under various
climate scenarios.
The study, published Jan. 26,
2009, in Proceedings of the National Academy of Sciences, showed that if
climate change continues to melt sea ice at the rates published in the latest
Intergovernmental Panel on Climate Change reports, the median population size
of the Terre Adelie penguin colony likely would shrink from its present size of
3,000 to only 400 breeding pairs by the end of the century. What’s more, the
researchers calculated a 40 to 80 percent probability that the population would
drastically decline (by 95 percent or more) and threaten it with extinction.
In the 1970s, reduced sea ice
conditions led to a 50-percent population decline in the Terre Adelie
population. But how sea ice changes affect the penguins is complex and still
not fully understood. Nor is it known how climate changes would affect other
emperor penguin populations throughout Antarctica, Caswell said.
“Unlike some other Antarctic bird
species that have altered their life cycles to changing conditions, penguins
are long-lived, so they adapt slowly,” Jenouvrier said. “This is a problem
because the climate is changing very fast.”
—Matt Villano
The research was supported by the
UNESCO/L’OREAL Women in Science program and the National Science Foundation.
RELATED LINKS:
» Hal Caswell's Web site
» Stephanie Jenouvrier's Web site
» Climate Change Likely to Devastate Emperor Penguin Populations in Antarctica
Podcast from Science Nation
The yellow mark of death in
corals
The effects of yellow band disease can be seen on the coral Montastraea in the Caribbean (top), as well as Indo-Pacific corals (bottom). Researchers found that YBD seems to be getting worse with global warming. (James Cervino, Pace University)
Coral reefs around the world are in serious trouble from
pollution, overfishing, climate change and more. The last thing they need is an
infection. But that’s exactly what yellow band disease (YBD) is—a bacterial
infection that sickens coral colonies. Researchers at the Woods Hole
Oceanographic Institution (WHOI) and colleagues have identified the bacteria
responsible for the disease and say that YBD seems to be getting worse with
global warming.
Just as a doctor can diagnose chicken pox by the small, round bumps on skin, scientists
can spot the characteristic markings of YBD. The affliction etches a swath of
pale-yellow or white lesions along the surface of an infected coral colony. The
discolored band is a mark of death. It indicates where the bacterial infection
has killed the corals’ photosynthetic symbionts, called zooxanthellae, which
provide their major source of energy. The coral host suffers from cellular
damage, starves, and usually does not recover.
In the November 2008 issue of the Journal
of Applied Microbiology, lead author James Cervino, a guest
investigator in the WHOI Marine Chemistry and Geochemistry Department, and colleagues
reported that they isolated the microbes that cause YBD: a group of four new
species of Vibrio, which
combine with existing Vibrio on the coral to attack the zooxanthellae. This is the first demonstration
that the same microbial culprits are to blame for the disease throughout the
Caribbean, as well as halfway around the world in Indonesia, Thailand, and the
Philippines.
The Vibrio that cause YBD are genetically close to shellfish pathogens. They are also distantly related to Vibrio cholera, the
pathogen that causes cholera in people, but there is no known danger to humans from YBD.
Cervino and colleagues grew Vibrio pathogens together with healthy coral. “Contrary to what many experts have
assumed, this disease occurs independently of warming temperatures,” he said. But
when water temperatures go up, infections do become more lethal. “Thermal
stress and pathogenic stress are a double-whammy for the organism,” he said. With ocean temperatures
on the rise and the Vibrio pathogens living in tropical oceans throughout the glob, the prognosis for the
spread of YBD is rather grim, he said.
Cervino, a professor at Pace University in New York, is a visiting scientist
at WHOI, working with WHOI geochemist Konrad Hughen. “You have biology and
chemistry merging together in this lab at WHOI, and it’s turning out to be an
amazing collaboration,” Cervino said.
—Juli Berwald
RELATED LINKS:
» James Cervino
No phosphorus? No worries! Marine
life finds substitutes
Benjamin Van Mooy, a geochemist at Woods Hole Oceanographic
Institution, and colleagues found microscopic plants
growing in the Sargasso Sea that make their cell membranes in a fundamentally different, and until now essentially unknown, way. (Tom Kleindinst, Woods Hole Oceanographic Institution)
Get ready to send the biology textbooks back to the
printer. In a new study, Benjamin
Van Mooy, a geochemist at Woods Hole Oceanographic Institution (WHOI), reported that microscopic plants
growing in the Sargasso Sea have come up with a completely unexpected way of
building their cell membranes.
Until now, scientists thought that all membranes surrounding cells contain
molecules called phospholipids—oily compounds that contain phosphorus and other
biochemical nutrients including nitrogen. However, Van Mooy and colleagues
found phytoplankton in the Sargasso Sea that make their cell membranes without
phospholipids—substituting instead lipids that don’t contain phosphorus. These
“substitute lipids” once were regarded as merely a molecular peculiarity of
phytoplankton grown in the laboratory, but now scientists recognize that phytoplankton
throughout the world’s oceans use these lipids.
Substitute lipids “are the most abundant membrane molecules in the sea, and
they were essentially unknown until now,” said Van Mooy. The finding, published
March 5, 2009, in the journal Nature, could help rewrite the fundamentals of cell biochemistry. The Sargasso Sea is
in the middle of the Atlantic Ocean—an area where phosphorus and nitrogen are as scarce as water in the desert. A molecule of phosphorus dissolved in
the Sargasso Sea remains there for perhaps an hour or two before a
phosphorus-starved cell greedily absorbs it. For comparison, phosphorous in the
Pacific Ocean may linger for nearly a year before plankton use it.
Nevertheless, small photosynthetic bacteria called cyanobacteria flourish in
the Sargasso Sea They do it by building a membrane lipid called SQDG, a
molecule based on sulfur rather than phosphorus.
“Cyanobacteria can make membranes that require essentially
no nutrients, no phosphorus, and no nitrogen,” Van Mooy explained.
Van Mooy and his colleagues—from WHOI, the University of Southern California,
University of Hawaii, the Czech Academy of Sciences, the Bermuda Institute of
Ocean Sciences, University of Southern Maine, and the Centre d’Océanologie de
Marseille—found that cyanobacteria aren’t the only class of plankton building
phosphorous-free cell membrane lipids. Studying more complex eukaryotic
phytoplankton in the Sargasso Sea, they found “this whole other class of
substitute lipids, which were betaine molecules,” Van Mooy said. “We are the first people to report
finding these molecules in the ocean.”
These betaine molecules have structures that resemble amino
acids, the building blocks of proteins, and contain nitrogen. Unlike the
cyanobacterial SQDG, the more structurally sophisticated plants have dodged the
phosphorus requirement, but they still have to have nitrogen.
Van Mooy thinks he’s on to something fundamental about the ways that
phytoplankton survive in the ocean.
"Our work provides an example of how much remains to be
discovered about the biochemicals that are present in marine organisms,” he
said, “and puts a biochemical face on the idea that all cells are not created
equal."
—Juli Berwald
Van Mooy’s
research was supported by the National Science Foundation, the Office of
Naval Research, and the WHOI Ocean Life Institute.
RELATED LINKS:
» Benjamin Van Mooy's Web site
Posted: September 2, 2009 [top] |
