ANNUAL REPORT FOR AWARD # 0327440
Will climate change affect hyporheic processes in arctic streams? An assessment of interactions among geomorphology, hydrology, and biogeochemistry in Arctic stream networks
Participant Individuals:
Co-Principal Investigator(s): William B Bowden; James P McNamara; Michael N Gooseff
Senior personnel(s): John Bradford
Graduate student(s): Jay Zarnetske; Morgan Johnston; Troy Brosten; Robert Payn; Julia Larouche
Undergraduate student(s): Kenneth Hill
Technician, programmer(s): Lael Rogan; Adrian Green
Research Experience for Undergraduates(s): Andrew Duling
Undergraduate student(s): Seth Bowden
Senior personnel(s): Kevin Griffin; William Schuster
Community college faculty(s): Kenneth Turner
Partner Organizations:
University of Alaska Fairbanks
Lael Rogan is a GIS/GPS/remote sensing expert employed by the Institute of Arctic Biology at the University of Alaska - Fairbanks. Lael's assistance with GIS, GPS, and remote sensing support in the field and at the Toolik Field Station was essential and greatly appreciated.
Marine Biological Laboratory
Adrian Green from the Ecosystem Center of the Marine Biological Laboratory provided essential field and analytical services during the 2004 field campaigns.
Utah State University
Utah State University was a full-partner in this research, lead by Mike Gooseff who is a co-PI on this project. Mike co-leads the overall research project and manages Objective 3 through a sub-contract from the University of Vermont. Jay Zarnetske is a graduate student working with Dr. Gooseff. During the 2005 field season Dr. Gooseff accepted a new position at the Colorado School of Mines (see separate entry). Management of this component of the project has shifted from USU to CSM. However, for logistical and academic reasons, Mr. Zarnetske remains at USU, still under the guidance of Dr. Gooseff.
Boise State University
Boise State University is a full-partner in this research, lead by Jim McNamara who is a co-PI on this project. Jim co-leads the overall research project and manages Objective 2 through a sub-contract from the University of Vermont. Jim is assisted in Objective 2 by John Bradford, who is the technical expert on GPR.
Colorado School of Mines
During the 2005 project year Dr. Gooseff moved from Utah State University to accept a new faculty position at the Colorado School of Mines. CSM has therefore taken over the grant management responsibilities for Dr. Gooseff's contributions to the project.
Other collaborators
In the course of this work on geomorphic controls affecting in-stream processes in Arctic streams and rivers, we have become increasingly interested in the potential effects of more frequent thermokarst formation due to warming in the Arctic region and the effects this increased thermokarst activity might have on the health of Arctic stream ecosystems. To this end we have begun to inquire among colleagues with expertise in thermokarst dynamics about future research collaborations.
During the 2005 project year we discussed this potential project with a number of colleagues including V. Romanovsky and L. Hinzman at the University of Alaska-Fairbanks. In addition, an initial collaborative project has been discussed with D. Sanzone of the Arctic National Parks Network of the National Parks Service.
Activities and findings
Research and Education Activities
Project Activities
The primary goal of this research is to assess how geomorphology and seasonal changes in the thawed region of soil and sediment around open stream channels control hydraulic and biogeochemical dynamics in the hyporheic zone of Arctic streams. The research is guided by two closely linked hypotheses. First, as the extent of the sub-stream thaw bulb increases through a summer, the physical dimensions of the hyporheic zone also increase, which increases the potential for biogeochemical processing in the hyporheic zone. Second, the interactions between thaw depth and hyporheic functions operate within a structure dictated by channel geomorphology. We have 4 specific objectives addressing these hypotheses in the current project, as follows:
1. to select and characterize stream reaches that represent a range of geomorphologic conditions in rivers of the North Slope of Arctic Alaska,
2. to monitor the sub-stream thaw bulb size through the thaw season using ground penetrating radar and subsurface temperature measurement in several stream cross-sections within each reach,
3. to conduct repeated hyporheic exchange studies (stream solute addition experiments) through the thaw season in each reach to determine hyporheic hydraulic characteristics, and
4. to conduct repeated measures of nutrient (N and P) concentrations and turnover time in the hyporheic zone through the thaw season in each reach to determine biogeochemical characteristics.
2004 Research Progress
We were able to accomplish some important preliminary field work at the end of 2003 field season, just after this award was granted. The 2004 field season was the first full field season for this new collaborative project. By the end of the September 2004 field campaign (one of 4 conducted in 2004) we substantially completed field work on objectives 1 through 3 and had tested approaches to address objective 4 in the 2005 field season.
