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Site descriptions: Rivers and Streams
The current stream research emphasizes long-term monitoring of two
tundra rivers, whole-river nutrient enrichment experiments,
intensive studies (15N tracer studies) and
extensive surveys of selected stream reaches of contrasting size and
Long-term Monitoring and Nutrient Enrichment Studies
The Kuparuk River has been our primary site for
long-term monitoring and whole-stream fertilization study. The Kuparuk River
is a fourth order stream where it crosses the Dalton Highway about 10-km
northeast of the Toolik Lake Research Station.
Phosphorus (as H2PO4) has been continuously added to the
Kuparuk River every summer since 1983. Within the first four years a
dramatic response to fertilization was observed at all trophic levels with
increases in epilithic chlorophyll accumulation and insect and fish (Thymallus
arcticus) growth rates.
The long-term fertilization of the Kuparuk River has led to major shifts in
primary producer species and in production. After ten years of
P-fertilization, the epilithic diatom dominated system has been replaced by
moss, primarily Hygrohypnum spp. There has been a large impact of the
increase in moss cover on the macroinvertebrate community structure.
While fertilization has stimulated growth in both young-of-the-year and
adult Arctic Grayling in most years, so far the moss-driven changes in the
lower trophic levels have had no apparent effect on fish. Photo
(right): Aerial view of the Kuparuk R., downstream of the Dalton
Highway and the pipeline.
A second stream, Oksrukuyik Creek is located approximately 20-km northeast
of the Toolik Station. Like the Kuparuk River, this stream is a clear-water
tundra river, but with discharge averageing about half that of the Kuparuk
River. Oksrukuyik Creek was a whole-stream fertilization study site for 6
years and continues to be a long-term monitoring site. The addition of
phosphorus plus nitrogen, every summer from 1991 through 1996, stimulated
production at all trophic levels. The recovery from fertilization was
monitored until 1999. We are currently conducting maintenance level
monitoring of an unfertilized reach (previous reference reach) of Oksrukuyik
Creek. Photo (left): Oksrukuyik Creek.
Kuparuk River (1983 - 1998) estimates of epilithic algal chlorophyll,
percent bryophyte cover in riffles, chironomid and Brachycentrus
densities, young-of-the-year and adult grayling growth from the reference
(above the phosphorus dripper) and the phosphorus fertilized reaches
Intensive Stream Reach Studies
The objective of these investigations is to increase our understanding of
nutrient processing by the stream ecosystem. Using 15-N labeled
ammonium tracers, we have intensively studied biogeochemical processing in
several different arctic stream types, including: lake outlet streams,
beaded and non-beaded tundra streams, ranging in low summer flows from 0.02
to 30 m3/sec. The first tracer addition studies took place
in the Kuparuk River in 1991 (reference) and 1995 (P-fertilized reach).
These whole-stream 15-N enrichments have continued every year since, in
order to study the ecology of arctic streams of different geomorphology and
size. In 1994, Blueberry Creek, the outlet stream of Lake I-8 in the
Toolik Lake drainage, was the site of the 15-N tracer study.
Intensive study reaches from 1996 through 2000 include the following: Lower
Kuparuk R. (coastal plain braided river), E-1 (1st order lake outlet stream
in the Toolik Lake drainage), Trevor Creek (glacier-fed stream), Hershey
Creek (second order lake outlet stream and tributary to the Kuparuk River),
and Toolik River (second order tundra stream). Photo (left): third
order lake outlet stream.
These studies have shown that tundra streams retain and recycle inorganic
nitrogen very rapidly. Uptake for NH4
occurs within a few tens to hundreds of meters in the smallest streams and
within a few kilometers in the largest streams in the basin (Wollheim et al.
