Lake's Mystery Moss
August 01, 2007
BY BEN LARSON
Storm clouds gather overhead and rain begins to dimple the choppy surface of
the wind-swept water, but Crater Lake biologist Mark Buktenica and his team are
The legendary lake still has secrets to tell, and the crew of the research
vessel Neuston is eager to uncover them. Even the wave-battered boat seems
restless, pulling against its tether like a race horse champing at the bit. The
crew cuts the boat loose and speeds into the gloom.
The soggy day of field work that Buktenica led July 18 is part of a broader
research program to monitor the lake's health and explore its unique ecology.
This summer, researchers are unleashing an arsenal of instruments on a complex
underwater moss colony that thrives on a platform of submerged volcanic rock
around Wizard Island on the lake's west side.
"It's very clear that there's this whole ecosystem buried in the moss that
we're totally unaware of," said Bob Collier, an Oregon State University
geochemist who will conduct further research at Crater Lake this month.
By now, the story of the lake's creation is familiar: A violent volcanic
explosion 7,700 years ago drained Mount Mazama of the magma within, and the
remaining mountaintop collapsed in on itself. After filling with water from snow
and rain, the volcanic basin -- a caldera -- would become one of Oregon's most
The lake bottom is as deep as 1,943 feet, making Crater Lake the nation's
deepest body of water. In 1902, the lake and the surrounding rim were protected
as a national park. In 1984, Congress established an ongoing research program to
ensure that the lake would be maintained in its natural condition.
When the project began, Buktenica -- then a graduate student studying trout
in the lake -- became the first research scientist dedicated to the study of the
"Crater Lake happens to be one of the largest clear lakes in the world, and
also one of the better protected, both politically and geographically, from
pollution," Buktenica said. "And because it's so pristine, it has tremendous
A self-described generalist with a detailed knowledge of the lake, Buktenica
has conducted research on everything from water quality to the abundance of
In 1995, the National Park Service expanded the operation and hired another
scientist, Scott Girdner. Buktenica and Girdner form the backbone of a research
operation that not only conducts fundamental research on lake ecology but also
attracts specialists from all over the United States.
Visiting scientists bring their expertise to bear on specific aspects of lake
ecology that remain poorly understood, such as the moss colony. The guest
researcher on the recent expedition, Bruce Hargreaves, is a specialist in optics
from Lehigh University in Pennsylvania.
One of the moss study's goals is to figure out how the moss contributes to
the organic matter in the lake. "It's all still very exploratory. We just don't
have a clue, because we've never had a tool to look at it before," said
Hargreaves, who brought with him an array of optical techniques to help answer
Plenty of questions
The moss grows in a narrow range between 100 and 460 feet deep. The submerged
platform around Wizard Island falls squarely within this band, and lush fields
of moss cover the watery terrain. A bed of moss consists of a soft green layer,
3 to 6 feet thick, set atop a layer cake of peatlike moss that can extend down
as far 20 feet.
Spread throughout the moss beds are cryptic circular pits the size of large
tree trunks that may be caused by warm water rising from hot springs below.
But this theory has some holes of its own, Collier concedes. "We're in a very
unconstrained thinking space."
Collier will bring in bottom-penetrating sonar and several types of coring
samplers from around the world. His goal is to develop a more detailed picture
of the interior of the strange green community.
Such exotic techniques are necessary because the depth of the moss prevents
scientists from using conventional methods. Scuba divers can get to the top of
the moss with just enough air to last about five minutes. Without costly
submersible operations, most of the samples come from camera tows that entangle
the moss when they collide with it.
The nutrient and carbon contents of the widespread colony are issues of
paramount importance to lake ecology.
"If there's this moss down there that's maybe 50 times the biomass of every
other living thing in the lake, it's obviously going to have an important role,"
Scientists are not all questions. They have hypotheses about several of the
interesting features. In particular, the growth pattern of the moss may have
something to do with the lake's trademark clarity.
Because Crater Lake has low biological productivity, sunlight penetrates into
the cobalt-blue water deeper than any other place in the world. Other more
productive lakes come equipped with a natural sunscreen: bits of particulate and
dissolved organic matter that absorb damaging ultraviolet rays.
Without this protection, moss in Crater Lake may not be able to withstand the
intense sunshine in the shallow reaches of the lake. But go too deep, and
there's not enough light.
"Undoubtedly, there's a lot of nutrient recycling and nutrient generation
going on in that moss," Buktenica said. "Nitrogen-fixing algae grows in the
moss; the biomass of earthworms is tremendous. Zooplankton, aquatic insects --
it's a whole community."
As the crew of the Neuston prepares to dunk an array of sensors into the
water, a tangible excitement fills the air. It's the first time Hargreaves will
deploy some of his optical devices in the cool mountain waters.
But a lightning strike rips through the sky, and thunder rumbles over the
lake. Buktenica, Girdner and their team move with a dexterity bred from years of
experience. Within minutes, they've packed up their operation and are cruising
away from the danger zone.
Not all experiments rely on fair weather. Last summer, Buktenica put a
mooring in the water loaded with sprigs of moss at regular intervals over the
entire depth range of the moss. He plans to use digital recognition software on
pictures of the moss to measure its growth rate, which may be mind-numbingly
Speculation is that the moss may double once a year -- a snail's pace
compared with other types of algae that double once a day.
Normally, scientists use naturally occurring radioactive carbon isotopes to
measure how fast a plant grows. But most of the Crater Lake carbon comes from
geothermal fluids pumped in at the lake bottom. This "old carbon" no longer
contains the radioactive isotopes necessary for growth rate measurements,
Scientists frequently must tap into their ingenuity to study a system that is
anything but ordinary. Even the lake itself can be used as a scientific
"The whole lake acts like one big leaky rain gauge," said Girdner, explaining
how lake height recorded the drought during the Dust Bowl of the 1930s.
Techniques have come a long way from the old days when a black and white disc
was used to measure optical properties of the lake. Researchers back then
lowered the disc until it disappeared, then recorded the distance as the depth
of light penetration.
"The real sophisticated stuff started in the early 90s," said Hargreaves, who
uses optical measurements taken continuously throughout the water column to
determine the abundance of chlorophyll, organic matter and certain types of
After the lake chased them off their last site, Hargreaves and the rest of
the Neuston crew found themselves on a quiet patch of water exactly where they
wanted to be: over the sprawling fields of moss around Wizard Island.
Once again, they prepared to lower their package of sensors into the water
and this time the lake cooperated. After bringing the package back on deck,
Hargreaves downloaded the data to his computer and looked at the signal
indicating concentration of dissolved organic matter
"If the signal increases close to the moss, then the moss could be a source
of organic matter," he said.
But the signal is flat, and the lake has concealed its secrets for another
Ben Larson: 503-221-8133;