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By Peter Rejcek
Scientists dive deep into unlocking mysteries of unique
marine ecosystem
There are mighty forests in Antarctica. Just don’t
expect to see them poking through the ice and snow.
The forests are underwater, composed of several species
of huge brown algae, or seaweed, which blanket the ocean
floor on the western side of the Antarctic Peninsula.
These macroalgae dominate the local ecosystem in ways
no other seaweed does anywhere else in the world.
This unique marine forest — comparable to the great
kelp forest off the coast of California in terms of sheer
biomass — and the marine organisms that inhabit it
has drawn a team of researchers from the University of
Alabama at Birmingham (UAB) and University of South Florida
(USF) down to the U.S. Antarctic Program’s Palmer
Station for more than a decade.
“We’ve learned that the community at Palmer
is structured very differently than lots of other communities
that look similar superficially,” said Charles Amsler
aboard the ARSV Laurence M. Gould a day before he and
the rest of a seven-member team headed south for Antarctica
from Punta Arenas, Chile, on a diving research expedition
that will stretch into June.
A professor at the UAB and one of three principal investigators
on the project, Amsler explained that the team’s
previous work has shown that the major brown algae and
some of the other marine organisms in the ecosystem use
chemical defenses to thwart predators. Much of scientists’
earlier work involved studying the function and evolution
of these chemical defenses. Some of the compounds they
have isolated in the past show promise as cancer therapies
or even pesticides.
Now, Amsler, James McClintock , also a professor at UAB,
and organic chemist Bill Baker from USF, are diving deeper
into the connections within the ecosystem. They want to
understand the ecological relations between the macroalgae,
the smaller algal species that seek refuge within the
poisonous seaweed, and the vast numbers of small crustaceans
called amphipods that swarm the ecosystem.
“This project is really about understanding how
this community works, and through understanding this unique
community, understanding more about how a kelp forest
works, other marine communities work, in contrast,”
Amsler said.
For example, the amphipods are essentially the marine
equivalents of insects. Normally, they would feast on
the brown algae — but that’s not the case because
of the evolutionary chemical defenses of the polar seaweeds.
“So imagine a forest or grassland at home with 100,000
plant-eating insects per meter squared, and yet the big
macrophytes [aquatic plants] that dominate the system
aren’t edible,” Amsler explained.
Aside from their ongoing work since the 1999-2000 field
season, there’s been little characterization of the
marine community around Palmer, according to McClintock.
“That makes it very exciting for us because it is
a frontier in that sense,” he said.
The study also establishes an important baseline to monitor
future changes to the environment, noted McClintock, a
marine invertebrate zoologist whose interests also range
to ocean acidification and the impacts of invasive subpolar
species in the Antarctic.
The Antarctic Peninsula is undergoing rapid evolution
from climate change, and it is one of the fastest-warming
regions on the planet. The average winter temperature
is about 6.5 degrees Celsius higher in the winter than
it was in the 1950s — a rate of increase more than
five times the global average.
Delving into this unique and quickly changing ecosystem
involves scuba diving in near-freezing waters. The seas
around Palmer are also home to leopard seals, a predator
dangerous enough to require an alarm system to alert divers
in the water if someone topside in the dive boat spies
one of the sharp-toothed critters
The divers head into the murky coldness to collect samples
for lab work at Palmer Station and back at their home
universities, as well as for in situ studies. One experiment
headed by PhD graduate students Kate Schoenrock and Ruth
McDowell from UAB involves studying the relationship between
the large algae and smaller, filamentous algae (referred
to as endophytes) that live off the dominant seaweeds.
The scientists already know how the endophytes benefit
from previous research: “You see them growing inside
the large, chemically defended macroalgae,” Amsler
said. “They’re living in there as a refuge from
all these amphipods.”
McClintock said that in an earlier experiment, which
excluded the amphipods in a controlled environment, that
“after several months, these [macro] algae look like
they’re covered with hair. … The amphipods are
like these mini-lawnmowers that are keeping the macroalgae
nice and clean and happier than they would be otherwise.”
The next question is what effect do the endophytes have
on the macroalgae? Maybe the relationship is one-sided,
and the endophytes inhibit growth of the macroalgae by
limiting the surface area available for photosynthesis.
Perhaps they act as pathogens.
To test such hypotheses, the divers transplant specimens
from the ocean onto a concrete substrate — a square
block of concrete secured to the bottom — which they
lower into the water with the help of lift bags filled
with air. [For detailed description, see blog entry by
Schoenrock.] The researchers then monitor the growth and
health of the brown algae attached to their artificial
reef.
USF graduate students Alan Maschek and Jason Cuce are
heading up some of the chemistry work, studying compounds
in other marine organisms that appear to inhibit the amphipods’
ability to molt, which prevents them from growing.
“That sort of thing has never been seen in a marine
environment,” Amsler said, adding that such a finding
would represent a significant discovery in marine chemical
ecology.
McClintock said that so far a sponge and a tunicate have
both shown these potentially molt-inhibiting compounds
“They are very differently phylogenetically, and
yet to both have evolved a compound that may be involved
in tricking crustaceans in terms of their ability to molt
would be very interesting,” he said
Both Amsler and McClintock have a long history of working
in Antarctica dating back to the 1980s. Amsler’s
wife, Maggie Amsler, a research assistant at UAB and member
of the dive team, first went to the ice in 1979. Her mentor
was Mary Alice McWhinnie, one of the first women to work
in the U.S. Antarctic Program, at the time called the
U.S. Antarctic Research Program. [See previous article:
Stepping into history.]
Despite the collective years they share of living and
working in Antarctica, the veteran scientists seem no
less enthusiastic about their latest adventure than when
they were graduate students. It’s a passion they
seem eager to pass on to the younger members of their
team firsthand.
“We believe it’s very important for the students
to see the [marine] communities they’re working on.
So many of our ideas come from being in these really special
communities,” Amsler said.
Now on his third deployment, Maschek said he was inspired
to be certified to dive after his first visit to the Ice.
“Diving down there is like no other experience I’ve
ever had. It truly is mind-numbing as you drop down,”
he said.
Added Maggie Amsler on the day of her 52nd birthday,
some three decades after her first trip to the Ice: “It’s
actually pretty wonderful that I’m doing this and
keep getting opportunities to come down. … You never
know where life is going to take you. For me, it seems
that it takes me back here.”
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