Selected Presentation from the INSTAAR Monday Noon Seminar Series. Institute of Arctic and Alpine Research, University of Colorado at Boulder. http://instaar.colorado.edu http://instaar.colorado.edu/other/seminar_mon_presentations This seminar presentation has been posted to the internet to foster communication with the science community and the public. Most of the INSTAAR presentations were originally given in PowerPoint format; they were converted to Adobe PDF for posting. You may need to install the free Adobe Acrobat Reader to view these files. These presentations are "works in progress". They are not peer reviewed. They should not be referenced for any kind of publication. Contact the author for proper references and additional information before any use, even for unpublished works such as your own presentations. LICENSING AGREEMENT. Free use of these presentations is limited to a nonprofit educational or private non-commercial context and requires that you contact the author, give credit to the author, and display the copyright notice. All rights to reproduce these presentations are retained by the copyright owner. Images remain the property of the copyright holder. By accessing these presentations, you are consenting to our licensing agreement. 09 Sep. 2002 Diane McKnight et al., INSTAAR, Email: [email protected]“Ecological response to nitrogen deposition and climate change in alpine lakes in the Colorado Front Range". Seminar given at INSTAAR, University of Colorado. Copyright 2002 Diane McKnight. All Rights Reserved. McKnight presentation (1.3 Mb PDF).
35
Embed
Selected Presentation from the INSTAAR Monday Noon Seminar …instaar.colorado.edu/other/seminar_mon_presentations/... · 2002. 12. 5. · Selected Presentation from the INSTAAR Monday
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Selected Presentation from the INSTAAR Monday Noon Seminar Series.
Institute of Arctic and Alpine Research, University of Colorado at Boulder.http://instaar.colorado.edu
This seminar presentation has been posted to the internet to foster communication with the science community and thepublic.
Most of the INSTAAR presentations were originally given in PowerPoint format; they were converted to Adobe PDF forposting. You may need to install the free Adobe Acrobat Reader to view these files.
These presentations are "works in progress". They are not peer reviewed. They should not be referenced for any kind ofpublication. Contact the author for proper references and additional information before any use, even for unpublishedworks such as your own presentations.
LICENSING AGREEMENT.Free use of these presentations is limited to a nonprofit educational or private non-commercial context and requires thatyou contact the author, give credit to the author, and display the copyright notice. All rights to reproduce thesepresentations are retained by the copyright owner. Images remain the property of the copyright holder. By accessingthese presentations, you are consenting to our licensing agreement.
09 Sep. 2002 Diane McKnight et al., INSTAAR, Email: [email protected]“Ecological response to nitrogen deposition and climate change in alpine lakes in the Colorado Front Range".Seminar given at INSTAAR, University of Colorado. Copyright 2002 Diane McKnight. All Rights Reserved.McKnight presentation (1.3 Mb PDF).
ALGAL AND BIOGEOCHEMICAL
RESPONSES TO ENVIRONMENTAL
CHANGE IN AN ALPINE LAKE
Summer B. Waters, Diane M. McKnight,
Alexander P. Wolfe, Rolf Vinebrooke, Sean
Sunderman, and Meaghan O’Brien
Institute of Arctic and Alpine Research, University of Colorado
And results of Koren R. Nydick, CSU
Support from NSF-LTER program
Sources of N
Colorado Front Range
N emission trends
Diatom changes in Sediment Core
1950-
1970
Alternative Hypothesis
Input of P-rich windborne agricultural dust and
volatile organic compounds?
Phosphorus Fertilizer, S. Platte Basin, CO
0
200
400
600
800
1945 1955 1965 1975 1985 1995
kg
x 1
000 p
er
yr
missing
data
Niwot Ridge LTER site
Green Lake 4
Green Lake 4: View southwest towards Arikaree Peak
(4008 m) from the shore near the outlet in late September.
Green Lake 4: Alpine lake surrounded by
talus, ice-covered from October to June
Green Lake 4
Changes in Rocky Mountain lakes
• Increased atmospheric deposition of nitrate
from agricultural use of fertilizers and urban
development- upslope winds bring pollution
to alpine environments
• Observed changes in climate include
decrease in ice-cover thickness in late
March, may be related to delay in winter
snowfall
Increases in N deposition and increases
in annual minimum nitrate
Decrease in ice cover thickness in
late March: more snow on ice?
Potential Climate Change Effects
• Delay in formation of ice-cover (longer
autumn)
• Earlier break-up of the ice-cover in early
summer (longer summer)
• Warmer summer temperatures
• Net effect: Longer ice-free period with
greater nitrate availability
Shallow Mountain Lake
Benthos
Pelagic Zone
....
...
.. .. ..
..
.. . .
.....
...
.. ..
Phytoplankton
Epipelic
Algae Epilithic
AlgaeSediment
Paleolimnological approach to
understanding response of Green Lake 4
• Few previous samples of phytoplankton,
difficult to sample in winter and ice-out
• Monitored phytoplankton and water quality
during the summer at surface, 3 m and 9 m
• Deployed sediment trap during summer
• Collected sediment core from lake center
Green Lake 4: sampling sites
Spring Bloom:
Ice cover breaks up
Phytoplankton grow
Diatoms and chlorophytes
are abundant
Nitrate decreases
Phytoplankton species distribution
• Diatoms about 50% or more of biovolume
• Small coccoid algae (chlorophytes?)abundant
• Dominant diatom species: Aulacoseira distans,Fragilaria construens, F. crotonensis, Meridioncirculare
• High species diversity and variability withdepth and time
GL4 sediment core dated by 210Pb
activity: 9 cm~1940
Recent sediments: more OM and diatom
pigments, more microbial source for OM
Diatoms in lake sediments represent
species in water column and in benthos
• Diatom species richness: watercolumn<sediment trap<sediment core
• most diatom species in water column werealso in sediment trap and core
• most diatom species in sediment trap werealso in sediment core
• most diatom species in sediment core werenot found in water column
Recent sediments: more benthic diatoms(Fragilaria pseudoconstruens, F.brevistrata)
Recent sediments: different planktonic
diatoms (less Aulacoseira distans, A.
periglabra, A. lirata, more A. ambigua)
PCA shows that first axis
explains 78.6% of variation
Sample scores for the first
axis have increased steadily
since 1940, corresponding to
introduction of N fertilizer
Why would increased N and thinner
ice cause more benthic diatoms?
• Benthic diatoms havegreater supply of Pfrom weathering insediments and canutilize increased N
• Benthic diatomsgrowing underthinning ice-coverare not flushed fromlake during snowmelt