June 9th USGCRP Seminar: Antarctic Update: An Ecosystem Perspective on UV Radiation and Climate Change Impacts

Tony Socci tsocci at usgcrp.gov
Wed Jun 4 11:26:29 EDT 1997

 U.S. Global Change Research Program Second Monday Seminar Series

               Antarctic Update: An Ecosystem Perspective on UV Radiation
                                   and Climate Change Impacts

What are the effects of recent climate changes on Antarctic ecosystems and
what are the implications for the future?  Is there a relationship between
ozone depletion and higher levels of UV radiation reaching the surface in
the Antarctic region?  What effects have seasonally increased levels of
UV-B radiation had on Antarctic ecosystems?  How will these changes affect
other ecosystems and food webs?

                                                    Public Invited

                                     Monday, June 9, 1997, 3:15-4:45 PM
                      Rayburn House Office Bldg., Room B369, Washington, DC
                                                Reception Following


Dr. Cornelius W. Sullivan, Director, Office of Polar Programs, National
Science Foundation, Arlington, VA


Dr. William R. Fraser, Biology Department, Montana State University, Bozeman, MT

Dr. Deneb Karentz, Departments of Biology and Environmental Science,
University of San Francisco, San Francisco, CA


Dr. Fraser and Dr. Karentz have concluded the following regarding the
impacts of ozone depletion and climate change in the Antarctic: 1) Changing
patterns of snow deposition and melt are affecting summer nesting habitats
of penguins in the West Antarctic peninsula by producing a mismatch between
the availability of breeding habitat and the requirements of penguins at
various stages in their breeding cycle; 2) These changes are consistent
with there having been warming in certain regions of the West Antarctic on
the order of 4-5 degrees C which are values generally consistent with
observations and model predictions; 3) Those Antarctic species found at the
periphery of their breeding ranges are most likely to undergo pronounced
changes due to climate change; 4) Antarctic marine organisms have different
sensitivities to UV exposure; 5) The amount of biological damage to Antarctic
marine organisms due to UVB radiation is directly correlated to the level of
ozone depletion; 6) Increased levels of UVB radiation in the Antarctic can, and
do, result in impairment of metabolic processes, decreases in growth,
reduction in reproductive potential, morphological abnormalities, genetic
damage, and death; and 7) UV-induced damage to marine organisms can further
lead to the disruption of entire ecosystems and food webs, and therefore,
the availability of food resources for humans and other ecosystems.

      Long-Term Changes in Certain Antarctic Predator Populations: Evidence of
                  Climate Warming in the Western Antarctic Peninsula Region

It  is estimated that a century ago the number of baleen whales feeding in
the Antarctic during summer totaled about one million, with a biomass of 43
million tons.  These whales fed  primarily on a small crustacean, the
Antarctic krill, taking an estimated 190 million tons annually.  By the
1930's, commercial whaling had reduced the whale population to about
340,000  individuals, and today the current biomass probably does not
exceed 7 million tons, or about one sixth of the initial stock.

A central tenet of Antarctic ecology holds that the depletion of baleen
whale stocks resulted in a "krill surplus."  Documented increases in the
abundance of krill-dependent predators such as seals and penguins following
the collapse of whale stocks have thus been attributed to the effects of
competitive release, or the idea that, without whales, other predators
benefited from the increased availability of krill.  Although this
hypothesis has been one of the dominant  elements guiding the
interpretation of data related to Southern Ocean food web dynamics, close
inspection of the long-term population trends of some of these predators
has revealed patterns that are inconsistent with this model.

These trends, based on two ecologically similar penguins (Chinstrap and
Adelie) found on the Antarctic Peninsula, suggest these species are
tracking the effects of a warming trend that is affecting the availability
of critical winter and summer habitats.  The suspected mechanism appears to
involve a decrease in the frequency of cold years with heavy sea ice, which
represents critical winter habitat.  Changing patterns of snow deposition
and melt, perhaps related to the absence of winter sea ice as well, are also
affecting summer nesting habitat, producing a temporal mismatch between
the availability of breeding habitat and the requirements of penguins, for
example, at various stages in their breeding cycles.  These observations
support the predictions of a number of climate model studies with respect
to where pronounced climatological and hence, ecological changes are likely
to occur (polar environments), what species will be affected (those found at the
periphery of their breeding range) and what biophysical processes may be
involved (the disruption of evolved natural history patterns by changing
the timing of physical events).  These observed physical changes, as well
as changes in patterns of behavior, are consistent with expectations of the
consequences of the observed regional increase in mid-winter temperatures
of 4-5 degrees C over the past half-century.

                      Ecological Considerations of Antarctic Ozone Depletion

Global scale ozone depletion attributed to anthropogenic pollution of the
atmosphere was predicted by scientists more the 20 years ago. Ozone is a
natural component of the Earth's atmosphere and ozone specifically absorbs
in the ultraviolet (UV) portion of the solar spectrum. Even under a
"normal" ozone column, harmful UVB radiation passes through to the Earth's
surface. Ozone depletion results in an increase in the amount of
biologically harmful ultraviolet B (UVB) radiation that reaches the Earth's
surface and that penetrates into the surface waters of the oceans.

UVB is biologically harmful, primarily because UVB is absorbed by key
biological molecules such as nucleic acids (DNA) and proteins. Absorption
of UV causes structural damage to these molecules, changing their physical
shape and interfering with the specific functions they provide for life.
Dr. Karentz and her colleagues have observed and documented, for example,
that increased levels of UVB radiation in the Antarctic provoke a range of
changes in marine organisms, such as impairment of metabolic processes,
decreases in growth, reduction in reproductive potential, morphological
abnormalities, genetic damage, and death. Thus, the evidence suggests that
UV-induced damage to specific organisms can initiate various degrees of
disruption in marine ecosystems, upsetting the balance between organisms
and their environment.