Specifically, in 2004 we established and monitored 9 key sites that were intended to represent a range of geomorphic stream types common in the Toolik Lake region. These sites included:
• tributaries leading into Green Cabin Lake (GC), • the main tributaries and confluence of the upper Kuparuk River (KH),
• the Kuparuk River at the pipeline (KP), • beads on lower Oksrukuyik Creek above the road (OC), • beads in upper Imnaviat Creek (IC, old R4D site), • I-Series Lake I-8 inlet (8I) and outlet (8O), • I-Series peaty swamp below I-7 (PI), and • Toolik Inlet stream (TI) at the dogleg above the bridge.
Each of these sites was visited during 4 campaigns executed in late May, mid-June, mid-August, and late-September.
Ground penetrating radar (GPR) transects were done on 1 to 12 permanent transects at each of the 9 sites during each of the 4 seasonal campaigns. A 10th site was occupied near the White Hills area on the main stem of the Kuparuk River about half way to the Arctic Coast, during the June 2004 campaign only. We observed a seasonal progression of thaw depth at all sites during these campaigns. However, it is noteworthy that our continuous temperature records indicate that thaw depth was already well advanced by late-May, before most of the surface snow and ice had thawed. Furthermore, the GPR data and some physical probing (see below) suggest that the thaw interface remained deep (in some places >1.8m) and that the lateral extent of thaw may have even increased in some places, well into late September.
We performed solute injection experiments with Rhodamine WT (RWT) at each site during the first three campaigns (i.e., solute injection experiments were not done during the September campaign). These experiments were done to characterize transient solute storage using the slug-injection approach and the STAMMT-L model developed by Haggerty and Reeves (2002). In general these experiments showed that transient solute storage did not increase significantly over the season while the thaw bulb depth did increase significantly. This results was at first counerintuitive, but is consistent with experimental results from 2005 which show that the hyporheic zone occupies only the upper portion of the thawed zone in these streams. (See 2005 results below.) It is also possible that the relationship between in-stream and hyporheic storage volumes changes over the season.
At the end of the 2003 field season we installed several thermocouple arrays (at KP, 8I, and PI) as a means to confirm that the temperature profile with depth in the sediment was consistent with our GPR data (i.e., that the thaw interface was where the GPR imaging placed it). Our intention was to use the thermocouple data only as a means to confirm our GPR data. We found, however, that the thermocouple data are valuable in and of themselves, to record the thermal dynamics in the benthic substrate and as possible input to a heat budget model for the benthic substrate. For these reasons we installed 3 additional thermocouple arrays with datalogging in mid-August 2004 (at the 8O and GC sites plus one site below Green Cabin Lake). Probing, which is required to install these thermocouples, indicated that the thaw interface was often deeper than the maximum extent of our insertion tool (~1.8m), especially at the alluvial sites (e.g. 8I, 8O).
In all, we eventually established 6 sites with from 1 to 5 thermocouple arrays. Each array generally consists of 5 thermocouples nested at 30 cm intervals down to a depth of up to 1.8 m in the substrate. Each site was equipped with solar panels and marine-grade batteries designed to carry them through the entire winter. The KP site established in late 2003 was partially destroyed by ice during the spring 2004 melt. The site was reactivated briefly but then abandoned in 2004. The site at 8I failed near Christmas 2004 when a critical wire broke in extremely cold conditions. Data to this point was retrieved safely in April 2005. The other four stations performed flawlessly over the entire 2004/2005 winter and data were successfully retrieved in April 2005.
As an ancillary part of this project we visited and mapped the Toolik River thermokarst site and sampled it and two other thermokarst sites (Kuparuk W-3 and Hershey Creek Lake 86, see above) for TSS and nutrients. Lael Rogan produced benchmark GIS polygons defining the extent of the Toolik River thermokarst. An initial attempt in August to obtain GPR data for the Toolik River site failed for technical reasons. Additional GPR data were collected in September 2004. These data not indicate an extensive thawed zone in the vicinity of the thermokarst at that time of year.
2005 Research Progress
In 2005 we shifted our research efforts in two important ways. First, we decided to focus our GPR and hydrodynamics efforts on two contrasting stream types: 1) a rocky-bottom, alluvial, high-gradient stream and 2) a peat-bottomed, low-gradient stream. Second, we ramped up the biogeochemical research initiative, the last of our four proposed objectives.
