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