2001). All components of the food web become labeled with the tracer
within a few weeks of addition. The pattern of tracer movements allows
us to determine the trophic connection in the food web. Finally,
tracer retention in the experimental reach has been measured for up to two
years after the tracer addition was stopped. The tracer data has made
possible the development and testing of models of nitrogen flow in tundra
Toolik Regional Stream Surveys
We have surveyed several different streams across the eastern North Slope
of Alaska, including tundra, glacier-fed, spring and mountain streams. The
goal of these surveys is to characterize the biogeochemical variability
among the major arctic stream types. The biogeochemical
characteristics of each stream type are mainly a function of landscape
geomorphology (e.g., glaciers and springs). The water sources for all
of these stream types are very different and are dictated by their landscape
position. By studying these different stream types we will increase
our understanding of the diversity of stream biota and the impact of
regional change upon the stream networks. Photo (left): Ivishak Hot Spring,
Spring streams derive water from underground sources. As a
result, springs are rich in cations and nutrients, flow year-round and have
stable water temperatures. This provides a stable, enriched habitat
for primary and secondary producers leading to high biomass and diversity of
algae, moss and insects. Photo (left): A spring stream tributary of
the Echooka River, 1997.
Glacier streams are fed from glacier melt water. While,
glacier-fed streams have moderate nutrient levels, supplied by subsurface
runoff of the melt water, they also have very high sediment loads. The
sediment is made up of fine rock particulates called glacial "flour".
This suspended sediment blocks light and scours the stream bottom. These
streams also have highly variable discharge and water temperature on a
diurnal cycle. They are high gradient streams with unstable substrate.
All of these factors inhibit the colonization of substantial amounts of
algae and insects, leading to the low biodiversity found in glacier-fed
streams. Photo (top left): Glacier located approximately 40
miles south of the Toolik Lake Field Station, 2000 and a glacial tributary
to the Ribdon River (top right), a glacier-fed river, 1998.
Mountain Streams are common along the North Slope of the Brooks
Range. They originate on the slopes of mountains and they are derived
from rainwater and spring snowmelt. Mountain streams also have a
moderate amount of nutrients mainly supplied by subsurface runoff of rain
and melting snow on the mountain slopes. Unlike glacial streams, the
mountain stream water is clear, with no glacial flour.
The unstable flow regimes and substrate lead to low levels of primary and
especially secondary production. Photo (right): tributary of the Atigun R.,
a mountain stream.
Tundra Streams drain the foothills and coastal plains of the North
Slope, which is underlain by permafrost. Tundra streams have clear
water that is often stained light brown with organic matter from the tundra.
Much of nutrients are locked within the permafrost, although there may be
pulses of high nutrient levels during the spring runoff. In contrast
to the mountain and glacier-fed streams, the low gradient and more stable
flows of most tundra streams allow for the colonization of benthic algae and
insects. However, a short growing season and the lack of phosphorus limit
substantial algal accumulation. Where lateral inputs of surface and
subsurface runoff (seeps and springs) occur, bryophytes usually become
established and local productivity may be as high as in some arctic spring
streams. Arctic Grayling densities are relatively high in tundra
streams, mainly due to the stable flow regimes and high macroinvertebrate
abundance. Photo: (left) Toolik River, a beaded stream.
The Kuparuk River and Oksrukuyik Creek are both examples of meandering
tundra streams. They have rocky bottoms with alternating stretches
of riffles and pools. There is little or no overhanging vegetation and
the dominant primary producers in these streams is epilithic diatoms,
filamentous algae and some moss. Photo: (bottom left) Kuparuk River.
The beaded streams ("beaded" refers to the pools connected by short, stream
segments) are formed by thermal erosion. Typically these low order
streams are shaded by overhanging vegetation (Salex spp.) and have
peaty bottoms and channels, resulting in large amounts of allochthonous
inputs (leaves and peat). Photo: (bottom right) Hershey Creek, and beaded
Wollheim, W.M., B.J. Peterson, L.A. Deegan, M.Bahr, J.E. Hobbie, D.Jones,
W.B. Bowden, A.E. Hershey, G.W. Kling, and M.C. Miller. 1999. A
coupled field and modeling approach for the analysis of nitrogen cycling in
streams. Journal of the North American Benthological Society 18(2):199-221.
Wollheim, W.M., B.J. Peterson, L.A. Deegan, B. Hooker, W.B. Bowden, K.J.
