Water Resources Research Act Program

Details for Project ID 2020AK339B

Constructing a strontium isotope map (isoscape) for watersheds in interior Alaska with broad applications for hydrologic and wildife research

Institute: Alaska
Year Established: 2020 Start Date: 2020-03-01 End Date: 2021-02-28
Total Federal Funds: $10,300 Total Non-Federal Funds: $20,600

Principal Investigators: Matthew Wooller

Project Summary: This project will support the ongoing PhD research of UAF graduate student Audrey Rowe who is working with Dr. Matthew Wooller at the Water and Environmental Research Center, UAF. We propose building a spatial model (isoscape) of strontium isotope ratios of watersheds in interior Alaska. This region encompasses the migration routes of the Fortymile caribou herd, which we are aiming to trace using strontium isotope analyses. Strontium isotope ratios of rivers, streams and surface hydrology can vary widely due to differences in underlying geology (i.e. differing ages and mineral compositions of the bedrock). Animals take up trace amounts of strontium from their environment through food and water, and this strontium is deposited in place of calcium in mineralized hard parts like bone, teeth, and fish ear bones (otoliths). Comparisons of strontium isotope values from animals to spatial models (isoscapes) can be used to investigate the mobility of caribou and a wide range of other wildlife and subsistence resources (e.g., bison, salmon). We plan to use the strontium isotope ratios in caribou teeth to recreate the movement of these individuals across the landscape while the teeth were growing. To do this, we propose to generate a map of strontium isotope ratios in water sources in interior Alaska that we can couple with the ratios found in caribou teeth. We propose to analyze 100 samples of water from across interior Alaska and within the region of the typical Fortymile herd migration. These water samples have already been collected and archived for us to analyze by our collaborators. We will analyze the strontium stable isotope values of these water samples using state-of-the-art instrumentation (MC-ICPMS) based at UAF, and interpolate these values to create a model for the region based on existing, published protocols applied by our collaborators. We have radio collar data from many of the same individuals for which we have tooth samples, allowing us to verify the strontium tracer method with known locations. We aim to show that this method of strontium isotope analysis can provide information about an animal's location. This approach can be also used to recreate the movement of animals when GPS or observation data is lacking. This includes ancient samples, as the strontium in mineralized parts can be preserved virtually unchanged for tens of thousands of years. For the purposes of our research, we plan to apply the findings of this study to caribou tooth samples from the early 20th century to gain insight into how migration behavior might have been different when the Fortymile herd had a much larger population and potentially ranged over a much larger span of watersheds. We propose to make all of our data and maps (isoscapes) openly available on a WERC website and will publish the findings in a peer reviewed journal article. The results of this study can also be more widely applicable for future researchers interested in hydrologic tracer research and the movement of fish and other wildlife resources in interior Alaska.