Research conducted in the Antarctic indicates that the amount of biological
damage to marine organisms is directly correlated to the level of ozone
depletion. It has also been observed that Antarctic organisms have
differential sensitivities to UV exposure such that a dose of UV that is
lethal to one species may only cause impairment in another. The degree of
tolerance is dependent on 1) the effectiveness of protective strategies
that serve to minimize damage by reducing exposure to UVB, and 2) repair
mechanisms that can correct UVB-induced damage. The combination of
protection and repair capabilities varies among species and will influence
survival, growth, and reproductive success under UVB stress. Because each
species responds differently, shifts in species composition (biodiversity)
are expected under an increased UVB regime. Even subtle alterations in the
quantity or quality of food sources (phytoplankton and krill) can
ultimately affect the larger Antarctic consumers such as penguins, seals,
and whales. Because the Antarctic marine ecosystem is directly linked to
the rest of the world's oceans, changes in the Antarctic region can
initiate changes in the rest of the biosphere.  We need, therefore, to
understand better what these changes might be and what impacts they could
have on humans and other ecosystems.


Dr. William R. Fraser  is currently an Assistant Professor in the Polar
Oceans Research Group of the Biology Department at Montana State University
in Bozeman, Montana.  His research  interests focus on understanding the
physical and biological interactions that control the distribution and
demography of seabirds.  His present research on the Antarctic Peninsula
began in 1974 while he was at the University of Minnesota, and has
continued to the present, evolving into a program that employs basic and
applied approaches to investigating issues involving the effects of climate
change, fisheries, and tourism on Antarctic ecosystems, most especially
seabird communities.

Dr. Fraser's work has emphasized long-term research, the rationale being
that the scale of the effort needs to match the scale of the processes
under investigation, and ecological time scales involve decades to
centuries.  It was this focus that in 1992, nearly two decades after his
research began, led him to propose that changes in sea ice conditions due
to climate warming were having a significant impact on the Antarctic
ecosystem.  Although other researchers had suggested a possible climate
effect, none had identified a mechanism by which changes in the physical
environment might lead to ecosystem-level responses.  This work became one
of the founding hypotheses supporting long-term research in Antarctica as
part of the National Science Foundation's prestigious Long-Term Ecological
Research Program.

Dr. Fraser is currently a U.S. representative to the Scientific Committee
on Antarctic Research, Bird Biology Subcommittee, and annually contributes
data and advises national and international programs concerned with
management of Antarctic marine living resources.  He received his B.S.
degree in Wildlife Management from Utah State University in 1973, and his
Ph.D. degree in Wildlife Ecology from the University of Minnesota in 1989.

Dr. Deneb Karentz is a Professor in the Departments of Biology and
Environmental Science at the University of San Francisco. She has studied
the UV-photobiology of Antarctic organisms since 1987 and was one of the
first scientists to document the biological effects of Antarctic ozone
depletion. Dr. Karentz's research has underscored the importance of
understanding species-specific responses to UV exposure as a vital
component in evaluating the ecological consequences of ozone depletion. Her
current research program focuses on characterizing tolerance (protection
and repair) mechanisms that determine the UV sensitivity of organisms.

Dr. Karentz has participated in a number of workshops and symposia relating
to the biological effects of UV exposure and the potential impacts of ozone
depletion on ecosystem change.  These include meetings sponsored by the
Scientific Committee on Problems of the Environment (SCOPE), the NATO
Advanced Science Institute Series on Global Environmental Change, the
International Congress of Scientific Unions (ICSU), Woods Hole
Oceanographic Institution and the American Association for the Advancement
of Science (AAAS).  She has received the Luigi Provasoli Award in
Recognition of an Outstanding Paper published in the Journal of Phycology
and the Arthur Furst Award for Outstanding Research from the University of
San Francisco.

Dr. Karentz's academic background is in marine biology.  She has a M.S.
degree from Oregon State University (1976) and a Ph.D. from the University
of Rhode Island (1982).  Dr. Karentz was a National Research Service Award
Post-Doctoral Fellow at the University of California Medical Center in San
Francisco (1983-1986) and is an instructor in the National Science
Foundation Antarctic Biology Course held at McMurdo Station, Antarctica
(1994, 1995, 1996).

                       The Next Seminar is scheduled for Monday, July 14, 1997

             Planned Topic: Wetlands Losses in the United States: Scope,
                                       Causes, Impacts and Future Prospects

For more information please contact:

Anthony D. Socci, Ph.D., U.S. Global Change Research Program Office, Code
YS-1, 300 E St., SW, Washington, DC 20546 Telephone: (202) 358-1532; Fax:
(202) 358-4103 E-Mail: TSOCCI at USGCRP.GOV.

Additional information on the U.S. Global Change Research Program (USGCRP)
and this Seminar Series is available on the USGCRP Home Page at:
http://www.usgcrp.gov. Normally these seminars are held on the second
Monday of each month.

Anthony D. Socci, Ph.D.
Program Associate
Office of the US Global Change Research Program (USGCRP)
Code YS-1
300 E St., SW
Washington, DC 20546

Tel: (202) 358-1532
Fax: (202) 358-4103
E-mail: tsocci at usgcrp.gov
World Wide Web Address: http://www.usgcrp.gov/

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