Edwardson, and D.B. Arscott. 2001. Influence of stream size on
ammonium and suspended particulate nitrogen processing. Limnology and
The Kuparuk River
The Kuparuk River arises in the foothills of the Brooks Range and flows
north draining a large area of the North Slope (Peterson et al. 1986). Our
study site is from its headwaters to 5 km below its intersection with the
Haul Road. The river down to this point has a main channel length of 25 km,
drains an area of 143 km2, and has an average channel slope of
3.13%. It is a clear-water stream, frozen solid from late September until
late May. The Kuparuk River has a spring flood resulting from melting snow
followed by lower flows in the summer. Summer water temperatures may reach
20oC and average 8-10oC. Stream discharge has ranged
from 0.3 to 28.3 m3 sec-1 and the total suspended sediment load ranged from
0.4 to 35 mg -1. Flow nearly ceases by late September and the
riffles become dry. The pools freeze solid in October and there is no flow
until mid to late May.
The watershed of the Kuparuk River has terrestrial vegetation typical of
this region. The vegetation of the upper basin consists of alpine
communities at the higher elevations and moist tundra communities,
predominantly the cotton grass Eriophorum vaginatum, in the
foothills. Along the stream banks there are patches of dwarf willows and
birches, some reaching 1 m in height. The upper layers of the soils consist
of 30 to 70 cm of peat underlain by alluvial and glacial deposits of coarse
sand and gravel. Permafrost is present throughout the area to a depth of up
to 800 m; the mean thawed depth of the active layer is about 40 cm during
Nutrients are low in the Kuparuk. Typical mean annual values are > 0.5 然
NH4-N, 1.5 然 NO3-N, 18 然 DON-N, 0.3 然 total
dissolved PO4-P, and 0.2 然 fine particulate P. Nitrate
concentrations are inversely correlated with flow whereas particulate
phosphorus concentrations increase during high flows.
About 92% of the total organic carbon export is dissolved organic carbon
(Peterson et al. 1986). The remaining 8% is particulate carbon (fine is 7%
and large is 0.7%). The lateral input of carbon from the tundra is mostly in
the form of peat because there is little movement of litter from the tundra
surface; estimated input from bank erosion ranged from 17 to 25 mol C m-2
y-1. The detritus (particulate organic carbon) on the river bottom
equals 2.3 mol C m-2 while epilithic algal biomass is 0.02 mol C
m-2 and net primary production averages about 1 mol C m-2
The insect community in the river is dominated by four species. Black
flies, predominantly Prosimulium martini, account for the major
portion of secondary production in the river. Baetis lapponicus, the
most abundant mayfly, contributes about 10 to 20% as much production as the
black flies. The dominant chironomid is Orthocladius rivulorum. The next
most important insect is Brachycentrus americanus, a caddisfly that
contributes about 1% of the secondary production in the river.
The fish community has only one species, the arctic grayling (Thymallus
arcticus), which feeds mainly on drifting insects and particulate matter
although they also forage on pool bottoms. We commonly observe from two to
five adult grayling (30-40 cm) in each pool. During the late summer,
grayling move upstream to a headwater lake where they overwinter.
Young-of-the-year (YOY) grayling exhibit high annual variations in
abundance. In a good year, such as 1990, there may be as many as several
hundred per pool. They are drift feeders almost from hatching, but also take
food off the bottom.
The Kuparuk River is similar to many temperate streams in that
allochthonous carbon inputs dominate the carbon cycle in the river in spite
of the absence of shading vegetation. Much of this carbon is more refractory
than the leaf and litter input to temperate streams. The standing stocks of
chlorophyll on the rocks and the levels of gross and net primary
productivity are low in comparison with temperate streams; apparently this
occurs because of phosphorus limitation and the short growing season. The
export of organic carbon from the watershed is about average for rivers but
because the Kuparuk watershed has low terrestrial net primary productivity,
the percentage of the total watershed organic carbon production exported via
the river is relatively high (2-6%). Dissolved organic carbon is over 90% of
the total export. The Kuparuk thus has a combination of characteristics that
make it similar in some respects, but quite different in others, to boreal
and temperate streams.
references (reviews, overviews, summaries)