The reason for making the first shift was that our 2004 field efforts showed clearly that the GPR provided useful information about the thawed zone beneath these headwater streams. With this information we effectively addressed objectives 2 and 3 of this project. In particular, our work showed that there were substantial and important differences in thaw depth as inferred by the GPR, between rocky-bottom, alluvial, high-gradient streams and peat-bottomed, low-gradient streams. This observation was consistent with conclusions inferred by WB Bowden and his graduate student C. Cappelletti, who had been estimating whole-stream metabolism on these same reaches as part of the Arctic LTER effort. Consequently, we decided to focus our 2005 field efforts on these two contrasting stream types.
The second shift (to address biogeochemical dynamics in the hyporheic zone) was planned as a part of the original proposal.
During the 2005 field season we conducted 3-D GPR surveys to investigate in detail the thaw response at geomorphologic transitions (i.e., riffle to pool). We carried out conservative solute injections experiments in which we collected both surface and subsurface (multiple depths) water samples. These experiments were done on both of the contrasting stream reaches, twice during the summer (early/June and late/August). To complement these geophysical and hydrodynamic measurements, we collected nutrient samples (NH4, NO3, PO4, and DOC) from surface water and 45 nested mini-piezometers in the two stream types. We installed 18 piezometers (9 nests, 2 depths each) in the Peat Inlet (PI) stream and 27 piezometers (9 nests, 3 depths each) in the Lake I-8 inlet stream. In both streams we installed 3 piezometer nests in each of three geomorphological features (pool, riffle head, riffle tail). Nutrient samples were taken from each piezometer in both streams at four times over the summer; twice in June and twice in August 2005.
In addition to the comparisons of the contrasting stream types, we conducted additional field experiments at a location on the upper Kuparuk River (GCL) where a gravel bar at a tributary junction had created a natural dam and that forced surface water into hyporheic flow. This site had been identified during the 2004 field season as a site of special significance because we could define the actual flow path of water through the gravel bar. This is usually difficult to do in most hyporheic studies. Thus, this gravel bar provided a natural 'laboratory' for us to study transport rates of water and transformation rates of nutrients. We conducted two experiments, one in June and one in August. A total of 40 mimi-piezometers were installed at the GCL gravel bar. In the June experment we obtained samples from 22 of the piezometers; in the August experiment we obtained samples from 28 piezometers. The water flow path was traced with Rhodamine WT dye and nutrient changes were noted across the flow paths in both space and time.
We continued to monitor hyporheic temperature trends, 4 times per day at 5 automated datalogging stations established in 2003/2004 (8I, 8O, PI, GCin and GCout). Data were downloaded from these sites in August 2005 and they were readied for the 2005/2006 winter. Data will be retrieved from these sites in June 2006 and they will be dismantled.
As a part of the ancillary activities associated with this project we revisited the Toolik River thermokarst site that we discovered in 2003 and revisited in 2004. We re-surveyed to thermokarst feature with the help of the UAF/Toolik Field Station Geo-Spatial Analysis team (A. Balser and L. Rogan). We also completed an extensive aerial survey of an area ~5km south and west to 50 km north of Toolik Lake, with the objective of identifying whether we could identify any new thermokarsts in this landscape, other than the one we previously located on the Toolik River. This survey revealed nearly 2 dozen new thermokarsts, one of which was many times larger than the one on the Toolik River.
Cumulative education activities
In the course of this project we have involved 5 graduate students and 3 undergraduate students in our work. Three of the graduate students are fully involved with this project, focusing on key aspects of the GPR (objective 2, T. Brosten), conservative tracer (objective 3, J. Zarnetske) and biogeochemical (objective 4, M. Johnston) work. A fourth graduate student (R. Payn) continues to be tangentially involved in the project and is working on a manuscript relevant to the project objectives. One of the undergraduate students (A. Duling) was an REU student on the closely-related Arctic LTER project and was mentored by WB Bowden who is a co-PI on both this and the Arctic LTER project. Andrew's project on geomorphic influences on stream tolerance of flood impacts was directly relevant to this project and in the course of his project he generated data that will be useful to us. A college science teacher (K. Turner, Art Institute of Seattle) assisted us with the June 2005 field campaign. Experiences he gained while helping us will be a valuable resource in his teaching efforts at home.