mcmurdo dry valley streams: ecosystems waiting for water mcmlter: pi-lyons, co-pi’s- doran,...
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McMurdo Dry Valley streams: Ecosystems Waiting for Water
MCMLTER: PI-Lyons, Co-PI’s- Doran, Fountain, McKnight,
Moorhead, Priscu,Virginia,Wall
McMurdo Dry Valleys, Antarctica
Polar desert: • Dry (<10 cm precip. Annually)• Cold (average air temp. = -20oC)
– Meltwater streams flow for 6 to 14 weeks– Streamflow is typically 0.01 to 5 cfs, stream
water temperature is typically 0.1 to 14 oC– Hyporheic zone is a key hydrologic feature– Habitat for benthic algae mats– Source and control of solute input to the lakes
Glacial meltwater streams:climatic connection between the glaciers and the lakes
Monitoring of streamflow and stream ecosystems
• Network of 19 stream gauges in Taylor and Wright Valleys-continuous (15 min)
• Collaboration between NSF and USGS
• Network of 18 transects to document ecological response to changing flow
USGS hydrologist gauging Onyx River
Creek
Canada Glacier
Commonwealth
Glacier
Crescent GlacierHoward
Glacier
Gre
en
Del
ta
Stre
amH
arnishStream
Von
GuerardStream
AikenCreek
Huey
Canada
Cre
ek
Stream
Stre amSeal
Lo
st
McK
nigh
t
Creek
Cre
sce n
tSt
reamN
2 km
RelictChannel
MCMLTER gauging stations
• Challenge-range of flows and unstable substrate
• Parshall flumes with weirs in cutoff wall-compound rating
• Natural channel controls
• Located at outlets to lake
• Temporary sites near glaciers
Parshall flume used to obtain accurate discharge at low flow
Maintenance of gauges to maintain record
Green Creek gauge moveddue to lake level riseSanta Fe gauge pummeled by 100 cfs (cubic feet/sec)
Fryxell basin: streamflow greater during 89-92 than during 93-present
0
100
200
300
400
500
600
90-91 91-92 92-93 93-94 94-95 95-96 96-97 97-98 98-99
Season
Vol
ume
(x10
6 m
3 )
CommonwealthLost SealHueyCanadaGreenAndersen
Wright Valley: Onyx River flow has also been lower since 93
0
2000
4000
6000
8000
10000
12000
14000
90-91 91-92 92-93 93-94 94-95 95-96 96-97 97-98 98-99
Season
Vol
ume
(x10
6 m
3)
Onyx River at Vanda
Onyx River at Lower Wright
Bonney basin: high streamflow from Taylor Glacier since 1993
0
200
400
600
800
1000
1200
90-91 91-92 92-93 93-94 94-95 95-96 96-97 97-98 98-99
Season
Vol
ume
(x10
6 m
3 )
Priscu
Lawson
Santa Fe
Santa Fe Creek on 12/21/00: 35 cfs
Filamentous cyanobacteria (blue-green algae): orange algal mats
Black algal mats at stream edge: intermittent flow
Orange algal mats in Von Guerard Stream:10-14 species in each sample
Black algal mats in Von Guerard Stream:1-2 species in each sample
Streams with stable habitat had few changes
Stream Habitat Mats 94-98
Canada Pavement abundant No change
Bowles Pavement abundant No change
Green Pavement abundant New green mats
Delta-upper
Pavement abundant New moss
Some streams with poor habitat had more abundant mats
Stream Habitat Mats 94-98
Huey Sandy sparse More orange new black
Delta-g Sandy sparse New orange
VonG-g Sandy sparse More mats!
Lawson Steep sparse More orange & moss
Hyporheic zone: under and adjacent to stream with active exchange of water
PermafrostPermafrost
Permafrost
Active Layer
In dry valley streams the “hyporheic zone” is observed as a wetted zone adjacent to stream
Dry valley streams flow through porous alluvium with high rates of “hyporheic exchange”.
In cold summers, glacial meltwater soaks in and sublimates in fall and winter.
Stream scale experiments to quantify biogeochemical processes
• Short term experimental perturbations to quantify nutrient uptake and hydrology
• Long term experiment studying ecological response to geomorphological evolution of stream networks
• Experiments reviewed through environmental assessment process
Experimental enrichment with nitrate and phosphate: 1.5 hrs
Sampling Green Creek during experiment
Stream algal mats win! Added nutrients are taken up and do not reach the lake.
In cold summers, streams retain water and nutrients, lakes fend for themselves.
Stream channel that had been inactive was “reactivated” by directing water to channel
with low sandbag wall
Algal mats in reactivated relict channel are most productive mats is Taylor Valley
Photosynthesis measured as rate of oxygen production by mat samples
Higher nutrients in relict channel water enhances growth
An axiom of ecology is: “Where there is water, there is life.” In Dry Valleys: “Where there has been and will be water, there is life.”
Dry valley stream ecosystems can withstand cold, desiccation annually and for longer periods, as long as decades or centuries.
The Stream Team gratefully acknowledgeslogistical support provided by PHI, ASA and Raytheon, and field assistance from other MCMLTER investigators